Evaluation of the efficacy of three Organic Extracts in controlling storage rot in Sweet Potato
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Date
2014-07-25
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Abstract
In the tropical regions the fresh tuber of sweet potato is generally considered to be difficult to store due to unfavourable climatic conditions. In this study the efficacy of three organic extract in controlling storage rots in three varieties of sweet potato was evaluated The work was done in laboratory and in the field to find out post harvest factors which contribute to sweet potato tuber loss in the study area Treatments used in the study included three sweet potato varieties (Ogyefo, Tek and Monami) and three plant extracts (neem seeds, onion bulb and ginger rhizome) plus a control(water). Data collected included weight loss, TSS, TTA, tuber firmness, moisture content (MC), dry matter content (DMC), sprouting index, weevil damage, decay and storability. Data collected were analyzed using Statistix 9 statistical software. Tukey HSD test at 5% was used for the mean differences. Ogyefo (control) had significantly the highest weight loss of 38.88% Neem treated Tek tubers (12.0N). were significantly the most firm. Ginger treated Tek recorded MC of 66.03% which was significantly higher than those to which treatment was applied. Neem treated Tek recorded DMC of 46.53% which was significantly the highest. Onion treated Tek recorded TTA of 6.07 which was significantly higher than those to which treatment were applied, onion treated Tek recorded TSS of 11.07 oBrix which was significantly higher than those to which treatment was applied. Neem seed extract treated Ogyefo tubers had highest sprouting (6.75%)., Ogyefo sweet potato variety treated with onion extract was least susceptible to weevil damage (1.00%). Ogyefo varieties were less susceptible to decay (1.6). Tubers treated with neem (1.8) .Across varieties, onion treated tubers (2.1) were less susceptible to decay. For storability of the varieties, Ogyefo had a storage life of 59 days, neem treated tubers had storage life of 59 days. The following fungi; Aspergillus flavus, and Rhizopus stolonifer were isolated from rotted tissues and found to be pathogenic to sweet potato tubers. The water extracts of these plants suppressed fungal growth in culture The highest percentage inhibition of 62.5% was obtained with the use of neem seed extract on Rhizopus stolonifer while ginger extract caused 42.7% inhibition of Aspergillus flavus. Rot development caused by Aspergillus flavus was reduced by 35.34% with the use of onion extract. Considering matrices of performance parameters it can be concluded that neem seed extract is the most efficacious of the three plant extracts. The effect of plant extract on the sensory attribute of the sweet potato tubers must be investigated.
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A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfillment of the requirements for the award of Master of Philosophy
(Mphil, Postharvest Technology) degree,