Antifungal effect of cinnamic acid and induced resistance of cinnamic acid-protocatechuic acid-CaCl2-NaCl-pullulan composite preservative to Trichoderma harzianum in postharvest Hypsizygus marmoreus

Hypsizygus marmoreus (H. marmoreus) spoilage caused by Trichoderma harzianum (T. harzianum) results in significant financial losses, and the natural preservatives are being sought after to replace synthetic preservatives. To determine the antifungal activity of cinnamic acid (CA) against T. harzianum and clarify the induced disease resistance mechanism of H. marmoreus to T. harzianum, the CA (0.113 mg·mL−1)-protocatechuic acid (0.121 mg·mL−1)-CaCl2 (0.83%)-NaCl (0.65%)-pullulan (0.35%) composite preservative (CACP) at the spray rate of 13:1 was used to coating on H. marmoreus and storage at 4 ± 1 °C. Results showed that the inhibition rate (CA 3.00 mg·mL−1), EC50 of mycelium growth and spore germination inhibition rate of CA to T. harzianum were 82.10%, 2.641 mg·mL−1 and 0.128 mg·mL−1, respectively. CACP treatment significantly reduced the rot rate and incidence of H. marmoreus. High levels of phenylalamine ammonia-lyase, peroxidase, polyphenol oxidase, ascorbate peroxidase, free proline, chitinase and β-1,3-glucanase in H. marmoreus treated with CACP significantly enhanced resistance to T. harzianum. Further, CACP treatment decreased the content of relative electrical conductivity and lessened the accumulation of malondialdehyde. Thus, the CACP may be used as an alternative bio-fungicide to control the severe disease caused by T. harzianum in H. marmoreus after harvest.