issue 111 July – August 2014

PAge 3 crown rot PAge 12 diseAse diAgnosis

PAge 14 nemAtodes PAge 18 rhizoctoniA

root And crown diseAses

GettinG to the root of the problem

2 Introduction

getting to the root of the problem

By dr Francis c. ogbonnaya

A suite of new national grdc programs has launched a fresh attack on root and crown diseases, which collectively cost Australian growers hundreds of millions of dollars in lost production and control costs each year. this Ground Cover Supplement reports on some of the activities from these national projects.

Crown rotThe national crown rot program, led by Dr Steven Simpfendorfer out of the New South Wales Department of Primary Industries, brings together crown rot researchers from across Australia to develop and extend integrated disease management strategies for this costly disease, which has grown to a $100-million issue in recent years.

The project is also focused on refining the PreDicta B® pre-sowing test for the disease to enable growers to make more informed rotation and management choices before embarking on their cropping programs.

The Crown Rot Initiative is concentrating on finding genetic solutions to the fungal disease, with pre-breeding research across Australia

Cover photo: Dr DamIen herDe, QueenslanD DaFF

ground cover suPPlement edited by Janet Paterson

identifying and sharing promising resistance genes for insertion into bread and durum wheat and barley.

Molecular research is unravelling how the crown rot pathogen operates to cause disease and investigating the potential for novel sources of crown rot resistance to generate durable sources of resistance against the disease (see page 3).

nematoDesA new national nematode research, development and extension program started in July 2013 and is being led by Dr Grant Hollaway out of the Victorian Department of Environment and Primary Industries.

The program spans the GRDC cropping regions and brings together nematode research specialists from across Australia.

A key focus of the new program is to determine the tolerance ratings of crop varieties to nematodes and in doing so quantify the economic impact of the soil pathogen on crop yields in each GRDC region.

Nematode resistance research will also continue under the national program to deliver crop rotation recommendations for winter and summer cropping systems across Australia.

rhIzoCtonIaWidespread adoption of minimum tillage has exacerbated the impact of rhizoctonia across southern Australia, as cultivation has traditionally been a major control option.

The soil-borne fungus is estimated to cost the cereal industry about $77 million in lost production each year.

New banding fungicides for rhizoctonia control being trialled in GRDC-funded research across southern Australia are proving very promising and could be available to growers as early as 2015 (see page 18).

preDICta B®

The national molecular diagnostic program being coordinated by Dr Alan McKay out of the South Australian Research and Development Institute is charged with further refining and development of the soil disease prediction service PreDicta B®.

PreDicta B® is used widely to assess the disease risk posed by soil-borne pathogens each season. New research is underway to make the test more accurate for crown rot and rhizoctonia and to promote the benefits of the testing service to the grains industry (see page 12). □

more information: Dr Francis C. Ogbonnaya, program

manager protection traits, GRDC, 02 6166 4500

Ground Cover is brought to you by growers and the Australian Government through the publisher, the Grains Research and Development Corporation (GRDC).

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3Crown rot

Know thy enemylong-term research by csiro scientist dr donald gardiner is unravelling how the crown rot pathogen operates at a molecular level to cause disease in cereals

By Janet Paterson

CSIRO SCIentISt DR Donald Gardiner has spent nearly a decade getting to know an infamous enemy of Australian cereal producers – the crown rot pathogen.

Having sequenced the entire 14,000 or so genes of the costly pathogen in 2012, Dr Gardiner is now trawling through the fungal chromosomes to unravel the nature of its disease-causing genes.

“We want to understand the function of the genes that cause crown rot so that we can better understand how the pathogen interacts with wheat and barley,” Dr Gardiner explains.

Dr Gardiner suspects there are hundreds of genes that act to cause crown rot. Isolating each gene is a tedious process – taking months of detailed laboratory work.

“In order to confirm that a particular gene plays a part in causing crown rot we actually have to knock out the suspect gene from the pathogen’s genome.”

the resultant crown rot mutants are then used to infect plants.

“If the gene does play a part then we would expect to see less disease

in plants exposed to a mutant form of the crown rot pathogen.”

So far, Dr Gardiner and his team have shown about 10 genes contribute to causing crown rot, but expect many more to be identified.

“We are starting to see a pattern emerge with these genes in that many appear to play a role in overcoming the immune system of cereals.”

Many of the genes encode for enzymes capable of degrading compounds produced as part of the immune response in wheat and barley.

“When a plant is invaded by the crown rot pathogen it produces antifungal compounds to attack the pathogen but, in a counterattack, the fungus produces enzymes to degrade these compounds and render it powerless.

“If we can work out how the pathogen is causing disease we will be in a better position to determine how plants can combat the fungus.”

the research is long term. “It will be a decade at least before we really understand the crown rot pathogen and how it causes disease,” Dr Gardiner says.

Dr Donald Gardiner and his team have isolated about 10 genes that play a role in crown rot expression, but the researchers suspect there could be hundreds of pathogen genes that work together to cause disease.

CSIRO research is trying to determine how the crown rot fungus recognises its cereal host environment. Researchers suspect the pathogen can detect specific plant metabolites, which in turn trigger the pathogen to become virulent. Pictured is crown rot pathogen growing on media varying in nutrient sources, many of which are key plant metabolites. The red pigment in the photo is aurofusarin, which is a secondary metabolite produced by the crown rot fungus to attack cereal plants.

Crown rot fungus (blue) infecting the water transport cells of wheat roots. The fungus restricts water movement to filling grain – especially in dry years.

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“the genetics of crown rot are multifaceted – there are tens if not hundreds of genes involved, which makes understanding the disease response and breeding for resistance very complex.

“But once we determine how the disease operates we will have the keys to switching off its impact in cereals.” □

grdc research code csP00154 more information: Dr Donald Gardiner,

CSIRO, 07 3214 2370,

donald.gardiner@csiro.au

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plants that have desirable traits developed using mutagenesis.

“the most widely grown Australian rice variety, Amaroo, has a semi-dwarf trait that was generated using mutagenesis,” Dr Fitzgerald says.

Recent international successes using mutagenesis include the development of novel sugarcane varieties with resistance to brown rust, wheat varieties with enhanced resistance to stripe, leaf and stem rust as well as powdery mildew, and a rice variety with enhanced resistance to rice blast.

Mutagenesis exposes crops to either chemical or physical forces, which results in genetic changes within the genomes of the crops.

“Physical mutagenesis results in large genetic deletions throughout the genome, completely removing a gene

or multiple genes,” Dr Fitzgerald says. “Chemical mutagenesis generates much smaller genetic changes within genes but is still capable of drastically altering or inactivating gene function.

“Mutagenesis produces huge numbers of gene variations that are not present within existing wheat varieties, which could lead to sudden and major breakthroughs in the quest for crown rot resistance,” Dr Fitzgerald says.

the researchers are screening two CSIRO-developed novel wheat populations for resistance to crown rot.

“the populations have been developed from two commercially available wheat varieties, YitpiA and CharaA, and are being used to identify novel variation in different traits, including crown rot,” Dr Fitzgerald explains.

By Janet Paterson

CSIRO ReSeARCHeRS ARe attempting to find new forms of disease resistance among novel wheat populations with the aim of generating durable crown rot resistance in wheat.

CSIRO scientist Dr tim Fitzgerald says mutagenesis, a conventional plant breeding method, offers potential novel sources of resistance against the costly pathogen.

mImICKIng natureDr Fitzgerald says genetic mutations occur in nature all the time. “All modern crops have evolved over thousands of years through genetic mutation and selection; we are mimicking this process in the lab,” he says.

there are many examples worldwide of registered crop and ornamental

4 Crown rot

novel wheats could deliver disease holy grailcsiro researchers are screening thousands of wheat plants developed using mutagenesis to detect novel forms of crown rot resistance

5Crown rot

Mutagenesis has been achieved in the YitpiA population chemically and physically in the CharaA population, using a process known as ‘heavy ion irradiation’.

