Induction of defense responses in apple fruit treated with Pichia guilliermondii and silicon against Penicillium expansum.

Regarding the wide infection of apple fruits to blue mould disease caused by Penicillium expansum in storages, the experiment was conducted to evaluate the potential of the yeast Pichia guilliermondii alone and in combination with silicon (Si) at 0.1, 0.3 and 0.5% w/v for control of P. expansum at 20 ˚C. The results showed that P. guilliermondii was effective in controlling of blue mould disease, but combination of the yeast with Si at 0.3% w/v increased its efficacy, significantly (p<0.05). The results indicated that the highest amount of phenolic compounds (PCs) was two days after pathogen inoculation and in ASP (P. guilliermondii + 0.1% Si (w/v)+ P.expansum) treatment. ASP treatment caused the increase in peroxidase (POX) activity that reached the maximum level four days after pathogen inoculation. The increasing in PCs and POX in infected apple treated by P. guilliermondii and Si may be one of the mechanisms responsible for its biocontrol activity.