Bio-agronomic and genetic variability of local lemon cultivars from Southern Italy

In Italy, lemon is a crucial economic cultivation, primarily grown in southern regions like Sicily, Calabria, Apulia and Campania. Despite its importance, the number of cultivars is limited and efforts are being made to both exploit and preserve local cultivars. Bio-agronomic and genetic characterization are essential steps towards achieving these goals. Our study explores the phenotypic and genetic diversity of four local cultivars from Campania region, ‘Ovale di Sorrento’, ‘Sfusato Amalfitano’, ‘Procida’ and ‘San Francesco’, over two years (2021 and 2022). We evaluated agronomic parameters of the entire plant, fruits and seeds, and conducted biochemical analyses of lemon juice. Furthermore, we addressed the challenges posed by low interspecific genetic variation through simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) marker analysis. Field data revealed significant differences in production between the two years and among the cultivars, with ‘Ovale di Sorrento’ and ‘Sfusato Amalfitano’ being the most productive, and ‘Procida’ recording the lowest values of soluble solids and acidity. Genotyping data from 19 SSR markers confirmed low variability, while ddRADSeq-based SNP analysis revealed clear structuration into three distinct groups: the first group comprised ‘Ovale di Sorrento’ and ‘San Francesco,’ differentiated from ‘Procida’ and ‘Sfusato Amalfitano’. Additionally, 29 high-effect variants provided valuable insights into the genetic distinctions and functional variations among the four lemon cultivars. In particular, the presence of variants in genes associated with mobile elements confirmed their significant contribution to the genetic diversity of plants. This study underscores the importance of combining phenotypic and genotypic analyses for better varietal characterization and valorization.