Genetic Diversity Of The Rhizoctonia Solani Collected From11Provinces Of China And Biocontrol Of Rice Sheath Blight

Recogonized as one of the most serious rice diseases, rice sheath blight brought enormous losses in the food production.With the purpose to test the genetic diversity of pathogenic fungi Rhizoctonia solani,we collected300disease samples from11provinces of China and260strains were isolated.Then we pick out220strains for the diversity test using the RAPD method.Bacillus cereus AR156, screened from forest soil, posses astonished biocontrol effect to tomato bacterial wilt, banana wilt disease as well as the root-knot nematode Meloidogyne incognita. Here we test the effect to rice sheath blight both under the condiction of greenhouse as well as paddy field. The results indicated that AR156posses considerable effect more than60%.Then we investigate the mechanism of induces systemic resistence by Bacillus cereus AR156.The results suggested that AR156could elicit the incuced systemic resistence (ISR) of rice against Rhizoctonia solani.1Genetic diversity of the isolated pathogenic fungi Rhizoctonia solaniTo test the genetic diversity of the Rhizoctonia solani which attacked the rice in China, we carry out the random amplified polymorphic DNA method with20random primers.After agarose gel electrophoresis; we found216different bands, of which there were14distinctive bands, while the Polymorphism is93.5%. From the cluster analysis, we found that at the similarity0.65,220different strains were divided into11clusters, while those from the same province gathered in the single cluster except the strain "AH-10" and "AH-18" which were isolated from Anhui rice samples but gathered in the Jiangsu provinve cluster.As well.we discoveried that the similarity of the strains isolated from the same field was100%. Moreover, the results indicated that the genetic distance was consisting with the geographic distance.2Studies on Bacillus cereus AR156induced rice systemic resistence against Rhizoctonia solaniThough the greenhouse test and the paddy test, we determined that the biocontrol effect of RSB were83.33%and73.70%, as well, we found AR156possed considerable growth promoting effect. At the third day after the AR156amplication, we deteced the amount of SOD, POD, PAL and CAT. The results indicated that the amount of POD, PAL and CAT increased with the inducing of Bacillus cereus AR156.With the increase of those defense-related enzymes, the pathogenic fungi could be disturbed to infect the rice tissues. From the results of the RT-PCR, we found that AR156could induce rice defense-related genes OsPR1b (U89895) and OsPR10(AF395880) expressed in advance so as to prevent the development of RSB.