The University of Florida’s Grape Breeding Program: Historical Insights and New Directions

Bunch grapes have been grown in Florida since the days of the early pioneers. However, all initial attempts at growing the European Vitis vinifera wine and fresh market cultivars were unsuccessful as vines eventually succumbed to Pierce’s disease (PD) infection. This xylem limited disease caused by Xylella fastidiosa is vectored by the glassy-winged sharpshooter and is endemic in Florida. Scientists identified several native grape species such as V. aestivalis, V. munsoniana, V. rotundifolia, V. simpsonii, and V. shuttleworthii and observed them to be thriving even under endemic PD conditions. This led to new breeding efforts at the University of Florida (UF), initially by Loren Stover, and subsequently by John Mortensen to introgress PD and other disease resistance genes from these wild species into Vinifera selections. The first bunch grape with adequate enological traits and disease resistance was the ‘Lake Emerald’ cultivar by Loren Stover in 1954. Since then, many other bunch grapes and muscadine hybrids have been released. The UF has not had an active grape breeding program since the retirement of Mortensen in 1991. To reinvigorate the conventional grape breeding program, promising bunch grape selections were identified from the old breeding program. These selections have several important traits such as abiotic stress tolerance, disease resistance, as well as loose, medium-sized clusters and berries. Replicated field trials are planned with several of these selections. We also identified several muscadine selections. The first crosses were made in 2022 and a large population of hybrid progeny is being evaluated.