Sensitivity Of Rhizoctonia Cerealis And R.solani To Jinggangmycin And Some Factors Influencing The Sensitivity

160 isolates of Rhizoctonia cerealis causing sharp eye spot of wheat and 51 isolates of R. solani causing rice sheath blight collected respectively from 56 counties and 16 counties of Jiangsu Province, were detected for their sensitivity to Jinggangmycin and some nutritive, physical and chemical factors influencing the sensitivity were studied.By comparison of the sensitivity of tested isolates to Jinggangmycin with that of wild ones and the sensitivity frequency distribution of tested isolates, R. cerealis did not develop the resistance to Jinggangmycin, which showed that Jinggangmycin was still an effective agricultural antibiotic to control sharp eye spot of wheat caused by R. cerealis. But the low and moderate resistance of some isolates of R. solani AG1-I A to Jinggangmycin was found in the field. The sensitivity of R. cerealis to Jinggangmycin was higher than that of R. solani. There were some differences in the sensitivity to the antibiotic among anastomosis groups of two pathogens.EC50 of the wild sensitive isolate and the mean EC50 in the normal distribution of tested were used to determine the sensitive lines. There were little difference in two sensitive lines. It is considered that the method of sensitivity distribution of population was more suitable.The concentration of nitrogen and potassium in Czapek's dox medium significantly affected the sensitivity of R. cerealis and R. solani to Jinggangmycin. The results showed that the higher concentration of nitrogen in the medium was the lower inhibition of Jinggangmycin to R. cerealis and R. solani and the higher concentration of potassium was, the higher inhibition. But the concentration of phosphorus in the medium had little influence on the inhibition of the antibiotic to two pathogenic fungi. The potted experiment indicated that the control effects of Jinggangmycin against sharp eye spot of wheat and rice sheath blight were significantly correlated to nitrogen and potassium contents of plants. The incidence of two diseases varied with nitrogen contents of plants, and higher nitrogen contents significantly reduced the control effects of Jinggangmycinagainst the diseases. While higher potassium contents of plants were of benefit to reduce the incidence of two diseases and obviously increased the control effects of the antibiotic. Cultural temperature, pH value of the medium, the usage of other fungicides and herbicides, especially the temperature and pH value showed influence on the inhibition rates of Jinggangmycin to R. cerealis and R. solani. At 22 C, the inhibitory effect of the antibiotic with 0.2 g/ml Jinggangmycin to R. cerealis was the highest, which was significantly different from that at 15C or 28 C. The second was at 28 C, but the inhibition rate at 28 C was not obviously different from that at 15 C. Furthermore, the inhibition of the antibiotic with 0.2 u g/ml Jinggangmycin to R. solani at 28 C was the highest, which was significantly different from at 21 C or 35 C, but there were not significant difference in the inhibition between at 21 C and at 35 "C. When pH value of the medium was 5 to 7, the inhibition of the antibiotic was higher than that on the medium of pH9. Thus, the stability of cultural temperature, pH value of media was of importance to detect the sensitivity of R. cerealis and R. solani to Jinggangmycin. The fungicides and herbicides tested, such as carbendazim, triadimefon, tebuconazole, fenoxaprop-p-ethyl, fluroxypyr, tribenuron methyl, acetochor, butachlor, had some inhibitor on the pathogen and could inhibit the mycelial growth. Furthermore, these fungicides and herbicides increased the inhibitory effects of Jinggangmycin against R. cerealis and R. solani. With increase in the concentration of these chemicals, the sensitivity of the pathogens to Jinggangmycin was increased, and the sensitivity of R. solani to the antibiotic was more obviously increased than that of R. cerealis.