Leaf Shape Locus Maps to Chromosome 1 in Muscadine Grape

Leaf shape in plants plays a vital role in water use, tolerance to abiotic stresses, and formation of canopy structures. Muscadine grapes ( Vitis rotundifolia ) are native to the southeastern United States and typically have unlobed leaves. A previous breeding effort successfully introduced the lobed-leaf trait of Vitis vinifera into the muscadine cultivar Southern Home via a series of interspecific hybridizations. A linkage-based high-density genetic map was developed using a biparental mapping population from a cross between the muscadine selection Ga. 8-1-313 (female, unlobed leaves) and ‘Southern Home’ (hermaphroditic, lobed leaves) to map quantitative trait loci (QTLs) associated with leaf lobing. The mapping population consisted of 130 F 1 progeny that were genotyped via a genotyping by sequencing method (GBSpoly). Single nucleotide polymorphism (SNP)-based genetic maps were constructed and verified by mapping the grape sex locus. Mature leaf samples from both parents and progeny were collected, digitally scanned, and 17-point landmarks were placed in well-defined biologically homologous points of each leaf image. The x, y coordinates of these landmarks were then used to analyze leaf shape using generalized Procrustes analysis (GPA). Significant variations in leaf shape were identified via principal component analysis (PCA). The principal component (PC) scores were used as phenotypes to perform QTL analysis, and a major QTL determining leaf lobing was identified on chromosome 1 in ‘Southern Home’, which explained 75.1% to 76.6% of total phenotypic variance. Further study of the identified QTL region can be carried out to identify candidate genes involved in leaf lobing in grapes.