Molecular characterisation of Musa L. cultivars cultivated in Malawi using microsatellite markers
Genetic diversity and relationships were assessed in 141 locally named banana cultivars growing in five districts of Malawi at 12 microsatellite loci. High allelic diversity (174 alleles) attributable to high frequency of duplicated alleles was observed. Primers discriminating power was high with mean polymorphism information content (PIC) of 0.74. Low mean genetic diversity contrary to actual allele count was detected by Nei’s gene diversity index (h, 0.12) and Shannon information index (I, 0.18). The low genetic diversity estimation could be due to loss of co-dominance by simple sequence repeats (SSR) loci in polyploids which leads to underestimation of allelic relationships in populations. The results also reveal that the genetic diversity of bananas from Chitipa, Karonga, Nkhata Bay, Thyolo, Mulanje, BRS local collection and BRS gene bank is not significantly different. Pooled northern region population (Chitipa, Karonga and Nkhata Bay) is as genetically diverse as pooled southern region population (Thyolo, Mulanje, Local collection and Gene bank). Cluster analysis showed that most cultivars were dissimilar probably due to multiplicity of mutations generated by high rate of cultivar multiplication by farmers. However, genetic relationships among some cultivars showed some possible synonyms.
Keywords: Bananas and plantains cultivars, genetic diversity, microsatellite markers.