การใช้เครื่องหมายโมเลกุลชนิด Single Nucleotide Polymorphisms (SNPs) เพื่อตรวจสอบลักษณะ Multi-pistillate Flower ในแตงกวา

Abstract

The multi-pistillate flower (MPF) trait, characterized by having more than one female flower per node in cucumber plants, plays a crucial role in cucumber yield improvement. The study made an assessment of cucumber varieties to select parents for creating the first (F1) and second (F2) hybrid populations, focusing on ensuring the homogeneity of the parental lines. Genetic characteristics, including MPFs per node, the number of nodes with MPF, MPF trait heterosis of mid-parent, and heterobeltiosis, were meticulously recorded. Subsequently, the presence of multi-pistillate flower traits was verified by the single nucleotide polymorphisms (SNPs) analysis. It was found that the selected female variety (EWSCU-809) exhibited the genetic trait of MPF and high genetic stability at 97.14%, significantly different from other varieties except EWSCU-173 and EWSCU-989; while the selected male variety (EWSCU-989) showed the genetic trait of single-pistillate flower (SPF) with a high genetic stability of 95.24%, significantly different from other varieties in the SPF group. The selected parental varieties were used to produce the F1 hybrid population. Then, the mid-parent heterosis and heritability for the MPF trait were determined using the number of MPFs per node and the number of nodes with MPF. The results unveiled a negative direction in the values. The heterosis and heterobeltiosis expressed by the number of MPFs per node were -50.23% and -72.07%, respectively while those shown by the number of nodes with MPFs were -90.08% and -95.04%, respectively. The F2 population, consisting of 219 plants, was used to create a linkage map with 244 SNP molecular markers covering all seven cucumber chromosomes. This map was then employed for QTL mapping analysis to identify molecular markers associated with the multi-pistillate flower trait. The dataset included two sets of information: average data for the MPFs per node and the number of nodes with MPFs. The QTL mapping analysis for the MPFs per node revealed three QTL positions, namely qMP2.1, qMP3, and qMP7, located on chromosomes 2, 3, and 7, respectively. These QTLs had LOD scores ranging from 4.34 to 7.53, and phenotypic variation explained (PVE) percentages between 5.6% and 10.3%. Regarding the data on the number of nodes with MPFs, four relevant QTL positions were identified: qMP2.2, qMP3, qMP4, and qMP7 on chromosomes 2, 3, 4, and 7, respectively. The LOD scores for these QTLs ranged from 4.29 to 7.58, and the PVE values were between 5.8% and 10.6%. The QTL analysis related to both datasets found that almost all QTLs were linked with the same SNP molecular markers or had closely adjacent positions. The exception was only qMP4 on chromosome 4, which showed a specific association with the trait related to the data on the number of nodes with more than one female flower. These QTLs demonstrate a promising trend for their potential use in supporting conventional breeding efforts to improve efficiency and accelerate the processes for achieving higher cucumber yields.