Changes in Germination and Biochemical Composition of Phaseolus lunatus (Lima bean) as Affected by Acanthoscelides obtectus Say Infestation

Aim: To assess changes in germination and biochemical (proximate, elemental and vitamin) composition of Phaseolus lunatus (P. lunatus) (Lima bean) caused by Acanthoscelides obtectus (A. obtectus) Say Infestation.

Experimental Design: The study was carried out in a complete randomized block design.

Place and Duration of Study: Department of Botany, University of Calabar, Calabar, Nigeria, between January and April, 2016.

Methodology: A mix of infested and non infested seeds of P. lunatus was bought, sorted and kept for three months after which the seeds were planted to determine the effect of A. obtectus infestation on germination. The other seeds were sundried, ground into powder and used for proximate, elemental and vitamin analysis.

Results: Analysis of variance revealed a progressive decrease in seed germination with severity of infestation on all soil types with sandy and loamy soils being more effective than clay soil. Changes in mean germination count and percentage germination showed similar pattern of an initial increase in germinated (day 3-5) followed by a progressive decline (day 6-9) in infested at all levels of infestation and non infested seeds. Infestation increased or decreased with severity of infestation. Highest decrease or increase in germination and biochemical nutrients occurred at slight level of infestation while lowest decrease or increase occurred at severe level of infestation. Infestation led to significant (P = .05) decrease in moisture, ash, fibre, fat and carbohydrate with highest reduction of 12.35, 48.1%, 22.4%, 24.1% and 11.9% at severe infestation (SI) and lowest reductions of 3.3%, 22.2%, 9.2%, 10.7% and 7.25 at slight infestation (SLI) respectively. Infestation of P. lunatus by A. obtectus engendered significant changes in elemental composition with decrease in K, Na, Fe, Zn, Cu, Mn and with increase in Ca, Mg and Ni. Infestation led to increase in the content of vitamin B1, B2, A, and C and decrease in vitamin B3, E and biotin when compared to the non infested.

Conclusion: Acanthoscelides obtectus infestation adversely affected the physiological and biochemical composition of P. lunatus necessitating control of the pest to maximize cultivation and nutritional quality.