SALINITY STRESS TOLERANCE OF THREE COWPEA CULTIVARS IN A SOUTHERN GUINEA SAVANNAH ECOLOGICAL ZONE OF NIGERIA

To combat the problem of food scarcity and insecurity in areas affected by salinity, crop varieties that are tolerant to the stressful conditions should be selected and used. Therefore, this study was carried out to investigate and know the effects of salinity stress on growth and yield of three cowpea cultivars to select the best salinity tolerant cultivar for optimum yield production. To achieve this, three separate experiments were concurrently carried out using ITIOK-298-15, IFE BROWN and SAMPEA 11 cowpea cultivars in the glass house of the Faculty of Agriculture, University of Ilorin, Nigeria. The salinity levels tested in each of the cultivars were 0mM (the control), 50mM, 100mM and 200mM sodium chloride (NaCl). The imposition of salinity stress was for a period of two weeks at maturity because this stage is the most sensitive stage for any crop grown under any environmental stress. The experiments were laid out in randomized complete block design (RCBD) with four replications. Data collection was centred on root length, plant height, number of leaves, leaf area, dry mass, final yield, chlorophyll content of leaves, crude protein and crude fat contents. From this work, it was found that 200mM NaCl decreased the final yield by 51% in ITIOK-298-15, 73% in IFE BROWN and 100% in SAMPEA-11 compared to the control. Furthermore, 100mM NaCl reduced crude protein contents of the leaves by 6% in ITIOK-298-15, 10% in IFE BROWN and 17% in SAMPEA-11 compared to the control. From the above results, it was found that ITIOK-298-15 was the most tolerant cultivar while SAMPEA-11 was the most susceptible cultivar to salinity stress. It is, therefore, recommended (subject to further confirmation) that ITIOK-298-15 cultivar, which is the most promising cultivar of the three cultivars experimented, be used in cowpea production in saline environments of the Southern Guinea savannah ecological areas of Nigeria.