| The sensitivity to metalaxyl of 108 Phytophthora capsici strains collected from different areas of Jiangxi were determined by mycelia growth inhibition method. The result showed that EC50 values ranged from 0.1890～0.7413μg/ml, with a mean EC50 as 0.4183±0.0120μg/ml, the most insensitive strain was 3.92 times of the most sensitive strain. The sensitivity of 108 Phytophthora capsici to metalaxyl distributed as a unimodel curve, which showed there was no resistant subpopulation among these strains. According to the general average,the weaker sensitivity was from Jishui, Nanchang, Shangyou, Chongyi, Jiujiang, Yifng, Leping. The strains of Jian county had the lowest average EC50 values, which was 0.2824 ug/ml and the range was 0.2458-0.3209μg/ml.But the highest average EC50 values was from Jiujiang,which was 0.4721μg/ml and the range was 0.3311-0.5451μg/ml. Although the average EC50 from Yongfeng was lower, the highest EC50value was 2.43 times of the lowest. The strains from Shangyou,Yifeng,Leping were 3.35,2.96,2.44 times of the lowest. It showed that the resistance of strains were different in the same area.Dimethomorph inhibited mycelial growth of Phytophthora capsici EC50 values range 0.1149μg/ml-0.2868 ug/ml, the average EC50 is (0.1845±0.0032)μg/ml, the most insensitive strains was 2.49 times of the most sensitive strain. The strains of Chongyi county had the lowest average EC50 values,which was0.13674μg/ml and the range was 0.1213-0.1462μg/ml.But the highest average EC50 values was from Jishui,which was 0.2185μg/ml and the range was 0.18045-0.2835μg/ml. According to the data on the different regions and strains of the same region Dimethomorph sensitivity were similar.Cymoxanil inhibited mycelial growth of Phytophthora capsici EC50 values range 1.2276-33.2608μg/ml, the average EC50 was (12.9910±0.6914)μg/ml, the most insensitive strain was 27.09 times of the most sensitive strain. Sensitivity of different regions to Cymoxanil have a greater differences. The strains of Jian county had the lowest average EC50 values,which was 17.8732ug/ml, But the highest average EC50 values was from Jiujiang,which was 6.6934μg/ml. Sensitivity of same regions to Cymoxanil have a greater differencs too, the most insensitive strain was 3.92 times of the most sensitive strain from Jian,8.46 times from Gaoan,7.53 times from Leping.The 54 strains of confrontation with the standard strains were cultured, the results showed that all the strains mating with A2 strain did not produced oospores,but mating with A1 were observed oospores, indicating that strains in Jiangxi Province in the mating type of Phytophthora capsici was A2.The determination of the 108 strains, mycelium was only discovered in the 0.1 ug/ml medium, and in the 1,10,100 ug/ml did not grow.,indicated that Phytophthora capsici was very sensitive to flumorph. flumorph inhibited the growth of Phytophthora capsici EC50 values range 0.0785-0.3862ug/ml, the average EC50 is (0.1816±0.0041ug/ml).Resistance identification showed that C17-1, C16-1, C17-3, C27-1, C33-1, C33-2 were sensitive to the four strains, indicating that these varieties were poor resistance to the disease; C4, C15-2, C32-2 showed different degrees of disease resistance to the three strains, indicating that these three varieties have good disease resistance; C15-1, C27-2, C27-3, C32-1, C32-4 expressed resistant to varying degrees in two strains; while the American shrub pepper, C15-3, C18-1, C17-2, C31-2, C34-1 were resensitive to one strain. |
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