RELATIONSHIP BETWEEN NIL, AUTO- AND ALLO-COMPETITION AND THEIR IMPLICATIONS IN COWPEA BREEDING

Abstract

Competition among genotypes encounters in the genetic and plant breeding studies, causing strong confounding effects not only on different genetic parameters [1] but also on performance per se and ranking of cultivars [2]. Therefore, the present study was undertaken to assess yield performance of cowpea cultivars under nil-, auto- and allo-competition and the impact of their relationships in cowpea breeding. Three cowpea (Vigna unguiculata L. Walp) cultivars differing in growth habit, maturity duration and yielding ability (IT82D-716, IT82E-18 and IT84E-124) were evaluated under the conditions of nil-, auto- and allo-competition for four growing seasons (summer and rainy seasons of 1987 and 1988). The 18 treatments that represented conditions of auto- and allo- competition were evaluated in a randomized complete block design with four replications following alternate-row design of Hanson et al. [3]. Each plot had a single-row of 2-m length spaced 40 cm apart with 10 cm distance between plants. The same set of treatments was also evaluated under nil-competition wherein all the treatments were arranged in a randomized complete block design with four replications at the plant spacing of 40 cm in 4-m long rows spaced 40 cm apart. At this spacing, the competition effects were found nonsignificant [4]. Ten plants from each row were harvested individually for seed yield. The average performance of cultivars under nil-, auto- and allo- competition was compared with each other. Correlation coefficients were estimated for grain yield under different competition situations.