QTL mapping and stability analysis of trichome density in zucchini ( L.).

Trichomes provide an excellent model for studying cell differentiation and proliferation. The aboveground tissues of plants with long dense trichomes (LDTs) can cause skin itching in people working in a zucchini field, in which management, pollination, and fruit harvesting are difficult. In this study, an F population was constructed with the LDT inbred line "16" and the sparse micro trichome (SMT) inbred line "63" for QTL analysis of type I and II trichome density. Two QTLs were identified on chromosomes 3 and 15 using the QTL-seq method. Additionally, 191 InDel markers were developed on 20 chromosomes, a genetic map was constructed for QTL mapping, and three QTLs were identified on chromosomes 3, 6, and 15. Two QTLs, and , were identified in both QTL-seq and genetic map-based QTL analyses, and was the major-effect QTL. The stability of and was confirmed using data from F plants under different environmental conditions. The major-effect QTL was located between markers chr15-4991349 and chr15-5766791, with a physical distance of 775.44 kb, and explained 12.71%-29.37% of the phenotypic variation observed in the three environments. was located between markers chr3-218350 and chr3-2891236, in a region with a physical distance of 2,672.89 kb, and explained 5.00%-10.64% of the phenotypic variation observed in the three environments. The functional annotations of the genes within the region were predicted, and five genes encoding transcription factors regulating trichome development were selected. encoded zinc finger protein (ZFP) and harbored nonsynonymous SNPs in the conserved ring finger domain between the two parental lines. There were significant differences in expression between "16" and "63", and a similar pattern was found between germplasm resources of LDT lines and SMT lines. It was presumed that might regulate trichome density in zucchini. These results lay a foundation for better understanding the density of multicellular nonglandular trichomes and the regulatory mechanism of trichome density in zucchini.