| Pyrimethanil is a new fungicide within the group of anilinopyrimidines (APs) with high activity against grey mould mainly caused by Botrytis cinerea. The modes of action of APs include inhibiting methionine biosynthesis, secreting hydrolytic enzymes and reducing host cell death at the site of fungal infection. Pyrimethanil had been widely used sine the end of the 1990s in China. Due to pyrimethanil with a single site of action and B. cinerea with the capacity of reproduction and mutation with high fitness, the combination of grey mould and pyrimehtanil is high risk of resistance; therefore, it is essential to embark on biological activity and resistance of pytimethanil to pathogenic fungi in China.Sensitivities of isolates A2 and A5 of Sclerotinia sclerotiorum to pyrimethanil were determined on potato dextrose agar (PDA) medium, malt extract agar (MEA) medium and chemically defined L-asparagine agar (L-asp) medium with mycelial growth test. The results revealed that L-asp medium is more sensitive for testing activity of pyrimethanil inhibiting mycelium growth of isolates A2 and A5. Growth inhibition rates were 78.43% and 87.50% at 10 u g mL-1 respectively for the both isolates. While, inhibition of mycelium growth was measured with 56.54% and 61.00% on PDA, 38.25% and 47.67% on MEA, respectively for the isolates A2 and A5.Of total 12 plant pathogens species tested on L-asp medium, pyrimethanil strongly inhibited the mycelium growth of B. cinerea, Alternaria solani and A.solani with EC50 values of 0.177, 0.274 and 0.278 u g mL-1 respectively. It also had high inhibition effect on the mycelium growth of Phoma asparagi, Colletotrichum gloeosporioid.es, Sclerotinia sclerotiorum and Rhizoctonia solani with EC50 values of 1.444, 1.623, 2.017 4.106 u g mL-1 respectively. With no or little effect on Gibberella zeae, Magnaporthe grisea, Sclerotium rolfsii, Phytophthora capsici and Cytospora carphosperma.Pyrimethanil strongly inhibited the germination of conidia of B.cinera within 12h treatment (EC50 value was 0.248 u g mL-1 of isolate h18). However, inhibition effect of germination of conidia of B.cinera descended with the treatment time gone on, but the development of germ tube was strongly inhibited. Therefore, the mode of action ofpyrimethanil was inhibiting the mycelium growth of B.cinerea and not the germination of conidia of B.cinera.22 isolates of B.cinrea were isolated from tomatoes sampling from Yancheng, Jiangsu Province in 2000 and 50 isolates of S. sclerotiorum were collected from Nantong, Tongzhou etc in 2001 where pyrimethanil had never been used before. The sensitivities to pyrimethanil were determined by the method of mycelial growth test on L-asp agar medium. The results showed that the EC50 value of B.cinrea was ranged from 0.038 0.418 u g mL-1 with the mean EC50 value of 0.174 ug mL-1 and 95% confidence interval was ranged from 0.125-0.222 u g mL-1. The EC50 value of S. sclerotiorum was ranged from 0.303-5.986 ug mL-1 with the mean EC50 value of 1.779ug mL-1 and 95% confidence interval was ranged from 1.738-2.296 u g mL-1.55 isolates of B.cinrea were collected from greenhouses or plastic tunnels in Huaiyin, Jiangsu Province in 2002 where pyrimethanil had been used for about 3 years. The sensitivities of these isolates to pyrimethanil were determined by the method of mycelial growth test on L-asp agar medium. The results showed that the EC50 value were ranged from 0.108-22.94 u g mL- 1with the mean EC50 value of 3.217 u g mL-1. Some isolates of B.cinrea in Huaiyin showed resistance to pyrimethanil and the proportion of resistant isolates was 43.64%. Among this resistant sub-population, 83.33% was moderate resistance and 16.67% was high resistantce.High resistance mutant Huvl6 to pyrimethanil was obtained by ultraviolet irradiation. EC50 of pyrimethanil to Huvl6 was 24.95 u g mL-1,162 times as that of its original isolate H16. Significant differences in growth rate, sporulation and conidium germination rate were found among isolates of B.cinerea. However, no correlation co...
|
PDF Full Text Request