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United States Department of Agriculture

Agricultural Research Service

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Research Project: Identification of Qtl for White Mold Resistance in Mesoamerican Beans

Location: Sunflower Research

2011 Annual Report


1a.Objectives (from AD-416)
The long term goals of this project are to develop pinto beans with enhanced levels of resistance to white mold.


1b.Approach (from AD-416)
The project is to phenotype a pinto bean RIL population for reaction to white mold over a multi-year period in field trials and greenhouse. The RIL population will be grown and evaluated in a 4-replicate white mold field nursery. The nursery, located at the Montcalm Research Farm in Entrican, Michigan, is naturally infested with high levels of Sclerotinia sclerotiorum, and is irrigated during and after flowering to further encourage disease development. The RILs will be planted in two row plots and will be flanked by two rows of a highly susceptible variety that serves as a spreader of the disease to further promote uniform white mold development. Resistance to white mold will be evaluated, along with yield under disease pressure, architecture, and agronomic desirability. Additionally, the RILs will be evaluated in the greenhouse for genetic resistance to white mold using the straw and oxalate tests. The QTL study will be to genotype the individual lines in the mapping populations and develop a molecular linkage map. The individual RILs of each population will be genotyped using available SSR, TRAP and SRAP markers. Upon completion of this genotyping step, mapping software will be employed to develop a linkage map for each population. Once a linkage map is obtained, QTL analysis software will be used to determine the location of QTL for white mold resistance in the mapping population, and the parent from which each QTL originated. In order to validate the potential of resistance QTL identified in this study a MAS study based on the same resistance QTL will be conducted under severe white mold pressure in a second pinto population during the final growing season. We will investigate the role of specific defense genes in conferring resistance to white mold in pinto bean and explore synteny of Phaseolus QTL with other legumes.


3.Progress Report

This project was initiated on July 1, 2010, research is ongoing, and the overall objective is to identify resistance genes important in plant defense responses of dry beans to Sclerotinia. ADODR monitoring activities to evaluate research progress included phone calls, meetings with the cooperator, and an annual meeting held each year in January.

We obtained a second season of evaluations for a second recombinant inbred line (RIL) pinto bean mapping population (AP647); developed from the cross of Michigan State University (MSU) pinto breeding line P02647 with pinto breeding line AN-37, reported to exhibit tolerance to white mold and released by USDA/ARS as USPT-WM-1. The population, consisting of 94 RILs, was evaluated in the field for reaction to white mold and data were also collected on other agronomic traits such as yield, maturity, height, lodging and seed size. The 96-entry test ranged in yield from 22.9 to 36.9 cwt/acre with a test mean of 29.1 cwt/acre and white mold ranged from 25 to 92% with a mean of 48%. The parental lines AN37 and P02647 yielded 27.4 to 30.2 respectively indicating transgressive segregation among progeny for yield under white mold pressure. The highest yielding entry P07720 exceeded the test mean by 26% in the 2010 trial. Greenhouse straw test scores in this population ranged from 1.5 to 7.0 with a mean of 3.71 (1-9 scale) and both greenhouse and field data will be used in QTL analysis. Microsatellite marker data revealed that 34 polymorphic markers associated with resistance from a full-sib population (AP630) are also segregating in this AP647 population, indicating that these markers can be used to validate the QTL from the first population and possibly be used in marker-assisted selection for resistance to white mold. Additionally, a new pinto bean line from the AP630 population, entry P07863 is being considered for variety release based on superior yield performance under white mold pressure. Over the past four years (2007-10) of testing under white mold pressure, this line exceeded the test mean by 21% and its performance and white mold resistance level is being confirmed in 2011 trials prior to release.


Last Modified: 9/21/2014
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