Pathogenicity Differentiation Of Magnaporthe Grisea In Jiangxi Province And The Resistance Analysis Of Rice Major Pi-genes

Rice blast specimens is collected from main production planting area of rice injiangxi province in2011, including53counties belonged to Shangrao, Ji’an, Nanchang,Yichun, Ganzhou, Jiujiang, cities of Jiangxi Province.169single spore isolates of rice blastfungus were isolated by isolation and purification from rice blast spciense.Thepathogencities and avirulence gence of the isolates against both30rice blast monogeniclines and7Chinese differential cultivars were measured at rice seedling stage. Thefollowing results were obtained. the pathogens accounted for0、0.59%、14.79%and84.62%respectively the pathogenicity frequency （PF） PF＜30%,30%-50%,50%-70%,and PF≥70%.the result showed that the most rice blast strains were broad-spectrumpathogenic.Rice blast strains could be divided into4groups and37physiological racesbased on the7Chinese differential cultivars. ZA and ZB group was test the most prevalent,the predominant races were ZA1、ZB1、ZA13、ZB5、ZA5、ZA9, with the frequency of21.89%、11.83%、8.28%、7.69%、5.33%、4.73%respectively.The resistance of30single Pi-genes to329isolates of rice blast fuguse（Magnaportheoryzae） arfained from rice blast sepcisens fields in Jiangxi Province of China during2006to2011were analysed. The results showed that7Pi-genes i.e. Pi-z^t, Pi-k, Pi-1（1）, Pi-z⁵,Pi-k（C）, Pi-k^pand Pi-9（t） had high resistance frequencies （RF）, with the values of85.11%,72.95%,71.12%,68.69%,63.53%,62.61%,61.09%respectively. The further analysisfound that the7Pi-genes had high resistance to the strains belonged to ZG1, ZC15orZB31, with RF of91.42%,85.71%,80.95%ï¼›low reistance to the strains belonged to ZA1、ZA（29）、ZB1、ZB7、ZB（21）、ZC7、ZC9、ZC（11）、ZE3, with RF below40%; no resistanceto the races ZC1or ZD1based on the resisstance of7Pi-genes to the25races withoccurrence frequencies above1%.7Pi genes were divided into two groups, the first groupincluded Pi-z^t, Pi-z⁵, Pi-9（t）, the second included Pi-k, Pi-1（1）, Pi-k（C）and Pi-k^pbased onanalysis by dps3.01software. Cluster analysis of affinity of30Pi-genes to rice blastfungus from Jiangxi were all made.The resistance of forty single spore strains collected from different areas in JiangxiProvince to Kasugamycin and Isoprothiolane were determined by indoor mycellumgrowth test. The results indicated that there was greatly different in the Ec₅₀ofKasugamycin ranged from6.28mg L to333.01mg L,ten low-resistance strains and onemiddle-resistance strain were found. The Ec₅₀of Isoprothiolane to rice blast ranged from5.63mg L to28.96mg L, two low-resistance strains were found. The result revealed thatthe resistance of rice blast fungus to both Kasugamycin and Isoprothiolane werelow.Cross-resistance or multi-resistance of rice blast strains to Kasugamycin andIsoprothiolane was not found by analyzing the resistant-strains.