Combined treatment with Rhodosporidium paludigenum and ammonium molybdate for the management of green mold in satsuma mandarin (Citrus unshiu Marc.)

Abstract

This study evaluated the effectiveness of the combined treatment of ammonium molybdate and Rhodosporidium paludigenum, a yeast species with broad-spectrum antifungal effects, in controlling green mold caused by Penicillium digitatum in satsuma mandarin (Citrus unshiu Marc.). The addition of 0.1 mmol L−1 ammonium molybdate markedly improved the biological activity of R. paludigenum against green mold and decreased disease incidence by 89.3%, and simultaneously discontinued mold development within 0–12 h of infection. Although treatment with ammonium molybdate alone did not effectively reduce the incidence of green mold, treatment with high doses of ammonium molybdate attenuated disease severity. The use of R. paludigenum markedly reduced the dose of ammonium molybdate required to control green mold. Ammonium molybdate significantly depressed the ecto-phosphatase activity of P. digitatum, as well as interrupted the environmental acidification caused by this pathogen. These results suggested that ammonium molybdate contributes to the control of green mold infection by suppressing P. digitatum spore germination and proton-pump activity on the surface of P. digitatum membranes. Moreover, the results indicated that ammonium molybdate may be utilized as an environmentally-friendly additive that can enhance the performance of R. paludigenum against green mold rot in satsuma mandarin fruit.