Grapes, production quality


From August to October of 2009, two separate studies were conducted to assess fruit shape of Vitis section Euvitis hybrid bunch grapes using digital photography (Study 1) and evaluate inheritance of leaf shape in unique populations of V. rotundifolia hybrids (Vitis section Muscadinia) (Study 2). All vines studied were located at the University of Arkansas Fruit Research Station, Clarksville. Study 1 used SigmaScan® digital photography analysis software to calculate shape factor, major:minor axis ratio, and compactness of highly variable, unique-shaped fruit from a population of 182 Euvitis seedlings. SigmaScan® accurately characterized fruit shape elongation as had been recorded in previous studies. Although elongated shapes were measured accurately, the calculations used were unable to conclusively analyze ovoid or pear-shaped fruits. Study 2 evaluated the inheritance of leaf shape (lobing) in several populations of V. rotundifolia crosses within the University of Arkansas fruit breeding program. Based on previous studies, it was hypothesized that leaf lobing was a dominant trait. The two populations expected to segregate into a 3:1, lobed:standard, phenotypic ratio were successfully observed, while only two of the six expected to demonstrate a 1:1, lobed:standard, phenotypic ratio were observed. Previous studies suggest the unexpected ratios observed may be attributed to a lethal allele combination, where homozygous dominant progeny are not viable, or modifier genes impacted leaf shape of the seedlings. Further evaluation of these and other populations in addition to molecular analysis would be helpful in characterizing inheritance of leaf lobing in muscadine hybrids