Inhibitory effect of exogenous sodium bicarbonate on development and pathogenicity of postharvest disease Penicillium expansum

Penicillium expansum, a widespread filamentous fungus, is a major causative agent of fruit decay and may lead to the production of patulin which causes harmful effects on human health. In this study, P. expansum isolated from naturally infected pears (Pyrus bretschneideri Rehd.) was identified by morphological observation and rDNA-internal transcribed spacer analysis. Then, the effects of exogenous sodium bicarbonate (NaHCO3) on development and pathogenicity of P. expansum were evaluated in vitro and in vivo. Results indicated that NaHCO3 at 0.6% (w/v) significantly (P < 0.05) reduced the germination of P. expansum conidia by up to 80% compared to the control after 10 h incubation. NaHCO3 also showed good ability to inhibit germ tube elongation, mycelia expansion and hypha production of P. expansum. The lesion diameter and disease incidence of blue molds were markedly reduced by 0.6% NaHCO3 treatment. Loss of membrane integrity was examined and quantified under 0.6% NaHCO3 condition by the method of propidium iodide fluorescent staining. Furthermore, we found that NaHCO3 obviously affected the relative expressions of four genes involved in patulin biosynthesis and effectively prevented patulin accumulation. These data will provide theoretical foundations for improving the application potential of NaHCO3 on postharvest horticulture pathogens control.