Assistant Professor Alabama State University, Montgomery, AL 36101 Montgomery, Alabama
Body of Abstract: Muscadine grape (Vitis rotundifolia) is cherished for its unique fruity flavor and high nutraceutical value but did not gain popularity as table grape due to presence of large seeds. Unfortunately, introgression of seedlessness from Bunch to muscadine grape is not feasible through conventional breeding due to their genetic incompatibility. Therefore, our research aimed at identifying gene(s) associated with parthenocarpy for possible development of seedless muscadine grape through gene editing system. Inflorescence and berries at different developmental stages (2mm, pea, veraison and ripe) were collected from non-parthenocarpic (cv. Noble) and parthenocarpic (cv. Fry Seedless) muscadine grapes for qRT-PCR and transcriptomics studies. We identified an ortholog of Tomato parthenocarpic gene SlAGL6 in grape (VvMADS3) through in silico analysis of bunch grape (Vitis vinifera) genome. The MADS3 genes was conserved in muscadine grapes and was highly expressed in inflorescence and immature berries but absent in leaves and ripe berries. The relative expression of VroMADS3 was higher in pea-stage berries of non-parthenocarpic cv. Noble and almost absent in parthenocarpic cv. Fry Seedless. The relative expression of VroMADS3 gene was positively correlated with seed content of muscadine cultivars irrespective of their berry size. The non-parthenocarpic cv. Jane Bell berries which had the highest seed weight, showed the highest VroMADS3 gene expression while it was minimal in seedless parthenocarpic cv. Fry Seedless. These findings suggest that VroMADS3 gene controls seed morphogenesis and is associated with parthenocarpy in muscadine grapes. Genome-wide RNA sequencing has already been conducted on inflorescence and berry tissues at different development stages of non-parthenocarpic and parthenocarpic muscadine grapes. The transcriptome analysis of RNA-seq data is underway to identify the differentially expressed gene(s) linked to parthenocarpy in muscadine grapes, which will be validated by qRT-PCR. This research will pave the way for developing a parthenocarpic seedless muscadine table grape through gene editing technology.