[Intraspecific variations of Paecilomyces fumosoroseus in temperature fitness and carbendazim resistance].
A total of six wild strains of fungal biocontrol agent Paecilomyces fumosoroseus were grown at 15 degrees C-35 degrees C to reveal their variations in colony growth, conidiation, and conidial viability. The results showed that the test three indices were the best at 25 degrees C, but differed significantly at different temperatures for a given strain or at a given temperature among test strains. The strains Pfr116 and Pfr6206 behaved better or more stably than other strains at 15 degrees C-35 degrees C. The sensitivities of the fungal strains to gradient concentrations of fungicide carbendazim were assayed at the optimal temperature, based on their colony growth diameters and the counts of colony forming units (CFU). The inhibitory effect of carbendazim concentration on CFU counts fitted well to a Logistic model, with high coefficients of determination being achieved for all the strains (r2 > or = 0.90). The fitted minimal inhibitory concentration (MIC) values showed a low carbendazim resistance of strains Pfr4205 and Pfr116 (MIC < or = 20.0 microg x ml(-1)), whereas the other four strains fell within medium resistance to the fungicide (20 < or = MIC < or = 100). The MIC of strain Pfr6206 (93.5 microg x ml(-1) was very close to the high resistance level of MIC > 100 microg x ml(-1). Therefore, strain Pfr6206 was satisfactory with both the temperature fitness and the carbendazim resistance, and could be considered as a candidate strain for a fungal formulation adapting to more variable crop systems against insect pests.
Zheng
Wu
W
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hingzhou 310058, China. zhengwu_hz@163.com
Feng
Ming-Guang
MG
D001562:Benzimidazoles / Q000494:pharmacology*; D002219:Carbamates / Q000494:pharmacology*; D015169:Colony Count, Microbial; D025141:Drug Resistance, Fungal; D005659:Fungicides, Industrial / Q000494:pharmacology; D016015:Logistic Models; D008826:Microbial Sensitivity Tests; D010143:Paecilomyces / Q000187:drug effects* / Q000254:growth & development; D013045:Species Specificity; D013696:Temperature
D001562:Benzimidazoles; D002219:Carbamates; D005659:Fungicides, Industrial; C006698:carbendazim