Effect of antagonistic yeast Pichia membranaefaciens on black spot decay of postharvest broccoli

Abstract

The inhibitory effect of yeast Pichia membranaefaciens on black spot decay of postharvest broccoli, caused by Alternaria alternata (Fr.) Keissler, was investigated and possible mechanisms were explored in both in vitro and in vivo experiments. There was a positive correlation between the concentration of yeast cells and reduction of hyphal growth or spore germination from 1 × 104 to 1 × 108 cells/ml. When the pathogen and yeast cells were co-cultured at 1 × 108 yeast cells/ml, swollen pathogen hyphae, inner substance leakage, and curved or fragmented spore germ tubes were observed. In postharvest tests, disease incidence and lesion diameter were significantly reduced at 1 × 108 yeast cells/ml at 10 ± 1 °C; the activities of cellulase and pectinase excreted by the pathogen were reduced and the chitinase activity in the pathogen-host system was increased significantly. Taken together, the results suggested that pathogen infection of wounds was inhibited, and the hydrolytic enzymes appeared to contribute to the control mechanism of P. membranaefaciens by inhibiting hyphal growth or spore germination.