Location:2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Identify, characterize, and tag genes/QTL conditioning resistance to diseases and abiotic stresses of economic importance in edible legume production. Subobjective 1A: Generate molecular markers in beans and peas with application for MAS of resistance to bacterial, fungal, and viral diseases and tolerance to drought and low soil fertility. Subobjective 1B: Develop dry bean germplasm with enhanced disease and/or abiotic stress resistance using MAS in combination with traditional breeding approaches. Objective 2: Develop improved disease management practices for several soilborne and emerging diseases of edible legumes, and determine environmental host – pathogen relationships. Subobjective 2A: Identify integrated pest management strategies to manage root rot in peas. Subobjective 2B: Investigate effects of environmental factors on edible legume host-pathogen relationships and pathogen biology.
1b. Approach (from AD-416):
Diseases and abiotic stresses (drought, low soil fertility) affecting edible legumes, such as beans, chickpeas, lentils, and peas, result in costly losses to farmers exceeding $100 million annually. Management of soilborne diseases is extremely challenging, because the same pathogens can affect several legumes grown in the same rotation, and the pathogens persist in the soil over many years. Resistant cultivars provide growers with a cost-effective, safe and environmentally friendly way to control most disease and abiotic stress problems. Breeding for resistance, however, is difficult due to the paucity of resistance sources, specifically for soilborne diseases, and lack of information concerning inheritance. Improved management of problematic soilborne diseases is predicated upon a better understanding of the ecology and epidemiology of each pathogen. The objectives of this research are to integrate marker-assisted (MAS) selection with traditional breeding approaches to develop bean germplasm with enhanced levels of disease and abiotic stress resistance, and to improve disease management practices for several soilborne diseases of edible legumes. Novel disease and abiotic stress resistance genes/QTL will be identified, characterized across environments, validated in different genetic backgrounds, and molecular markers with application for MAS of such resistance will be developed and used to breed edible legume germplasm with enhanced resistance. A basis for the improvement of sustainable disease management strategies will be formed through the integration of genetic resistance, chemical and cultural tactics, and improved understanding of the epidemiology and population biology of several economically important pathogens of edible legumes.
3. Progress Report:
Field, greenhouse and laboratory experiments were successfully used to identify new genes for resistance to major bacterial (halo bacterial blight on bean), fungal (white mold on bean and pea; Fusarium root rot and Aphanomyces root rot on pea), and viral (beet curly top on bean; Pea enation mosaic virus on pea) disease problems limiting common bean and pea production in the U.S. The relative importance of the newly discovered resistance genes in plant breeding programs was characterized. Genetic markers were generated for three halo blight resistance genes in bean; three genes for resistance to white mold in bean and two in pea; five genes for resistance to Aphanomyces root rot in pea and two genes for resistance to beet curly top virus in bean. Traditional and marker-assisted selection was used to develop and release pinto (one), cranberry (two), kidney bean (one) and green pea (six) germplasm lines with improved disease resistance. Genomic mapping and gene expression studies were used to examine partial resistance to white mold disease and provide tools for discovery of the actual genes underpinning the resistance in bean. Two pea lines with superior resistance to white mold across multiple environmental conditions were discovered. Integrated pest management practices reducing soil compaction and applying early applications of phosphorous acid were determined to significantly improve dry pea production. In addition, fertilization practices utilizing in-furrow applications of sulfur, zinc and boron significantly improved yield in dry land green pea production areas in Oregon over the standard commercial practice. Use of lime to improve pea yields in low pH soils in Oregon did not yield immediate benefits to growers within a five year period. The pea cultivars: Strike and Freezer 43 with anticipated resistance to Pythium root rot at low soil temperatures did not demonstrate any resistance to this pathogen and did not result in the discovery of any resistance genes to this pathogen. Isolates of the Pythium root rot pathogen with resistance to the fungicide metalaxyl were more than 100 times more resistant to metalaxyl and had faster growth rates and were more aggressive than sensitive isolates making them a greater threat to food security in the Columbia Basin of Washington.
1. White mold is rated the number one disease problem of dry bean in the United States. Pinto bean is the most important market class, but the most susceptible to white mold. USDA-ARS at Prosser, WA, with assistance from scientists at Michigan State University and University of Nebraska, developed and released "USPT-WM-12" pinto bean germplasm line with partial resistance to white mold disease. This line has performed exceptionally well under severe white mold pressure in national trials in 2010 and 2011. "USPT-WM-12" has better yield performance and better overall resistance to white mold than the previous USDA-ARS germplasm line USPT-WM-1 released in 2005. This new germplasm release is being used by breeders to develop pinto bean cultivars with improved resistance to white mold. Pinto beans with partial resistance to white mold will save growers millions of dollars from lost production.
2. New Fusarium root rot resistant germplasm lines released. Fusarium root rot diseases are currently a major concern for the green and dry pea industries worldwide and resistant germplasm lines to these diseases with agronomically acceptable characteristics are seriously lacking. Six advanced breeding lines containing both high levels of field resistance to Fusarium root rot and Fusarium wilt races 1 and 2, in addition to highly desireable characteristics associated with increased yield, uniform seed coat color and anti-lodging characteristics were developed and released by an USDA-ARS scientist. These breeding lines reduced mean root rot severity in field trials by 38 to 50% compared to the susceptible commercial standard, Bolero. These lines are currently being used by private breeders as a resource for developing root-rot-resistant cultivars serving the canning, freezer, and dry pea industries.
Soule, M., Porter, L., Medina, J., Santana, G., Blair, M., Miklas, P.N. 2011. Comparative QTL map for white mold resistance in common bean, and characterization of partial resistance in dry bean lines VA19 and I9365-31. Crop Science. 51:123-139.