Resistance Against Fusarium Root Rot of Dry Beans
February 21, 2007

Research Objectives:  The objectives of this research project are to (1) identify new sources of genetic resistance to root rot, (2) determine the genetics of the resistance in segregating populations, and (3) facilitate the introgression of the genetic resistance into the NDSU dry bean breeding program.

Research Method: Previous research supported by Northarvest helped us develop a reliable greenhouse and laboratory test for dry bean root rot.  We used that procedure to assess disease resistance/susceptibility in eleven dry bean cultivars representing different market classes.  This research also suggested that the dry bean line known as Vax 3 had the least root rot severity rating when tested under field and greenhouse conditions and may be of value to the breeding program.

To understand the mode of inheritance and the number of genes controlling the trait for Fusarium root rot resistance, populations were developed from genetic crosses between Vax 3, a small red bean, and Red Hawk, a dark red kidney bean highly susceptible to root rot.  Progeny of the crosses were evaluated for disease reactions in the greenhouse and in the laboratory for resistance to root rot using a procedure known as the sand-cornmeal-inoculum layer method.  This inoculation method was selected based on its positive correlations between greenhouse and laboratory experiments with the field results.  Progeny of crosses were advanced to the F3 generation in the greenhouse to facilitate additional genetic studies and to develop the progeny into recombinant inbred populations that can be used by the breeding program.

Results:  Eighty F1 generation seedlings were tested for their response to Fusarium root rot in replicated trials over time.  All F1 progeny were found to be resistant, suggesting that root rot resistance in Vax 3 is conditioned by one or more dominant genes.

Currently F2, and F3 generation is being tested for its resistance to Fusarium root rot, while F4, F5, and F6 generations are being developed into recombinant inbred populations.  The data that will be obtained from these tests will help determine the segregation ratio and if there is a single gene or more than one gene responsible for resistance.

The knowledge of gene(s) controlling resistance will help in the breeding programs that aim to develop Fusarium root rot resistant cultivars.




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