This research’s objectives focused on using two male-sterile systems, apetaloid and petaloid types, as female parents for the F₁ marigold cut flower hybrid development. These female lines’ creation came from the same original line, the gynomonoecious line, with five backcrosses to obtain two female lines, FY1502 and FY1502AP. Their crossing with 10 male lines progressed during the summer from April to August 2016. Then, growing the progenies of 20 crosses and four commercial varieties as checks for characterization and evaluation continued in a lattice design with two replications. Planting them in six blocks contained 10 plants per treatment. The data recorded on eight horticultural characteristics include flower diameter, number of petals per flower, calyx length, peduncle length, flower weight, the number of days from sowing to first flowering, plant height, and plant bush diameter, as well as, the morphology of flowers. The results showed that progenies from two female apetaloid and petaloid with the same male line gave similar outcomes; all progenies produced male sterile double-flowers with golden-yellow flowers, except progenies of MY1501 and MY1502, which created yellow flowers. FY1502 gave the same superior F₁ progenies as FY1502AP in the diameter of the flower. Based on the results, both females could give good characteristics on flower diameter, calyx length, plant height and bush diameter, and early flowering. However, the heterobeltiosis of the F₁ progenies of a few vegetative and reproductive characteristics differed. The FY1502AP gave better progenies in peduncle length heterobeltiosis than those of FY1502 and slightly better for plant bush diameter, whereas FY1502 gave slightly better in flower weight heterobeltiosis than those of FY1502AP. The findings of this study indicate that this apetaloid type could benefit Thailand’s marigold seed production program.

Keywords: American marigolds (Tagetes erecta L.), F₁ progeny, male sterility, petaloid, apetaloid, horticultural characteristics

Key findings: Two forms of male sterile marigolds, apetaloid and petaloid, could give similar F₁ hybrids. The apetaloid line has an advantage over the petaloid one due to its stability in genetic control. Presently, the petaloid male sterility technique in Thailand is prevalent for hybrid marigold production. The results from this study show that marigold seed production in Thailand could employ this apetaloid type in the seed production program.