Author : Otinggue Mohammad Masnar

Summary : Unvernalized mother bulbs of Red Creole onion did not flower in Los Banos, Laguna, the Philippines. Those vernalized at 5, 10, and 15 degree C for 75 days had 56, 67, and 51 percent flowering, respectively. All vernalization treatments produced seeds. A subsequent field experiment showed that mother bulbs vernalized with daily shifting at 10 and 20 degree C had significantly higher degree of flowering than those exposed to a constant temperature (10 degree C) treatment. Planting date affected flowering of Red Creole onion in Los Ba¤os but not in Batac, Ilocos Norte or Buguias Province, both in the Philippines. Late planting in Los Ba¤os resulted in higher proportion of flowering plants than earlier plantings. The range of flowering was 6-59, 33-39, and 98-99 percent in Los Ba¤os, Batac, and Buguias, respectively. Seed yields were low (4-20 kg/ha) and their planting date were not significantly different in Los Ba¤os and Batac. No seed was harvested in Buguias because of severe disease damage. Germination of locally-produced seeds was generally low (13-52 percent). Further vernalization of plants in Buguias, pre-conditioning by exposure to warm temperatures (15, 20, or 25 degree C) before planting, bulb size, or gibberellic acid (GA (subscript 3)) did not improve flowering or seed production of vernalized Red Creole onion in Los Ba¤os, but GA (subscript 3) inhibited the formation of bulbils. Seedlings vernalized in Buguias did not flower, both in Buguias and Los Ba¤os. The following constraints were identified in local onion seed production: 1) in spite of vernalization, the degree of bolting and flowering and, consequently, seed yields, were too low in low elavation areas (Los Baños and Batac); 2) conditions in the high elevation areas (Buguias) were favorable for flowering, but the dry period was too short for seed maturation; and 3) low bee activity contributed to the low seed yields.