Action mechanisms and biocontrol of Purpureocillium lilacinum against green mould caused by Penicillium digitatum in orange fruit.

Abstract

The present study evaluated, for the first time, the inhibitory effects of the filtrate of Purpureocillium lilacinum against Penicillium digitatum. No direct contact between P. lilacinum and P. digitatum was observed during the dual culture test and the inhibition zone was 6·1mm. The filtrate of P. lilacinum completely inhibited P. digitatum growth and spore germination at the concentration of 64%. The filtrate increased the permeability of the cell membrane and the content of MDA in P. digitatum. The ergosterol content in P. digitatum was strongly inhibited at 32% by 81·1%. The green mould incidence and severity in filtrate-treated fruit at 64% were 71·7 and 80·7% lower than in the control, respectively. The filtrate enhanced the activity of PAL, PPO and POD enzymes in orange fruit. The POD and PAL gene expression levels were significantly upregulated in the fruit treated with the filtrate. This study indicated that the antifungal mechanism of P. lilacinum filtrate against P. digitatum is mainly by the damage of the fungal cell membrane and its components. This work provides the pioneer evidence on the application of P. lilacinum filtrate as a novel biocontrol agent for orange green mould.