What are the races of the “remnant” population of the pathogen?
Our field tests indicate the presence of new races of the pathogen in WSU, WA and UC Davis, CA
How diverse are the pathogen isolates?We are currently examining the extent of genetic
diversity of the field isolates of the pathogen by the use of amplified fragment length polymorphism (AFLP)
We are also studying the differences among the isolates from different locations by the use of molecular markers
Emerging and re-emerging plant diseases
In the past two decades, emerging and re-emerging plant diseases have posed new threats to food production. Emerging diseases are those which have always been present in an area but have grown in importance over the years. Re-emerging diseases are those that have been previously controlled but are once more a major problem. Diseases emerge or re-emerge due to changes in farming practices, development of new strains of the pathogen, climate change, introduction of the pathogen to new geographical locations, or introduction of more efficient pathogen vectors.
Tilletia caries, causal agent of common bunt of wheat
Bunted and healthy kernels
Fig. 2. Percent bunt infection of selected winter wheat cultivars.
Selected races of the bunt pathogen
Perc
ent
bunt
infe
ctio
n
Disease Status Crop host
Scab (Fusarium Head Blight) Re-emerging Wheat and barley
Karnal bunt & common bunt Emerging Wheat and other cereals
Tomato spotted wilt (tospovirus) & Tomato yellow leaf curl (geminivirus)
Re-emerging / Emerging
Tomato
Silver scurf, pink rot & dry rot Re-emerging Potato
Raspberry bushy dwarf (idaeovirus)
Re-emerging Raspberries
Anthracnose Emerging Strawberry
Blueberry shock (ilarvirus) New Blueberry
Black leg Re-emerging Cabbage, cauliflower, broccoli
High plains virus disease New Corn and other cereals
Sorghum ergot Emerging Sorghum
Potato late blight (new strains) Re-emerging Potato & tomato
What are the bunt resistance genes in modern wheat cultivars?
Table 1. New, emerging and re-emerging diseases of selected crops in the United States.
Janet B. Matanguihan and Stephen S. JonesDepartment of Crop and Soil Sciences, Washington State University
Mount Vernon Northwestern Washington Research and Extension Center
We will identify the bunt resistance genes present in 12 selected modern wheat cultivars
We will use molecular markers and nulli-tetrasomic lines of wheat to identify the location of the resistance genes in specific wheat chromosomes
Fig. 1. Major pathogens causing emerging infectious plant diseases (Anderson et.al. 2004)
Impact of emerging plant diseases:
Threat to human welfare~ 42% of the attainable crop production is lostBarrier to international commerceNegative effects on health and well-being
Threat to biodiversity and ecosystemsDecline of host populationsExtinction of host species or other organisms dependent on
the host for habitat
What should be done?
Damsteegt, 1999; Fry and Goodwin, 1997; du Toit, L. (pers.comm); Inglis, D. (pers.comm); Manners, 2004; McMullen et.al. 1997; Randyopadhyay & Frederiksen, 2004; www.ces.ncsu.edu/depts/ent/clinic
HOST RESISTANCEPre-emptive breedingDurable/broad resistance
MANAGEMENT PRACTICESExamine impactHost diversity
MONITORING (local & global)Identification/diagnosticsPathogen virulence & genetics
QUARANTINE (local, national & global)
Scientific principles of plant protection
Risk assessmentPolicy adoptionEducation
Adapted from Fry and Goodwin, 1997; Manners, 2004
Fusarium head blight (Photo by M. McMullen)
Karnal bunt on grains, www.apsnet.org
Late blight of potato, www.ctahr.hawaii.edu
Tomato spotted wilt, www.colostate.edu
http://ipm.ncsu.edu
Blueberry shock, http://whatcom.wsu.edu
Ergot of sorghum (photos by G. Obvody)