ForwarD anD reverse genetICstwo approaches are being used to hone in on novel crown-rot-resistance genes. the first, called ‘forward genetics’, involves large-scale screening of thousands of mutagenised wheat lines from the YitpiA and CharaA populations for resistance to crown rot.

Disease scores from these new lines are then compared with commercially available YitpiA and CharaA lines and other wheat varieties with varying crown-rot-resistance ratings. Once new lines with improved resistance are identified, the task turns to understanding the genetics of the resistance.

“Understanding the genetics and back-crossing to remove unwanted genetic mutations from the resistant lines should help to incorporate the resistance into new wheat varieties,” Dr Fitzgerald says.

Over the past two years, the researchers have screened 1800 new wheat lines, which have delivered seven

CSIRO researcher Dr Tim Fitzgerald examines an ancient relative of wheat, Brachypodium, for crown rot resistance. The wild relative, which shares similar genetics to wheat but is easier to work with, is helping Dr Fitzgerald locate crown rot resistance genes in modern wheat.

Over the past two years, CSIRO researchers have screened 1800 mutant wheat lines, which have delivered seven lines displaying increased resistance to crown rot in the glasshouse. The lines will be tested in field trials.

lines displaying increased resistance to crown rot in the glasshouse. these lines will now be tested in field trials.

the second approach, known as ‘reverse genetics’, involves identifying genes that contribute to crown rot susceptibility in wheat and then using mutagenesis to inactivate these genes in the wheat genome.

“We have developed a special screening method that enables us to screen large numbers of plants relatively quickly to identify gene deletions of interest,” Dr Fitzgerald explains.

However, the genome of wheat is very complex (effectively containing three copies of every gene) and therefore deleting the genes of interest is no easy task.

“We must first find the gene of interest then ensure it is deleted three times within the genome, a process that can often result in other bits of the genome being deleted too and the plant being rendered infertile or unviable.”

to help overcome this issue, Dr Fitzgerald is scanning the genome of a crown-rot-infected ancient wheat relative called Brachypodium, which has a simpler genome – making it easier to work with.

“Once we identify a crown-rot-susceptible gene in Brachypodium we

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will then look for this gene in the wheat genome and inactivate it to see if this enhances crown rot resistance.”

new varIetIesDr Fitzgerald says it is difficult to estimate how long it might take for the research to deliver wheat varieties with enhanced resistance to crown rot.

“the fact that these new lines have been developed from elite Australian wheat cultivars should speed the development of new varieties once we find resistance genes of interest.

“In a best-case scenario, where strong crown rot resistance with simple inheritance is identified, a new elite variety incorporating this resistance might be developed within five years,” he says.

“For resistance resulting from specific gene deletions, genetic markers for the targeted genes would be immediately available to breeders to incorporate the resistance into new varieties as rapidly as possible.” □

grdc research code csP00155 more information: Dr Tim Fitzgerald,

CSIRO Queensland Bioscience Precinct,

07 3214 2377, timothy.fitzgerald@csiro.au

6 Crown rot

roadblocks overcome in resistance questQueensland department of Agriculture, Fisheries and Forestry pre-breeding research has so far delivered 71 breeding lines with improved crown rot resistance to wheat breeding programs across Australia

By Janet Paterson

CROWn ROt ReSIStAnCe has eluded cereal researchers and breeding companies for decades, but plant pathologist Dr Stephen neate is confident that years of painstaking investigation are starting to pay dividends against the costly disease.

“Crown rot is a complex disease genetically and environmentally, which has made it very difficult for us to hone in on the genes controlling its resistance.”

Many cereal genes are thought to interact with the disease, which itself contains many virulence genes to perfect its attack.

“It is this complex interaction of cereal, pathogen and environment that renders the disease so challenging,” Dr neate explains.

“Diseases such as rust are controlled by relatively few genes within cereals but crown rot resistance is controlled by many smaller genes scattered throughout the cereal genome and all interacting to respond to the disease.”

to make inroads into developing cereals with strong crown rot resistance these smaller genes must first be identified and incorporated into commercial breeding lines. “It is a bit like herding cats,” Dr neate says.

to make matters worse, even when resistance genes have been identified and captured in a breeding line the effect of the genes can sometimes disappear over subsequent generations of crosses.

“Sometimes we develop a breeding line that has good resistance but with time the crosses made with this line lose the crown

rot resistance because of the intricate interactions possible between and within the genetics of the wheat and the pathogen.

“It’s not as simple as finding a gene for crown rot resistance and then making a breeding line that permanently confers resistance in all wheat varieties bred from this breeding line,” Dr neate says. “We wish it was that simple but unfortunately it isn’t.”

Crown rot InItIatIve projeCtsCrown Rot Initiative Projects (CRIPs) involve several germplasm development components in a competitive-collaborative model. CRIPs are making progress towards providing Australian growers with world-class protection against crown rot of wheat and barley.

these projects maximise value within existing investments through stronger integration; for example, through linking epidemiology and genome knowledge from sequencing of the crown rot pathogen. CRIPs make targeted efforts at increasing the robustness of phenotyping. CRIPs also recognise the necessity for Managed environment Facilities (MeF) to minimise the effects of the environment on annual disease expression.

Consequently, germplasm is being developed that, when transferred to breeding companies, will result in the development of resistant and tolerant varieties.

this is facilitated by collaborative yield loss trials of material produced by CRIPs germplasm enhancement projects as well as independent off-station evaluation of near-to-release variety trials to ensure

that accurate management packages and yield performance with and without crown rot data are available to growers.

natIonal programDr neate and his colleague Dr Cassandra Percy at the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) are part of a national GRDC-funded wheat pre-breeding program focused on crown rot. It started in 2010 and includes the University of Southern Queensland, the University of Queensland, the University of Sydney and the South Australian Research and Development Institute.

the University of Sydney project is being run by Dr Phil Davies out of narrabri and has two components. the first is focused on developing wheats adapted to the northern GRDC cropping region using a novel breeding strategy called Marker Assisted Recurrent Selection (MARS).

MARS improves the efficiency of pyramiding resistance genes from multiple parental sources, a perennial issue with breeding for crown rot resistance. the project also has a strong focus on crown rot tolerance (the ability of wheat varieties to maintain yield despite infection).

the second component, based at the South Australian Research and Development Institute (SARDI), is being run by Dr Hugh Wallwork. It is focused on developing wheats adapted to southern and western Australia by stacking together resistance genes that already exist in elite wheat varieties.

Dr Wallwork has found that varieties such as KukriA, emu RockA and LongReach SpitfireA all have the same crown-rot-resistance gene on chromosome 4B that provides resistance at about the moderately susceptible (MS) level. the varieties Sunco and Sentinel 3RA have resistance genes on chromosome 2B, which could be combined with the 4B gene to generate a moderately resistant to moderately susceptible (MR-MS) level of crown rot resistance. the plan is to achieve even higher levels of resistance by adding other minor crown-rot-resistance genes from other sources.

“the fact that there are three universities and two state departments

working on crown rot resistance speaks volumes for the complex challenge that the pathogen has thrown at us,” Dr neate says.

the national program has a strong link to Australian plant breeding programs, many of which were part of the initial planning for the crown rot resistance research.

“the breeding companies nominated wheat cultivars that they wanted us to use as background breeding material for crown rot resistance,” Dr neate explains.

