Principles and Practices of Organic Pea Seed Production

A Publication of NOVIC:

the Northern Organic Vegetable Improvement Collaborative

Written and Compiled by James Keach & Dr. Michael Mazourek Cornell University, Dept. of Plant Breeding, Ithaca, NY

This publication made possible through a grant from the

USDA NIFA Organic Research and Extension Initiative (OREI) program

Table of Contents

Crop History, Lifecycle, and Basic Biology .......................................................................................... 3

Growing Pea Seed ..................................................................................................................................... 3

Climatic Requirements ............................................................................................................................. 3

Planting .................................................................................................................................................... 3

Spacing...................................................................................................................................................... 4

Isolation Requirements ............................................................................................................................ 4

Genetic Maintenance ................................................................................................................................ 4

Population size .......................................................................................................................................... 4

Selection Criteria ...................................................................................................................................... 4

Seedling Vigor and Color .......................................................................................................................... 5

Plant Form ................................................................................................................................................ 5

Leaf Type ................................................................................................................................................... 5

Pod Characteristics ................................................................................................................................... 6

Quality ...................................................................................................................................................... 7

Harvesting and Cleaning ......................................................................................................................... 7

Harvesting and Drying Seed .................................................................................................................... 7

Seed Cleaning............................................................................................................................................ 7

Seed Storage .............................................................................................................................................. 8

Diseases....................................................................................................................................................... 8

Fungal Diseases ........................................................................................................................................ 8

Bacterial diseases ....................................................................................................................................... 9

Viral Diseases ......................................................................................................................................... 10

Insect & Animal Pests ............................................................................................................................ 10

Additional Resources ............................................................................................................................. 11

References................................................................................................................................................. 11

Table of common genes affecting pea traits important to growers. .............................................. 14

Crop History, Lifecycle, and Basic Biology The pea, Pisum sativum, is an Old World crop native to the Middle East and cultivated by many civilizations throughout the ancient and modern world. From millennia of cultivation, several forms of peas have emerged for different purposes, including peas for animal forage, shelling peas for their fresh seeds, field peas for their dry seeds, and edible-podded peas, such as snow and snap peas. In genetics, peas are famous for being the plant Gregor Mendel, the Austrian monk, used for discovering the rules of genetic inheritance. As a legume, peas can form symbiotic relationships with bacteria in the soil, leading to the fixing of nitrogen and reducing the need for fertilization. This process occurs in swollen nodules on the roots.

Growing Pea Seed

Climatic Requirements

Although peas are native to the Middle East, they are often grown as a cool weather crop in the United States. Most peas show some degree of cold hardiness and frost resistance and some, such as Austrian Winter peas, are even grown as winter cover

crops under snow banks (reviewed in Markarian & Andersen, 1966). Extreme heat or drought can result in poor bed establishment and may stress the plants, making them more susceptible to pests and disease. However, temperatures of 70ºF (21ºC) or above are necessary for proper expression of the stringless trait in lines containing it. Generally, it takes a minimum of ninety days from planting to dry seed, although this is strongly influenced by the particular cultivar. Daylength sensitivity, while not common in most commcercial varieties, may be present in more unusual lines and should be investigated in cases of poor or no flowering.

Planting

Planting time varies with the season the peas are being grown for. Early peas are often planted as soon as the ground has thawed in the spring. Austrian Winter Peas are planted at the same time as winter wheat in the Fall, and then stay dormant over the winter. Seed is normally treated with an organic-approved inoculant and direct sown in furrows. While soaking seed is commonly practiced by gardeners to speed germination, this is often impractical for larger productions and unsuitable for mechanical planters.

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Spacing For optimal production, no more than 18-20 plants per yard are recommended, with some leeway given depending on seed and plant size. This is particularly appropriate for plants grown on a trellis; plants grown in a bed may be spaced closer, but may be more susceptible to disease.

