Biocontrol of Rhizoctonia solani Kühn Using Fermentative Solution of Streptomyces corchorusii Strain NF0919

A strain of Streptomyces corchorusii （NY0919） antagonistic to Rhizoctonia solani Ktthn was isolated, which produced alkyl glycoside with high antifungal activity. To investigate the antifungal activity of Streptomyces corchorusii strain NF0919, the treatments amended with the non-sterilized supernatant resulted in the highest growth inhibition rate of about 100% at a concentration of 20%. The antifungal compound, which inhibited the growth of Rhizoctonia solani Kuhn, was extracted by EtOAC and purified by silica gel, Sephadex LH-20 column, and HPLC, where an active fraction was confirmed by LC-MS and NMR techniques. These results suggested that NF0919 had a high potential in the biocontrol of Rhizoctonia solani Kuhn, which was mainly due to surface active agent APG.

Toxicity Test and Field Control Effects of 4 Different Fungicides on Grape Downy Mildew

[Objective] This study was conducted to investigate the biocontrol activity of Streptomyces corchorusii strain NF0919 and Bacillus subtilis D J-6 WP to grape downy mildew. [Methed] We determined the indoor toxicity of the supernatant of S. corchorusii strain NF0919, 1.0×1011 cfu/g B. subtilis D J-6 WP, mancozeb and dimethomorph on Plasmopara viticola by the leaf disc method, respectively, and a field efficacy trial was conducted. [Result] The results showed that the ECso values of the supernatant of strain NF0919, 1.0×1011cfu/g B. subtilis D J-6 WP, mancozeb and dimethomorph were 96.285 9, 86.603 8, 69.947 2 and 7.263 6 μg/ml, respec- tively. The values of field efficacy in preventive experiments for grape downy mildew on the 7th day after 2 times of spraying 20 times diluent of the supernatant of strain NF0919 and 1 000 times diluent of 1.0×1011 cfu/g B. subtilis D J-6 WP were 71.55% and 70.71%, respectively, and the values of field efficacy on the 14th day after the 2 times of fungicide application were 67.54% and 68.19%, respectively. The values of field efficacy in curative experiments on the 7th day after 2 times of spraying 20 times diluent of the supematant of strain NF0919 and 1 000 times diluent of 1.0×1011 cfu/g B. subtilis D J-6 WP were 59.72% and 56.07%, respectively, and the val- ues of field efficacy on the 14th day after the 2 times of fungicide application were 56.88% and 57.46%, respectively. The field efficacy values of the 2 tested biocon- trol agents were equivalent. The protective effect showed no significant difference between each of tested biocontrol agents and 300 times diluent of 50% mancozeb WP, but there was a significant difference in the efficacy between each of tested biocontrol agents and 200 times diluent of 40% dimethomorph SC. [Conclusion] The S. corchorusii strain NF0919 and B. subtilis D J-6 WP had certain biocontrol poten- tial to grape downy mildew and development value.