“In that way, when we deliver to them breeding lines containing crown rot resistance the lines already possess the agronomic traits suited to a particular GRDC region, so they are of immediate use as parents in wheat breeding programs.”

resIstanCe hurDlesDr Percy says getting a breeding line with crown rot resistance to a breeder-ready stage is no easy task, requiring tens of thousands of wheat crosses and years of detailed field and laboratory work.

the task is threefold. First, crosses between promising resistant material and commercial wheat cultivars must be made in an attempt to transfer the resistance genes into regionally adapted wheat varieties.

the progeny of these crosses must then be grown-out in the field and assessed for crown rot resistance.

Finally, the genomes of progeny assessed as being resistant must be scanned to identify specific molecular markers that will help breeders confirm the presence of the resistance genes as they advance elite lines into their breeding programs.

“each of these tasks has its own peculiar challenges,” Dr Percy says.

“For example, each year we make up to 200 individual crosses, which might not sound like many but in order to achieve this number we must pollinate thousands of individual florets.”

Four staff work full time for several months to achieve the 200 or so annual crosses – going into the field daily to

collect pollen from the anthers of specific wheat lines and transferring this to individual and specific wheat florets that have to be dissected carefully to expose the stigma upon which the pollen is placed.

the pollinated wheat heads are then bagged so that the crosses remain pure.

Seed (progeny) from the crosses (which are not always successful) is then grown-out in specialised growth rooms and assessed for crown rot resistance at the seedling stage. the growth rooms allow several generations to be grown within a year, which significantly speeds the discovery of resistant breeding material.

“those seedlings showing good crown rot resistance at the seedling stage are then grown-out under field conditions to assess their resistance under commercial wheat production conditions.”

Another challenge emerges at this stage due to the strong impact of environmental conditions on crown rot expression.

“Crown rot is strongly influenced by the season, so in assessing breeding material for crown rot resistance we need to be sure that what we are rating is the genetic response to the pathogen not just the environmental response,” Dr Percy says.

It can take several years of screening data before the researchers are confident that what they are looking at in the field is indeed crown rot resistance and not just low infection rates due to seasonal conditions.

Dr neate and colleagues have developed specialised screening tests for crown rot that help tease out the environmental and genetic responses to the disease.

“the screening procedures help improve the accuracy of selecting a breeding line that really does contain genetic resistance to crown rot,” he says

each year, Dr neate’s team collects 100,000 individual plant samples for crown rot assessment from field trials at their field site in Wellcamp, Queensland.

“It is the result of these many thousands of assessments that drive the crown-rot-resistance work,” Dr neate says.

“Plants identified as resistant to crown rot are then further assessed to determine if they carry molecular markers known to be associated with crown rot resistance.”

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Dr Cassandra Percy examines crown-rot-infected wheat as part of the Queensland Department of Agriculture, Fisheries and

Forestry’s wheat pre-breeding program. It is hoped new wheat varieties with improved

crown rot resistance will be available to growers within the next few years.

7Crown rot

8 Crown rot

Crown rot pre-breedinG proGramsBy dr Phil davies

COLLABORAtIve YIeLD LOSS testing of breeding lines produced through the GRDC-funded crown rot pre-breeding programs has been undertaken since 2012, designed to assess the yield potential of material under crown rot conditions and to assess the level of tolerance these lines have to crown rot.

these trials are sown at the University of Sydney’s Plant Breeding Institute in narrabri, new South Wales, and trial plots are artificially inoculated with crown rot to generate the disease. Inoculated plots are compared with neighbouring plots free of the disease to assess the degree of yield loss associated with crown rot in individual lines. the purpose is to identify material with either high yield potential under crown rot conditions or with low levels of yield loss to crown rot. Other agronomic traits including maturity and rust resistance are also assessed.

the molecular marker work, which is done in collaboration with the University of Southern Queensland, is not without its issues either.

“Molecular markers mark the start and end of a region on a chromosome that is suspected of containing a gene or genes of interest,” Dr neate explains.

“For crown rot these regions can be relatively large and it is an ongoing research goal to narrow down the areas known to contain the resistance genes.

“As the resistance areas are relatively large some of the chromosomal area can be damaged or left behind during the crossing procedure.

“this can mean that occasionally even though a plant shows up as containing a marker it might not have the resistance gene and, equally, although a plant contains the resistance gene the marker may not have come across with the cross, but it is still a very useful technique.”

resIstant wheatsDespite all these challenges Dr neate is hopeful that wheat varieties with improved crown rot resistance will be available to growers within the next few years.

“We are starting to see measurable improvements in crown rot resistance in national variety trials material, as the breeding companies are making progress,” Dr neate says.

Over the past five years, the Queensland DAFF wheat pre-breeding program has

Pictured is the fungus that causes crown rot, Fusarium species, growing on nutrient media. Researchers at the Queensland Department of Agriculture, Fisheries and Forestry grow and purify the Fusarium to infect wheat breeding lines. Plants that survive the infection are investigated further to determine if they carry crown-rot-resistance genes.

delivered 72 breeding lines with good crown rot resistance to Australian wheat breeding and pre-breeding programs.

the University of Sydney program has delivered 69 breeding lines with improved crown rot resistance and yield potential exceeding current commercial crown rot standards.

the SARDI program, which commenced in 2010, started delivering potentially resistant lines to breeding programs in 2013 and a second batch of 19 lines with confirmed resistance was sent to breeders in April 2014.

“the breeders are keen to receive the lines we produce each year along with any molecular markers to screen their breeding populations,” Dr neate says.

the quest for crown rot resistance is ongoing and the procedures used to identify resistance genes and insert (and keep) these in commercially acceptable wheat breeding lines are continually being refined.

“We are working closely with the plant breeding companies to ensure we deliver what they need to develop varieties with strong and durable crown rot resistance.” □

grdc research code dAQ00167, us00054 more information: Dr Cassandra Percy,

Queensland DAFF, 07 4639 8862,

cassandra.percy@daff.qld.gov.au; Dr Phil

Davies, University of Sydney, 0403 613 974,

philip.davies@sydney.edu.au;

Dr Hugh Wallwork, SARDI, 08 8303 9382,

hugh.wallwork@sa.gov.au

9Crown rot

Rainout shelters over crown rot yield loss trials in 2013. Shelters are used to induce post anthesis drought to increase crown rot severity.

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photo: Dr phIl DavIes

FIGURE 1 Lines performing better than SuntopA under disease-free conditions

Mean kg/ha (nil) Mean kg/ha (plus)

Kilograms per hectare3500

3000

2500

2000

1500

1000

500

0

1364

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PBIC

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PBIC

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-32

PBIC

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-37

PBIC

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More recently, these trials were assessed for grain quality to fully assess the usefulness of these lines as parental material in commercial breeding programs.

the trials include material contributed by CSIRO, the Queensland Department of Agriculture, Fisheries and Forestry, the nSW Department of Primary Industries, the South Australian Research and Development Institute, the University of Queensland, the University of Southern Queensland and the University of Sydney, and has allowed the direct comparison of material from the participating organisations.

Rather than being competitive in nature, these trials aim to foster collaboration and have led to the exchange of material between pre-breeding organisations. these trials also act as a conduit for material to enter commercial breeding programs, with data forwarded to the breeding companies to complement internal testing by the pre-breeding organisations.

Given that a plant’s reaction to crown rot is strongly environmentally influenced, with particular regard to post-anthesis moisture stress, several strategies have been implemented to ensure useful and reliable data can be collected each year. A subset of material sent for yield loss evaluation each year is also tested in a managed

field environment, where large rain-exclusion shelters are placed over the trial to ensure post-anthesis drought, thereby guaranteeing full expression of the disease.

