Genetic Variation in the Stilbenes Content and Composition of Muscadine Grape Genotypes

Stilbenes are secondary metabolites produced in certain Vitis species that have wide implications in plant disease resistance and human health.  Muscadine grapes (Vitis rotundifolia) have been reported to be a good source of phytochemicals such as stilbenes, flavonoids, anthocyanins, phenolics, etc. They are primarily grown in SE USA in lieu of bunch grapes because of their tolerance to Pierce’s disease. The primary objective of this research was to determine the extent of genetic variation in stilbenes content and composition among the muscadine genotypes. Fully ripe berries were collected from 49 muscadine grape genotypes, juice was extracted by crushing and its stilbenes content and composition was analyzed by HPLC coupled to a UV detector. The identity of stilbenes was determined using known stilbene standards. The HPLC analysis of berry extracts revealed presence of 10 to15 peaks. Of these, five were identified as piceid, pterostilbene, trans-resveratrol, cis- and trans-stilbenes and present in variable amounts among the dark, bronze and pink skinned berries. Dark skinned genotypes exhibited higher amount of stilbenes compared to bronze and pink skinned genotypes. The stilbenes concentration was found to vary between 5 to 200 µg/g among the 49 muscadine genotypes tested. The observed genetic variation in stilbenes content of muscadine genotypes was confirmed by measuring stilbene synthase gene expression using real time PCR, and correlating with expression levels of stilbenes among the genotypes. The results showed that certain muscadine genotypes are rich in stilbenes and appears to be an excellent source of phytochemicals to promote human health.