Genetic resistance to Phoma medicaginis in pea
2008
McPhee, K., USDA-ARS, Pullman, WA (USA) | Wang, X., Washington State University, Pullman, WA (USA). Crop and Soil Science Department
Phoma medicaginis var. pinodella causes a blackening on stems near the soil surface and has been referred to as black stem rot or Phoma foot rot. Genetic resistance to P. medicaginis is available in Pisum germplasm, however resistance has been incorporated into few modern cultivars. A detached leaf assay was used in our laboratory to identify variation for resistance to P. medicaginis var. pinodella. Thirty-five registered cultivars and breeding lines were evaluated for disease development. Significant differences in lesion expansion were observed and ranged from 2.6 to 173.1 mm2 9 days after inoculation. These results indicated that genetic resistance is present in available germplasm. Parents of several recombinant inbred line mapping populations were included in the germplasm screen and Shawnee and Bohatyr, the parents of PRIL-12 developed susceptible and resistant reactions, respectively. Area under the disease progress curve (AUDPC) was also calculated and used for QTL analysis. A genetic map of PRIL 12 was developed and comprises 8 linkage groups (LG) and aligns with the consensus Pisum map. Results from this QTL analysis require cross validation in additional mapping populations; however, the presence of a single strong QTL indicates that resistance should be highly heritable and genetic gain from selection is possible.
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