Effects Of Selenium On Control Of Postharvest Diseases And Simultaneous Se-enrichment Of Fruits Production

Penicillium expansum and Botrytis cinerea are two kinds of the major postharvest pathogens in plants which may cause vegetables and fruits rot and heavy economic losses. Selenium (Se) is an essential trace element which has many beneficial effects for human beings and many other forms of life. Se can strengthen the plant disease resistance and enhance antioxidant capacity effectively at lower concentration owing to its unique antioxidant activity and is of great interest in biochemistry, chemistry, medicine, and medicine-related fields. Both toxic effects and protective functions exist in Se which depends on the certain concentration. Lower concentration can eliminate reactive oxygen free radicals while higher concentration can inhibit cell growth and accelerate cell apoptosis. Nowadays some studies have showed that exogenous Se can inhibit the growth of certain pathogens. In this study, the inhibitory effect of Se against Penicillium expansum and Botrytis cinerea and the influence on the storage and Se-enrichment of fruits were systematically studied. We explored the possible mechanisms by cell biology, biochemistry and molecular biology. The main results are as followings:1. The antifungal experiments showed that Se donor sodium selenite could significantly inhibit the growth of P. expansum and B. cinerea at 10 mg/L and 12 mg/L respectively, and the inhibitory effects was dependent on dose and time.2. Through the propidium iodide staining, we analysised that 20 mg/L and 24 mg/L Se treatment could increase extracellular soluble carbohydrate and protein of P. expansum and B. cinerea respectively. The results confirmed that Se inhibited the growth and development of two pathogens by causing plasma membrane damage.3. Through dichlorofluorescein fluorescence probe (DCHF-DA) detection, we found that 15 mg/L and 18 mg/L Se could increase the level of reactive oxygen species (ROS) of P. expansum and B. cinerea respectively. In addition, spore intracellular antioxidant system was destroyed and antioxidant enzyme activity was decreased, which indicated that the generation of ROS was induced by Se.4. Through Pre-harvest and Post-harvest treatment of Se on fruits, we found that Se could effectively delay ripening and senescence and prolong the storage time of postharvest fruits. In addition, high level of antioxidant enzyme activity was maintained inside the fruits which promote a better quality of fruits and induce a plant disease resistance.5. Through atomic fluorescence spectrophotometer (AFS) detection of apple and tomato fruits, we found that both Pre-harvest and Post-harvest could enhance Se accumulation in fruits. Se concentration could reach 6.02-fold (apple) and 5.53-fold (tomato) compared to control groups. What’s more, supply of Se resulted in Se-biofortified tomato and apple fruits, with Se levels low enough not to pose a health risk, which means that Se might serve as a potential alternative to synthetic fungicides for the control of the postharvest disease of fruit and vegetables caused by P. expansum and B. cinerea.