Population Structure Of Rhizoctonia Spp. From Maize In Southwest China And Evalutation Of Maize Germplasm For Resistance

Maize is one of the most important crops in China. The cultivation area of maize is only less than rice. With the rapid development of husbandry and food processing industry, the demand of output and quality for maize has been increased in the recent years. Diseases are the main factors to of influence the maize yield, resulting in the yield loss of 6%-10%. In Southwest China, maize banded leaf and sheath blight has become the one of major diseases due to high temperature and high humid. Because of implementation of free (less) cultivation, increasing in fertilizer input, promotion of the planting density and the lack of resistant varieties, corn banded leaf and sheath blight has recently serve in the area. The investigation of the pathogen and the evaluation of the resistance of maize germplasm were concluded in this researched and the yellow results were obtained.1.275 isolates were obtained from 533 disease samples in Southest China.244 were identified as Rhizoctonia solani and Rhizoctonia zeae. Anastomosis group identification showed that the isolates belonged to multinucleate Rhizoctonia AG1-â… A, AG1-â… B, AG2-2â…¢B,AG4-HGI,AG-5 and WAG-Z. Rhizoctonia AG-1-â… A was the major anastomosis group, which accounted for 78.7% of the samples, followed by WAG-Z.2. Cultural characteristics of representative strains of different anastnomosis groups were observed. The results showed that the differences in different groups were obvious. The colony and sclerotium of representative strains in the same group were similar.3. The pathogenicity to maize of different anastnomosis groups was significantly different on Chuandan13. The pathogenicty of most strains were cosistency in seeding stage and adult stage. There was difference among the strains in the same anastnomosis groups. AG-1IA was the domiant virlence group, while the pathogenicities of the all other were low. The pathogenicity of AG1-â… A,AG4-HGI,AG2-2â…¢B,WAG-Z were obvserved by 23 varieties.4.20 representative isolates were analyzed with UP-PCR (Universally Primed PCR). The results showed the diversity of different anastnomosis groups. It completely matched with the result of anastomosis group identification analysis.5. The resistance of maize germplasm were evaluated by AG1-â… A. There were no plant immune or highly resistant materials. The number of resistant germplasm was 36, and the percent of resistant and middle resistant germplasm were 5.3% and 23.7%. The germplasms were susceptible of the germplasm were suspectale or high susceptible.