Study On Gene Mapping Of Soybean Resistance To Cyst Nematode Race 4

Soybean Cyst Nematode(SCN)is one of the devastating diseases in soybean production.Molecular marker linkage analysis was used to locate QTL for resistance to soybean cyst nematode and obtain linkage markers to lay the foundation for molecular marker-assisted selection of soybean cyst nematode resistant varieties.In this study,a recombinant inbred line population(RIL)derived from a cross between the disease-susceptible variety Jindou 28 and the disease-resistant variety Chibuliu black beans was used as test material for QTL analysis of disease resistance.The main findings are as follows:1.Genetic analysis of disease resistance in both parents and the RIL population using major gene + polygenic genetic segregation analysis showed that the optimal model for resistance to cyst nematodes was MX2-AI-AI,a mixed inheritance model with 2 pairs of additive-epistatic major genes + additive-epistatic polygenes.The additive effect of the 2 pairs of major genes was 13.1960 and 12.9956,respectively,and the epistatic effect of the major genes was 12.9731,with a master gene heritability of46.10% and a polygenic heritability of 52.62%.The genetic analysis of the soybean RIL population was carried out to determine the optimum model and grasp its inheritance pattern,providing a theoretical basis for selecting the progeny of this population for resistance to cyst nematodes in soybean.2.The RIL population and parents were amplified using 117 pairs of polymorphic SSR markers.QTL analysis of soybean resistance to Cyst nematode race 4 was performed using the compound interval mapping method in the software win QTLcart2.5.The results showed that in the RIL population,soybean resistance to cyst nematode race 4 was normally and continuously distributed,and a total of two QTL loci for resistance to cyst nematode race 4 were detected.qSCN4-1 was detected in 2019 within the interval AW132402-Satt089 of the A2 linkage group(Chr8),with an LOD value of 2.50,a contribution of 9.01% and an additive effectof-11.62.qSCN4-2 was located within the Satt309-Satt235 interval of the G linkage group(Chr18).qSCN4-2 was detected in both the 2019 and 2020 environments.The 2019 LOD value was 2.28,with a contribution of 8.32%and an additive effect of-11.26.where the 2020 LOD value was 4.71,with a contribution of11.01%,with an additive effect of-11.39.The results of this study provide a basis for the fine localization of the small species of soybean resistant to cyst nematode race 4.3.Whole-genome resequencing of each line and both parents of the RIL population resulted in the construction of a high-density Bin Map with a total genetic distance length of 3624.391 c M and an average genetic distance between markers of 0.692 c M.Based on 5239 bin markers localized to four QTL intervals,the explained phenotypic variation rate ranged from 5.08% to 6.63%,with an additive effect size of-8.60 to-9.84.Of these,qSCN4-3 was detected with a contribution of 5.47% and an additive effect of-9.03,located between chr08_bin2358 and chr08_bin2365 on chromosome 8.qSCN4-4 was detected with a contribution of 5.67% and an additive effect of-9.16,located between chr11_bin3545 and chr11_bin3551 on chromosomes 11.qSCN4-5was detected with a contribution of 6.63% and an additive effect of-9.84,located between chr18_bin5443 and chr18_bin5450 on chromosome 18.qSCN4-6 was detected with a contribution of 5.08% and an additive effect of-8.60,located between chr18_bin5450 and chr18_bin5453 on chromosome18.This study further narrowed the interval of QTL loci and laid the foundation for cyst nematode resistance studies in soybean.