An emerging problem affecting apple production: Neofusicoccum parvum. Aureobasidium pullulans L1 and L8 strains as an alternative control strategy

Aureobasidium pullulans strains L1 and L8 were used as an alternative strategy against Neofusicoccum parvum, pathogen of apple wood and fruit. Both strains displayed a great ability to reduce pathogen conidia germination of almost 50% and totally stop its sporification in wood of ‘Gala’ and ‘Fuji’ apple cultivars. In addition, by in vitro tests the antagonistic activity displayed by non-volatile metabolites produced by both yeasts was highlighted by 70% of reduction of the pathogen mycelial growth. On apple fruit, the pathogen severity was reduced by 66% and 50% in ‘Gala’, and 70% and 60% in ‘Fuji’ by L1 and L8 respectively. In wood, no statistical differences were observed between L1, L8 and the control, except for ‘Fuji’ wood, where L8 strain displayed a wood lesion reduction of 23% with respect to the untreated control. Infrared analysis showed how the presence of both strains on woody tissues helped preserving cellulose content, preventing in this way the faster wood degradation by the pathogen. In addition, L1 and L8 simply colonized the wood surface, probably displaying an endophytic attitude, an essential requirement for controlling N. parvum in field.