Association Between Leaf Pubescence Status And Resistance To Globular Stink Bug And Mapping Pubescence Gene In Soybean

Insect resistance of crop is often related to crop morphology, and the looking for suitable living environment and food of insects is often based on the feeling toward plant. Soybean [Glycine max (L.) Merr.] accessions with prostrate leaf blade pubescence show higher resistance than those with erect leaf blade pubescence. Classic genetics indicates that the trait of leaf blade pubescence status is controlled by several genes, however its phenotype also shows quantitative trait character which is easily affected by genotype, growing stage and environment conditions.Globular stink bug (GSB) [Megacota cribraria (Fabricius)] can cause great damage to yield and quality of soybean. And it is the main pest in eastern coast of China in recent 20 years, showing increasing damage tendency. Breeding resistant varieties is an important measure to reduce the soybean loss caused by M. cribraria. Revealing genetic variation and exploring resistant genes in soybean varieties are priorities in the work of soybean insect-resistant breeding.In this study, the researchers investigated the association between soybean leaf pubescence status and M. cribraria resistance of varieties, and compared leaf blade pubescence status with leaf petiole pubescence status to find out which association is more closely with M. cribraria resistance by using 400 varieties from 24 provinces of China. Furthermore, a gene controlling leaf blade pubescence status was verified and mapped by using recombinant inbred lines and high generation inbred separation lines.The main results of this experiment are listed as follows:(1) The coefficients of variation of leaf pubescence status and the resistance to M. cribraria were large in the selected soybean germplasm, and the relationship between varieties for GSB resistance and leaf pubescence status were detected to be significant correlation. There were more high resistant accessions and less high susceptible accessions in Southern China eco-region (including Middle and lower changjiang valleys, Central-south, Southwest plateau and Southwest trophic eco-regions) than that in Northeast China and HuangHuaiHai valleys in China, indicating resistance to M. cribraria in soybean being related with the geographic sources.(2) Significant correlations were detected between leaf pubescence status and geographic sources damage rate. The correlation between resistance levels of varieties to M. cribraria and leaf pubescence status had also reached a significant level. Prostrate leaf pubescence was resistant, erect leaf pubescence was susceptible to GBS in field. Compare leaf blade pubescence status with leaf petiole pubescence status, leaf blade pubescence status showed a more significant correlation with M. cribraria resistant of soybean.(3) There were 85 lines with erect leaf blade pubescence and 91 lines with prostrate leaf blade pubescence in recombined inbred lines (NJRISX). It fitted the expected genotype segregation ratio of 1:1. According to the linkage analysis between the genotype (including 218 SSR markers and 3 morphological markers) and pheonotype informations, the gene cotrolling leaf blade pubescence was located at the end part of H linkage group,36.6 cM away from SSR marker Satt317.(4) Some high generation inbred seperation lines were constructed. The population is selected from the lines derived from the cross of two soybean varieties T and A. Firstly, four single plants with heterozygous marker genotypes at the targeted genome regions were selected, and other genome regions of these plants remained homozygous. By subsequently genotypic and field phenotypic investigation, seven different heterozygous lines of the leaf blade pubescence status were developed. The pooled lines contained 353 plants, in which 252 plants showed dominant phenotype (prostrate leaf blade pubescence) and 101 plants showed recessive phenotype (erect leaf blade pubescence). The phenotype segregation pattern fitted 3:1 expected ratio. Based on the 1:1 genotype segregation ratio of recombined inbred lines (NJRISX), the conclusion that this character was controlled by a single major gene was verified. Using the high generation inbred seperation lines and 9 SSR markers to fine map the targeted gene, the result showed the targeted gene was tightly linked with two SSR markers Satt434 and 12-1364a, and located the gene around the marker Satt434 about 4.6 cM.