A three-year trial on onion (Allium cepa L.) seed production by "seed-to-seed" method

Field trials on an early onion cultivar 'Texas Grano' and a late one 'Dorata di Parma' were carried out at Cadriano, Bologna (northeast Italy) in 1988, 1989, and 1990 with the aim of studying the effect of three sowing times (July, August, and September) for the "seed-to-seed" (40 plants m(-2)) method, and three GA(3) doses (0-200 and 400 ppm, applied before bolting) on seed production. These treatments were compared with the traditional "bulb-to-seed" (10 bulbs m(-2)) method (control). Seed yield was strongly affected by season's environments, plant densities, cultivars, and planting times, but not as much by GA3 applications. When these factors occurred in a favorable combination, seed yield from the "seed-to-seed" crop was almost equal to that from the "bulb-to-seed" one. This was mainly due to a four-fold higher plant density of the former crop method, which however, as compared to the bulb-to-seed crop method, produced one umbel per plant instead of four. Occasionally, GA3 applications increased, although not significantly, the seed yield and the 400 ppm dose seemed to be the best one. 'Dorata di Parma' gave, on average, a higher but less constant seed yield than 'Texas Grano'. The latter gave a higher yield after July-August sowings, the former after August sowings or September transplant. However, the "seed-to-seed" method was a much more demanding crop system in comparison with the "bulb-to-seed " system.