Salinity and Sodicity Induced Responses on Total Phenols, Flavonoids and Tannins Accumulation on Cowpea (Vigna unguiculata (L) Walp)

Abstract

Food shortage remains a developmental hindrance in globally with about 25% of world’s population suffering from continued food and nutritional insecurity especially in ASALs. Reduced arable tracts of land for cultivation, increased population and variation in non-living factors such as water and salinity are challenges facing the world. Cowpea is commonly grown on ASALs which are greatly affected by salinity. The study involved 4 cowpea varieties; K80, M66, Kunde 1 and KVU 27-1 that were subjected to both CaCl_2(aq) and NaCl_(aq)  at levels of 0 (control), four, eight and twelve dS/m. A complete randomized design in replicates of three in a greenhouse was used at Jomo Kenyatta University of Science and Technology, Juja Sub county, Kiambu County on October 2021-January 2022.The salts concentrations (NaCl and CaCl₂) were applied to the soil from time of sowing and constant levels were monitored throughout by use of an EC probe Determination of total phenols, tannins, and flavonoids content was done using a UV-VIS spectrophotometer. The obtained data were evaluated using 2-way ANOVA at 5% significance level using SPSS (software version 21). As salinity and sodicity levels increased, the phenols, tannins and flavonoids content also increased. Variety M66 recorded the highest total phenols, tannins and flavonoids above 8 dS/m hence it developed a defense mechanism against salt stress. Therefore, variety M66 was better adapted to high salt levels because it performed better at high saline and sodic levels. Therefore, farmers especially in marginal areas affected by salinity should adopt growing of M66 cowpea variety.