Isolation Requirements

Peas are predominately inbreeders, due to their naturally closed flowers. For this reason, limited isolation is normally practiced. Some commercial operations separate different varieties by as much as 350 feet (100m). However for most growers 20 feet between varieties, enough to ensure that they do not actually overlap and mix seeds, is generally considered enough (OSA, 2010). Insects have been known to eat and open pea flowers in some locations, leading to cross-pollination (including pea weevil: Clement, 1992). If the pea flowers appear to be heavily frequented by the local insect population, increased isolation distances may be necessary. Another approach is to physically separate the varieties with a different, preferably taller, crop which can act as a barrier and distraction for the insects. Despite similarity in name and shape, true peas (Pisum sativum)

will not cross pollinate with sweet peas (Lathyrus sp.).

Genetic Maintenance

Population size

As peas naturally inbreed, relatively small populations can be maintained and remain true to type. While it is possible to save seed from just a single plant, it can be difficult to obtain sufficient seed for future plantings, and variation within a variety which is invisible to the naked eye may be lost. A minimum population of 10-20 plants will better preserve existing diversity (OSA, 2010).

Selection Criteria

In order to keep a variety true to its type, it will sometimes be necessary to go through the field and take out or separate plants that do not resemble the others, or do not match the common description of the variety; this is commonly known as ‘rogueing’. While variants can be interesting and potentially useful, seed from them must be saved separately from seed of the ‘normal’ variety. Many traits can vary between varieties, some invisible to the naked eye, and some general traits to look for are discussed in the following sections. These sections are by no

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means comprehensive, and other forms of variation should be noted and evaluated according to the variety.

Seedling Vigor and Color Some growers prefer to plant at high densities (i.e. every inch) and later thin to a more manageable density (i.e. every three inches) to help select for good emergence and rapid growth, which may lead to better early establishment of a variety. Likewise, this will help select against seed dormancy and lateness. Coloration on the plant can also sometimes be selected at the seedling stage, to remove off-types. Presence of pigment on the stem or at the base of the axil leaves roughly translates to color in the flowers and sometimes the seed or pod, depending on the variety (i.e. purple marks purple flowers, red marks red or pink flowers, no marks white flowers). Pigmentation, especially of the seeds, is generally considered unfavorable, as it can result in a bitter flavor and unattractive cooked color. Most edible-podded peas will have white flowers, green seeds, and no pigment on the stems or leaves.

Plant Form

A wide range of heights and growth habits exist in cultivated peas. While traditional pea cultivars tended to be

taller and vining, more dwarfed bushy varieties have become common in the last century or two. Generally, being tall is dominant to being short or dwarfed, and so outcrosses in a dwarf variety will be easy to detect. Attention should also be given to getting rid of plants which are late or low-yielding, as these can be more subtle forms of a change in growth habit through unfavorable mutations, crosses with different varieties, or shifting within the variety.

Leaf Type

In peas, there are a number of different mutations that produce different combinations of leaves and tendrils. While many varieties have several leaflets followed by tendrils at the end of each branch, the afila peas have all of the leaflets replaced with tendrils, giving them a better ability to remain standing by supporting themselves against their neighbors. This is particularly common in modern field or winter pea cultivars, but is also being introduced into edible-podded pea types. It is important to know what the normal growth habit of a cultivar is, so that off-types can be recognized and removed, and trellising options can be chosen accordingly.

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A normal pea leaf with leaflets and tendrils (L), compared to an afila type (R) with only tendrils.

Pod Characteristics

Minor details in the shape of the pod can help differentiate between similar-looking cultivars. A blunt tip of the flower end is dominant to a pointed tip in the mature pod. The number of flowers or pods at a node is also variable, normally ranging from one to two, but with higher numbers occasionally manifesting. There is also a wide range in the number of seeds in a pod, with some varieties like ‘Green Arrow’ having ten or more and others normally varying from four to seven. Pod type, such as shelling, snow, or snap, is the result of three genes that affect pod parchment (the fibrous tissue inside) and thickness. Shelling is PPVVNN, with all three genes dominant, producing parchment in thin pods. Snow is ppvvNN, with p and v recessive, removing the parchment, but N dominant, leaving the pods thin. Snap is ppvvnn, with all three genes recessive, removing

