Dry edible bean (Phaseolus vulgaris) genetics and germplasm enhancement
Domestic consumption of dry beans continues to rise in response to consumer and scientific recognition of beans as a major health food. In addition to being high in fiber and protein, beans serve as an important natural source of folate and other B-vitamins, minerals, and anti-oxidants. Dry edible beans are grown on 1.9 million acres and snap beans on 280,000 acres across the United States with a farm-gate value averaging $ 850 million. Thirty-five percent of the dry bean crop is exported, contributing favorably to U.S. trade balance. The Pacific Northwest (Idaho, Oregon, and Washington) produces 150,000 acres of dry edible beans. More than 22,000 acres of snap beans on average are grown in the Willamette Valley alone. Eighty-five percent of the seed industry for dry edible beans and snap beans is based in the Pacific Northwest. The 30,000 acres of seed production in the Pacific Northwest is for export as well as domestic use and is valued at $ 75 million. Snap bean seed production in the Columbia Basin is on the rise as seed companies realize the benefits of the early planting season offered by this region.
There is an estimated annual production of 125,000 acres of dry edible peas, 150,000 acres of peas for canning and freezing, 70,000 acres of seed peas, and 12,000 acres of Austrian winter peas in the Pacific Northwest. The estimated farm-gate value of these crops often exceeds $ 100 million. Besides their economic value, peas are used in place of summer fallow, where soil moisture is adequate and cereal-legume rotations offer an improved soil fertility and pest management options. In addition, pea stubble is an excellent no-till seedbed for cereals. The yield of beans and peas is in constant flux due to adverse climate, poor soils, insects, diseases and other stresses. The long-term improvement of yield of beans and peas will depend on the introgression of resistant genes from available germplasm, primitive forms and cultivars from throughout the world. Public research on germplasm improvement in peas has declined dramatically in the last 10 years with only two scientists left in the U.S. Both private and University breeding programs on beans and peas are not geared toward using exotic germplasm because of the long-term commitment needed to recover the desired traits within acceptable horticultural types.
1. Development of multiple disease resistant bean germplasm and cultivars.
The USDA-ARS Bean Project at Prosser has made valuable contributions to the industry over the last 40 years under the guidance of Drs. D. Burke, M. Silbernagel, and more recently P. Miklas. Excellent studies were conducted on the biology and pathogenic variability of bean common mosaic virus, curly top virus, and the root rot complex of pathogens plaguing commercial and seed production in the west and commercial bean production across the U.S. Numerous beans with resistance to virus and root rot pathogens have been released, and some cultivars continue to dominate the pink and small red bean acreage (70, 000 acres) across the U.S. today. Othello pinto bean (released by USDA-ARS at Prosser) is grown on about 30% of the acreage in the Pacific Northwest and has generated 68 million dollars revenue in the state of Idaho alone in the last 5 years. Many new public and private dry bean cultivars have some Prosser developed materials in their parentage, therefore, the impact of our bean germplasm project is quite significant.
2. Marker-assisted selection for sustainable disease resistance in beans
Using linked markers to combine two independent epistatic genes for resistance to the highly variable rust pathogen and circumvent the need for testcross and progeny tests was initially described by Dr. Miklas and led to release of the first bean germplasm line to capitalize upon molecular marker-assisted selection in its development. Other DNA markers identified by Dr. Miklas have been used to develop beans with enhanced resistance to bean golden mosaic virus (BGMV), common bacterial blight, and bean common mosaic virus. One marker is being used worldwide by breeders to quickly introgress the single most effective gene (bgm-1) for BGMV resistance into commercial cultivars. The increased selection efficiency obtained with the marker reduces breeding time and costs and hastens availability of resistant cultivars, saving growers and processors from losing millions of dollars to BGMV each year in Florida alone.
3. Development of multiple disease resistant pea germplasm
Dr. Kraft was the first to develop multiple root disease resistant pea germplasm with acceptable horticultural characteristics (i.e. white flowers, wrinkled seed, canning and freezing types). These 30 lines have been used by public and private breeders in the United States, New Zealand, France, and Australia to improve germplasm and cultivars. These parent lines have been used in producing approximately 20 commercial processing pea varieties which are now on the market. These lines possess resistant genes for Aphanomyces root rot, Fusarium root rot, Fusarium wilt races 1, 2, 5, and 6, powdery mildew, and/or pea seedborne mosaic virus.
