Variability for seedling vigour in tropical cowpea (Vigna unguiculata (L) Walp

Abstract

Variations in seedling vigour and the effectiveness of emergence (E%), emergence index (E1), emergence rate index (ERI), growth rate (GR) and relative growth rate (RGR) as selection criteria among 10 Nigerian cowpea (Vigna unguiculata (L.) Walp.) genotypes were examined. Genotypes were grown under two locations to maximize environmental diversity. Considerable variation in seedling vigour was observed among the genotypes for E%, ERI, GR and RGR, suggesting that selection for further improvement in cowpea is possible due to large variability present, which may be attributed to diverse genetic backgrounds of the genotypes. Among the genotypes, AGRIBVI and IT97K-1035-17 recorded higher E% across the two environments. ERI was in most cases above 10 days. Only AGRIBVI, IT97K-1035-17 and IFE BROWN had ERI below 10 days, indicating that it would take these genotypes less than 10 days for 100% emergence to occur, when other factors are not limiting. Genotypic and phenotypic variances were generally high for E%. Broadsense heritability estimates and environmental variances indicated that E%, EI, ERI and RGR would be more reliable indices for seedling vigour. The expression of growth rate was influenced more by the environment than the genetic constitution of seedlings. EI and ERI had high positive relationship with ERI and GR respectively. The GR mutually correlated with RGR.


Key Words: Emergence index; emergence rate index; genotype; growth rate; relative growth rate


Moor J. Agric. Res. Vol.4(1) 2003: 54-59