Research On Mapping And Molecular Marker-assisted Selection Of Sorghum Aphid Resistance Gene

Sorghum is one of the most important forage and energy crop, ranking fifth in acreage among the cereals in the world. The sorghum aphid is a key pest to sorghum and other cereals,causing great losses directly and indirectly. Practice shows that resistance breeding and its use are the most effective and economical method. In the process of resistance breeding, it can shorten the breeding period and reduce the heavy workload,finally achieve the aim of improvement in the breeding efficiency,if the molecular markers linked to traits about anti-aphid can be used in molecular marker-assisted selection breeding.It will be important meaning to sorghum and the other crops which damaged seriously by aphid theoretically and practically.This experiment studied the inheritance of the resistance to sorghum aphid with the F2,BC1,F2:3 population of the cross between QS and HN16 and defined the AFLP genetic linkage map of sorghum which had been built used the F2 population with the SSR markers, also located the aphid resistance gene. At the same time,the AFLP marker most tightly linked to the resistance gene was transformed into stable performance and easily operated SCAR marker. The SCAR markers and AFLP markers were used to detect different separation groups. That provided a theoretical basis for the use of molecular marker-assisted selection technology to sorghum aphid resistance breeding .1. A molecular genetic map for sorghum was constructed based on AFLPs (Amplified Fragment Length Polymorphism) markers and SSR markers using DNA samples extracted from 100 F2 popμlation which derived from the cross between QS and HN16.The high dense linkage map constructed by Mapmaker3.0 software,which consisted of 13 linkage groups,9 SSR markers and 109 AFLP markers. It covered 991 cM of sorghum genome, with the average interval of 8.39 cM.2. Locating the aphid resistance gene. Two AFLP markers most tightly linked to the resistant gene were E61/M4-475 and E61/M50-390.They were identified on linkage group 1,with the estimated genetic distance of 6 cM and 10 cM. Then transforming E61/M50-390 into stable and easier SCAR marker,named SCA50.3. SCA50 marker was used to detect the F2,BC1,F2:3 population. The selective efficiency of BC1 population is 86.8 %, F2 populations'is 91.1 % and F2:3 populations'is 86.3 %,the average is 88.2 %, that had reached a high selective efficiency. AFLP markers were used to detect the F2 population. The selective efficiency of E61/M54-475 is 87.7 %, E61/M50-390'is 89.7 %. E61/M54-475 and SCA50 were used to select together, the selective efficiency achieved to 95.9 %, the efficiency is obviously higher than one marker.