ANTIOXIDANT GENE EXPRESSION, HORMONAL ACTIVITY AND GROWTH PERFORMANCE OF TOLERANT VIGNA UNGUICULATA (L.WALP.) GENOTYPES IN A FERRUGINOUS ULTISOL – VALIDATION OF TOLERANCE

SUMMARY

The findings from this study shows that there were no effects of soil variability (different ferruginous soil types) on the morphological parameters studied in all the tolerant genotypes.Iron levels were significantly increased in plants parts; stem, leaf and root in all the cowpea genotypes studied. However, highest levels were observed in the stem of Tvu-3742, in the root of Tvu-5883 and Tvu-6193 and lowest in the leaves of the genotypes.There was no effect of iron toxicity on the malondialdehyde levels and superoxide dismutase activity in the different soil samples. While increased levels of Proline, tocopherol and glutathione peroxidase activities were observed, the catalase activities were reduced in the possible tolerant genotypes.Soil types and genotype variability was shown to down-regulate the expression of the iron-specific SOD gene (99.7%), differentially regulated the expression of the iron-specific catalase gene (90.7%) and up-regulate the expression of the glutathione peroxidase gene (99.1%) in the possible tolerant genotypes.Soil types and genotype variability were shown to have no effect on the levels of the hormonal parameters (Auxin, abscisic acid and Brassinosteroids) investigated among the possible tolerant genotypes.