The Influence of Genotype, Temperature and Moisture on Seed Longevity in Chickpea, Cowpea and Soya bean

Abstract

Seed of three chickpea (Cicer arietinum L.), three cowpea [Vigna unguiculata (L.) Walp.] and four soya bean [Glycine max (L.) Merr.] cultivars were hermetically stored for up to 2 years in various constant environments which included temperatures from —20 to 70 °C and moisture contents (fresh weight basis) from 5 to 25 per cent. In all cases the survival curves could be described by negative cumulative normal distributions. The longevity of the various seed lots differed but the value of the standard deviation (the reciprocal of which gives the slope of the survival curve when percentage germination is transformed to probit) was the same for all cultivars within a species when stored under similar conditions. Within each species the relative effects of moisture and temperature on longevity did not differ significantly between cultivars. In all three species there was a negative logarithmic relationship between seed moisture content and longevity, but the relative effect of moisture content differed between the species: differences in the longevity of soya bean seed as a function of moisture content were less than for either cowpea or chickpea. The relative effect of temperature on seed longevity did not differ between the three species, and the seed of all three species showed increasing temperature coefficients for the change in rate of loss of viability with increase in temperature. The complete pattern of loss in viability in all three species can be described by a single equation which was developed for barley and has also been shown to apply to onion seed. The constants applicable to the three grain legumes have been calculated so that it is now possible to predict percentage viability of any seed lot of these species after any storage period under a very wide range of storage conditions.