The importance of seed size in early growth of wild and domesticated cowpeas

Abstract

SummaryDomesticated cowpeas (Vigna unguiculata (L.) Walp.) have larger seeds than their wild relatives. The effects of this increase in seed size on seedling emergence and growth were investigated. In shallow sowings, to 5 cm, seed size had no effect on emergence, but in deeper plantings ahigher proportion of the larger-seeded accessions emerged, and they emerged earlier than smaller-seeded accessions. The size of seedlings just after emergence was inversely related to depth of planting and directly related to seed size. The greater size of the seedlings of larger-seeded accessions was maintained until at least 40 days after sowing, despite the higher relative growth rates of smaller, wild seedlings. When compared at the same size there was no general difference in the growth rate of wild accessions and that of domesticates. During the evolution of domesticated cowpeas, large seeds have probably been advantageous because of their better emergence and establishment under agricultural conditions, and because of the greater size of plants arising from them.