Comparative effect of acanthoscelides obtectus (Say) infestation on nutrients of phaseolus vulgaris (Linn.) and phaseolus acutifolius (Gray)

Abstract

Background and Objective: Acanthoscelides obtectus is a destructive post-harvest pest of beans. The destructions caused by this beans weevil are of economic and nutritional importance. This study was carried out to compare the effect of A. obtectus infestation on the nutrients of Phaseolus vulgaris L. and Phaseolus acutifolius G. Materials and Methods: A mix of infested and non-infested seeds of P. vulgaris and P. acutifolius was purchased from the Watt Market Calabar, Nigeria. The infested seeds were sorted from the non-infested ones into 3 groups (slight (SLI), moderate (MI) and severe (SI)) according to their levels of infestation. The seeds were kept for 3 months, sundried for 1 week, ground separately into powder and analyzed for nutrients using standard methods. Results: Results revealed a progressive decrease in some nutrients of P. vulgaris and P. acutifolius and increase in others according to the severity of A. obtectus infestation. Infestation led to significantly (p = 0.05) higher reduction/increase in nutrients of P. vulgaris than P. acutifolius. Effect of A. obtectus infestation on proximate nutrients revealed a reduction in moisture, protein, fat and carbohydrate with an increase in ash content. Percentage reduction in carbohydrate had values of 27.6, 28.1 and 30.5% for infested P. vulgaris at SLI, MI and SI levels compared to values of 10.2, 13.3, 22.2%, respectively for P. acutifolius. Effect of A. obtectus infestation on mineral nutrients showed a decrease in Na, Mg, Fe, Co with an increase in K and Zn for both P. vulgaris and P. acutifolius. In P. vulgaris, the beans weevil engendered reduction in Ca, Cu, Mn but caused an increase in Ca, Cu, Mn and Ni content in P. acutifolius. Reduction/increase in mineral nutrients due to infestation was higher in P. vulgaris compared to P. acutifolius except for Co and Mn which was higher in P. acutifolius. Reduction in Mg was higher for infested P. vulgaris with values of 12.5, 15.4 and 20.8% compared to values of 7.5, 9.8 and12.5%, respectively for P. acutifolius at SLI, MI and SI. Increase in Zn content of infested P. vulgaris had values of 21.4, 37.1 and 41.8% as against values for infested P. acutifolius of 19.6, 23.3 and 23.7%, respectively. Effect of infestation on vitamins depicted higher reduction in vitamin A and B1 with an increase in vitamin E in both species at all levels of infestation. Conclusion: Comparatively, A. obtectus infestation caused higher significant reduction in some nutrients with an increase in others in infested P. vulgaris when compared to P. acutifolius resulting in nutrients fluctuation.