Study On Resistance To Major Postharvest Diseases And Storage Quality Of Blueberry Treated With Carvacrol

Blueberry is a popular fruit that is known for its high nutritional and economic values. However, blueberry is highly susceptible to deterioration and pathological infection after harvest, resulting in the loss of its market values. Using local blueberry cultivars in zhejiang province as test materials, the type of pathogens and the postharvest diseases of blueberry were studied. The changes of quality and postharvest senescence in blueberries fumigated with different concentrations (0、50、100、150 μmol/L) of carvacrol and different amounts (0、1、2、3g) of carvacrol-β-CD inclusion complex were also investigated. Effects of carvacrol treatments on the control of blueberry gray mold and blue mold that were caused by Botrytis cinerea and Penicillium digitatum, respectively, were also examined. The results will provide theoretical basis for blueberry postharvest preservation and biological control. The main results are as follows:(1) The pathogens were isolated from rotten blueberries, then inoculated into fresh blueberry fruit. The major pathogens were identified by morphological characteristics analysis. Seven species were found as the disease causing pathogens. These pathogens belong in Botrytis, Phomopsis, Fusarium, Penicillium, and Aspergillus.(2) The results showed that treatment with carvacrol could significantly inhibit blue mold decay caused by Penicillium digitatum and gray mold decay caused by Botrytis cinerea on blueberry fruit. Disease resistance of blueberries was induced after treated with 100 or 150 μmol/L carvacrol, but the treatment of 150 μmol/L carvacrol had undesirable effects on blueberry quality. The activities of PAL、PPO、POD、CHT and GLU disease-resistant enzymes were also increased. The results demonstrated that the control of postharvest diseases in blueberries by carvacrol may involve the activation of the disease-related defense system and had inhibition effect on pathogenic fungi. The concentration of 100μmol/L carvacrol was found to be significantly effective than all the other treatments, therefore, this concentration was designated as an optimum carvacrol treatment for maintaining the storage quality of blueberries.(3) These results showed that an optimal concentration of carvacrol could not only significantly inhibit the degradation of TA TSS, and the loss of firmness, but also could maintain its physiological quality to improve the freshness retention and extent shelf life. Carvacrol significantly inhibited the increase of the MDA content and LOX activity, suppressed the decrease of VC and anthocyanin contents, and maintained total phenolic content during the whole storage periods. Carvacrol treatments also enhanced the activities of PAL, POD, PPO, CHT and GLU. Furthermore, carvacrol had a potential on enhancing activities of disease-resistant enzymes. The concentration of 100 μmol/L Carvacrol was found to be significantly effective than all the other treatments, therefore, this concentration was designated as an optimum carvacrol treatment for maintaining the storage quality of blueberries.(4) The optimal amount of carvacrol-β-CD inclusion complex had a potential on inhibiting the quality degeneration of blueberry, as well as maintaining total phenolic content during the whole storage periods, extending shelf life and greatly improved the preservation quality. Carvacrol-β-CD inclusion complex treatments can activate and prolong PAL, POD, PPO, CHT and GLU activity peaks, therefore, enhanced the activities of disease-resistant enzymes and effectively improved disease resistance of blueberries. The blueberry could maintain its freshness at the best state under 1.0% and 1.5% carvacrol-β-CD inclusion complex compared with the other treatments.