Towards Identification, Isolation and Characterization of Disease Resistant Genes from the Native North American Grape Species Vitis Shuttleworthii

Diseases such as Pierce's disease, anthracnose, and downy mildew are the limited factors of growing the European grapes (Vitis vinifera) in the southeast United States. On the other hand, many native North American grape species are tolerant/ resistant to these diseases. However, little has been know about the mechanism and genetic basis of the host resistance, which has been greatly hampering our ability to genetically manipulate the host resistant genes for cultivar improvement. To improve disease resistance of the European grape varieties by using the host resistance from the native American species, a functional genomic project with emphasis on identifying, isolating, and characterizing disease resistant genes was initiated at the Center for Viticulture and Small Fruit Research, Florida A&M University, in collaboration with the USDA-ARS Horticultural Research Laboratory at Fort Pierce, Florida. Vitis shuttleworthii, one of the most disease/pest resistant grape species originated from the southeastern United States, was chosen for the EST sequencing. We have sequenced 22,500 ESTs, from which about 9,000 unigenes were generated. Functional annotation revealed that more than 7% of them were correlated to disease resistance. Comparative genomic analysis indicated that about 20% of the genes found in the native grapes did not have homology in the European grapes (screening approximately 170,000 ESTs and 23,000 unigenes). The potential usefulness of these unique genes as genetic markers linked to disease resistance, and their role in disease resistance pathways are being further examined using microarray analysis. Among the homologous gene sequences between V. shualwworthii and V. vinifera, a high frequency of SNPs was detected between the two genomes. Functional analysis revealed that high percentage of these SNP variations may be correlated to disease resistance.