the parchment and thickening the pod walls. Thus, any outcrosses between types will result in the dominant form (eg. anything crossed with shelling will result in a shelling type, crossing a snow and a snap will result in a snow type). Mutations sometimes occur spontaneously in the V gene, and so it is important to occasionally check snow and snap peas to make sure they have not developed parchment. Stringlessness is a recessive trait, and can have variable expression in a plant. It is especially sensitive to temperature variation and, as mentioned above, may not be present when the plant grows in a cool environment under 70ºF (21ºC). For this reason, it is important to look at pods several times throughout the season, even on the same plant.

Three main types of pea pods: shelling, snow, and snap (L-R). The arrow points to the thin, fibrous parchment layer which is absent in snow and snap pods. Notice how much thicker the snap pod walls are than either the shelling or snow.

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Quality The eating quality of the pods and peas is a subjective trait, which will vary greatly depending on the pod type and person tasting it. Generally, traits worth noting are texture of the chewed pod (for edible-podded types), sweetness, tenderness, and flavor, including any off-flavors and the strength of the traditional pea flavor. As mentioned previously, purple-flowered and other pigmented plants tend to have a different, less-agreeable flavor than the more common, white-flowered cultivars (Taurick & McLellan, 1986). Preparing a small number of pods or peas the way they are intended to be eaten can also be a good way to select superior lines or maintain preferred cultivars, but may not be feasible for larger populations.

Harvesting and Cleaning Harvesting and Drying Seed

Peas can be harvested for seed approximately four weeks past the stage for eating, or when parchment has formed within the pod and the seeds rattle inside. It is also possible to harvest seeds when the pods are completely dry, as long as the local climate is amenable, but in some

cultivars the mature pods may ‘shatter’ and scatter the seeds.

Three pods at increasing maturity (L-R). All are at acceptable stages for harvest, if provided with additional drying time. The middle pod is ideal as the seeds inside are completely mature (which may not be true for the pod on the left), but the pod has not become brittle and prone to shattering (as may be the case for the pod on the right).

Additional drying indoors for a week or more, using low heat (85ºF [30ºC] or below) and lots of air movement, is recommended especially in moist areas. However, it is important to not over-dry seeds, as they may harden and then not germinate unless they are scarified (abraded with a file, sandpaper, etc.). In excessively rainy or moist areas, where drying in the field is not feasible, the plants may be cut early: when the foliage has begun to dry and the seeds have a starchy taste and can easily be disconnected from the pod. These plants should then be dried indoors.

Seed Cleaning

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A ten minute soak in 1% bleach, followed by a water rinse and drying, may reduce the presence of seedborne bacteria and fungi; however, it is important to check with your certifier to check on whether this is permitted under local organic regulations (limited chlorine use is permitted under NOP Regulation §205.601(a)2, but interpretation of its role may vary; it has been recommended for dealing with the same pathogen in organic nightshades: http://web.pppmb.cals.cornell.edu/resourceguide/cmp/solanaceous.php#d1).

Seed Storage

Dry seed will generally remain viable for three or more years, as long as it is kept in a dry, cool, and dark place; germination can drop below 50% after approximately eight years in storage, but is greatly dependent on the condition of the seed when stored and the cultivar (Nozzolillo & Lorenzetti, 1998). For longer, more secure storage it can be placed into a mason jar with a desiccant such as DriRite or silica gel, sealed, and stored in a refrigerator or freezer. Naturally occurring chemicals in the pea seed coat can help deter feeding by rodents and insects, but should not be relied upon as the only method of preventing infestation.

