QTL Mapping of Tomato Fruit Weight-Related Traits Using Solanum pimpinellifolium Introgression Lines

As the primary harvested organ, fruit size and weight hold significant economic importance during tomato production. Therefore, elucidating the genetic mechanisms underlying fruit size and weight is of considerable agronomic value. In this study, the Solanum pimpinellifolium introgression lines were constructed with “LA2093” as the donor and “Jina” as the recipient, and a genetic linkage map was constructed. Preliminary QTL mapping was conducted using four fruit-related traits: single fruit weight, fruit diameter, fruit length, and fruit shape index. A total of 10 QTLs were identified, including one for single fruit weight (qFw-3), five for fruit diameter (qFtd-3-1, qFtd-3-2, qFtd-4, qFtd-7, and qFtd-12), two for fruit length (qFl-3 and qFl-11), and two for fruit shape index (qFsi-2 and qFsi-3). To explore the key regulatory genes of the single fruit weight QTL qFw-3 locus, it was further finely mapped between SSR3-14 and C03M65101. The SSR3-14 and C03M65101 interval contained 57 genes on chromosome 3 (64.68–65.10 Mb) in the reference genome. Among these, eight genes, including Solyc03g114830, Solyc03g114870, Solyc03g114880, Solyc03g114890, Solyc03g114900, Solyc03g114910, Solyc03g115200, and Solyc03g115380, were identified as candidate genes involved in regulating fruit weight. These studies provide a basis for future functional validation of key regulatory genes and offer valuable genetic resources for the improvement of fruit size and weight during tomato breeding.