QTL analysis and candidate gene prediction for melon petal size

Petal size is a key agronomic trait for plant reproduction. However, the genetic basis and developmental regulation of melon petal size remain unexplored. In this study, the examination of F₂ populations derived from M1–15 (large-petaled) and PI 614174 (small-petaled) melon lines suggested that petal size is a quantitative trait. Microscopic observation revealed that the difference in petal size between parental lines was due mainly to the cell number and size. Bulk segregant analysis sequencing (BSA-seq) and genetic mapping of data from 2023 to 2024 identified a major effective stable QTL Cmqps8.1 for petal size in a 1.42 Mb region on chromosome 8. MELO3C024520.2 (annotated as ethylene-responsive transcription factor ERF024) was preliminarily predicted as the candidate gene for melon petal size through in silico BSA, gene expression analysis, and the cloning of promoter and coding region sequences in the parental lines and a natural melon panel with different petal sizes. The InDel marker Chr08_9521560 located in the mapping region, co-segregated with large and small petals in F₂ individuals and 19 melon germplasms, and could serve as the marker in marker-assisted selection. These results provide a theoretical basis for further fine mapping and functional analysis of key genes related to melon petal size.