Ozone treatment inhibits dry rot development and diacetoxyscirpenol accumulation in inoculated potato tuber by influencing growth of Fusarium sulphureum and ergosterol biosynthesis

Fusarium sulphureum is a major causal agent of dry rot of potato and fusarium rot of muskmelon fruit. Ozone (O3), a kind of strong oxidant, is widely tested to control postharvest disease in fruit and vegetables by inhibiting the growth of pathogenic fungi. In this study, the effect of ozone treatment on dry rot development, growth of F. sulphureum, diacetoxyscirpenol (DAS) accumulation in vivo and in vitro, and ergosterol biosynthesis were evaluated. The results showed that 2 mg L−1 O3 treatment effectively suppressed dry rot development, DAS accumulation in vivo and in vitro, and significantly inhibited mycelial growth of F. sulphureum. The colony edges and scanning electron microscopy (SEM) observation showed that O3 treatment significantly changed morphological structure of the mycelia; it became shorter, shriveled and rough. Transmission electron microscopy (TEM) results revealed that degradation of organelles intensified, distribution of cytoplasm became uneven, and the integrity of cell membrane was destroyed. Moreover, O3 treatment decreased ergosterol content and DAS accumulation by down-regulating expression of genes involved in ergosterol and DAS biosynthesis pathway. In addition, there was positive correlation between ergosterol content and DAS accumulation in vitro. These results indicate that ozone suppresses dry rot development and DAS accumulation by affecting growth of F. sulphureum and down-regulates expression of genes involved in ergosterol and DAS biosynthesis.