Variability In Resistance Of Botrytis Cinerea To Procymidone And Natural Fitness Of Resistant Mutants

5 strains of Botrytis cinerea (HY2-1, HY2-2, HY2-3, DF2-2, XY6-1) sensitive to procymidone were isolated from vegetables in Jiangsu province. 67 mutants resistant to the fungicide were obtained from the sensitive strain conidia treated with ultraviolet, N-methyl-N-nitroguanidine and procymidone. Of all resistant mutants, the low-resistant (1 g/ml00 g/ml) ones accounted for 16.42%, 2.98% and 80.60% respectively. The mutant frequency of the strains by the treatment of ultraviolet reached 0.413 10-6 while those by the treatment of N-methyl-N-nitroguanidine and procymidone were 0.252 10-6 and 0.190 10-6 respectively. The mutant frequency of XY6-1 was 0.591 10-6, higher than that of others and all mutants from XY6-1 had high resistance. But the resistant mutation in HY2-3 was more difficult than other strains, with the low mutant frequency of 0.147 10-6.XY6-1 (DicSNpeR) with the sensitivity to procymidone and the resistance to diethofexcarb, and XY6-1 140 (DicRNpcS) with the resistance to procymidone and the sensitivity to diethofexcarb were obtained and inoculated opposite on PSA. Anastomosis region was formed between the two colonies after cultured 4 day. Anastomosis mycelia were moved and cultured for sporulation on PSA. 18 strains resistant to two fungicides (DicRNpcR) were screened out from 203 conidium progenies by single spore isolation. Of 18 resistant strains with DicRNpcR, there were 16 strains with same resistant level to procymidone as their resistant parent and two strains with the lower resistant level than the resistant parent.The resistant mutants were continuously transferred from tube to tube for 20 times or generations and each generation was grown on PSA for 3d. 79.1% of all progenies were as resistant to procymidone as the original strains and 13.4% lost resistance. Moreover, 87.0% of the high resistant mutants were stable, more than the moderate or low resistant ones (46.2%).455 single conidium progenies were obtained from 6 mutants high resistant toprocymidone. 86.8% of all progenies could keep high resistance. Moreover, the resistance of single spore progenies from DF2-2 050, HY2-2 070 and XY6-1 140 was stable while 24.3% of single spore progenies from HY2-3 050, HY2-1 200 and Dl-3 appeared some decline in resistance.The biological characters such as mycelium growth rate, sporulation capacity and pathogenicity of resistant mutants were compared those of their original sensitive strains. The results showed that the mycelia of mutants grew more slowly than their original sensitive strains. But there were no regular differences in sporulation capacity and pathogenicity between resistant mutants and their original sensitive strains.The competitive ability of resistant mutants on tomato leaves were compared by inoculating the conidial suspension mixed from resistant mutants and their original sensitive strains in proportion of 1:1. Then the conidia on lesions were isolated on PSA amended with procymidone at 100 g/ml and the natural fitness of resistant mutants was determined. The results showed that two resistant mutants was more competitive than their original strains while fitness of 2 other resistant mutants was lower than that of the original strains. Moreover, the competition of wild resistant isolate Dl-3 was lower than that of sensitive isolates.