RESISTANCE TO BLUE MOULD (PENICILLIUM EXPANSUM) IN SARDINIAN PEAR GERMPLASM

The objective of this research was to evaluate the natural resistance of different Sardinian pear germplasm accessions to P. expansum, the causal agent of postharvest blue mold. Experiments were carried out in vivo and in vitro with seven accessions of pears (‘Sarmentina’, ‘Vacchesa’, ‘De Puleu’, ‘De su Duca’, ‘Natalina’, ‘Oliena’ and ‘Laconi5’) belonging to the CNR‐ISPA ex situ collection and one national cultivar (‘Abate’) which was used as a control. P. expansum was isolated from blue mould-decayed Sardinian pear fruit and selected for its aggressiveness and patulin production. Mycelial growth and patulin accumulation of P. expansum were evaluated in vivo on wounded fruits and in vitro on a standard growth medium (Potato Dextrose Agar, PDA) and Pear Puree Agar Medium (PAM), for 7 days at 23°C. P. expansum growth was evaluated by means of daily measurements of the colony diameter and by observations made using a scanning electron microscope (SEM). Patulin production was monitored by high-pressure liquid chromatography-mass spectrometry. The expression of a isoepoxydon dehydrogenase gene (idh), involved in patulin biosynthesis, was monitored by real time PCR. Mycelial growth of P. expansum on Sardinian PAMs was inhibited in comparison to ‘Abate’ PAM and PDA. In particular the accessions ‘Sarmentina’ and ‘Vacchesa’ showed the maximum inhibitory activity both in vitro and in vivo. Patulin concentration on PAMs from Sardinian accessions was lower than patulin detected in PDA indicating a positive correlation between fungal growth, patulin production, and idh gene expression. Sardinian pear accessions seem to have a significant effect on the development of blue mold decay and the inhibition of patulin production.