Dry mycelium of Penicillium chrysogenum induces expression of pathogenesis-related protein genes and resistance against wilt diseases in Bt transgenic cotton

Dry mycelium (DM) of Penicillium chrysogenum (PEN), a waste product of the pharmaceutical industry, is used as an organic fertilizer for agricultural production. Our previous studies have indicated that DM of PEN is effective in controlling a number of soil born fungal diseases, but the mode of action is unclear. In the present study, DM of PEN was extracted with water and applied to the roots of the Bt (Bacillus thuringiensis) transgenic cotton (Gossypium hirsutum) cultivar SCRC 21. The efficacy in controlling Fusarium oxysporum f.sp vasinfectum (Fov) and Verticillium dahliae Kleb (Vd), as well as the accumulation of pathogenesis-related (PR) protein transcripts in the plants were examined. The results showed that soil drench with PEN provided significant protection against Fov and Vd. The controlling efficacy of PEN was dose-dependent, and the highest efficacy was obtained with 5–7% PEN. Soil drench with 5% induced the accumulation of six PR protein transcripts, PR-1a, PR-1b, PR-2, PR-3, A-C and B-C in cotyledons of cotton seedlings, suggesting that these PR proteins may be involved in induced resistance against wilt diseases in cotton by PEN. It seems that DM of PEN represents a new agent capable of inducing both resistance and the accumulation of PR protein transcripts.