A small subset of material is also tested independently at multiple locations across the northern grain region by Crown Analytical Services, an independent organisation that also assesses the crown rot yield-loss response of pre-release lines from commercial breeding programs. the co-location of pre-breeding trials and elite commercial trials ensures the relevance of the data to the breeding companies and the grains industry at large.

the aim of pre-breeding for crown rot

is to incorporate resistance and tolerance traits found in largely unadapted sources together with yield and agronomic traits found in elite germplasm, to allow the exploitation of these sources by commercial breeding programs. Data from the 2013 yield loss trials identified a number of lines with superior yield under crown rot conditions compared with current industry standards, without compromising the yield potential under disease-free conditions (Figure 1).

While a silver-bullet solution to crown rot is unlikely, these trials demonstrate that incremental gains in resistance and tolerance to crown rot are being made. □

10 Crown rot

Crown rot resistanCe in Cereal breedinG pipelinegrdc research across Australia is focused on identifying new sources of crown rot resistance for barley and durum

By Janet Paterson

CSIRO ReSeARCH HAS identified three areas of the barley genome that confer strong resistance to crown rot.

the discovery follows large-scale screening of thousands of wild and commercial barleys from across the world.

the new sources of crown rot resistance were located in barleys from Japan and Iran.

Plant geneticist Dr Chunji Liu says the goal now is to develop diagnostic markers for the genome areas conferring crown rot resistance so that they can be introduced into commercial barley varieties.

“the ultimate goal would be to stack each of the resistance areas together and insert this genetic stack into barley varieties suited to each of the GRDC regions,” Dr Liu says.

“However, we still need to determine if this stacking is feasible.”

Dr Liu’s glasshouse research has shown that stacking the three genetic regions together can reduce crown rot expression in barley by up to 60 per cent.

He will now determine if the genetic stacking is successful under field conditions.

“these are critical genetic areas on the barley genome and if we can add them together and deliver them into barley breeding lines we will be able to reduce the impact of crown rot in barley significantly.”

Barley is more tolerant of crown rot than wheat and accumulates more crown rot pathogen than wheat at all stages of infection.

It is hoped that developing resistant barley varieties will not only help

manage the disease in barley but might also lessen the disease’s effect on subsequent wheat crops through a reduction in seasonal inoculum load.

resIstanCe sIDe eFFeCtsDr Liu has discovered that one of the genome areas conferring crown rot resistance is closely aligned with the genes that control plant height.

“We need to have a closer look at how the crown rot genetics interact with important agronomic traits such as plant height to ensure that in our quest for disease resistance we don’t interfere with the crop’s agronomy,” Dr Liu says.

to do this, Dr Liu and colleagues have developed barley populations that are genetically identical except for crown rot resistance.

“We can use these populations to determine how crown rot resistance is connected with traits such as flowering time, plant height and other important agronomic characteristics,” he says.

Given the close connection between crown rot resistance and plant height, Dr Liu says it is important that any markers developed to track crown rot resistance are accurate and reliable.

“We need to fully understand how crown rot resistance and other important traits interact in the barley genome so that we can be sure of passing on the best markers for crown rot resistance to plant breeders.” □

grdc research codes usQ00012, usQ00013, csP00149 more information: Dr Chunji Liu, CSIRO Plant

Industry, 07 3214 2223, chunji.liu@csiro.au

Durum breeder Dr Jason Able

makes a durum cross between an

elite breeding line and a potential

source of reduced

crown rot susceptibility.

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durum crown rot resistAnceDurum wheats are very susceptible to crown rot and screening activities to date have failed to identify even moderately susceptible lines.

A new five-year GRDC research program, which will run until 2018, involves researchers in Queensland, New South Wales and South Australia. The program has been established to transfer crown-rot-resistance genes from bread wheat and other tetraploid wheat sources into durum varieties.

Project leader and University of Southern Queensland researcher Dr Anke Martin says the new project will further advance durum/bread wheat crosses made more than a decade ago by durum breeder Dr Ray Hare, as well as sourcing new crown rot resistance via the national GRDC-funded Crown Rot Initiative.

Bread wheat crosses to three elite durum breeding lines including EGA BellaroiA have been advanced to the point where stable resistance has been identified over several generations in multiple families within these crosses. Crossing durum with bread wheats presents technical challenges because of the different genomics of the two species.

“Bread wheat has three genomes while durum has only two of these, so making successful crosses and then back-crossing to ensure the progeny are pure durum wheats takes time,” Dr Martin explains.

The new project will further advance these successful durum/bread wheat crosses and develop markers to track the crown rot resistance between subsequent generations of the breeding material.

The markers and advanced breeding material will be delivered to durum breeders in NSW and SA.

“We will also source the best crown-rot-resistance genes coming out of the national Crown Rot Initiative and cross these into elite durum varieties to gather multiple resistance genes into breeding lines.”

Dr Martin says new durum lines with improved crown rot resistance will be available to durum breeders within the next few years.

grdc research codes, usQ00013 more information: Dr Anke Martin,

University of Southern Queensland,

07 4631 2261, anke.martin@usq.edu.au

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11Crown rot

Cultivation Can exaCerbate Crown rot stubble management practices such as cultivation can lead to increased infection and expression of crown rot

By dr steven simpfendorfer

WHILe PAtHOGen LOAD is important in crown rot expression, soil moisture level and temperature during grain-fill are the driving forces behind the extent of yield loss caused by the disease.

northern region research shows even a low starting inoculum level can cause up to 25 per cent yield loss if the crop becomes severely stressed during grain-fill (Figure 1A). In years of high crown rot load, the seasonal finish plays the major role in crown rot expression: a soft finish (no moisture stress) resulting in very little disease damage while a hot dry finish can halve crop yields (Figure 1B).

CultIvatIonWhile cultivation can reduce inoculum loads by speeding up stubble decomposition, in years of low rainfall (and reduced stubble degradation) cultivation can increase the crown rot infection rate of subsequent winter cereals.

Cultivation (even shallow) distributes infected residue more evenly across paddocks and into the below-ground infection zones for crown rot.

Crown rot infection occurs when physical contact is made between infected residue and the underground ‘crown’ of cereal plants.

Cultivating crown-rot-infected cereal stubble effectively breaks the inoculum into smaller pieces and spreads it more evenly through the paddock – increasing the chance of it coming into contact with emerging cereal plants.

Cultivation also results in a loss of soil moisture, which may also increase the expression of crown rot in a dry year.

Stubble burning does not remove inoculum from below ground and, depending on the timing of the burn, significant levels of soil moisture storage can be lost through the lack of stubble cover during the fallow period. this can have a significant effect on the expression of crown rot later in the season.

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Fcrown rotCrown rot has three distinct and separate phases: survival, infection and expression.

survIval The crown rot fungus survives as a cottony growth (called mycelium) inside winter cereal stubble and grass weed residues, which have been infected in previous seasons. The crown rot fungus can survive inside plant residues for as long as the residues remain intact – sometimes for years if soil and weather conditions slow its decomposition.

InFeCtIon Soil moisture stimulates the growth of mycelium from infected stubble and weed residues to infect newly emerged winter cereals either via underground plant parts such as the coleoptile, sub-crown internode or crown tissue, or above-ground leaf sheathes at the soil surface. Direct contact between infected stubble and crop plants is required for infection. Wet seasons coupled with high stubble inoculum loads can lead to significant build-up of paddock inoculum levels.

expressIon Moisture and temperature stress throughout flowering and grain-fill trigger the crown rot fungus to proliferate in the base of infected tillers, restricting water movement from the roots through the stems and producing characteristic whiteheads that contain either no grain or lightweight, shrivelled grain.

