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Importance of orange-fleshed sweetpotato cultivars in Malawi: a consolidation of morphological, organoleptic and beta-carotene analysis
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In order to better understand farmers’ sweetpotato varieties grown in Malawi for subsequent improvement and effective contribution of agricultural research to livelihood, a study which involved germplasm collection and indigenous knowledge documentation survey in 2003 in Chikwawa and Nsanje Districts of the Shire Valley where vitamin A deficiency is prevalent was conducted. A total of 115 accessions were collected and planted at Bvumbwe Research Station in 2004 and 2005 seasons for morphological characterisation. A preference study by naive panelists was conducted at Bvumbwe Research Station to identify organoleptic attributes considered valuable by farmers on storage roots of 15 sweetpotato cultivars. Among other attributes, these 15 cultivars were selected to represent a wider range of storage root flesh colour and those prevalently grown in Malawi and the Shire Valley . Determination on beta-carotene content of the 15 genotypes was conducted where Babache and Mfumu, white fleshed cultivars and the most prevalent cultivars in the Shire Valley Districts registered low levels of beta-carotene (0.19 and 0.76 mg/100g fresh weight respectively). Morphological analysis indicated that Nsanje District has 4% pale orange cultivars, 1% intermediate orange and 1% dark orange, Chikwawa District has none at all in these character states of flesh colour. By use of a preference scoring scale of 1-5, different cultivars were preferred most for different organoleptic characteristics (texture, taste, flavour and flesh colour). An important revelation however showed that the naïve panel preferred Zondeni most an orange fleshed colour and a local cultivar which registered the highest beta-carotene content (13.93mg/100g fresh weight) at five months old suggesting that colour may not be a barrier to promoting orange fleshed cultivars in the communities where these cultivars are less popular. However, since it appears to be a challenge to develop and identify an ideal genotype that contain all of the preferred traits, researchers can easy their work, by combining attributes into different genotypes with the knowledge base that farmers will select, manage and maintain multiples of cultivars. Further, the study has revealed that local cultivars are good sources for valuable attributes including yield which needs to be exploited in trait combination before justifying new or exotic germplasm introduction for adaptability or genes introgression.