"Rotting of Cocoyam [Xanthosoma Sagittifolium (L.) Schott] Cormels in Storage: Aetiology and Control"

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Date

1999-12

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University of Ghana

Abstract

A survey was carried out in November, 1997 in Accra to obtain basic information on the post-harvest handling and deterioration of cocoyam cormels from retailers and consumers. Studies were also undertaken between December, 1997 and July, 1998 to identify the pathogens responsible for rots in cocoyam cormels, to investigate the influence of variety and the presence of'natural wounds' on the rotting o f cocoyam cormels and to assess the efficacy o f thiabendazole and lime in controlling cocoyam rots in storage. The survey revealed that there are three varieties o f cocoyam available on: the markets and o f these the pink variety (Amankanipa) is the commonest and most preferred. It was also apparent that cocoyam for sale in Accra is obtained mainly through middlemen and that these come mostly from the Eastern Region o f Ghana. Cocoyam supplies to markets in Accra are done in bits and these take up to one week to be disposed of. Cocoyam cormel rots encountered by respondents is therefore low (0 - 5%). No measures are taken by respondents to control rots in cocoyam. Isolations made from 123 partially-rotten cormels obtained from markets in Accra and a storage bam revealed that storage rots in cocoyam are caused by Aspergillus flavus (2.4%), Botryodiplodia theobromae (12.20/o), Fusarium oxysporum (31.7%), Fusarium solani (45.5%), Penicillium citrinum (4.9%), and Rhizopus stolonifer (3.3%). A consistently higher weight loss was associated with Amankanipa (21.27%) compared with Amankanifitaa (20.28%) and Amankani Serwa (20.97%) varieties after 16 weeks o f storage. This was, however, significant only in the first - two weeks o f storage. On the other hand, the Amankanifitaa and Amankani Serwa varieties recorded significantly higher percent sprouts (17.50% and 12.50% respectively) than the Amankanipa variety (1.25%). Incidence o f rots was highest in the Amankanifitaa variety followed by Amankani Serwa and then Amankanipa variety reaching their respective peaks at 90.0%, 75.0% and 76.3% after a 16-week storage period. The 'natural' wounds at the proximal ends o f cormels were the dominant infection courts for rot-causing pathogens. Control was, therefore, targeted at this point. Both thiabendazole and lime were observed to be effective in checking the growth o f the rot-causing fungi in vitro. Thiabendazole was observed to perform better in reducing the incidence and spread of rots in cocoyam during the first six weeks o f storage.

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Thesis(MPHIL)-University of Ghana, 1999

Keywords

Cocoyam Cormels, Aetiology, Control, Aetiology

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