APPLICATIONS OF POLYPLOIDS IN MUSCADINE GRAPE (VITIS ROTUNDIFOLIA MICHX.) BREEDING

Abstract

The Florida grape industry is an undeveloped agricultural enterprise because of serious disease problems. The muscadine grape (Vitis Rotundifolia Michx.) is resistant to many diseases and therefore is very important for regional grape production. Unfortunately, all muscadine grape cultivars contain large seeds that fall short of consumer expectations for table grape consumption. Seedlessness is one of the most desirable characters in developing new muscadine grape cultivars. Attempts to introduce seedlessness from V. vinifera grapes into muscadine grapes have been made by regional breeders for decades and success has been rare due to genetic barriers between these two genera. An alternative approach is to develop triploid (3x) seedless muscadine grapes by crossing tetraploids (4x) and diploids (2x). The creation of a seedless 3x grape has been recognized in V. vinifera and some other grape cultivars (Vitis complex) in Asia, particularly Japan and South Korea. The objectives of this research were to characterize tetraploids/aneuploids in muscadine grapes and to utilize them in 3x seedless muscadine grape breeding. Sixteen polyploids, including 4x and aneuploids, have been identified in muscadine grape. Twelve resulted from colchicine treatment while the rest were identified from thousands of seedlings derived from open pollination of 2x ?Darlene?, ?Pam? and ?Supreme?. The ploidy status was confirmed by flow cytometry and chromosome counting. The polyploids were also morphologically distinguished from 2x muscadine origins by their earlier budbreak, weaker vegetative growth, shorter internodes, greener and thicker leaves, fewer succulent stems, and earlier ripening. Further investigation revealed that the polyploids had lower pollen viability with more floating seeds. These polyploids are being hybridized with diploids to develop 3x seedless muscadine grape cultivars.