Assessment on genotypic variability and character association using Rhizobium cultures on growth and nodulation of cowpea (Vigna unguiculata L. Walp.)

Abstract

The present experiment was carried out with five genotypes of cowpea and three rhizobium cultures to assess the extent of genetic variability and character association for growth and nodulation. Field measurements and other studies reveal that nodulation and nitrogen fixation is a complex character being sensitive to environmental and genetic factors affecting the plant, bacteria and their interaction. Significant variability was also found for most of the characters when grown with rhizobium culture. Variable interaction was found with the genotypes e.g., groundnut culture showing positive interaction with cowpea genotypes. EC-101943 was found to be the best performing cowpea genotype in terms of grain yield spreading over the treatments. Grain protein content was not found to be correlated with the nodule characters directly though was found to be correlated with other non-nodulating characters. Shoot nitrogen content was found to be correlated with matured grain protein content indicating the possibility of assimilation of fixed nitrogen being utilized in a defined pathway. The enhanced effect of nitrogen fixation as evidenced from the results on grain yield might be due to indirect contribution of other correlated nodulating and non-nodulating characters, hence selection to be done accordingly.