Strawberry proanthocyanidins:: Biochemical markers for Botrytis cinerea resistance and shelf life predictability

Botrytis cinerea, a major fruit pathogen that causes grey mold, is a limiting factor in strawberry preservation. Grey mold causes extensive losses and methods other than pesticides are favoured to control this disease. Fruit antioxidants protect tissues against stresses and participate in disease resistance. However, they cannot be used on their own as indicators of postharvest preservation: postharvest disease resistance can also be induced by specific antifungal molecules e.g. phenolic compounds, phytoalexins and proanthocyanidins. Strawberry proanthocyanidins (flavan-3-of dimers and oligomers) may act both as antifungal compounds to extend shelf life, and as antioxidants to enhance quality preservation. The present study was initiated to determine whether proanthocyanidins can serve as biochemical markers of resistance to grey mold, and whether the level of these chemicals in strawberry cultivars correlates with maintenance of fruit quality and extension of shelf life. Proanthocyanidins (PA) were extracted from six strawberry genotypes and assessed for their ability to control germination and growth of Botfytis. Mycelium growth was determined on Potato Dextrose Agar (PDA). Germination was evaluated in Potato Dextrose Broth (PDB) enriched with PA. A panel evaluated shelf-life (first mold appearance) and quality of the cultivars after 14 days of storage at 2 C. Strawberry proanthocyanidin extracts inhibited Botrytis development. Radial growth of the mycelium on PDA enriched with PA was significantly reduced (as much as 75% inhibition) and showed significant correlation with preservation of the cultivars. Germination and germ tube elongation were reduced in PA enriched PDB and multiple branching of hypha was observed. The results of this research suggest that proanthocyanidin content can be used as an indicator of grey mold resistance in order to screen strawberry selections and cultivars for improved shelf-life and quality.