Study On Cotton Verticillium Wilt Resistance By Molecular Marker Tchnology

A Upland cotton RILs created by crossing between chang kang cotton and TM-1, using SSR marker technology to construct an Upland cotton genetic map and search verticillium wilt QTLs in Upland cotton. In order to improve the accuracy of array, this study selected common breeding field and disease nursery as different environmental conditions to identify cotton disease index against verticillium wilt and every test environment includes 3 repeat experiment. The results showed that disease index from common breeding field belongs normal distribution, but data from disease nursery are segregation, the reason is that seeding or plants always died in nursery. Befor using these data we have to adjust them.This study selected 8454 pairs SSR primers to screen parents'molecular genetic polymorphism, however the difference between the paternal plant and the femal plant was not significant. The polymorphism rate was only 1.43%. In order to improve the molecular markers polymorphism efficiency in cotton verticillium wilt research, we searched the gen bank and got 24 verticillium wilt resistance gene sequences, then designed 12 pairs resistance-related SSR primers, they were used to analysis molecular markers polymorphism, 3 pairs of primers among them showed polymorphism.Using RILs as mapping population to construct genetic linkage map, we got a map constituted by 10 linkage groups, this map contains 85 markers, its length is 619.5cM, the average distance between two markers is 0.8~11.52cM. the numbers of markers on each lingkage group are 3~14. In order to construct high-density genetic map, we tried to integrated this map with another genetic lingkage map that generated by F2 population from crossing between chang kang cotton×TM-1. The integrated map includes 10 lingkage groups, length is 661.1cM, total markers are 95.After constructing a high density genetic lingkage map, we operated Single interval mapping and Composite interval mapping analysis by software WinQTLCart2.5. When the LOD value was set to 6, 6 Upland cotton QTLs can been detected. There were 2 QTLs that have the largest heredity contribution rate, they wre located on sixth lingkage group and heredity contribution was 37.51%,47.25% respectively.This study also aimed at improving the selective efficiency in upland cotton Verticillium wilt resistance breeding. The molecular marker assisted selection is the main technology during this study.18 SSR markers related to Verticillium wilt resisitance have been chosen. Among them, 3 markers present remarkable differential disease index between markered and non-markered genotypes, they are BNL1721,BNL2733 and BNL3452. Research showed that the selective effect could be stably transmitted in different generations comparing single marker and multiple markers' assisted efficiency, the effective combination of different markers is for the best . The technology of MAS could be used to improve efficiency and speed up the pace in cotton resistance breeding.