SOURCE: NSW DPI

FIGURE 1 Impact of crown rot inoculum load (A) and moisture stress during grain-fill (B) on yield loss to crown rot in 2007.

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Increasing moisture/heat stressduring grain-fill in 2007

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Inter-row sowIngIn a no-till system, the crown rot fungus becomes confined to the previous cereal rows and is more reliant on infection through the outer leaf sheathes at the soil surface.

this is why inter-row sowing (using GPS guidance) in no-till systems has been shown to halve the number of plants infected with crown rot, resulting in a five to 10 per cent yield increase.

Cultivation or harrowing negates the benefits of inter-row sowing as a crown rot management strategy. □

grdc research code dAn00175 more information: Dr Steven Simpfendorfer,

NSW DPI, 02 6763 1261, steven.

simpfendorfer@industry.nsw.gov.au

Typical crown rot symptoms in wheat showing honey-brown discoloration on the lower leaf sheaths and internodes of bread wheat tillers at flowering. Pictured are glasshouse-grown wheat plants inoculated with the fungus at the seedling stage as part of crown rot research being carried out by the Queensland Department of Agriculture, Forestry and Fisheries.

Disease diagnosis12

disease diagnosis predicts potential yield lossoriginally developed in 1997, Predicta B® is a dnA-based soil-testing service that quantifies the levels of a broad range of fungal pathogens and nematodes that affect broadacre cereals and some rotation crops

By Janet Paterson

tHe IMPACt OF maternal caffeine, nicotine and other drugs on the development of baby sleep patterns may seem a world away from crop disease management, but agricultural scientist and recent ex-grower Shawn Rowe says he is looking forward to combining his diverse research and farming skills to extend the benefits of the PreDicta B® disease-identification service.

Coming from a mixed-cropping and cross-bred lamb property on the border of victoria and South Australia, Mr Rowe completed an agricultural science degree majoring in animal science at the University of Adelaide. He side-stepped into medical research to investigate the impact of drugs on neurotransmitters in newborns and then returned to manage the family farm.

“After 12 years of farming I am back in the city at the South Australian Research and Development Institute (SARDI) to tackle a new GRDC-funded project with the aim of extending the value of the PreDicta B® service to growers across Australia,” Mr Rowe says.

Mr Rowe says PreDicta B® was developed because most decisions to reduce the disease impact of soil-borne pathogens have to be made before crops are sown.

“Identifying the main disease risks before sowing means growers can implement management practices such as fungicide seed dressings, crop rotations and modifying sowing techniques and timing to lower their risk of crop yield loss.”

PreDicta B® can test for most of the soil-borne pathogens (including fungal and nematode) that growers need to be aware of including take-all, rhizoctonia, crown rot, blackspot of peas, cereal cyst nematode, stem nematode and root lesion nematode (Pratylenchus species).

“each test result comes with a risk category, based on trial work, that indicates the likely impact of the pathogen load on potential crop yield,” Mr Rowe says.

Regional risk categories have been

implemented for Pratylenchus and work is underway to develop regional risk categories for other pathogens.

Further tests under development include Bipolaris (common root rot), Pythium root rot and additional Pratylenchus species. “At the moment these diseases are only reported as levels as we are still establishing their risk ratings for potential yield losses.”

the SARDI researchers are also developing tests for stubble-borne pathogens, including those associated with yellow leaf spot, eyespot and white grain.

extenDIng BeneFItsthe overall aim of the new PreDicta B® project is to increase the value of the service to growers.

“PreDicta B® adoption among the research community has grown exponentially over the years, with 35,000 tests done on behalf of research projects in 2013.

“Grower adoption of the service is lower, at 600 tests per year, and we’d like to understand why this is, as well as embarking on a concerted communication effort about the benefits of the testing service.”

Mr Rowe says southern-region durum growers in particular are using the testing service to select disease-free paddocks for durum crops.

“Durum is very intolerant to crown rot so testing paddocks to determine crown rot loads pre-season means growers avoid the inevitable yield and profit losses that come from planting durum in high-risk paddocks.”

PreDicta B® was launched in the northern region in late 2013, in collaboration with Crown Analytical Service, where it is being used to determine Pratylenchus nematode numbers in cropping paddocks, a major issue in the region.

Mr Rowe says an increased risk in 2014 from take-all is driving demand for PreDicta B® in the southern and western regions.

the SARDI PreDicta B® team carried out widespread soil sampling throughout

the southern Mallee region in March and April 2014 and detected a significant increase in the levels of take-all, rhizoctonia and crown rot, and high levels of Pratylenchus neglectus in some areas.

“take-all risk across southern Australia is the highest we have seen for at least a decade, most likely due to the string of relatively good seasons across much of the region since 2010.”

ImprovementsPreliminary results from the new South Wales Department of Primary Industries show the addition of stubble to the PreDicta B® soil sample significantly improves the detection of crown rot.

“the stubble research was done because PreDicta B® failed to detect significant risk from crown rot in 22 per cent of northern region research samples in 2013,” Mr Rowe says.

“We think this was probably due to the rapid breakdown of crown rot inoculum in the soil, but not in standing stubble, over the wet summer.”

Mr Rowe says adding stubble to the PreDicta B® soil sample will also enable the development of tests for stubble-borne pathogens including those associated with yellow leaf spot, eyespot and white grain.

Research is also underway to check that all Fusarium species known to cause crown rot are being detected by the current PreDicta B® assay tests.

“So far we have sequenced and tested several hundred isolates from around Australia and found that all Fusarium pseudograminearum and F. culmorum isolates have been detected by the PreDicta B® assays.”

the survey has uncovered several other Fusarium species, isolated from crown-rot-affected plants, which may cause crown rot, and these will be investigated further over the next few years.

Rhizoctonia is also proving difficult to detect using PreDicta B® assays in some regions of Western Australia, and this is being investigated in collaboration with the

13Disease diagnosis

Department of Agriculture and Food, WA.“We want to investigate whether the

poor detection of rhizoctonia in these paddocks is due to a sampling issue or due to inoculum loads dropping to very low levels over summer despite being high during the growing season,” Mr Rowe says. “It may be that we will have to test these paddocks during spring of the preceding crop.”

pathogen DIstrIButIon mapsAccording to Mr Rowe, communication is the key to improving grower uptake of PreDicta B®.

“We know that some growers don’t know about PreDicta B® and we know others have heard of it but have not taken the next step of adopting it,” Mr Rowe says.

“It’s time to set up the extension phase and we have a series of activities planned to achieve this.”

Maps showing PreDicta B® results for each pathogen are currently being loaded onto the SARDI website (www.sardi.sa.gov.au).

“the maps summarise the test results from grower samples across Australia and provide growers with an indication of soil pathogen loads in their area.”

the maps can be viewed by all growers regardless of whether they are subscribers of the PreDicta B® service and will be

Agricultural scientist and recent ex-grower Shawn Rowe (pictured with trusty canine friend Charlie) has been appointed to the South Australian Research and Development Institute to extend the benefits of the PreDicta B® crop disease identification service to growers across Australia.

chAnge to PredictA B® soil-sAmPling ProtocolsGrain growers can access PreDicta B® via agronomists accredited by the South Australian Research and Development Institute (SARDI), who can interpret the results and provide advice on management options to reduce the risk of yield loss.

PreDicta B® samples are processed weekly from February to the end of May (before sowing) to assist with planning the cropping program.

In 2013, some PreDicta B® samples did not adequately detect crown rot risks in some southern region samples. It is suspected that this was due to samplers avoiding stubble, which is the recommendation for soil nutrition testing.