Diseases In addition to the cultural management practices and resistant cultivars described below, a number of organic-approved solutions and biological controls for pea diseases have been approved. A good review of them and their target diseases can be found in the relevant section of: http://nysipm.cornell.edu/organic_guide/pea.pdf

Fungal Diseases Fusarium Root Rot (Fusarium solani) is a common soilborne disease that can lead to the damping off of pea seedlings (Kraft & Pfleger, 2001). Brown or red streaks at the base of the seedling or plant are common, and will eventually come together to girdle the stem. This fungus thrives in standing water in compacted soils, and so drainage from improved soil structure can act as a preventative. Rotation will also help to prevent disease buildup. Resistance is present in varying degrees across a number of varieties, but is not well described or publicized (Grunwald et al., 2003; Infantino et al., 2006). A related disease, Fusarium Wilt (Fusarium oxysporum), tends to infect older plants and result in them collapsing from fungi infesting their stems; it can be recognized by the presence of reddish streaks when the stem is cut open. Control is similar

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to Fusarium Root Rot, with good soil health and long rotations (including leguminous cover crops) being the best forms of control, but many cultivars with known resistance to the main races have also been released, although they are not always documented as being so (Bani et al., 2012; Kraft & Pfleger, 2001; McPhee et al., 1999). Powdery Mildew (Erysiphe pisi) is a foliar disease of peas (Kraft & Pfleger, 2001). Unlike many fungi, this disease is more of a problem in drier areas. Fuzzy white patches form on older leaves and then slowly spread to the rest of plant, lowering yields and quality of the pods and seeds. Debris from infected plants can also carry the disease. Removing this debris will help reduce disease pressure in future years, as will crop rotation. Resistance is present in quite a few commercial cultivars, including Oregon Sugar Pod II, and can help prevent or reduce the infestation. Early-maturing varieties are often also able to escape some or all infection.

Top: Cultivars resistant (L) and susceptible (R) to Powdery Mildew. Bottom: Close-up of infected (L) and uninfected (R) leaves.

Bacterial diseases

The main bacterial disease of peas is bacterial blight (Pseudomonas syringae pv. pisi). Plants may not show any sign of the disease until water sits on the leaves or pods for a while, at which point sunken, brown circles can appear. These lesions are particularly problematic on the pods, as they can transmit the bacteria to the seed. Unfortunately, the bacteria is very easy to spread, and debris, infected seed, and even contaminated machinery can all act as inoculum. Prevention is the best control: removing debris and cleaning machinery coming from other fields will prevent spreading the bacteria. It may be possible to

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reduce the amount of the bacteria in the soil using solarization, raising the temperature by covering it in clear plastic to trap the heat of the sun, (reviewed by Bashan, 1997). As a last resort and method to clean up a seed lot, the seeds can be soaked in dilute bleach, as described above (and when permitted by your certifier). Resistance to some strains of the bacteria is also present in many cultivars, including ‘Lincoln’ and ‘Fortune’, although not all of them are documented as possessing it (Taylor et al., 1989; Bevan et al., 1995); there is some evidence that cultivars resistant to Fusarium may be more resistant to bacterial blight (Daniels et al., 1987).

Viral Diseases Pea seedborne mosaic virus is perhaps the most important pea virus for seed production as, like the name suggests, it is seedborne. Symptoms can be mild to severe, with unusual leaf patterns and mosaic-like patterns, as well as curled leaves, and sometimes severe dwarfing with an inability to set flowers or pods, and crackling of the seed surface. Other legumes may be susceptible, and can spread the disease via a variety of aphids, including the potato aphid. Eliminating infected plants is the best form of control, as well controlling the aphids that spread it. Good resistance is present

in a number of commercial cultivars, controlled by single, recessive genes.

Insect & Animal Pests

Just as many people enjoy eating pea sprouts, many animals also enjoy feasting upon the pea plant and its tender shoots. Exclusion by an electric fence is generally effective for larger animals, and hot pepper sprays may deter smaller herbivores. Some farmers also recommend scattering hot pepper flakes in with the pea seed, to discourage rodents from digging up and eating the seeds and young seedlings. One insect pest which can wreak havoc, either on the plant or seed, is the pea weevil. Feeding on the plant results in cut leaves and fewer nitrogen-fixing nodules, while seed infestation manifests as holes penetrating throughout the seeds; both types of damage can provide entryways for other pathogens and diseases. A range of biological controls are available commercially to control various insects and pests, including predatory insects, parasitic nematodes, and fungi such as Beauveria bassiana which has been found effective against pea aphids (Andarge, 2001). Alternatively, hot pepper wax sprays can serve dual purposes at preventing mammals and weevils. Covering emerging seedlings with floating row cover

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may allow the plants to get sufficiently established to survive attacks as adults.

