Inheritance Of Resistance Of Soybean To Leaf-feeding Insects And Mapping Of Related Genes With SSR Markers

One objective of this study was to determine the inheritances of resistance to leaf-feeding insects in the field and that to cotton worm (Prodenia lintra, Fabricius) in the net room. Recombinant inbred populations of 139 F2-derived lines from the cross of N20226 and N3039 was used. In the field, the plants were evaluated for the amount of defoliation .The result indicated a two major genes plus polygene mixed inheritance model for insect resistance. At early damage stage, there were two major gene and polygene functioning together or only two major genes working, later both major gene and polygene played their roles again. The heritability values of major genes were about 69.68%, greater than those of polygenes that were only 7.17%. The RIL populations were planted in the net room and leaves from each line were picked. Cotton worm larvae were reared on individual lines of the RIL populations and several larval traits were examined. Analysis of mean weight of surviving larvae indicated that two major genes and polygenes controlled the inheritances. The heritability of two major genes was about 51.19%, thus major genes played the key role for resistance. Analyses of mean pupae weight and length of larval developmental duration demonstrated the similar result, however the heritability of polygenes with about 48.54% was greater than the major genes.Another objective of this study was to determine quantitative trait loci (QTLs) associated with the soybean insect resistance (SIR) by estimating linkage to simple sequence repeat (SSR) markers. The same recombinant inbred (RIL) population from the cross of N20226 and N3039 was tested. Eggs or larvae of cotton worm were obtained from the soybean field. Larval weight, larval stage and pupal weight were examined in as index of resistance. Data recorded were larval weight at 10d; pupal weight at 3d after pupation; number of days to reach pupal. Using the intergrated genetic linkage map of soybean (Cregan et al. 1999), we chose 103 SSR markers scattering on 8 linkage groups (LGs) that had the potential to map SIR QTL to be screened between N20226 and N3039. It was found that 18 SSR showed polymorphic DNA bands between these lines. With t-test analysis and one-way analysis of variance, five markers (Satt363, Satt135, Satt311, Satt574, Satt434) were found linked with these traits situating on three LGs, i.e. D2, C2, and H. Theindividual effect of each QTL was reported as R2 value. The effect was about 2.89%-9.73%.