Onion (Allium cepa L) is one of the important condiments widely used in all households through the year. Onions may be eaten raw, fried and pickled. The green leaves and immature and mature bulbs are eaten raw or used in preparation of vegetables. Onions are used in soups, sauces and for seasoning foods. The small bulbs are pickled in vinegar. Recent research has suggested that onions in the diet may play a part in preventing heat stroke and other ailments. Onion bulb is rich in phosphorus, calcium and carbohydrates. The composition of onion bulb is given in table 1. The pungency in onion is due to a volatile oil known as allyl-propyl disulphide.
Onion is commercially grown on an area of 131.4 thousand hectares with the production of 1.8 million tones (Table 2). The major onion growing districts are Kasur and Vehari, in Punjab; Hyderabad, Sanghar, Mirpurkhas, Nawabshah, Dadu , Badin, N. Feroze, Ghotki and Shikarpur in Sindh; Swat and Dir in NWFP and Chaghi, Kharan, Kalat, Nasirabad, Mastung, Killa Saifullah, Khuzdar, Turbat and Jaffarabad in Balochistan. These 22 districts account for more than 77 percent of the total production of onion in Pakistan. More than 50 percent of the total production comes from eight districts namely Hyderabad, Sanghar, Mirpurkhas, Nawabshah, Swat, Chaghi, Kharan and Kalat. Top ten onion producing districts are Chaghi, Hyderabad, Sanghar, Swat, Kharan, Kalat, Mirpurkhas, Nawabshah, Nasirabad and Dir contributing more than 59% of total production. The total production of onion from Punjab is equivalent to the total production of two districts of Balochistan (Chaghi and Kharan). Hyderabad and Sanghar districts of Sindh produce 3% more than that of whole Punjab