Additional Resources Breed Your Own Vegetable Varieties by Carol Deppe The Seed Savers Handbook by Jeremy Cherfas, and Michel and Jude Fanton. Seed to Seed by Suzanne Ashworth and Kent Whealy. Pea and Bean Weevil Organic Gardening Practices http://www.organicgardeningpractices.com/peaandbeanweevil.php 'Pea Breeding' by Earl T. Gritton in: Breeding Vegetable Crops, edited by: M. J. Bassett 1986. AVI Publishing Co. PDF: http://www.agron.iastate.edu/faculty/fehr/BVC/08BVC.PDF Pea Diseases and their Control http://permanent.access.gpo.gov/gpo21087/CAT87208312.pdf Handbook of Pea Diseases by D.J. Hagedorn http://learningstore.uwex.edu/assets/pdfs/A1167.pdf

Production Guide for Organic Peas for Processing http://nysipm.cornell.edu/organic_guide/pea.pdf ‘A Seed Saving Guide’ by the Organic Seed Alliance http://www.seedalliance.org/Publications/#SeedSavingGuide

References The Pathology of Food and Pasture Legumes by D.J. Allen and J.M. Lenne. 1998. ‘Aspects of bio-intensive pea aphid, Acyrthospihon pisum (Harris) management on lentil, Lens culinaris (Medikus)’. by Alemtaye Andarge. in a thesis from Free State, South Africa. 2001. Summary at: http://bit.ly/R2cdvV 'A detailed evaluation method to identify sources of quantitative resistance to Fusarium oxysporum f. sp. pisi race 2 within a Pisum spp. germplasm collection'. by M. Bani, D. Rubiales, and N. Rispail. in: Plant Pathology. Vol 61, 2012. pp. 532–542.

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'Alternative Strategies for Controlling Plant Diseases Caused by Pseudomonas syringae'. by Y. Bashan in: Developments in Plant Pathology: Pseudomonas syringae Pathovars and Related Pathogens, Vol 9., 1997. edited by K. Rudolph, T.J. Burr, J.W. Mansfield, D. Stead, A. Vivian and J. von Kietzell http://bashanfoundation.org/gmaweb/pdfs/alternative.pdf ‘Genetics of specific resistance in pea (Pisum sativum) cultivars to seven races of Pseudomonas syringae pv. pisi' by J. R. Bevan, J. D. Taylor, I. R. Crute, P. J. Hunter, and A. Vivian. in: Plant Pathology, Vol. 44, 1995. pp. 98–108. 'On the function of pea flower feeding by Bruchus pisorum' by S. L. Clement. in: Entomologia Experimentalis et Applicata. Vol 63, No. 2, 1992. pp. 115-121. 'Pea genes associated with non-host disease resistance to Fusarium are also active in race-specific disease resistance to Pseudomonas' by C. H. Daniels, B. Fristensky, W. Wagoner and L. A. Hadwiger in: Plant Molecular Biology, Vol. 8, No. 4, 1987. pp. 309-316 'Sources of Partial Resistance to Fusarium Root Rot in the Pisum Core Collection.'

