Seed Longevity and Vigour of Watermelon (Citrillus lanatus Thumb Mansf.) Seeds Stored Under Ambient Humid Tropical Conditions

Abstract

Affordability and availability of  high quality watermelon seed as well as maintenance of longevity during storage are major problems to watermelon growers in Nigeria. The extent of variation in seed viability and vigour among nine watermelon (Citrullus lanatus (Thumb) Mansf) genotypes under humid storage conditions was investigated. Seeds of each genotype were stored for 240 days under ambient conditions in two locations; Federal University of Agriculture, Abeokuta and National Horticultural Research Institute, Ibadan. Seed viability and seedling vigor were monitored. Seed survival was evaluated by probit modelling of the serial seed viability survival pattern. The result indicated that viability of seeds at the earlier periods (0-120 days) of storage showed low deterioration as higher viability was still retained in most cases. Seed viability sharply declined from 180-240 days and the genotypes Sugar baby and Minna local had seed viability of 75-80% at the end of storage. The genotypes; Iseyin, Oyo, Abeokuta and Ogbomoso locals had poor viability as they retained less than 40% values at the end of storage. In order to retain high seed viability in some watermelon genotypes the storage duration should not be more than 180 days under ambient humid conditions. Seedling vigour was however, best in Sugar baby and Minna local genotypes while Abeokuta local and Ogbomosho local had the poorest after 240 days of storage. Probit analysis showed negative slope values for all the seed lots suggesting certain degrees of deterioration irrespective of genotype. The values of the slope revealed that the speed of deterioration was fairly reduced implying that seed longevity was prolonged. The half-life (P,) values derived by probit analysis of viability curves declined during storage of seeds of the watermelon genotypes. The highest seed storage life of 13 and 12 months were derived for seeds of 'Sugarbaby'and 'Abeokuta local', respectively, while the shortest of approximately 136 days was estimated for seeds of Ogbomoso local. Storage of seeds under favourable humid conditions offer good potential for watermelon seed viability and vigor.