Evaluation of efficacy of false yam (Icacina oliviformis) as surface protectant against rot pathogens of white yam (Dioscora rotundata Poir)

E N.K Sowley,F Kankam,R M Nsarko

doi:10.4314/gjas.v54i1.1

E N.K Sowley, F Kankam + Show 1 more

Open Access

https://doi.org/10.4314/gjas.v54i1.1

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Abstract

Rots in yam tubers are the dominant cause of postharvest losses. Therefore, studies were conducted to identify the rot-causing organisms in yam and to evaluate the efficacy of false yam (Icacina oliviformis) plant extracts as surface protectants in the storage of yam. The experiment was laid out in a completely randomized design (CRD) design with five treatments (fruit, root and leaf extract of false yam, Mancozeb and tap water) replicated three times. Two concentrations (50% and 100%) of each extract were also tested. Species were identified based on the structural features, the characteristics and properties of the spore and mycelium. A spore suspension of yam rot fungi was sprayed on healthy yam tubers that had been pretreated with the extracts. Results showed that fungi isolated from rotted yams were Aspergillus niger, A. flavus and Penicillium sclerotigenum. Leaf extracts (both 50% and 100%) had the highest growth inhibitions on all the three fungi isolated in vitro. Tubers treated with root and leaf extracts of false yam had a decreased tuber rot lengths of 1.80 mm2 and 2.17 mm2, respectively. The leaves and roots of false yam can be used as a surface protectant of yam in place of Mancozeb. Keywords: Icacina oliviformis; Dioscora rotundata; Mancozeb; Pathogenicity; Aspergillus spp.

Highlights

Yam (Dioscorea spp.) is one of the most important dietary sources of energy and a basic foodstuff in the tropical and humid regions of Africa, South America, India and South-East Asia (Achi, 2000; Adegbite et al, 2006; Babajide et al, 2007; Oluwole et al, 2013)
At 100% leaf concentration, growth inhibition on A. flavus was 61.63%, A. niger was 65.8% and P. sclerotigenum was 64.4% compared to 50% leaf concentration where growth inhibition on A. flavus was 54.66%, A. niger was 59.1% and P. sclerotigenum was 60.0%
Growth inhibition at 50% root extract were A. flavus, 45.78%, A. niger, 51.7% and P. sclerotigenum, 55.3% while at 100% root extract, growth inhibition on A. flavus was 55.09%, A. niger was 58.0% and P. sclerotigenum was 58.7%

Summary

Introduction

Yam (Dioscorea spp.) is one of the most important dietary sources of energy and a basic foodstuff in the tropical and humid regions of Africa, South America, India and South-East Asia (Achi, 2000; Adegbite et al, 2006; Babajide et al, 2007; Oluwole et al, 2013). Yam is considered the food of choice on many occasions and festivals. It is an indispensable part of the bride price in the Northern Regions of Ghana and part of Nigeria (Hahn et al, 1987). It has become a source of foreign exchange for some countries in the yam

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