Location:2008 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. Formerly 5354-21220-015-00D (4/08).
3. Progress Report
In support of NP 301 - Problem Statement 2C: Genetic Analyses and Mapping of Important Traits: the Pse-2 gene for resistance to halo bacterial blight in dry bean was found to condition resistance to 7 of 9 differential races of the pathogen. Markers tightly linked with the genes/QTL will be useful for marker-assisted breeding, and facilitate integration of the resistance traits on the core linkage map. Genetic populations for characterizing quantitative resistance to halo blight were developed. With assistance from researchers, at the Center for Tropical Agriculture, CIAT, Colombia, the genetic marker for the Pse-2 gene for halo bacterial blight resistance was located to linkage group B10 of the Phaseolus consensus map. In support of NP 301 - Problem Statement 3C: Germplasm Enhancement/Release of Improved Genetic Resources and Varieties: participated as a leader and team member in the release of two germplasm releases, i) with University of Idaho and Michigan State breeders in the release of common bacterial blight cranberry germplasm line USCR-CBB-20, and ii) with University of Idaho and Colorado State University breeders in the release of white mold resistant germplasm line A-195. For future germplasm development efforts more than 30 biparental crosses were made to combine genes for enhanced resistance to individual pathogens. In support of NP 301, Component 3, Genetic Improvement of Crops by identifying novel traits for resistance to diseases and abiotic stresses, ten pea lines previous determined to possess potential resistance to Sclerotinia sclerotiorum were assessed. at 24 different combinations of temperature (15.6, 18.3, 21.1, 23.9, 29.4ºC) and incubation period (12, 24, 48, 72 hours) in a growth chamber at 90-100% RH. Novel white mold resistant characteristics were identified in pea lines 103709, 164972, and 169603 and mapping populations have been developed for 103709 and 169603 to identify the genes associated with the observed resistance. Future efforts will concentrate on identifying quantitative trait loci associated with prolonged infection periods observed in the resistant lines that can be incorporated into current and future pea cultivars. In separate research, Pythium isolates were collected from 50 fields, with and without, a pea cropping history and isolates will now be tested for resistance to mefenoxam.
1. Characterizing, tagging, and mapping halo blight resistance genes in dry bean. Halo blight is a seed-borne bacterial disease of common bean that is prevalent in cooler humid regions of the upper Midwest (MI, MN, ND, NE) and in similar climates worldwide. Genetic resistance can be used to control this disease but inheritance is not well understood. Characterization and molecular tagging and mapping of two genes conferring resistance to halo blight have been completed by ARS scientists in the Vegetable and Forrage Crops Production Research Unit in Prosser, WA. The genes Pse-1 and Pse-2 confer resistance to four and seven isolates of the pathogen, respectively, and both are located on the same chromosome but are loosely linked. The molecular markers linked with these genes, via marker-assisted selection, will facilitate development and deployment of resistant bean cultivars for better control of this disease in the U.S.A. and worldwide. This work addresses NP 301 (Plant Genetic Resources, Genomics and Genetic Improvement) Component 3, Genetic Improvement of Crops - Problem Statement 3A: Genetic Theory and Methods of Crop Improvement
5. Significant Activities that Support Special Target Populations