Project Number: 2090-21000-034-00-D
Project Type: In-House Appropriated
Start Date: Apr 22, 2018
End Date: Apr 21, 2023
Dry peas, lentils, and chickpeas are integral components of dryland agriculture systems throughout the U.S. and have served as globally important nutrition sources of protein, fiber, and minerals for millennia. These crops form symbiotic associations with rhizobacteria that results in biological nitrogen fixation that contributes to productivity and profitability of cropping systems. Peas, lentils, and chickpeas are typically sown in the spring, and the development of autumn sown legumes may provide alternatives to winter wheat. Diseases cause considerable losses in these crops every year and are primarily managed by the use of resistant varieties. However, resistance is lacking to several important diseases, including root rots caused by Aphanomyces and Fusarium, Ascochyta blight, Pythium seed rot, and Sclerotinia white mold. Improved understanding of fungicide resistance and mechanisms of pathogenicity and virulence will accelerate the development of effective and efficient practices for managing diseases of these crops. Over the next five years this research project has the following objectives. Objective 1: Develop and release improved germplasm and cultivars of peas, lentils, and chickpeas that have desirable agronomic traits coupled with enhancements in nutritional characteristics and the ability to form symbiotic effective relationships with nitrogen-fixing rhizobacteria. Subobjective 1A: Develop improved germplasm and cultivars of peas, lentils, and chickpeas that have enhanced field performance and nutritional quality. Subobjective 1B: Characterize factors that influence biological nitrogen fixation resulting from symbiosis between autumn sown pea and Rhizobium leguminosarum. Objective 2: Develop increased understanding of the population structure of selected pathogens, host resistance, and mechanisms of virulence and pathogenicity, and use the knowledge to improve integrated disease management practices and methods for identifying resistant plants. Subobjective 2A: Characterize fungicide resistant populations of Pythium ultimum and Ascochyta rabiei and develop management strategies for fungicide resistance. Subobjective 2B: Identify sources of resistance in pea, lentil, and chickpea to Fusarium root rot, Pythium seed rot, and Aphanomyces root rot, respectively. Subobjective 2C: Increase understanding of factors conditioning virulence and pathogenicity of Sclerotinia sclerotiorum. The advances resulting from these studies will provide comprehensive technology platforms for developing new and improved cultivars of cool season food legumes and effective integrated disease control strategies for these crops.
1A. Research Goal: Develop and release new cultivars of peas, lentils and chickpeas that have superior agronomic performance and nutritional qualities. Crossing blocks will be established for peas, lentils, and chickpeas. Families and lines will be selected for plant height, disease resistance, tolerance to lodging, early flowering, and seed traits. Remote sensing will be used to estimate canopy vigor of field plots. Correlations will be determined between remote sensing and ground truth data. Promising breeding lines will be released as either germplasm or cultivars. Molecular markers will be detected that are associated with disease resistance and desirable seed nutritional qualities. If desirable traits such as disease resistance are linked to undesirable commercial traits then large population sizes and backcross breeding approaches may be necessary to introduce traits into adapted backgrounds. 1B. Hypothesis: Biological nitrogen fixation in elite winter pea genotypes is conditioned by effects of plant genotype, genotype of the Rhizobium leguminosarum strain, the environment, and interaction effects between these sources of variance. Tests will be performed in growth chambers to evaluate plant and rhizobia genotype effects on biological nitrogen (N) fixation. 15N/14N ratios will be estimated from ground pea tissues to determine %Ndfa. Winter pea lines will be tested in the field for ability to be colonized by endemic rhizobacteria. Plots will be mechanically harvested and the contribution of biological nitrogen fixation to total seed N will be determined. If results based on field studies do not support growth chamber results, the growth chamber conditions will be changed to better reflect field conditions. 2A. Hypothesis: Characterizing and understanding fungicide-resistant pathogen populations will improve efficacy of management of fungicide resistance. The stability of metalaxyl resistance (MR) in MR isolates of Pythium ultimum will be determined, as will the fitness of MR isolates of the pathogen. Microsatelllite DNA markers will be used to survey genetic variation in P. ultimum. Isolates of Ascochyta rabiei will be evaluated for sensitivity to Qol fungicides. 2B. Research Goal: Improve resistance to Pythium seed rot in chickpea and Aphanomyces root rot in lentil. The chickpea single plant core collection will be tested for resistance to Pythium seed rot using a recently developed growth chamber assay. More than 300 accessions from the National Plant Germplasm System (NPGS) lentil core collection will be evaluated for resistance to Aphanomyces root rot using a greenhouse screening assay. Sources of resistance in lentil to Aphanomyces root rot may only be detected in the secondary gene pool. 2C. Research Goal: Increase our understanding of virulence mechanisms of Sclerotinia sclerotiorum by investigating and validating roles of pathogenicity effectors of the pathogen. Seventeen mRNA transcripts of the fungus will be targets of gene-knockout (KO) experiments and the virulence of the KO mutants will be determined. Yeast two-hybrid systems will be used to identify host receptors targeted by pathogen effectors.