Genetic characterization of cultivated bananas and plantains (Musa ssp) in Kenya
Onguso, Justus Mong'are
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Bananas and plantains (Musa spp) are a major staple food for millions of people in the tropical world. World banana production has been estimated at 80.6 million tonnes (FAO, 1994) of which only 15% in exported. The dessert banana is a major export crop of the Caribbean countries where the Cavendish bananas account for 10% of the world's production of bananas and Plantains. In the East African highlands, the annual per capita consumption is about three hundred kilogrammes, the highest consumption figure in the world. In Kenya, banana and plantain nomenclature is not standardized. This is because different communities refer to the local cultivars by different names. The conventional method of describing Musa germplasm is based on fifteen morphological traits. The field testing requires elaborate experimentation and one or two years for the plant to flower and fruit. However, the subjective nature of the scoring process makes it prone to error (Bhat et al., 1995). Environmental effects on gene expression make direct comparison of clones growing in different locations impossible. Cytoplasmic genetic effects on morphology may be an additional factor contributing to ambiguities encountered in the results of key derived genomic classification. The extent to which cytoplasmic genetic effects confound efforts to differentiate clones based upon their morphological characteristics, especially within the hybrid group AB, ABB and AAB, has not been systematically examined. In this study, a polymerase chain reaction (PCR)-based approach, namely, random amplified polymorphic DNA (RAPD) was used to estimate the genetic relationships of twenty selected banana cultivars from different regions of Kenya. Nineteen random primers were used. The polymorphism in PCR amplification products were scored as discrete variables. The data was used to calculate Jaccard's similarity coefficients. The similarity measures were subjected to cluster analysis based on the unweighted pair group method analysis (UPGMA) for classification of the cultivars. Cluster analysis separated the twenty cultivars into three clusters. The first cluster consisted of Ng'ombe, Nusu Ng'ombe, Ntobe, Sialamule, Kumuga, Kibuzi, Sibusi, Bukamba, Mfupi and Gitigi. They were of the genome AAA. The second cluster had Manyatta, Mokoya, Murure, and Horn plantain whose genome was AAB. The third cluster consisted of Pekera, Muraru, Spambia, Matumbo, Nyar Sausett and Mtama whose genome was AA. The cultivars that clustered together were thought to be similar and distinctly different from those that clustered far away from them. The study revealed that RAPD analysis is useful for clonal identification. This is very important for researchers who do Musa germplasm classification and management. It is recommended that further work be done using more cultivars and more specific molecular markers such as restriction fragment length polymorphisms (RFLPs), amplified fragment length polymorphisms (AFLPs) or simple sequence repeats (SSRs).