Biocontrol of blue and gray mold diseases of pear fruit by integration of antagonistic yeast with salicylic acid.

This study was conducted to evaluate the efficacy of the biocontrol yeast Cryptococcus laurentii and salicylic acid (SA) in suppressing the blue and gray mould rots in pear fruit and to explore possible mode of action involved. Our results showed that the combined treatment of pear fruit with C. laurentii with SA at 100 microg ml(-1) resulted in a remarkably improved control of Penicillium expansum and Botrytis cinerea infections, including the pre-inoculated P. expansum, in comparison with the application of C. laurentii or SA alone. The biocontrol yeast C. laurentii proliferated rapidly within the first 24 h of incubation in pear fruit wounds. Although SA at 100 microg ml(-1) neither affected the population growth of C. laurentii nor directly inhibited the blue mold when the inoculation concentrations of P. expansum were above 5 x 10(2) spore per ml in vivo, it induced the fruit resistance to the blue and gray mold rots when the time interval between SA treatment and pathogens inoculation was more than 48 h, being associated with a rapid and strong activation of the peroxidase activity in pear fruit. Thus we assume that SA may be regarded as a secondary defense line in a combination of C. laurentii and SA, which could reinforce the biocontrol efficacy of C. laurentii by induction of the fruit natural resistance.