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Title: THE ROLE OF CITRUS PEEL COMPOUNDS IN HOST RECOGNITION BY PENICILLIUM DIGITATUM AND P. ITALICUM

Author
item Stange, Richard
item McCollum, Thomas
item MIDLAND, S - UNIV. CALIF. RIVERSIDE
item SIMS, J - UNIV. CALIF. RIVERSIDE

Submitted to: International Society of Citriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/27/2004
Publication Date: 2/1/2004
Citation: Stange,Jr.,R.R.,Mccollum,T.G.,Midland,S.L.,Sims,J.J.2004.The role of citrus peel compounds in host recognition by penicillium digitatum and p. italicum. International Society of Citriculture Proceedings.

Interpretive Summary: Worldwide, Penicillium molds are the most significant cause of postharvest losses of fresh citrus fruit. We are interested in identifying compounds in citrus fruit that affect the growth of Penicillium. We have made extracts of citrus peel, partitioned extracts using chemical and chromatographic methods and assayed the fractions for their effects on Penicillium growth. These experiments have allowed to identify epoxybergamottin as one of the constituents in citrus peel that stimulates the growth of Penicillium. The results of this work have implications for the development of bio-rational methods to control postharvest decay of citrus fruit.

Technical Abstract: Components of citrus peel stimulate the growth of Penicillium digitatum and P. italicum, suggesting that components in the host play a role in recognition by the pathogen. To determine which components of the peel are responsible for this stimulation, flavedo of Citrus medica and C. paradisi was extracted with 80% ethanol. These extracts were further separated into hexane- (H), or ethyl acetate-partitioning (E), and aqueous remaining (A) fractions. The effect of these fractions, in factorial combination, was assessed using a vital stain (MTT) to quantify fungal growth. Optimal growth was obtained only when fractions H and A were combined. Bioassay-guided purification of the active components in fraction H was performed using fraction A as a background. Following chromatography on silica gel and C-18, the components in active fractions were identified by NMR. Epoxybergamottin was identified from C. paradisa. The active fraction from C. medica contained a related compound, prangolarin, and citropene. This suggests that host recognition by P. digitatum and P. italicum may involve a small number of related compounds.