DOMINANCE AND HETEROSIS IN F1 WATERMELON HYBRIDS

Purpose. To evaluate heterosis in new F1 hybrids and to select the best ones with the greatest dominance and heterosis for the "growing period length", "yield", "marketability" and "mean marketable fruit weight" traits for further use in breeding for heterosis. Object. Twenty-seven F1 watermelon hybrids and 22 parents. Methods. General scientific, measuring and weighing, computational and statistical. Results. F1 watermelon hybrids and their parents were screened for the following characteristics: lengths of interphase periods, total yield, marketability, and mean marketable fruit weight. Analysis of the growing period and its parts showed that in the hybrids the "emergence - ripening" period ranged 71 to 80 days in 2021 and 60 to 84 days in 2022. The variation limits were from 6 to 24 days. The "anthesis of male flowers - anthesis of female flowers" and "anthesis of female flowers – fruit setting" were the most stable interphase periods across the years both in the hybrids and in the parents. Eleven hybrids were classed as ultra-early, as their "emergence - ripening" period did not last longer than 63 days in 2022 or 72 days in 2021. On average in the hybrids across the study years, the variation amplitude (Am) of the "total yield" trait was 30.9 t/ha; of the “marketability” trait – 16%; of the "mean marketable fruit weight" trait – 2.9 kg. In the parents, Am was 43.1 t/ha, 20% and 2.8 kg for the ‘total yield’, ‘marketability” and "mean marketable fruit weight" traits, respectively. The variation limits (Lim) of the "yield" and "marketability" traits in the parents were wider than those in the hybrids. On the opposite, the variation limits of the "% to the check accession" and "mean marketable fruit weight" traits in the study years were wider in the hybrids. In breeding for yield, 10 F1 hybrids, which were significantly superior to the check F1 hybrid, ‘Kazka’, (130-166% to the check hybrid), are of practical value. Analysis of dominance and heterosis in the F1 hybrids allowed us to select the best combinations with the greatest dominance and heterosis for yield (hp=0.39-3.94; X=101-136), marketability (hp=0.11-7.00; X=101-106) and mean marketable fruit weight (hp=0.26-99.00; X=100-164). Based on high indicators of dominance and heterosis, 10 F1 hybrids were selected for further breeding; they were also noticeable for a set of economically valuable characteristics: early ripening, high yield, marketability, evenness, resistance to biotic factors, etc. Fruits of the selected hybrids are attractive in appearance and have excellent palatability. The selected F1 hybrids are valuable for breeding to create competitive first-generation watermelon hybrids. Conclusions. The interphase periods that were most stable across the years were determined. Eleven ultra-early hybrids were selected. Ten F1 hybrids, which in two study years were significantly superior to the check F1 hybrid, ‘Kazka’, (130-166% to the check hybrid), are of practical value. High marketability was noted in 6 hybrids. Analysis of dominance and heterosis in the F1 hybrids allowed us to select 10 combinations with the greatest dominance and heterosis for yield (hp=0.39-3.94; X=101-136), marketability (hp=0.11-7.00; X=101-106) and mean marketable fruit weight (hp=0.26-99.00; X=100-164) for further breeding, as they are of practical value for heterosis breeding.