Screening of Local and Exotic Onion (allium Cepa L.) Cultivars for Seed Production Potentiality

Onion (Allium cepa L., 2n=16) is a cross-pollinated and biennial short type vegetable and most of the important spice as well as vegetable crops throughout the world. Bulb is the main edible portion of onion plant, which is a modified organ and constituted by the thickened fleshy leaf sheaths and stem plate (Purseglove, 1988). The leading onion producing countries of the world are China, India, Poland, Japan, Turkey, Brazil and United States of America (FAO, 2007). In Bangladesh, it is widely cultivated in the larger districts of Faridpur, Pabna, Rangpur, Rajshahi, Dinajpur Jessore, Dhaka, Comilla, Mymensingh and Barisal (Rashid, 1976). It ranks first among the spice crop grown in Bangladesh and occupies an area of 40, 842 hectare with total production of 2, 10,000 tons of bulb during the period 2006-2007 (BBS, 2008) against the estimated annual demand of 4,50,000 tons (Ara et al., 2000). Onion production sometimes hampers due to scarcity of seeds. Enormous differences are observed on the average seed yield as it depends on genotype, locality, season and method of seed production (Brewster, 1994). Bulb size influences the plant growth in onion as well as the splitting of bulb (Brewster, 1994). Planting of suitable size bulbs increases the yield of onion (Singh and Sachan, 1998; Abedin et al., 1999; Khokhar et al., 2001). The average seed yield in our country varies from 370 to 500 kg per hectare, (HRDP, 1995) which is very low compared to other countries of the world (1000 to 1200 kg/ha) (Rahim, 1991; Brewster, 1994). Bangladesh produced only 150 metric tons of onion seed per annum against the requirement of 300 metric tons (Abedin et al., 1999). Therefore a great scarcity of onion seed is noticed every year, limiting its cultivation in Bangladesh. Due to shortage of onion seeds, Bangladesh has to import huge quality of seeds at the cost of hard-earned foreign currency every year. Seed production of onion is one of the crucial problems associated with onion production in Bangladesh. Seed ISSN 1330-7142 UDK = 635.25:631.53.01