Fruit shape morphometric analysis and QTL detection in a set of eggplant introgression lines

Eggplant fruit shape is an important quantitative agronomic trait. The use of introgression lines (ILs) for QTLs identification is a powerful tool for the elucidation of the genetic control of eggplant fruit shape. In the present study, a set of 16 eggplant ILs, each harboring a single marker-defined chromosomal segment from the wild eggplant relative S. incanum in the genetic background of S. melongena, was evaluated for fruit shape in two environments (open field and screenhouse). A detailed phenotyping of the fruits of the two parents, hybrid and ILs was performed using 32 morphological descriptors of the phenomics tool Tomato Analyzer. Several morphological differences were found between parents, and the hybrid displayed negative heterosis for many fruit shape traits, being more similar to the S. incanum parent. Significant differences for most fruit shape descriptors were found between ILs and the recipient parent. For many descriptors, the genotype factor had the highest contribution to the percentage of the sum of squares. Although the contributions of the environment and the G x E interaction were significant for almost all descriptors, their effects on fruit shape were relatively low. Hierarchical clustering revealed nine clusters of highly correlated traits and six ILs groups. A total of 41 stable QTLs spread over ten chromosomes were detected. Of these, twenty QTLs associated to Basic Measurement and Fruit Shape Index descriptors were syntenic to other previously reported in several intraspecific and interspecific eggplant populations, while twenty-one QTLs, including Blockiness, Homogeneity, Asymmetry and Internal Eccentricity, were new. In addition, mutations associated to genes belonging to SUN, OVATE and YABBY families described in tomato were reported in the QTLs genomic regions identified in eggplant. Eleven SUN and YABBY genes were proposed as potential candidate controlling fruit shape variations in eggplant. Our results provide novel and highly relevant insights on the genetics of fruit shape in eggplant and have important implications for eggplant breeding.