Morphological and Genetic Characterization of Fruit Abscission Zone in Muscadine

Muscadines face limitations to fresh market production due to high manual labor costs. Mechanical harvesting holds promise for reducing the costs associated with muscadine production but requires cultivars with easily detached berries at maturity. This study aimed to determine muscadine fruit and pedicel characteristics influencing fruit detachment force and to unravel the genes, hormones, and regulatory networks governing muscadine abscission. We characterized the fruit detachment force of muscadine berries across eighteen genotypes and at four developmental stages. Following this, we performed a transcriptome analysis using the mature pedicel tissue of two genotypes, a genotype with high fruit detachment force at maturity and a genotype with low fruit detachment force at maturity, to identify differentially expressed and uniquely expressed genes contributing to fruit detachment. We found that pedicel length, pedicel-fruit junction area, and fruit diameter were all positively correlated with fruit detachment force. This study also identifies novel candidate genes, transcription factor families, and pathways associated with muscadine fruit abscission. These findings provide valuable knowledge on the progression of fruit abscission and insights for reducing fruit detachment force, particularly in developing machine-harvestable muscadine cultivars and fostering sustainability and efficiency in muscadine production. By studying grape physical characteristics such as abscission zone morphology, fruit and pedicel characteristics, and fruit detachment force in conjunction with a transcriptomic analysis, we offer a comprehensive approach to studying muscadine abscission on a level that has not been previously reported in any grape species. This study identifies several muscadine genotypes with the potential for mechanical harvesting.