Pichia angustaePichia fermentans: due modelli per lo studio dell’interazione antagonistica tra lieviti, frutti e patogeni in post-raccolta

Yeasts are particularly suitable as biocontrol agents against several phitopathogenic fungi and represent an effective alternative to fungicide application during fresh fruit storage but the mechanisms that rule their antagonism remain still largely unexplored at molecular level. In order to start to fill this gap the efficacy ofPichia angustaagainst common postharvest pathogens of apple fruit was evaluated and confirmed for the first time. Given its complete genomic sequence, this model can serve to elucidate the mechanisms related to biocontrol capacity.To gain knowledge about the line between antagonism and pathogenicity, we have deepened the case ofPichia fermentans, a yeast-like antagonist againstMonilinia fructicolaon apple fruit but also a pathogen showing pseudohyphal growth on peach fruit. Two complementary suppressive subtractive hybridization strategies were performed to identify genes differentially expressed byP. fermentansgrown on apple versus peach fruit. Among the genes whose expression was significantly higher on peach none of them was related to lytic enzyme production, suggesting thatP. fermentansmay not be directly pathogenic on peach and that its invasive growth could be stimulated by a linked series of commodity-related events. This emphasizes anyway the need for a thorough risk analysis of potential antagonists so to avoid unpredictable results that could harm the effectiveness and safety of post-harvest biocontrol strategies.