Biological and physical approaches to improve induced resistance against green mold of stored citrus fruit.

Health and environmental concerns have point out the need to improve or change several manufacturing steps in the food chain. In this context particular attention should be given to the technologies involved in fruits and vegetables production. Nearly all fresh fruit and vegetables are subjected to different periods of storage and/or shelf-life before of their consumption. This implies the need to protect the commodities from microbial spoilage. Some Citrus species (e.g. lemon and grapefruit) may be stored for several months before consumption and then post-harvest treatments are essential to contain green (Penicillium digitatum) and blue (P. italicum) moulds. Alternative approaches to chemicals usually have a lower efficacy in containing rots but fulfill the consumer's expectation. Among the alternative strategies, the improvement of host natural resistance is promising. In this regard, we report some results concerning the use of biotic (yeast) and abiotic agents as inducers of phytoalexin (i.e. scoparone and/or scopoletin) accumulation in Citrus rind and its importance in the control of fungal decay. In all experiments the inducers were applied on fruits before or 24 h after inoculation with P. digitatum and the rot severity was monitored 7 days later. The accumulation of phytoalexins was monitored according to a standard methodology by HPLC. In all experiments a positive correlation was found between increase of the phytoalexin scoparone in host tissue and reduction of decay.