4. Development of screening techniques for evaluating peas for resistance to diseases
Screening techniques have been developed whereby prospective germplasm and Plant Introduction lines can be quickly evaluated for resistance to root rot and wilt in the seedling stage. Techniques have been developed whereby large numbers of progeny can be evaluated quickly and accurately. A polyclonal antiserum was developed whereby resistance to Aphanomyces root rot can be quantified in the root system of inoculated plants.
5. Integrated pest management to control root diseases of peas
Two IPM studies were conducted in the Blue Mountain area of Northeastern Oregon and Southeastern Washington. Data on the use of reduced tillage, green manure plowdowns, residue management and seed treatments to control Aphanomyces and Fusarium root rot of peas were collected and presented as an Extension Bulletin which is being utilized by growers in the above area.
Present bean research is geared toward: conducting basic and applied research on germplasm enhancement; developing innovative screening methodologies to evaluate beans for resistance to economically important abiotic and biotic stresses; defining breeding strategies, including marker-assisted selection, for deploying novel traits in adapted lines; examining host-pathogen interactions; and developing populations and protocols to study genetic inheritance and obtain molecular markers tightly linked to agronomically important traits. Recently, the project has emphasized breeding beans for resistance and tolerance to white mold (Sclerotinia stem rot), the #1 rated disease of bean in the U.S. based on economic significance. Likewise, white mold is the most important disease of bean in the Pacific Northwest, and is on the rise due to increased bean production under center pivot irrigation systems. Identifying DNA markers for indirect selection of white mold disease has become a major priority. Emphasis has also been placed on breeding beans for increased tolerance to heat stress, as well as increasing yield potential in kidney bean through introgression of vining growth habit.
The bean program has evolved to a point where there is an excellent infrastructure in which dry and snap bean disease and germplasm enhancement research is conducted productively, efficiently, and has garnered a wide customer base. A rapport has been established with this customer base that is extremely supportive of ARS research efforts. Field nurseries have been established that facilitate long-term research on the complex of bean root rot organisms, curly top virus, and white mold disease. Facilities and equipment have been obtained for conducting the cutting-edge marker-assisted selection research that is fundamental to genetic introgression work and disease screening efforts.
Public research on pea pathological problems has declined dramatically during the last 10 years due to funding constraints. The major pea seed and processing production states include Minnesota, Wisconsin, California, Oregon, Washington, Idaho and most recently North and South Dakota. Essentially no public breeding or germplasm enhancement programs are left except for two ARS positions in Washington State and a .3 SY at Oregon State University at Corvallis. Germplasm enhancement and disease control research needs to continue for this crop to be a viable rotational crop in the Pacific Northwest and in the U.S. New pea disease problems are continually appearing and old ones are reappearing due to changes in cultural practices. As an example, Pea Cyst Nematode, not found in the U.S. until 1996, now threatens the pea processing industry in Northwestern Washington. The obligate fungus which causes Downy Mildew, once controlled by metalaxyl fungicide, has developed resistance to this class of fungicides. A breeding program needs to be emphasized to develop resistant varieties to curtail further development of fungicide resistance by this pathogen. In addition, seed transmitted fungal and bacterial diseases, not a problem before seed was grown under center pivot irrigation are reappearing. More and more seed fields are under center pivot systems in the Pacific Northwest which is the center of pea seed production for the U.S. This creates a climate conducive to the development of these diseases. Future research programs have to address these disease problems once thought to be extinct. In summary, a Plant Pathologist/Germplasm Developer needs to be hired at the Prosser ARS unit to continue the current research initiated by Dr. Kraft, as he retires in September of 2000. Existing university funding will not support research concentrating just on peas.
Dry Bean Yield Trials
Dry Bean Multiple Stress Plot Trials
White Mold Trials - Paterson, WA
Dry Edible Bean Releases by Market Class
DNA Markers (SCARs) for Resistance Traits 2010