New genomic regions associated with white mold resistance in dry bean using a MAGIC population

Authors: ESCOBAR, EDGAR - North Dakota State University; OLADZAD, ATENA - North Dakota State University; SIMONS, KRISTIN - North Dakota State University; Miklas, Phillip - Phil; LEE, RIAN - North Dakota State University; SCHRODER, STEPHAN - Hazera Genetics, Ltd; BANDILLO, NONOY - North Dakota State University; WUNSCH, MICHAEL - North Dakota State University; MCCLEAN, PHIL - North Dakota State University; OSORNO, JUAN - North Dakota State University

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2021
Publication Date: 2/2/2022
Citation: Escobar, E., Oladzad, A., Simons, K., Miklas, P.N., Lee, R., Schroder, S., Bandillo, N., Wunsch, M., McClean, P., Osorno, J. 2022. New genomic regions associated with white mold resistance in dry bean using a MAGIC population. The Plant Genome. 15(1). Article e20190. https://doi.org/10.1002/tpg2.20190.
DOI: https://doi.org/10.1002/tpg2.20190

Interpretive Summary: Pinto beans are the most widely grown dry bean in the U.S. The major limiting production constraint is white mold disease which can cause complete crop loss. Researchers and breeders continue to search for sources of resistance to white mold, and then once found combine these sources in hopes of generating porgeny lines with improved resistance. This study reports the result of combining the resistance from eight pinto beans into a MAGIC population. MAGIC is a fancy abbreviation for a population developed by intermating among mulitple parents. Genetic recombination in such a population can lead to enhanced germplasm lines, in this particular case with improved resistance to white mold. A MAGIC population is also often used to discover new genes that condition a quantiative trait, such as resistance to white mold. In this particular case, the MAGIC population developed, generated 15 pinto lines with improved resistance to white mold and discovered four novel genes which influenced resistance. These materials and information generated will be useful to breeders in their pursuit of developing pinto beans with imoroved resistance to white mold disease.

Technical Abstract: Dry bean (Phaseolus vulgaris L.) is one of the most important grain legume crops cultivated around the world. For many temperature regions, dry bean production is threatened by white mold disease caused by the fungal pathogen Sclerotinia sclerotiorum, as complete yield loss can occur under cool moist conditions favorable for the pathogen. The low heritability, polygenic inheritance, and cumbersome screening protocols make it difficult to breed for improved genetic resistance to combat white mold. Our objectives were to develop pinto bean germplasm with improved resistance to white mold and to identify genetic factors associated with the resistance. A MAGIC population was developed to facilitate breeding improvements for white mold resistance. A seedling straw test method provided a quick protocol to phenotype the population for response to white mold (isolate 1980), and an optimized GBS protocol was used to sequence the population. Nineteen MAGIC lines (15 pinto and 4 great northern) were identified with improved resistance when compared to the parents of the population. For GWAS, we transformed the data into three phenotypic distributions: quantitative, polynomial, and binomial. These phenotypic distributions revealed four new novel genomic regions and validated two previously reported. Cumulative R2 values were 57% for binomial distribution using 13 genomic intervals, 41% for polynomial using eight intervals, and 40% for quantitative using 11 intervals. We also confirmed the equal contribution of each parent in the offspring. This research provides new resistant germplasm for breeders and the localization of new genomic regions associated with resistance for further investigation.