Effects of Mutagenic Treatments on Drought Tolerance Indices of Selected Cowpea Mutant Lines from Niger State, Nigeria

Abstract

Cowpea (<i>Vigna unguiculata</i> (L.) Walp.) is an important legume crop cultivated in many regions of Nigeria. It serves as a source of protein, nutrients and income for communities. However, its production and yield potential are severely affected by drought which has been a prevalent constraint over the years, posing a significant threat to cowpea production and food security hence the need to develop mutant lines that can withstand drought conditions for continuous sustenance of lives and livelihoods. This study aimed to determine the effects of mutagens on drought tolerance indices in selected cowpea mutant lines treated with gamma irradiated and Ethyl Methane Sulphonate (EMS) collected from the gene bank of Plant Biology, Federal University of Technology Minna, Niger State. These mutant lines were subjected to water stress for two weeks and assessed for drought tolerance potential. The study revealed that gamma rays and EMS had significantly effects on drought tolerance indices. The Geometric Mean Productivity (GMP) ranged from 4.11 (V2G4) to 7.11 (V3EG3). Stress Intensity (SI) values ranged from 0.050 (V1EG4) to 0.585 (V2G4). V1EG4 exhibited the lowest SI. The SSI values of the cowpea mutant lines ranged from 0.43 in genotype V1EG4 to 2.69 in genotype V2G4. It was observed that four mutant lines namely; V1EG4 (0.43), V1G4 (0.47), V3EG3 (0.48), VIEG3 (0.58), V3EG1 (0.95) respectively had SSI value less than one (1). The Tolerance Index (TOL) ranged from 8.60 (V3EG3) to 12.93 (V2G4). The TOL values of the mutant lines V3EG3 exhibited the lowest and in contrast; V2G4 had the highest TOL, Stress Tolerance Index (STI) values of the cowpea mutant lines ranged from 0.407 in genotype V2G4 to 1.949 in genotype V3EG3. Mutant lines VIG4 (1.741) V1EG3 (1.893), V1EG4 (1.816) and V1EG3 (1.893) also had higher STI as compared to mutant lines V2EG4 (0.892), V1EG2 (0.714) V3G4 (0.709) and V3G1 (0.548). YI values ranged from 0.32 in genotype V2G4 to 2.24 in genotype V3EG3. The HM values ranged from 3.86 in genotype V2G4 to 7.08 in genotype V3EG. Drought tolerance indices studied confirms that mutagen treatments such as gamma rays and EMS significantly affected the tolerance and productivity of cowpea positively. Mutant lines such as such as V3EG3, V1G4 and V1EG4 exhibited enhanced drought tolerance as evidenced in their high MP, GMP, and STI values, along with low TOL and SSI values suggesting this mutant lines could be used for improving drought tolerance in cowpea breeding initiatives.