RECENT ACHIEVEMENTS IN ONION RESEARCH IN MAURITIUS

Mauritius is a small volcanic island (1,865 km²) in the Indian Ocean at latitude 20° South and longitude 57° East. Mauritius enjoys a subtropical climate characterized by two seasons. The summer season, from November to April, has mean temperatures of 21-28°C; the winter season, from May to October, has mean temperatures of 17-24°C. According to rainfall distributed, Mauritius is categorized into super-humid (3,000-3,500 mm), humid (1,250-3,000 mm) and sub-humid (< 1,250 mm) zones. The land rises from coastal plain to discontinuous mountains encircling the central plateau. The relative humidity ranges from 60-68% in dry coastal areas and up to 87% on the high plateau. Onion is an important vegetable crop, consumed daily by all sectors of the Mauritian society in the form of salad, cooked in curries, boiled, fried, baked and pickled. Onion production in Mauritius followed an upward trend from 1990 to 2002 (Fig. 1). The area devoted to onion production has remained more or less stable (325 ha). Nevertheless, the production is insufficient to cover the national consumption estimated at 16,000 tonnes. Hence, onion has to be imported for an annual value of about Rs 70 million annually. In Mauritius, onion production is carried out mainly by two methods. The first method involves onion production from setts with open-pollinated varieties ‘Local Red’, ‘Véronique’ and ‘Noflaye’. 15-16% of total production is carried out by this method where both green onion and fresh bulb onion are harvested. The bulk of onion in Mauritius is produced through transplants with hybrid varieties. The monthly production of onion increases from April to December with a peak production of 3,200 tonnes by November (Fig. 2). There is a surplus of 1600 to 1800 tonnes of onion on the market during this period, which needs storage. Over the past years, the main constraints facing the onion industry in Mauritius have been the lack of improved varieties with better yield and storage quality of different agro-climatic conditions in Mauritius. The open-pollinated varieties commonly grown such as ‘Local’, ‘Veronique’ and ‘Noflaye’ are characterized by low yields of 8-15 t/ha. These varieties are well appreciated for pungency, shape, colour and shelf life. On the other hand, the hybrid varieties such as ‘Yellow Dessex’, ‘Sivan’ and ‘Red Granex’ produced yields in the range of 40-50 t/ha. However, these varieties are also characterised by relatively poor storability, leading to high percentage of post harvest losses. Furthermore, due to the seasonal surplus of onion during October to December, high percentage of post harvest losses occurred during this period.