Mapping Of QTLs And Breeding Intrgression Lines Resistance To Sheath Blight In Rice

Sheath blight,caused by Rhizoctonia solani ,is one of the most important disease of rice, so far there is little advance in breeding rice varities resistance to this desease.The QTLs for resistance to sheath blight were detected using the reciprocal introgression line (IL) populations derived from the cross of Lemont/Teqing. Moreover, lines resistant to sheath blight were selected by successive artificial inoculation from BC2F2 to BC2F5 populations, which developed from 2 recurrent parents (Minghui86 and Shuhui527) and 3 donors (Teqing, Jiangxisimiao and Mengguandamagu), and QTLs resistance to R. solani were analyzed byχ2-test among these 6 introgressed line populations.The main results were listed as following:1. Genetic background and environmental significantly affect the expression of QTLs resistance to sheath blight.6 and 9main-effect QTLs were deteced in Teqing-ILs and Lemont-ILs respectively. Only two QTLs among them, Qsb4 and Qsb8a, were both detected in the reciprocal ILs, indicating that QTLs for sheath blight resistance were affected by genetic background. 6 main-effect QTLs were detected in successive two years in Teqing-ILs, whereas, no QTL was expressed in the two years in Lemont-ILs.2. A total of 60 significent loci were detected in the above selected BC populations. Qsb6a and Qsb6b could be detected in Shuhui527-ILs with 3 different donors, Qsb7a and Qsb7b could be detected in Minghui86-ILs with 3 different donors. 2 QTLs could be detected in populations with different recurrent parents, further suggesting that genetic background had significant effect on QTLs for sheath blight resistance.3. 152 homozygous ILs with stable resistance have been selected from 6 back-cross (BC) populations developed from 2 recurrent parents Minghui86 and Shuhui527 by artificial inoculation. The resistant ILs were classified into 9 types (T1-T9) based on their sheath blight resistance and relative yield performance to the recurrent parent. 6 elite lines carrying 1-5 QTLs resistance to sheath blight were selected based on sheath blight resistance and grain yield. The sheath blight resistance and yield after inocuation of these lines have been significantly improved, but there were no significant difference in normal condition.These elite lines will be useful materials for rice breeding program.