by N.J. Grunwald, V. A. Coffman, & J. M. Kraft in: Plant Disease, Vol. 87, No. 10, 2003. pp. 1197-1200. http://web.science.oregonstate.edu/bpp/labs/grunwald/publications/PD-2003.pdf 'Screening techniques and sources of resistance to root diseases in cool season food legumes'. by Alessandro Infantino, Mohamed Kharrat, Luca Riccioni, Clarice J. Coyne, Kevin E. McPhee and Niklaus J. Grünwald. in: Euphytica. Vol. 147, No. 1-2, 2006. pp. 201-221. http://www.science.oregonstate.edu/bpp/labs/grunwald/publications/Euphytica-2006.pdf Compendium of Pea Diseases and Pests by John M. Kraft and Francis L. Pfleger. 2001. 'The Inheritance of Winter Hardiness in Pisum'. by Deran Markarian and R. L . Andersen in: Euphytica, Vol. 15. 1966. pp. 102-110. 'Resistance to Fusarium Wilt Race 2 in the Pisum Core Collection'. by Kevin E. McPhee, Abebe Tullu, John M. Kraft, and Fred J. Muehlbauer in: Journal of the American Society of Horticultural Scientists. Vol 124, 1999. pp. 28-31.

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'Viability of pea seeds in storage'. by C. Nozzolillo and F. Lorenzetti in: Pisum Genetics, Vol. 30, 1998. pp. 15-21 http://pisum.narod.ru/pg/30/storage.htm 'Use of Sensory Analysis for the Observation of Single Gene Effects on the Quality of Canned Peas (Pisum sativumL.)' by G. R. Taurick & M. R. McLellan. in: Journal of Food Science, Vol 51, No. 6, 1986. pp. 1565-1566. 'Genetic relationship between races of Pseudomonas syringae pv.pisi and cultivars of Pisum sativum.' by J. D. Taylor, J. R. Bevan, I. R. Crute, and S. L. Reader. in: Plant Pathology, Vol. 38, 1989. pp. 364–375

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Table of common genes affecting pea traits important to growers. Lower-case gene letters signify it is inherited recessively, while upper-case letters signify it is dominant over the recessive form (masks it when present). Additional gene information can be found at http://data.jic.ac.uk/cgi-bin/pgene/default.asp Commercial sources listed are only a fraction of cultivars known to carry those genes, and do not denote an

endorsement. Varieties with these genes which are publicly available from the USDA can also be found at

http://www.ars-grin.gov/cgi-bin/npgs/html/desclist.pl?173

Gene Effect Commercial Source

A Anthocyanin present throughout plant (purple flowers), a is white-flowered

Dwarf Grey Sugar

af Most leaves replaced with tendrils Sugar Lace II

b With A: pink/salmon flowers, with Pu & Pur: red pods

Pink Flowered, Mummy Pea

cr With A: red flowers, With A & b: rose flowers, often linked to gp

Apple Blossom

dp Darker bluish-green pods and more intensely pigmented flowers, with gp: darker yellow pods

Miragreen

er1 Resistance to Powdery Mildew Oregon Sugar Pod II

En Resistance to Pea enation mosaic virus Oregon Sugar Pod II

fn Two flowers per node, with fna: more flowers many available

fna Two flowers per node, with fn: more flowers many available

Fw Resistance to Fusarium wilts or near-wilts, various forms of this gene exist with different resistance to different forms of the fungus

Dark Skin Perfection, various

gp Yellow pods and young shoots Golden Snow

le Dwarf plants (not ‘pole’ types) many available

lm ‘Micro’ dwarf plants Tom Thumb

n With v & p: snap pods many available, Sugar Snap

p With v: snow pods many available, Oregon

Sugar Pod II

Pu With A & Pur: purple pods Caruther’s Purple Podded,

Blauschokker

Pur With A & Pu: purple pods Caruther’s Purple Podded ,

Blauschokker

r Wrinkled, sweeter seeds, can combine with rb for stronger effect

many available

rb Wrinkled, sweeter seeds, can combine with r for stronger effect

many available

sin2 Stringless pods under warm temperatures, less vigorous plants, poor pollen inheritance

Sugar Daddy, Sugar Lace II

smb Resistance to Pea seedborne mosaic virus, various forms of this gene exist with differing resistances to different strains of the virus

Avon, Dark Skin Perfection, Quincy

v With p: snow pods many available, Oregon

Sugar Pod II