Improving The Resistance Of Rice Sterile Lines To Rice Blast Using Molecular Marker-assisted Selection

Rice is the most important cereal crop, which provides stable food for half of the global population. Rice blast disease, caused by fungal pathogen Magnaporthe grisea (Hebert) Barr, is one of the most serious diseases of rice worldwide. Pi-1, Pi~2 and Pi-9 are a wide- spectrum and dominant rice blast resistant genes. The objective of this study was to find new SSR markers linked to above-mentioned three genes on the basis of others' researches, and to introgress Pi-1, Pi-2 and Pi-9 gene from a donor parent LAC23 {Pi-1), 5173 (Pi-2) and 75-1-127 (Pi-9) into jin23B, jinshanB-1 and jinshanS-2, by marker-assisted selection. Main results are as follows:1. Using the published information of rice genome searched SSRs and 20 pairs of SSR primers were designed, in addition, 3 SSR markers that reported already amount to 23. Six pairs of SSR primers showing polymorphism between the receptor parent and donor parent were found. SSR markers MRG4766 and RM224, which were closely linked to the rice blast-resistant gene Pi-1 were obtained; SSR markers AP22, SRM22, SRM24 and SRM91, which were closely linked to the rice blast-resistant gene Pi-2 (Pi-9) were obtained.2. Pi-1, Pi-2 and Pi-9 genes were introgressed three receptor parents respectively by marker-assisted backcross breeding. It was respectively obtained which 48 near-isogenic lines of jin23B and test crossing sterile lines, 26 near-isogenic lines of jinshanB-1, 10 near-isogenic lines of jinshanS-2 carry Pi~1 gene, which 44 near-isogenic lines of jin23B and test crossing sterile lines, 14 near-isogenic lines of jinshanB-1, 9 near-isogenic lines of jinshanS-2 carry Pi-2 gene, which 26 near-isogenic lines of jin23B and test crossing sterile lines, 16 near-isogenic lines of jinshanB-1, 5 near-isogenic lines of jinshanS-2 carry Pi-9 gene. Near-isogenic lines carrying different resistinggenes were crossing respectively. Six individuals carrying Pi~l and Pi~9, seven individuals carrying Pi-1 and Pi-2were obtained respectively.3. Later generation of disease-resistant background (BC3) was selected to detect by using morphological traits, SSR markers and SRAP markers for comparing their difference in background selection. The study showed the result of morphological traits and SSR markers displayed unanimity; proving some quantitative character, traits of higher heritability can reflect the genetic variation of the close sample of the blood reason. The result SRAP was not in accordance with morphological traits and SSR markers. Therefore, it could be selected by morphological traits in backcross selection of low backcross generations. It could combine SSR markers to do backcross selection in high backcross generations (e.g.: BC3) because it was difficult to select only by morphological traits.