Resistance Spectrums Of Identifying Varieties To Rice Blast And The Effectiveness Of Resistance Genes

Rice blast is one of the most important factors to influence the rice high- and stable-yield. To monitor the change of Magnaporthe grisea races, research the resistance spectrum of resistance gene for rice blast and prove the availability of breeding the durable and broad-spectrum varieties by accumulating resistance genes. In this experiment, Japan identifying varieties, China identifying varieties, two sets of NILs ( near-isogenic lines) which are developed by IRRI respectively using Lijiangxintuanheigu(LTH) and Co39 as recurrent parents and restore lines Duoxi NO.1, Chenghui 047, Minghui 63 and Shuhui 527, restain lines D62B, D702B, D59B, DUB and S-14B, and the F1 progenies produced by acrossing these restore lines with these relative sterile lines of the restain lines are used. The identification abilities of the four sets of identifying varieties are identified by inoculating Magnaporthe grisea isolates. The results show that the identification ability of Japan identifying varieties is poorer, the identification ability of China identifying varieties is correspond to that of Co39-NILs or a little stronger than the latter, LTH-NILs display the strongest identification ability in the four sets of identifying varieties. So LTH-NILs can be used to accurately identify the races of Magnaporthe grisea isolates and forecast the change of Magnaporthe grisea races. Besides, the sensitivities of resistance genes to Magnaporthe grisea show the specialities of rice subspecies. In the other words, the resistance genes from indica rice are more sensitive to Magnaporthe grisea from the places in which indica rice is planted, and the resistant genes from japonica rice are more sensitive to Magnaporthe grisea from the places in whichjaponica rice is planted.At the same time, 31 Magnaporthe grisea isolates are used to inoculate LTH-NILs in the experiment. The four broad-spectrum resistance genes Pi-z, Pi-z-5, Pi-z-t and Pi-9(t) are discovered. Their resistance frequencies are respectively 93.2%, 96.8%, 90%and 96.4%. To elucidate the feasibility of developing the durable and broad-spectrum breeds by accumulating resistant genes, the combinations of resistant monogenes are inoculated, show much stronger resistance to the tested isolates than their parents, and display the complement effect and dosage effect of accumulated resistance genes. But the resistance spectrums of theF1 progenies produced by crossing the restore lines with sterile lines are broader, or narrower, or no change than these of their parents. In short, only to some extent, the result of the experiment shows the feasibility of breeding durable and abroad-spectrum varieties by accumulating resistance genes.