Application of SNP molecular markers for bitterness trait in nineteen parental lines of parthenocarpic cucumber

Bitterness in cucumber fruit and foliage is due to the presence of cucurbitacin.
Cucumber plants carrying the bi allele exhibit non-bitter foliage and fruits, regardless of environmental conditions.
The dominant Bi allele, responsible for bitterness in cucumber, encodes oxidosqualene cyclase.
Therefore, this research aims to utilize DNA markers for selecting cucumber cultivars with genes controlling bitterness, thereby accelerating the breeding process.
The search for single nucleotide polymorphism (SNP) sites in the bitterness gene revealed a single point mutation at the C393Y position of the Bi gene sequence in cucumber (Bi_C393Y). This mutation changes cysteine to tyrosine, altering the protein structure.
Furthermore, it results in a reduced catalytic rate of cucurbitadienol synthesis, contributing to bitterness in cucumbers.
Evaluations were conducted on 19 parental cucumber lines, and the detection of the Bi gene using the Bi_C393Y marker revealed that non-bitter cultivars were homozygous for the T base, while bitter cultivars were homozygous for the C base.
It was found that 13 parental lines lacked the bitter gene genotype, and nine parental lines possessed the bitter gene genotype, consistent with the results of cucumber leaf taste tests.
This molecular marker will be beneficial for selecting the Bi gene in breeding parthenocarpic cucumber cultivars without bitterness.

International Symposium on Biotechnological Tools in Horticulture

P. Laklai, N. Nitwatthakul, A. Tira-umphon

Cucumis sativus, parthenocarpy, marker-assisted selection, cucurbitacin, breeding

https://doi.org/10.17660/ActaHortic.2026.1454.72