Genome-wide association study reveals the candidate genes for petiole length and diameter in cucumber

Increasing planting density is an effective method to improve crop yield. Petiole length is one of the main factors determining how many plants can be effectively cultivated per unit area. However, the genetic factors controlling petiole-related traits remained largely unexplored. In this study, we investigated petiole length (PL) and petiole diameter (PD) in 130 accessions of the cucumber core germplasm which originate from four distinct geographical groups. A Genome-Wide Association Study (GWAS) was performed to identify the genes associated with PL and PD. Three genetic loci for petiole length (gPL4.1, gPL4.2, gPL7.1) were repeatedly detected in three experiments, and a total of seven genetic loci for petiole diameter (gPD2.1, gPD2.2, gPD3.1, gPD6.1, gPD7.1, gPD7.2, gPD7.3) were detected, of which, gPD2.2 was detected in all three experiments. By using haplotype analysis and evaluating gene expression levels, we pinpointed four candidate genes within the regions identified via GWAS. These genes include CsaV3_4G036380 for gPL4.1, CsaV3_4G036610 for gPL4.2, CsaV3_2G014690 for gPD2.2, and CsaV3_7G026710 for gPL7.1/gPD7.2. This study therefore sheds light on the genetic underpinnings of petiolerelated traits in cucumbers, providing valuable insights for crop breeding and agricultural practices aimed at maximizing yield through dense planting strategies.