Enhancement of biocontrol efficacy of Pichia membranaefaciens by hot water treatment in postharvest diseases of citrus fruit

Abstract

Effects of hot water treatment (HWT; 53 °C for 2 min) and Pichia membranaefaciens, either alone or in combination, on controlling Penicillium italicum, Penicillium digitatum, and natural infection in citrus fruit were investigated. Results showed that the combined treatment significantly reduced disease incidence and lesion diameters of blue and green molds in artificially inoculated fruit whether the pathogens were inoculated after or before the treatment compared with the treatment of P. membranaefaciens or HWT alone. The combination of P. membranaefaciens with HWT was as effective as the fungicide treatment in natural infection trials. Application of HWT did not affect the growth of P. membranaefaciens in the wounds of citrus fruit at 20 °C or 4 °C. P. membranaefaciens combined with HWT effectively enhanced the phenylalanine ammonia-lyase, peroxidase, polyphenoloxidase, chitinase, and β-1,3-glucanase activities and stimulated the synthesis of phenolic compounds. These results suggest that the use of HWT is a useful approach to improve the efficacy of P. membranaefaciens in postharvest diseases of citrus fruit.