Genetic and histological characterization of a dwarf mutant in melon (Cucumis melo L.) reveals potential for breeding semi-dwarf cultivars.

Key message: A missense mutation from proline to leucine at position of 141 in the CmTUB8 protein causes dwarfism in melon. The dwarfing trait is of considerable agronomic importance, as it enables increased planting density and reduced management costs. In melon (Cucumis melo L.), a high-value cucurbit crop, semi-dwarf plant architecture is particularly beneficial for lowering labor requirements in greenhouse trellis cultivation. In this study, a stably inherited dwarf mutant was identified from an ethyl methanesulfonate (EMS)-mutagenized population of thin-skinned inbred line ssp. agrestis '13C'. Using bulked segregant analysis sequencing in combination with MutMap and molecular marker validation, a key missense mutation in the CmTUB8 gene was identified, which completely co-segregates with the dwarf phenotype. This mutation leads to the substitution of proline with leucine at position 141 in the CmTUB8 protein. Histological analysis showed that homozygous mutant stems have significantly reduced vascular bundle size and smaller parenchyma cells. Heterozygous plants exhibited a semi-dwarf phenotype intermediate between the wild-type and homozygous mutants, indicating potential utility in breeding. These findings provide valuable genetic resources and a theoretical basis for the development of dwarf melon cultivars.