Effects of Varietal Differences and Severity of Seed Damage by Callosobruchus maculatus(F.) on the Weight and Germination of Some Improved Cowpea Seeds.

Abstract

The effects of varietal differences and severity of seed damage by the cowpea bruchid, Callosobruchus maculatus, on the weight and germination of some improved cowpea seeds were investigated in a 5 x 4 factorial experiment laid out in a completely randomized design replicated three times. Five improved cowpea seed varieties, namely, -SAMPEA 6, SAMPEA 7, SAMPEA 9, SAMPEA 10 and SAMPEA 11, were exposed to infestation and damage by C. maculatus. The damaged seeds were sorted, based on the number of exit hole( s) in them, into – no-hole, one hole, two hole, and three-hole groups and thereafter placed on moist tissue paper in Petri dishes. The emergence of radicles and primary leaves 96 hours after placement (HAP) were used as germination indicators. SAMPEA 6 and SAMPEA 7 had the highest and lowest mean weight per seed (207.5mg and 159.2mg) respectively and both differed significantly (P<0.05)from other varieties. SAMPEA6 and SAMPEA 7 both had a significantly higher (P<0.05)mean percentage germination (100.0%) than other varieties based on the emergence of radicles. Similarly, SAMPEA 7 and SAMPEA 11 had the highest mean percentage germination (25.0%) based on the emergence of primary leaves but were significantly different (P<O.OS) from SAMPEA6 and SAMPEA 10 only. The mean weight value (193.7mg) of seeds with no holes differed significantly (P<0.05)from those of seeds with one or more holes. Based on the emergence of radicles and primary leaves, seeds with no hole had highest percentage germination (93.33% and 61.33%) respectively and were significantly (P<0.05)different from those with hole(s). Significant interaction effects were also observed between variety and number of holes at P=0.05.