In light of this, interim recommendations for collecting PreDicta B® soil samples in the southern and western GRDC regions have been developed: ¢ collect three cores (1cm in diameter by 10cm deep) from each of 15 different locations

within the target paddock or sampling zone;¢ take cores from along the rows of previous cereal crop if visible

and retain any stubble collected by the core;¢ add one piece of cereal stubble (if present) to the sample

bag at each of the 15 sampling locations – each piece should include the segment from the crown to the first node (discard material from above the first node); and

¢ note that the maximum sample weight should not exceed 500 grams.

regularly updated. Growers can look at the maps and see the frequency and levels of detection for each pathogen.

Mr Rowe is also keen to establish a list of PreDicta B®-trained agronomists on the SARDI website so that growers can access an agronomist in their area familiar with the soil-sampling procedure and risk ratings delivered via the

PreDicta B® service. Field day and grower updates will also be used to extend the advantages of using the PreDicta B® service. □

grdc research codes dAs00137, dAs00123 more information: Shawn Rowe, SARDI,

08 8303 9392, shawn.rowe@sa.gov.au

photo: sarDI

Post preDicta B® samples to:

C/- sarDI rDtslocked Bag 100

glen osmond sa 5064

14 nematodes

rotate to reduce nematode riskwell-managed rotations will minimise the damage caused by root lesion nematodes in cereal production systems

By dr Kirsty owen

nORtHeRn ReGIOn neMAtODe research has identified the impact of a range of summer crops on the nematode populations in subsequent winter wheat crops.

the research suggests that susceptible wheat crops require more than one resistant crop rotation in the sequence to sufficiently lower nematode levels.

Queensland Department of Agriculture, Fisheries and Forestry researchers monitored the nematode populations within mungbean, soybean, sorghum, sunflower and maize plots compared with a bare fallow.

the crops and fallows were established on sites that differed in initial populations of Pratylenchus thornei due to their

cropping histories but had similar soil chemical and physical properties.

the low P. thornei site had 0.05 nematodes per gram of soil in the top 0 to 90 centimetres and the moderate P. thornei

site had almost 48 times this amount at 2.4/g soil. there were no differences in the yield of the summer crops between the two trials, indicating that the summer crops tested were all tolerant of P. thornei.

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FIGURE 1 Impact of northern GRDC region summer crops (compared to a fallow treatment) on the population density of the root lesion nematode Pratylenchus thornei. Pratylenchus thornei

Note: Varieties of sunflowers, maize, sorghum, mungbean cv. EmeraldA and soybean cv. Soya791 did not differ significantly from the fallow treatment (P<0.05). P

P. thornei per gram of soil (0-15 cm)P. thornei

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Pratylenchus thornei

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Dr Kirsty Owen, from Queensland DAFF, in the glasshouse preparing a pot trial to determine the nematode resistance ratings of a range of northern region crops.

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15nematodes

At the moderate P. thornei site one month after harvest of sunflowers, maize and sorghum, populations of P. thornei were similar to the fallow treatment and there were no differences between crop varieties (Figure 1).

Following soybeans and mungbeans, populations of P. thornei increased compared with the fallow treatment and there were differences between varieties.

the soybean cultivar Soya791 proved moderately resistant to P. thornei, but all other soybean varieties were very susceptible and resulted in increased populations of P. thornei to 12 to 20.6/g soil at 0 to 15cm (Figure 1).

the mungbean cultivar emeraldA was also moderately resistant, with nematode levels not significantly different from the fallow treatment. However, all other

the research suggests that susceptible wheat crops require more than one resistant crop rotation in sequence to sufficiently lower nematode levels.

economic imPAct oF nemAtodesA new, nationally coordinated nematode research program that commenced in July 2013 will quantify the yield and economic impacts of root lesion nematodes in crop production systems across GRDC growing regions.

The project will also further refine management options for these costly soil pathogens and improve relationships between PreDicta B® test results and likely on-farm yield loss to better guide on-farm management of nematodes.

Coordinated by Dr Grant Hollaway, from the Victorian Department of Environment and Primary Industries, the program brings together Australia’s leading field crop nematology scientists from across each of the GRDC growing regions.

To quantify the impact of nematodes across all regions, trial sites are being established with high and low nematode numbers so that the nematode tolerance ratings of a range of crops can be evaluated.

For tolerant cultivars, there will be little difference in yield between the ‘high’ and ‘low’ nematode populations. Subsequent analysis will determine the yield risk of varying nematode levels for a range of crop varieties.

The western region research will focus on the resistance and tolerance of wheat, barley, lupin and canola varieties to the root lesion nematode species Pratylenchus neglectus, P. teres and P. penetrans.

The southern region research will quantify the yield tolerance and resistance ratings of wheat, barley, field pea, lentil, chickpea and canola varieties to P. thornei and P. neglectus.

The northern region research will assess the tolerance and resistance of wheat, barley, canola, mungbean, sorghum, maize, chickpea and faba bean varieties to P. thornei and P. neglectus.

mAnAging nemAtodesWith no in-crop options available to curb nematode damage, managing this costly pest relies on:¢ choosing varieties with some resistance to root lesion

nematodes and rotating susceptible crops with a resistant break crop or pasture to minimise nematode reproduction; and

¢ using wheat or barley varieties with tolerance to the root lesion nematode species in a paddock – keeping in mind that some tolerant varieties may further increase nematode numbers.

Choosing the most profitable crop for a paddock will depend on the type and population size of the nematode species and the nematode tolerance/resistance rating of the crop.

Making use of available testing services such as PreDicta B® and AGWEST Plant Laboratories to determine nematode species and levels can help choose the best management strategy for specific paddocks.

Root lesion nematodes inside a wheat root.

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mungbean varieties proved susceptible, with two to four times the P. thornei populations of the fallow treatment (Figure 1).

At the low P. thornei site, there were no differences between crop varieties and although populations increased slightly they remained less than 0.25/g soil at 0 to 15cm.

wheat yIelDsDuring 2013, the P. thornei-tolerant wheat variety eGA WylieA and the intolerant variety StrzeleckiA were planted into the summer crop plots.

Grain yield of StrzeleckiA (1900 kilograms per hectare) was 49 per cent lower than eGA WylieA (3700kg/ha) at the moderate P. thornei site.

In contrast, at the low P. thornei site, there was only a four per cent difference in

yield between StrzeleckiA (3600kg/ha) and eGA WylieA (3700kg/ha).

there was a strong negative relationship between populations of P. thornei after the summer crops and yield of the following intolerant wheat variety StrzeleckiA. the results indicate that a single resistant crop before wheat was not enough to sufficiently reduce populations of P. thornei (Figure 2).

In contrast, there was no relationship between populations of P. thornei and yield of the tolerant wheat eGA WylieA, an expected result because of the good level of tolerance of eGA WylieA to P. thornei (Figure 2). □

grdc research code dAv00128 more information: Dr Grant Hollaway,

Victorian DEPI, 03 5362 2111,

grant.hollaway@depi.vic.gov.au

16 nematodes

nematode-resistant wheat in pipelinedecades of pre-breeding research could lead to the release of wheat breeding lines with resistance to root lesion nematode species by early 2015

By Janet Paterson

WHeAt BReeDInG LIneS with resistance to both Pratylenchus thornei and P. neglectus nematode species will be available to wheat breeding companies across Australia from early 2015.

Development of the valuable breeding germplasm is the culmination of decades of pre-breeding research by the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) in collaboration with the Australian Wheat and Barley Molecular Marker Program (AWBMMP) based in Adelaide. Project leader Dr John thompson says the breeding lines could enable commercial wheat varieties with strong resistance to both species of root lesion nematodes to be available to growers within the next few years.

