Improvement Of The Bacterial Blight Resistance And Foundation Of Near-Isogenic Lines Of Huahui1035

Rice bacterial blight (BB) is one of the three major diseases in rice production in China. It can threaten the rice production, yield stability and quality in epidemic years. BB seriously affects rice production in Asia, especially hybrid rice, because most parents have not resistant genes. Cultivating varieties with bacterial blight resistant genes from rice oneself is the most effective way for preventing this disease. Molecular marker-assisted selection (MAS) has become a mature and efficient method for improving the disease resistance in crop genetics and breeding in recent years.The objective of this study was to improve the BB resistance of Huahui1035 by MAS and backcrossing methods, which was an elite restorer line of hybrid rice. Four resistant genes, Xa7, Xa21, Xa22,Xa23 were used as target genes. The main results are as following:1. We have introgressed Xa7, Xa21, Xa22, Xa23 into Huahui1035 through MAS and backcrossing methods, and ten near-isogenic lines(NILs) containing single gene Xa7, Xa21, Xa22, Xa23 or double genes (Xa7,Xa21) were obtained whose phenotype was similar to original Huahui1035.2. Three Xoo strains, PXO61, PXO99 and ZHE173, were used for identifying BB resistance of Huahui1035 and derived 10 NILs and donor parents in the field. The results showed that the resistant levels of the lines containing Xa21, Xa7, Xa23 were significantly higher than HuaHuil035. But the resistant levels of the lines containing Xa22 were similar to Huahui1035.3. Two Xoo strains from Southern China, IV and V types, were used for identifying the BB resistance of 11 F1 hybrids from above devived or original Huahuil035 lines and three-line CMS Jinke1A. The results showed that the resistant levels to BB were improved significantly, except for the lines containing Xa22.4. Nine representative strains from China were inoculated in 10 devived lines, receptor and donor parents. The results of resistance spectrum analysis showed that the HBQ810 line containing Xa23 had a broad spectrum, which was resistant to eight bacterial strains except for HN11 strain.5. The results of combining ability analysis showed that the main agronomic traits of improved lines were similar to HuaHui 1035. General combining ability effect of HBQ807 was maximum in valid panicle, yield per plant and grains per panicle, and its variance of effect of specific combining ability was maximum. General combining ability effect of HBQ803 was maximum in seed setting rate and 1000-grain weight; variance of effect of specific combining ability of HBQ808 was maximum in yield per plant.6. Through the heterosis analysis, we have screened out four superior hybrids, Jinkel A/HBQ806, Hua201S/HBQ801,Hua201S/HBQ805, and Hua201S/ HBQ- 808. The competitive yield heterosis values over CK hybrid IIyou838, were 11.69%, 16.01%, 10.03% and 42.16%, respectively, but their growth period was longer 2-6 days than CK. Two combinations have been selected for following small-scale propagation of hybrid.