Abstract
Characterization of landraces is central to any conservation measures devised for sweet potato in Malawi. Studies were therefore conducted using seven morphological descriptors and farmers’ indigenous knowledge systems (IKS) to investigate the phenotypical diversity of 286 landraces and 35 introductions of sweet potato from the north, south east and lower Shire. The accessions were planted in a check plot design at Bvumbwe Agricultural Research Station. The results showed that farmers’ knowledge (IKS) is a means for preliminary characterization of accessions as evidenced by elimination of 75 duplicate accessions by 12 farmers. Analysis of variance (ANOVA) showed that all accessions and populations were phenotypically variable (p≤0.01) and Chi-square test of the morphological descriptors used in the study varied significantly among the three eco-geographical areas and among the landraces and introductions (p≤0.05 and p≤0.01), implying high variability of the accessions. However, the accessions clustered at 50% dissimilarity and generally irrespective of eco-geographical origin, signifying some similarity probably due to gene flow. Shannon Weaver Diversity Index (H’) indicated that different traits had different source areas of highest diversity which were significantly different (p≤0.05); nonetheless Shire Valley had the highest mean diversity for all traits (H’=0.67) which was significantly different from the other two populations (p≤0.05) inferring that the lower shire would be ideal for in situ conservation of sweet potato diversity. Key words: Field evaluation, germplasm, phenotype, population, root crop, variability.
Highlights
Plant genetic resources for food and agriculture (PGRFA)which comprise diversity of genetic material contained in landraces, modern cultivars, wild relatives and other wild species are the basis of global food security (Rao, 2004)
In the complementary identification studies at Bvumbwe Research Station, a long term sweet potato farmers from Nsanje and Chikwawa, major sweet potato growing areas, competently identified cultivars grown in their districts including three from Phalombe which were obvious duplicates of accessions from their areas
With the aid of the farmers, 75 phenotypic and obvious duplicates were identified, tagged and eliminated. This outcome is consistent with the fact that from time in memorial farmers have used morphological traits to distinguish different cultivars of crops including sweet potato (Zimmerer and Douches 1991; Rodriguez-Bonilla et al, 2014)
Summary
Plant genetic resources for food and agriculture (PGRFA)which comprise diversity of genetic material contained in landraces, modern cultivars, wild relatives and other wild species are the basis of global food security (Rao, 2004). Sweet potato (Ipomoea batatas (L.) Lam) is one of the most important staple and food security root crops in the world, ranked second after cassava in area and production in the tropical and sub-tropical regions (FAOSTAT, 2012; Boney et al, 2014). It is generally accepted that an understanding of genetic variability, which is manifested through phenotypic differentiation, is vital for any crop improvement through possible choice of appropriate selection and breeding programs (Demelie and Aragaw, 2016). This study was conducted to characterize existing local and introduced sweet potato accessions in order to evaluate phenotypic diversity for effective utilization in breeding programs
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