Dissecting genetic diversity and population structure in intergeneric citrus population using morphological and SSR...

Understanding morphological and genetic variability in the segregating citrus populations is essential for effective selection and genetic improvement. In current study, 120 F₁ hybrids derived from 'Daisy' tangerine (♀) × Carrizo citrange (♂) were evaluated using integrated morphological characterization (qualitative 47 and quantitative 18 traits) and microsatellite (SSR) marker-based molecular analyses. Morphological diversity was recorded nearly in all vegetative traits, such as growth habit, branching pattern, leaf morphology, stem, and spine characteristics. Quantitative traits such as plant height, branch size, spine length, leaf chlorophyll content, and leaf biomass exhibited wide variation, high genotypic and phenotypic coefficients of variation, and exceptionally high broad-sense heritability (94.62-99.91%) coupled with high genetic advance, indicating strong additive genetic control and suitability for phenotypic selection. Correlation analysis between genotypic and phenotypic data revealed strong positive associations among leaf size, branching traits, internodal length, stem girth, and plant height, suggesting coordinated genetic regulation of plant vigour. Multivariate analyses showed that principal components associated with vegetative vigour and leaf traits accounted for a major proportion of total morphological variation, while hierarchical clustering clearly distinguished parental groups and hybrid classes. Molecular analysis using 153 polymorphic SSR markers confirmed high genetic diversity and heterozygosity within the population. UPGMA, AMOVA, principal coordinate and STRUCTURE analyses consistently indicated extensive recombination among the hybrids and predominant genetic variation within the individuals. Overall, integrated morphological and molecular data highlight, this F₁ hybrid population as a valuable genetic resource for marker-assisted selection and QTL mapping aimed towards developing resilient citrus rootstocks.