Study of resistant genes and distribution of cowpea aphid (Aphis craccivora Koch.) resistance in yardlong bean and cowpea

Abstract

Genetic analysis of resistance to cowpea aphid (Aphis craccivora koch) in four crosses of yardlong bean and cowpea was studied. Six generations including P1, P2, F1, F2, BC1 and BC2 from each cross were evaluated in a Randomized Complete Block Design under a screenhouse condition at Plant Science Department, Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Songkhla from February to May 2007. Five apterous adult aphids were released on each plant at 3 weeks after seed emergence and the visual damage was scored. The results showed that the distribution of damage rating score of F1 and BC2 were close to the resistant parent in all crosses. However in F2 and BC1 the number of resistant and susceptible progenies which fit 3 : 1 and 1 : 1 ratios, respectively was only found in selected-PSU x IT82E - 16 cross. This indicates that resistance to cowpea aphid in IT82E - 16 is controlled by a single dominant gene. In other crosses, the inheritance to cowpea aphid was found to be more complex.