“We have worked closely with breeding companies for the past five years and they are all eagerly awaiting the dual-resistance breeding material so it should only be a matter of a few years before

growers have access to wheat varieties with resistance to both root lesion nematode species,” Dr thompson says.

“We consulted with the plant breeding companies at the start of the project and again about half way through to ensure we inserted the resistant genetics into wheat lines already adapted agronomically to the northern and other GRDC growing regions.”

Dr thompson says the impending handover of the first lot of dual-resistant germplasm represents an exciting stage in the pre-breeding research, which has run in parallel with another pre-breeding program to combine genetic tolerance and resistance to root lesion nematodes in wheat.

“Growers now have a fairly good selection of tolerant wheat varieties that yield well under high nematode pressure,” says Dr thompson. “But the Holy Grail in nematode management has always been resistant wheat varieties that both yield well and thwart nematode build-up in cropping paddocks and this is what we are starting to deliver into breeding programs.”

orIgInal resIstanCeIronically, the first source of nematode resistance came from the highly susceptible wheat variety Gatcher in the mid 1980s.

“It was easy to pick the resistant Gatcher mutants in the field,” Dr thompson explains. “they stood tall and green above the many more susceptible plants, which were stunted and yellow from the nematode pressure of the paddock.”

Dr thompson and colleagues selected the resistant plants and developed a fixed line known as GS50A, which conferred strong resistance to P. thornei but not to P. neglectus.

“this line was backcrossed into the commercial wheat varieties of the time and also shared with the international breeding program at the International Maize and Wheat Improvement Center (CIMMYt) in Mexico.”

Unfortunately, despite conferring strong resistance to P. thornei and yielding more than the available tolerant varieties, the new crosses did not immediately make it into commercial varieties due to the widespread breakdown of a rust-resistant gene contained within the nematode-resistant crosses.

“Breeders of the time chose to release other wheat varieties instead, which held up well against rust but not nematodes so the GS50A genetics have, until recently, been placed on the back burner.”

new BreeDIng phaseRenewed pre-breeding efforts for nematode resistance began at Queensland DAFF in 2011 with a GRDC-funded project to pursue novel sources of genetic resistance to value add to that already found in GS50A.

Queensland DAFF nematologist Jason Sheedy says the aim of the new project was to set up a pre-breeding pipeline to enable nematode-resistant material to be continually fed through to breeders in adapted wheat lines.

“By using adapted wheat lines as our background material we can ensure that the nematode-resistant lines are breeder ready as soon as they come out the other end.”SOURCE: QUEENSLAND DAFF

FIGURE 1 Impact of nematode resistance genetics on wheat yield and nematode numbers at 0 to 90 centimetres compared with commercially available tolerant wheat varieties.

Wheat yieldNematode resistance genetics

Commercially available tolerant wheat varieties

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17nemetodes

So far the project has delivered five breeding lines based on GS50A to Australian plant breeders. the lines all yield higher than current tolerant nematode wheat varieties and carry strong resistance to P. thornei (Figure 1).

to gather new resistance genes, the Queensland DAFF researchers screened hundreds of ancient wheat landraces from the Middle east and north Africa to determine if they carried resistance to either of the main root lesion nematode species.

“these ancient wheat landraces have evolved side-by-side with nematodes and have been selected for production traits for thousands of years so it made sense that some of them might have developed genetic resistance to the root pathogens,” Mr Sheedy says.

the landraces were screened in glasshouse experiments, with the extent of their resistance determined by measuring the number of P. thornei remaining in the soil after the plants had been grown for 16 weeks.

“the glasshouse screening procedure is highly predictive of field resistance and allows us to quickly and efficiently screen large collections and identify elite germplasm.”

the research team has identified several lines from Morocco, Iraq and Iran that consistently produce fewer nematodes than GS50A and the researchers are now in the process of incorporating these genetics into adapted wheat breeding lines.

the good news is that the resistant genes are also highly heritable and confer additive resistance when collected together in breeding lines.

“this means that if we make crosses from parents with strong resistance then progeny from these crosses will possess even stronger nematode resistance,” Mr Sheedy says.

Research trials show that wheat lines with several of the known nematode resistance genes can reduce nematode populations by as much as 98 per cent compared with susceptible wheat lines.

Dual resIstanCeWItH A tHIRD of paddocks in the northern region infected with both P. thornei and P. neglectus, Mr Sheedy says it is imperative wheat varieties with resistance to both nematode species are developed.

“If we develop only wheats with P. thornei resistance then crops and wheat varieties susceptible to P. neglectus will

encourage build-up of this nematode species in cropping paddocks.”

In an attempt to find dual nematode resistance, Dr thompson and Mr Sheedy turned their attention to the original parents of modern bread wheats – an ancient wild grass, known as goat grass, and durum wheat.

“Modern bread wheat is the result of a durum and wild grass cross,” Dr thompson says.

“When wheat breeders cross goat grass with modern durum varieties we create what are known as synthetic wheats, which are fully compatible with modern bread wheats and can be used in breeding programs to transfer ancient genetics into modern wheat varieties.”

Dr thompson and colleagues have screened hundreds of synthetic wheats and identified five promising lines that have resistance to both P. thornei and P. neglectus.

“Molecular genetics research by Dr Diane Mather and Dr Kelvin Khoo in the AWBMMP show that the resistant genetics are located on two separate sections of the wheat genome.”

the AWBMMP has developed user-friendly molecular markers for the resistance genetics so that breeders can

easily screen their lines to determine if they carry the valuable nematode resistance.

the resistant synthetic wheats have now been crossed with modern Australian wheat varieties and the first fixed lines from these crosses will be available for plant breeders by early 2015.

Importantly, the five synthetic wheats also carry valuable sources of resistance to the fungal diseases yellow spot and Septoria tritici blotch and two carry a resistance gene to cereal cyst nematode.

Dr thompson says if resistance to all these diseases can be transferred to produce multiple-disease-resistant wheat varieties the financial benefit to the wheat industry would be immense.

“It’s a very exciting time for the project,” Dr thompson says.

“Once growers have access to nematode-resistant wheat varieties it will remove a significant crop production constraint that currently costs Australian growers more than $123 million each year.” □

grdc research code dAQ00171 more information: Dr John Thompson,

Centre for Crop Health, University of

Southern Queensland, 07 4639 8806,

john.thompson@usq.edu.au

Dr John Thompson (left) and Jason Sheedy examine wheat plants for resistance to root lesion nematodes.

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18 rhizoctonia

By Alan mcKay and daniel hüberli

GRDC-FUnDeD ReSeARCH In Western Australia and South Australia has shown that liquid banding of a new fungicide increased wheat and barley yields by up to 0.87 tonnes per hectare in a paddock with very high levels of rhizoctonia in the soil before sowing.

the most consistent yield responses resulted when the fungicide was banded simultaneously above the seed on the soil surface behind the press wheel and at the base of the furrow about 3.5 centimetres below the seed.

the Australian Pesticides and veterinary Medicines Authority is reviewing submissions by Syngenta and Bayer to enable banding of selected fungicides to improve control of

rhizoctonia. If approved, registration should be granted by 2015.

Syngenta and Bayer have secured permits to carry out large-scale evaluation of banding fungicides in 2014 – and demonstration paddocks will be on show at local field days across the GRDC growing regions.

FungICIDe trIalsResearch by the South Australian Research and Development Institute (SARDI) and the Department of Agriculture and Food, WA (DAFWA), evaluated banding the Syngenta fungicide Uniform® (registration pending) in wheat and barley for rhizoctonia control.

