An integrated strategy to control postharvest blue and grey mould rots of apple fruit by combining biocontrol yeast with gibberellic acid

Strains of Cryptococcus laurentii are useful biocontrol yeasts in controlling postharvest fruit diseases. Gibberellic acid (GA(3)), as a plant growth regulator, is associated with many plant growth and development processes. The results from this study showed that the combination of C. laurentii at 1 x 10(8) cells mL(-1) and GA(3) at 200 mu g mL(-1) could produce a more efficient control of both the blue and grey mould rots of apple fruit caused by Penicillium expansum and Botrytis cinerea, respectively. Moreover, this combined treatment could stimulate a great increase in the activities of both superoxide dismutase and catalase, however, it suppressed the increase of peroxidase activity in apple fruit. In addition, GA(3) alone at 200 mu g mL(-1) had little influence on the incidence and development of both the diseases on apple wounds, and it had no effect on the spore germination of both P. eypansuin and B. cinerea in vitro as well as the population of C. laurentii in vivo. Therefore, we deduced that the efficacy of this combined treatment in controlling the postharvest diseases in apple fruit could be linked to its capability of adjusting the fruit-mediated resistance on the basis of the antagonistic activity of the biocontrol yeast itself.