GAMETOCIDAL EFFECTS OF GIBBERELLIC ACID (GA₃, GA₄₊₇) ON COMMON ONION (ALLIUM CEPA L.)

Two experiments aiming at identifying gametocidal substances useful either for breeding purposes or for hybrid seed production without resorting to male sterility, were carried out during 1978 and 1979. Gibberellic acid compounds, GA₃ and GA₄₊₇, were tested on the cv. 'Dorata di Parma'. The concentrations studied were 0.02, 0.06, 0.1, 0.2, 0.4, 0.6% for GA₃ and 0.02, 0.06, 0.1, 0.3, 0.5% for GA₄₊₇. The plants were sprayed at intervals of 1–3 days for 1 month starting from the bolting stage.

The treatments were 10 and 15 respectively in 1978 and 1979; the 1 plant-unit was repeated 4 times in experiment 1 and 10 times in experiment 2.

Per each plant 3 umbels were maintained: 1 bagged to control the selfing rate in presence of blowflies, the second one bagged without blowflies, the third umbel free to open pollination. The data recorded for each umbel were: total number of flowers, number of seeded flowers, number of perfect seeds, weight and germination of perfect seeds. In the 1979 experiment, the pollen germination of the 'open' umbels was also tested.

The most efficient concentrations resulted to be 2 000 ppm for GA₃ and 5 000 ppm for GA₄₊₇ sprayed 10 times at 2–3 day intervals starting from the bolting stage.