Yield responses for six treatments of Uniform® are presented in table 1 for wheat and table 2 for barley (note: some treatments were evaluated in 2012 and 2013 only). treatments included:

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liquid banding of Uniform® as a split application, with half the rate banded on the soil surface and half in-furrow below the seed; applying the fungicide in-furrow below the seed only; and in-furrow below the seed combined with a seed treatment of vibrance®.

the results are presented as net yield increases (t/ha) for each treatment, with untreated yields (t/ha) and pre-sowing rhizoctonia levels included to help characterise each site. Rhizoctonia field trials are inherently variable and it was difficult to detect statistically significant yield responses of less than 10 per cent.

Disease severity ranged from low to very high in the trials, which used the natural rhizoctonia present in the paddock. trial sites were selected based on evidence of rhizoctonia in the previous year’s

Plant pathologist Daniel Hüberli examines rhizoctonia trials in the Western Australian wheatbelt. The research, which is being carried out in WA and South Australia, is evaluating the efficacy of new fungicides in controlling the costly pathogen.

integrAted mAnAgement oF rhizoctoniAFungicides should be used as part of an integrated management approach for rhizoctonia.

Factors that lower the disease risk of rhizoctonia include:¢ rotating cereals with canola to lower

rhizoctonia inoculum;¢ controlling the autumn green bridge,

which can host rhizoctonia;¢ sowing early within the optimum

sowing window and disturbing the soil at least 10 centimetres below the seed to encourage rapid root growth down the soil profile;

¢ applying seed treatments (yield responses average about five per cent);

¢ increasing seeding rate to reduce impact of lost tillers from rhizoctonia damage to crown roots;

¢ encouraging high seedling vigour by applying adequate nutrition – especially nitrogen – and not incorporating stubble (which can increase risk of nitrogen deficiency);

¢ addressing in-crop nutrient and trace element deficiencies with foliar applications; and

¢ using knifepoint soil openers rather than discs to sow crop.

new fungicide options on way for rhizoctoniacollaborative research between the south Australian research and development institute, the university of south Australia, the department of Agriculture and Food, western Australia, and agrichemical companies could result in new banding fungicide options for rhizoctonia control in cereals by 2015

19rhizoctonia

taBle 1 summary of net wheat yield responses (t/ha) in rhizoctonia fungicide application trials with uniform® and vibrance®. Site

Year

Pre-sowing rhizoctonia DNA

(pg/g soil)

Untreated yield (t/ha)

Vibrance®

Vibrance® + Uniform®

rate 1

Rate 2 Uniform®

Rate 3 Uniform®

Rate 2 (1/2 Sur + 1/2 Uniform®)

Rate 3 (1/2 Sur + 1/2 Uniform®)

Weetulta (SA) 2013 205 0.88 0.40** 0.49**

Lameroo (SA) 2013 106 2.29 0.09 0.18** 0.13** 0.19** 0.24** 0.20**

Wynarka (SA) 2013 257 1.79 0.03 0.22** 0.28** 0.21** 0.38** 0.53**

Katanning (WA) 2013 6 4.28 0.04 0.00 –0.02 0.04 0.15* 0.23*

Karoonda (SA) 2012 138 1.36 0.25** 0.47** 0.33** 0.42** 0.39**

Port Julia (SA) 2012 102 2.88 0.02 0.14* 0.14* 0.09 0.11

Lake Grace (WA) 2012 65 0.71 0.09* 0.05 0.02 0.08* 0.11*

Keith (SA) 2011 76 2.70 0.02 0.07 0.14

Minnipa (SA) 2011 109 1.98 0.08* 0.09** 0.12**

Yumali (SA) 2011 219 1.33 0.06 0.20** 0.20** 0.19**

Corrigin (WA) 2011 62 2.84 0.00 0.09 0.26**

Ongerup (WA) 2011 161 1.82 0.12 –0.09 0.00

*   Significant (P < 0.05) or ** Significant (P < 0.001), compared with untreated plots. Vibrance® seed treatment applied at 360mL/100kg seed, Uniform® applied in-furrow (3-4cm below seed), Sur = Uniform® applied on furrow surface.

taBle 2 summary of net barley yield responses (t/ha) in rhizoctonia fungicide application trials with uniform® and vibrance®.

Site YearPre-sowing rhizoctonia

DNA(pg/g soil)

Untreated yield (t/ha)

Vibrance®

Vibrance® + Uniform®

rate 1

Rate 2 Uniform®

Rate 3 Uniform®

Rate 2 (1/2 Sur + 1/2 Uniform®)

Rate 3 (1/2 Sur + 1/2 Uniform®)

Lameroo (SA) 2013 106 2.77 0.21** 0.17** 0.30** 0.31** 0.40** 0.37**

Wynarka (SA) 2013 257 1.93 0.09 0.62** 0.69** 0.53** 0.69** 0.87**

Kojonup (WA) 2013 22 4.38 0.04 0.18 –0.21 0.36* 0.25* 0.13

Karoonda (SA) 2012 138 2.63 –0.12 0.18 0.44* 0.49* 0.24

Port Julia (SA) 2012 102 2.99 –0.03 0.01 0.16 –0.15 0.15

Calingiri (WA) 2012 13 1.20 0.05 0.17** 0.25** 0.26** –0.05

Keith (SA) 2011 76 2.93 –0.03 0.18 0.09

Minnipa (SA) 2011 109 2.61 0.09 0.12 0.28**

Yumali (SA) 2011 219 1.53 –0.07 0.20* 0.12

Salmon Gums (WA) 2011 136 0.46 0.01 0.0 –0.01

* Significant (P < 0.05) or ** Significant (P < 0.001), compared with untreated plots.

cereal crop and a medium to high level of rhizoctonia DnA (PreDicta B® test) in the soil before sowing.

In wheat, yield responses increased significantly by 0.11 to 0.39t/ha with a medium-rate split application, while at a higher rate the yields were 0.23 to 0.53t/ha higher than the untreated control (table 1).

For barley there was a 0.2 to 0.69t/ha yield improvement from a medium split rate and 0.37 to 0.87t/ha from the high split rate (table 2).

Banding fungicide below the seed at the low rate in combination with the seed treatment vibrance® increased yield significantly in wheat in six of the 11 trials (table 1) and in barley in four of the 10 trials (table 2).

Seed fungicide treatment alone increased yields significantly in only three (Karoonda,

SA; Lake Grace, WA; Minnipa, SA) of the 11 wheat trials (table 1) and one (Lameroo, SA) of the 10 barley trials (table 2).

In the SA trials, the surface application treatment applied behind the press wheel was using a low-volume, narrow-angle nozzle set to spray along its narrow side creating a narrow band about 2cm wide.

In WA, the surface band treatment was applied as a trickle in a separate pass following the first-pass application of fungicide as a trickle below the seed using GPS-controlled auto-steer.

Future worKOngoing SA research will explore ways to reduce the impact of rhizoctonia in crops sown with disc seeders, including optimising fungicide placement and reducing the amount of inoculum being pushed into the seed zone.

Also under investigation will be the role of in-season rainfall on rhizoctonia’s impact and the rhizoctonia hosting capacity of different crop varieties.

In WA, large-scale paddock demonstrations showing the benefits of various treatment applications of Uniform® and of a canola rotation to combat rhizoctonia will be carried out across the wheatbelt.

Results from the trials will be shown during field days in 2014 and 2015. □

grdc research codes dAs00122, dAs00123, dAs00125, cse00150, dAw00174, uwA00152 more information: Alan McKay, SARDI,

08 8303 9375, alan.mckay@sa.gov.au;

Daniel Hüberli, DAFWA, 0427 426 522,

daniel.huberli@agric.wa.gov.au

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