| Rice (Oryza sativa L.) is one of the important monocotyledonous crops in the world, and provides the staple food for more than half of the world’s population. Rice blast, caused by Magnaporthe grisea (Hebert) Barr, is one of the most widespread and destructive diseases of rice. To breed and grow resistant-blast cultivars is the most effective and economical way for controlling this disease in rice production.1. The japonica rice landraces in Taihu lake area in China is the special genetic resource in China as this region has a long history of rice-growing. In usual rice landraces have broad-spectrum resistance to rice blast because of the coevolution between the host and pathogen. This study aims at exploration of blast-resistance of japonica landrace Bodao in Taihu lake area and identification of resistance loci by SSR molecular markers to serve rice blast-resistance breeding in delta of Yangtze River.2. Fifty-one Chinese rice blast isolates collected in Jiangsu, Hunan and Guangdong provinces in China, and two Japanese isolates were inoculated in japonica landrace Bodao to identify its resistance spectrum to the blast. The results showed that Bodao is highly resistant to forty-six isolates with the lesion score 0, and moderately resistant to other five isolates. It further proved that the landrace Bodao is a broad-spectrum and highly resistant-blast resourceg.3. One population of recombinant inbred lines (RILs) consisting of 155 lines were obtained by SSD method from the cross of Bodao (resistant)×Suyunuo (susceptible).30 lines randomly selected from RILs population were inoculated with 53 isolates including 51 Chinese and 2 Japanese as well their arents in the primary experiment. Based on the result of primary experiment 13 isolates with obviously different virulence, are selected for further researching. Genetic model of rice blast resistance is analyzed based on the lesion scores by using major gene-polygene mixed inheritance models and joint analysis of P1, P2, F2:8. It was found that rice-blast resistance of Bodao is controlled by two or more major genes. The resistance to the blast has significant major gene effect, indicating that major gene’s effect as well polygene’s effect might be responsible for blast resistance.4.1,687 pairs of SSR markers were used to be amplified polymorphisms between the two parents.159 SSR markers with polymorphisms between the two parents were used for constructing the linkage map, with a total distance of 1,716.7 cM and an average distance of about 10.8 cM between every two markers, covering the whole rice genome according to the information from the International Rice Microsatellite Initiative (IRMI). The different reactions of RILs corresponding to 13 isolates are used for QTL analysis. According to the average disease score of each line,13 QTLs, distributing on chromosome 1,2,9,11 and 12, are detected corresponding to 13 isolates. According to the average lesion sixe of each line, 7 QTLs, distributing on chromosome 1,2,7,11 and 12, are detected corresponding to 13 isolates. According to the average lesion number of each line,8 QTLs, distributing on chromosome 1,4,8 and 11, are detected corresponding to 13 isolates. More interestingly, QTLs detected on chromosome 11 are conferring 13 isolates. It is deduced that a resistance gene cluster on chromosome 11 was existed in Bodao. Most of the resistance QTLs detected in this research was near located resistance QTLs or cloned resistance genes in previous research, a new QTL site was detected on chromosome 1,9 and 12, respectively. The average lesion number and average lesion size method used to detect resistance QTLs in this research was not reported.7 new QTL sites were found, which showed a broad-spectrum resistance on top of the resistance gene cluster of the chromosome 11,2 QTL sites were detected by all three methods, they could be new sites and will be used for further study. |
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