Inheritance of resistance to the soybean looper in soybean.
This study was conducted to determine the inheritance of resistance to the soybean looper (Pseudoplusia includens [Chrysodeixis includens]) in soyabean. The insect-resistant breeding line D86-3429 and the more susceptible cultivar Braxton were crossed to produce F1, F2, backcross and selfed-backcross generations. Defoliation occurring in 0.068-ha field cages at Stoneville, Mississippi, USA in 1990 and 1991 from insect releases was estimated by the whole plant visual rating method in 1990 and the partitioned plant average visual method in 1991. The data from the preliminary study in 1990 showed a trend towards quantitative inheritance, therefore the 1991 data were analysed quantitatively. Mather's scaling test was applied to the data generated from each of two cages, and the results indicated that generation means depend only on additive gene effects. Utilizing Hayman's methodology in the generation means analysis, an epistatic effect was suggested, but the primary effect is assumed to be additive as was indicated in the scaling test. Estimates of gene numbers indicate that the two parents differed by two genes for resistance to soybean looper. Heritability for resistance was estimated to be 63%, indicating that a breeder should be able to make progress by selecting in the F2 or F3 generations.