Improving Blast Resistance Of Parental Lines Of Drought Resistant Hybrids And Screening For Blast Resistance Resource In Rice

Rice blast is one of the most devastating diseases in cultivated rice. Identification of resistance resource and breeding of resistance cultivarhave have been considered as the most effective and economical strategy to control rice blast. Using backcrossing and marker assisted selection, blast resistance genes(Pi1, Pi2 and Pi9) were introgressed into four parental lines of drought resistant hybrid rice, i.e. HuhanlB as the maintainer, japonica variety Xiushui123, Hanhui No.3 and Xiangqing as the restorer. The improved lines can be used as candidate parental lines with blast resistance for breeding of water-saving and drought-resistance hybrid rice.A diverse panel of rice germplasm was used in this study, which mainly include diverse landraces or varieties from a putative mini-core collection of Chinese rice germplasm, along with some widely used parental lines in genetic analysis or breeding (a few from abroad). The population was evaluated for blast resistance in the three points. The major results were as follow:1. The blast resistant sources 75-1-127 and BL6 were crossed with four receptor parents, that is Huhan1B, Hanhui No.3, Xiangqing, Xiushui123. Their progenies carrying Pi1, Pi2 or Pi9 gene were backcrossed with recurrent parents. BC2F4 progenies were obtained by marker-assisted backcross breeding and marker survey, the progenies includes 51 BC2F4 plants harboring Pi1,84 BC2F4 plants harboring Pi2 and 76 BC2F4 plants harboring Pi9. Preliminary evaluation of the disease resistance was conducted at BC2F3 using in vitro leaves inoculation. The lines carrying one or two target genes showed medium resistance or high resistance. Their resistance to blast increased significantly in comparison with that of the recurrent parents and the lines without any target genes. One hundred and forty-five entries, including varieties and lines, were tested in the rice blast nursery in Fujian Province in 2010. The results also indicated that their resistance to blast increased significantly.2 According to the results of previous studies, synthesis of 9 primers was used for MAS detection. At least 2 makers per gene were used for assisted selection. Background SSR analysis showed that the recovery rate of the selected lines reached 82.1%-93.6%.3 A hundred and twenty accessions of rice germplasm including 109 accessions from putative mini-core collection of Chinese rice germplasm were tested in the rice blast nursery in Fujian Province and Guangxi Province. This set of germplasm was inoculated for neck blast using mixed rice blast strains in Hainan. Sixty-one SSR makers linking to blast resistance genes were used for dissecting the genetic variation. The results of cluster analysis preliminary divided the 120 germplasm into two parts:resistant and susceptible.