10th U6+ Consortium of African Universities International Conference

Cowpea (Vigna unguiculata) is an important food crop in Kenya, especially in the semi-arid areas; many of which also have saline soils. Adoption of salt resistant varieties could improve production in these areas. Cowpeas form significant symbiotic nitrogen fixing association with Bradyrhizobium spp. Climate change could exacerbate the soil salinity posing significant challenges to both cowpea growth and its beneficial association with bradyrhizobia. Information on salt-tolerant cowpeas and associated bradyrhizobia strains is limited. This study was conducted to investigate the salt tolerance of selected Kenyan cowpea varieties and their ability to form effective nitrogen-fixing associations with Bradyrhizobia under medium to high salinity. The plants were raised in the greenhouse in sand-containing pots that were irrigated with water at 0.3, 4.0, 8.0, 12.0, 14.0 and 15.0 dS m-1 with six replicates. The plants were harvested at the 40th day after sowing (DAS), and measurements were made and recorded for number of branches, number of leaves, leaf area, leaf fresh weight, plant fresh height, shoot fresh weight; root number, length and weight. The plants were dried at 65C for 48 hours and assessed for root and shoot dry weight. Data on root-to-shoot ratio and percentage of water content were generated. The data was subjected to two-way analysis of variance. Counts and ratio data were log-transformed before analysis, and means were separated using Tukey test at p<0.05. The salinity significantly (P<0.05) reduced cowpea germination and growth: none of the cowpea accessions germinated at 15.0 dS m-1. The salinity significantly (P<0.05) reduced all the measured growth parameters. None of the accessions was more affected than the others, however Kunde Kubwa and Ken Kunde maintained higher growth performance at the highest salinity level. It is concluded that Cowpea variety; Kunde Kubwa and Ken Kunde are more resistant to salt stress.