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The rice blast became more severe in Heilongjiang province during the past few years, causing a large loss of rice yield. A total of 173 Magnaporthe oryzae (M. oryzae) isolates, collected from different rice-cropping districts of the province in 2006, were tested for their pathogenicity against 9 Japanese and 7 Chinese differential varieties (DVs) together with 31 rice monogenic lines (MLs) with different blast resistance genes and 12 local leading cultivars. Out of these 173 isolates, 55 Japanese races (pathotypes) were identified by using the Japanese DVs, and the predominant races were 017, 077, 037, 377, and 047, accounting for 42.29% of all the tested isolates. The comparison of differential ability between Japanese and Chinese DVs testified that the former one was much more suitable for M. oryzae pathotyping in Heilongjiang province. Among 12 leading cultivars tested, only Longjing 14 and Longdun 104 still kept good resistance to blast disease. The resistance gene Pi9 showed broadest resistance spectrum (on average 94.80%) to all the blast isolates tested, and was of the highest utilization value in rice blast resistance breeding. The resistance genes Pi-z5(CA), Pi-z5(R), Pi-ta2(R), Pi-ta2(P), , and Pi20(t) also showed high utilization values due to their resistance spectra of around 70%. The most effective breeding strategy for blast resistance should be as follows: 1) to utilize rationally Longjing 14, Longdun 104 and Pi9 as resistance donors, and pyramid one to several more broad-spectrum resistance genes into elite leading cultivars by means of marker-assisted selection; 2) to strengthen the monitoring of predominant virulent 第 1 期 雷财林等: 黑龙江省稻瘟病菌生理小种毒力基因分析与抗病育种策略 19 races and their temporal and spatial variation; and 3) to explore new resistance resources extensively and transfer the new broad-spectrum resistance genes into leading cultivars purposefully.

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