Date of this Version
An efficient screening method was developed and used to identify bean lines resistant to Rhizoctonia Root Rot caused by Rhizoctonia solani Kuhn. Two sets of 163 and 111 lines previously evaluated for drought tolerance at Mitchell, NE and Isabela, PR were evaluated for Rhizoctonia Root Rot resistance under greenhouse conditions. This root rot data was also correlated with yield under drought stress and non stress conditions. In the first set of lines the rhizoctonia mean score ranged from 1.7 to 3.9; and in the second set the rhizoctonia mean score was between 2.6 and 5.7. There was no significant correlation between drought tolerance and Rhizoctonia Root Rot resistance, but there were drought tolerant lines that also had Rhizoctonia Root Rot resistance. Lines with both traits can be used as parents in breeding programs looking for improvement of both drought tolerance and Rhizoctonia Root Rot resistance in dry beans.
A new source of resistance of Common Bean Rust from the tertiary gene pool of common beans was mapped. Two linkage maps from RILs of a reciprocal interspecific cross between Phaseolus acutifolius (G40022) and Phaseolus parvifolius (G40186) (AP and PA RIL population) were constructed. A total cumulative map length for the AP population was 746 cM, with an average chromosome length of 62.2 cM and an average distance between markers of 11.3 cM. In the PA RIL population, the total cumulative map length was 920.8 cM, with an average chromosome length of 61.4 cM; and the average distance between markers distributed in this map was 11.3 cM. The QTL analyses revealed a putative QTL located on the linkage group LG5 of the AP RIL population was located at 67.7 cM, and it had a LOD 20.1. More molecular markers are needed to saturate the map and be able to identify a marker at least at 5 cM from the QTL.