1a. Objectives (from AD-416):
To screen the USDA Core Collection of common bean (Phaseolus vulgaris L.) for resistance to halo blight (Pseudomonas syringae pv. phaseolicola) for US bean improvement.
1b. Approach (from AD-416):
The USDA-NPGS bean core collection will be screened in the greenhouse for resistance to halo blight. We will use race 6 and race 2, the two most predominant races of the pathogen in U.S. in the screening experiment. Priority will be given to those accessions reported as insensitive to photoperiod by Urrea and Porch (2010) which is a set of 300 accessions approximately. If none of the accessions in this subset is resistant, then the rest of the core collection will be evaluated. The core will be initially screened using race 6 isolates of halo blight collected from ND which have been shown to be highly virulent on dry beans. We will use the seedling screening method specified by the Bean Improvement Cooperative (http://www.css.msu.edu/bic/PDF/Halo_Blight.pdf) for resistance evaluation. Basically, seedlings with fully expanded primary leaves will be inoculated and rated on a 1-5 rating scale after disease development. At least two plants and two leaves per plant will be evaluated and experiment be repeated a minimum of two times. Accessions showing high resistance to race 6 will be screened again with a mixture of race 2 and 6 to confirm results and check the reaction to the second race detected in the state.
3. Progress Report:
We received 383 accessions that are part of the bean core collection were from ARS common bean germplasm curator at the Western Regional Plant Introduction Station (WRPIS) in Pullman, WA. Since only 20 seeds per accession were received, we are increasing the seeds for replicated screening for resistance to halo blight in the future. Four seeds from each accession was replicated and resulted in a total of 1,532 plants in the greenhouse now. The plants were trimmed at an interval of every two days and watered daily. Once they reached maturity, seeds were harvested on a daily basis until all seeds were collected. A PhD graduate student in the Department of Plant Sciences, NDSU, Fargo, ND, is in charge of this project, which will be a part of his dissertation research. Up to date, we have harvested only 283 of the total 383 accessions which flowered and produced seeds. The remaining entries are presumably photoperiod sensitive and will never flower in our greenhouse. We will use the original seeds of these accessions for our replicated experiment. Evaluation of germplasm for disease resistance is an important component of germplasm curatorial programs at the WRPIS. This project will generate information on the reaction of the 383 common bean germplasm accessions to halo blight inoculation. The results will be uploaded to the GRIN (Genetic Resource Information Network) database. Researchers and breeders worldwide can access the database to select desirable accessions to be used in their research breeding program. This progress is related to objective 3 of the parent project: Strategically characterize (“genotype”) and evaluate (“phenotype”) crop core subsets and other priority germplasm for molecular markers, morphological descriptors, and key agronomic or horticultural traits, such as general adaptation, phenology, and growth potential.