Evaluation Of Rice Varieties Against The False Smut And Genetic Diversity Of Ustilaginoidea Virens

Rice false smut is an important grain disease,caused by Ustilaginodea virens (cooke) Tak,after booting in worldwide rice.The sexual stage of the pathogens is Claviceps oryzae-sativa Hashioka,and its asexual stage is Ustilaginoidea virens(Cooke)Takahashi.It is not only greatly decrease both yield and quality of rice, but its may also cause the toxicosis incidents of human and animal from taking rice which contains high level of ustiloxins happened usually,to human and animals.Recent years,the disease has become more and more serious,such as loss 137 millions kg rice (equivalent to200 million RMB ) in Hunan Province in 2004.The investigation for rice false smut spatial distributing of 12 cultivars was carried out in rice area of Hengnan County in 2006.DPS software was used to analyse the spatial distributing aggregation indexes determination of the survey data.The data The results showed that the spatial distributing of rice false smut subjected to aggregation distributing pattern and the five-point sampling is the best method through compared with the results of the other investigation methods.The main components analysis among the three components viz.disease grain number of the average each panicle(X1),percentage of infected panicle(X2),disease grain number in1000 grains(X3),displayed that X1 was the main component,.Then X1 used as index of clustering analysis in 101 varieties with cluster-average method.The result clearly indicated the 101 rice varieties were divided into 6 groups at 0.40 threshold level,which the matching scale value(X1) of field resistance of the 6 group verities were 0:0.000～0.111(height resistance,HR);1:0.112～0.400(resistance,R);3: 0.401～0.610(moderately resistant,MR);5:0.611～1.010(moderately susceptible,SR); 7:1.011～1.760(susceptible,S);9:＞1.761(highly susceptible),separately.The regression analysis was based on X1 with 1000-grain weighty(g),yield loss rate and sterile grain rate of 15 cultivars.The results showed that relationship between X1 and 1000-grain weighty was obviously negative,and between X1 and both sterile grain and yield loss rate was significantly positive. Rice false smut of different cultivars of 33 counties and districts in Hunan in 2007 was investigated.The results showed that both the disease on hybrid rice and conventional cultivars are common occurrence,but severity level was obviously variation.As usual,the main cultivated cultivars in Hunan illustrate low level resistance. Besides,the hybrid cultivars using Zhun-S,Chuanxiang28A(29A),Xiang8A, Zhenshan97A as sterile line suggested having better resistant to the disease.The severity of rice false smut in different rice cultured areas displayed that the mountainous area was more serious than hills and the plain area.PAL,POD,PPO activity of 12 cultivars,1d,3d,5d,7d after inoculating conidia of rice false smut with the injection at 7～10d before heading was detected.The results showed that these enzyme's activity quickly enhanced and changed in the resistant cultivars after inoculating,but slowly in the susceptibility cultivars.The pure false smut fungus is very difficult isolated in laboratory because it slowly grows and is usually associated with a lot of bacteria and fungi on the spore balls.The tissue isolation in the study was the most convenient and effective method of isolates obtained of Ustilaginodea virens in several isolation methods and Xieben medium in the several media was the best one to get pure culture.Genomic fingerprints of 53 strains of U.virens from Hunan 24 counties and districts were analyzed by using 10 RAPD primers.The results showed that:all strains tested were divided into five genetic lineages(Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ) at 0.78 level of the genetic similarity through the clustering method of UPGMA.The five genetic lineages separately held 42,7,2,1 and 1 strains and they accounted for the rates of 79%,13%, 4%,2%and 2%in total strains,respectively.It was also obviously that the lineage I was the dominant one with the rates of 79%.The resultt showed that the genetic diversity of U.virens in Hunan was not significant.Besides,most strains obtained from the same cultivar in same and the different regions were grouped in the same lineage.The preliminary analysis showed that the genetic diversity of U.virens in Hunan was not significant.The screening of fungicide against rice false smut was conducted in Chengguan Township,YouCounty and Jiwei farm Huayuan.the results showed that efficacys of 24%Fenbuconazole SC and 15%triadimenol WP produced by Dow AgroSciences U.S.,430g/L Tebuconazole SC produced by Bayer CropScience(China) Co.Ltd.and 30%Difenoconazole·propiconazol EC,produced by Syngenta,against rice false smut, were all at above 80%.While,impacts of 15.5%Jianggangmeisu·triadimefon WP produced by Suling agricultural chemicals Co.Ltd in Yangzhou.,and 300g/L Difenoconazole·propiconazol EC produced by Hengda Co.Ltd.in Jilin,on the diseas possessed about 75%.