GENETIC, MORPHOLOGICAL AND SOCIO-ECONOMIC CHARACTERISATION OF MUSA (BANANA) CULTIVARS GROWING IN MALAWI

Abstract

Genetic diversity in domesticated crop species provides a source of variation which is a raw material for the improvement of agricultural crops. Investigation of genetic diversity of bananas growing in Malawi has never been done, yet proper and accurate identification of banana cultivars is necessary before engaging in any genetic improvement programme hence the need to genetically, morphologically and socio-economically characterise Malawian banana cultivars. This study characterised locally named banana cultivars growing in the major banana districts of Chitipa, Karonga, Nkhata Bay, Mulanje and Thyolo. High microsatellite allelic diversity was observed among the 96 banana cultivars analysed using 12 DNA microsatellite loci. A total of 174 alleles with mean number of 14.5 and a range of 1-30 per locus were generated. However, low mean genetic diversity contrary to estimates by actual allele count was revealed by three indices of genetic diversity used in this study; Percentage Polymorphic loci or band (PPB, 37%), Nei’s gene diversity (h, 0.11) and Shannon Information Index (I, 0.17). This was possibly due to loss of codominance by microsatellite loci in polyploids which leads to underestimation of allelic relationships in populations. Pooled northern region banana population (Chitipa, Karonga and Nkhata Bay) is not genetically significantly different from pooled southern region population (Thyolo, Mulanje, Local collection and Gene bank) (p≥.0.005). Conversely, in terms of gene combinations (heterozygosity), pooled northern population is significantly more heterozygous than pooled southern region population (p≤0.05). Genetic similarity analysis showed that most cultivars are as different as local names ascribed to them in the study areas. Microsatellite and morphological characterisation results, when compared, were not analogous (r=0.063, p=0.695). Nevertheless, some distinct dendrogram subgroups were exceptionally analogous indicating that both techniques are complimentary. Dendrograms from both methods showed that most cultivars were different from each other implying high morphological and genetic polymorphism among the banana cultivars. Socio-economic analysis of banana production system in Malawi based on 118 questionnaires revealed several characteristics consistent with a subsistence production system. There is no significant relationship between amount of land allocated to banana production and money from sales (Fisher’s exact test=36.936, p=0.164), signifying low production as well as considerable domestic consumption of bananas. Cavendish bananas such as Kabuthu (dwarf Cavendish) and Mulanje (Cavendish) are most important in the south and are also the most widely distributed banana cultivars in Malawi. Plantains and cooking bananas are more important and widely distributed in the north. On average a northern farmer plants significantly more cultivars (six cultivars) at a time than a southern farmer (four cultivars) (p≤0.05). This stresses the importance of bananas as a staple in the north. Farmers’ choice of cultivars in the south is influenced by early formation and maturity of bunches reflecting a business attitude of southern farmers while in the north, familiarity of the cultivar is the most important attribute because bananas and plantains are a staple food. The majority of farmers in the south (85.3%), unlike in the north (14%), are aware of and willing to adopt improved cultivars. The results revealed that region, experience in banana farming and awareness of improved banana cultivars were significant predictors of adoption of modern banana cultivars (p ≤ 0.05).