VARIATIONS IN SEED PHYTIC AND OXALIC ACID CONTENTS AMONG NIGERIAN COWPEA ACCESSIONS AND THEIR RELATIONSHIP WITH GRAIN YIELD

A total of 99 Nigerian cowpea landraces collected from the Genetic Resources Unit of the International Institute of Tropic Agriculture (IITA), Ibadan Nigeria, were studied for variability in seed contents of phytic acid and oxalic acid and for the relationships among the antinutrients and grain yield. Phytic acid and oxalic acid concentrations were determined using spectrophotometric and titrimetric methods respectively, while grain yield parameters were measured in a greenhouse under ambient environmental conditions. The result showed very significant variations in both the antinutrients and grain yield (p<0.0001). Phytic acid values ranged from 2.58 – 3.87 with a mean of 3.10 ± 0.23 mg/g; oxalic acid varied from 0.58 - 0.97 with an average value of 0.78 ± 0.08 mg/g; seed weight per plant (SWPP) ranged from 1.50 - 11.92 with a mean value of 6.96 ± 2.97 g; pod length (PL) ranged from 11.06 - 28.10 with an average value of 16.01 ± 2.84 cm; while seed number per pod (SNPP) varied from 8.60 - 19.20 with a mean value of 13.29 ± 3.16. The study revealed wide variations in the antinutirents and grain yield among the cowpea cultivars. Some of these variations may be genetic and may provide an opportunity for genetic development of cowpea lines with superior grain yield quality, low in the antinutrients. No significant correlations were detected among the antinutrients and any of the grain yield indices suggesting that grain yielding capacity has no influence on the seed content of phytic and oxalic acids in cowpea.