Effect of membrane integrity on survival competition ofBotrytis cinereaupon QoI fungicide pyraclostrobin

Botrytis cinerea, the causal agent of the grey mould disease, developed resistance to multiple fungicides. However, the role of cell membrane in survival competition ofB. cinereaupon quinone outside inhibitor (QoI) fungicide has not yet been elucidated. In this paper, the enhancement of cystamine, a transglutaminase inhibitor, on membrane integrity ofB. cinereawas determined, and the effect of the enhancement on the sensitivity ofB. cinereato pyraclostrobin was investigated. The results showed that pyraclostrobin inhibited mycelial growth with EC(50)as 1.122 and 3.042 mu g/ml at 24 and 48 hr, respectively. In the treatment of 5 and 50 mu g/ml pyraclostrobin, membrane integrity ofB. cinereawas broken, causing high permeability, lipid peroxidation, flocculent and malformed surface with vague septum and abundant agglomerates inside and outside the mycelia. Cystamine even at 50 and 200 mu g/ml had little inhibitory effect on mycelial growth. However, in presence of 50 or 200 mu g/ml cystamine, the mycelia from pyraclostrobin treatment possessed a significantly reduced leakage, lower MDA content, and a revived fibrous and transparent surface. Meanwhile,SEMimages showed that membrane integrity of the mycelia was significantly improved and the agglomerates were dramatically disappeared. Synergy assays further revealed thatB. cinerearegained less sensitivity to pyraclostrobin inhibition. In conclusion, membrane integrity controls mycelia sensitivity and is required for survival competition ofB. cinereaupon pyraclostrobin.