Resistance to White Mold in Dry Bean
February 21, 2007

Research Objectives: The objectives of this research are to identify new sources of resistance to white mold and to incorporate that genetic resistance into the breeding program.

Research Method: In previous work, potential new sources of resistance to white mold were identified in dry bean lines from
Mexico, Central America, and South America.  Those lines were crossed with a susceptible cultivar adapted to this region (Othello) and progeny of these crosses were developed into recombinant inbred (RI) populations that would segregate for reaction to white mold.  Those populations were analyzed in the greenhouse and in the field to identify parents for the breeding program.  Several RI lines with good resistance to white mold and adequate seed coat characteristics were identified.  These were crossed to cultivars such as Maverick, Matterhorn, Condor, and others, as a mechanism to combine genetic resistance with excellent agronomic characteristics.

In this work, progeny of these crosses were developed into F2 populations in the greenhouse.  F2 progeny were evaluated in the greenhouse for resistance to white mold.  Those experiments were based on the straw test, the best way to evaluate white mold reaction in the greenhouse.  Plants were evaluated on a scale of 1 (no disease) to 9 (dead plant) several days after inoculation.

Results:   Five F2 populations were developed.  To date, approximately 30 F2 individuals from each population (150 total) have been evaluated in the greenhouse.  The majority of F2 progeny in each cross showed intermediate to high levels of susceptibility.  Plant death resulting from severe white mold infection was common.  However, each population had at least a few progeny that showed resistance to white mold that was superior to the susceptible parental variety.  Those plants were allowed to advance to the F3 generation.  Analysis of additional F2 progeny is underway.  The experiments suggest that genetic resistance to white mold is controlled by multiple genes but is heritable. 





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