| This research lead to the identification and confirmation of quantitative trait loci (QTL) associated with root rot and bacterial brown spot, two important diseases of snap beans (Phaseolus vulgaris L.). The source of resistance to root rot and bacterial brown spot was the Mexican landrace, 'Puebla 152'. A recombinant inbred line (RIL), and inbred backcross (IBC) populations were developed using Puebla 152 as a donor to identify and identify and confirm QTL.; A major QTL for root rot resistance tightly linked AD09.950 and S18.1500 RAPD markers was identified, and later confirmed using field based for marker assisted selection. The QTL explained 25--49% of the variability for root rot severity and plant biomass. Greenhouse experiments indicated that root rot resistance observed over three years of field evaluation corresponded to variation in severity caused by Aphanomyces euteiches f.sp. phaseoli.; The same RIL population was used to identify four linkage groups associated with bacterial brown spot resistance; the importance of linkage groups B1 and B6 was confirmed using a closely related inbred backcross population.; Results of these studies are important to the development of programs to genetically improve snap beans for root rot and bacterial brown spot resistance. |
