Standardization of different aspects of onion seed production

Abstract

Onion is the second most important vegetable crop after tomato in the world. Pakistan is producing only 20% onion seed of its needs and remaining seed is imported causing big loss to the economy. The cause of low onion seed production is the lack of knowledge regarding its production technology. To improve yield and quality of onion seed, a series of experiments were executed in the field during 2013-14 using onion cultivars under split plot design. In first experiment, impact of set/bulb size on yield and quality of onion seed was evaluated. Three set sizes (1-2.5, 2.6-4, 4.1-5.5 g) and three bulb sizes (41-70, 71-100, 101-130 g) were used. In second experiment, nine combinations of phosphorus and potassium (30:25, 30:50, 30:75, 60:25, 60:50, 60:75, 90:25, 90:50 and 90:75 kg/acre) were assessed for quality onion seed production. In third experiment, gibberellin application (GA3 @ 100 mg/L of H2O) effects at different plant growth stages (2-3 leaf stage, 6-7 leaf stage and at the time of flowering) were assessed for enhanced yield and quality of onion seed. Maximum bulb size (101-130 g) in cultivar Phulkara performed the best regarding vegetative (plant height, number of leaves per plant, leaf area) and floral traits (days taken to start flowering, days taken to 50% flowering, days taken to complete flowering, number of flowering stalks per plant, length of flowering stalk), while cultivar Dark Red with the same bulb size (101-130 g) gave maximum yield. Seed quality traits like seedling vigour index and speed of germination were improved with increase in bulb size regardless of cultivars. Among onion cultivars, Dark Red showed maximum improvement in vegetative, floral and yield related traits when treated with phosphorus and potash @ 60:75 kg/acre. Seed quality traits like germination percentage, speed of germination and seed viability were significantly improved when mother seed plants were treated with phosphorus and potash @ 30:75 kg/acre. GA3 application at the time of 2-3 leaf stage and 6-7 leaf stage significantly improved vegetative and floral traits in cultivar Phulkara. However, maximum seed yield was observed in cultivar Dark Red when GA3 was sprayed at 6-7 leaf stage. Foliar spray of GA3 at 6-7 leaf stage and at the time of flowering in Dark Red produced seeds, which exhibited higher germination percentage, higher speed of germination and reduced days taken to complete 50 percent germination.