Establishing genetic diversity of Rwanda highland banana using random amplified polymorphic DNA markers.

Abstract

The characterization of the banana germplasm collection from Rubona - Rwanda was investigated using morphological and cytological characteristics of the genomic groups. Genetic diversity was assessed using Random Amplified Polymorphic DNA analysis. The survey was conducted to evaluate the distribution of banana cultivars in the four major growing regions of Rwanda. A total of 90 accessions from the National Banana Germplasm Collection at Rubona Rwanda were characterized and six characters of the fingers (length, width, weight, green life, post green life and length/width ratio) were subjected to principal component analysis (PCA). The cooking and beer clones were separated. The cooking clones were further grouped into three clone sets: Musakala, Nakabululu, and one that constitutes Nakitembe and Nfuuka clone sets. The AAB genomic group was separated from AAA, AB and ABB genomic groups. The results from the survey showed that East African Highland bananas are the most important genotype group in the four major banana growing regions of Rwanda ranging between 60 - 90% of banana mats counted. Several new Highland banana cultivars were recorded, such as 'Intokatoke', 'Igihuna', 'Ingenge', 'Ingaju', 'Icyerwa', 'Mitoki', 'Madamu', 'Inkokobora', 'Intokekazi', 'Bugoyi', 'Ishoki'. Amongst these cultivars, some were classified as cooking and others as brewing bananas. However, in the National Banana Germplasm Collection at Rubona - Rwanda, the uses of these cultivars are recorded differently therefore increasing the need for agro-morphological characterization. The assessment of ploidy level of accessions from the National Banana Germplasm Collection at Rubona - Rwanda, by flow cytometry showed misclassification of some accessions such as 'Pomme', 'Kamaramasenge', 'Gisubi kayinja', 'Gisubi kagongo', and 'Dibis' which were classified as diploid, diploid, triploid, and tetraploid respectively. They IV were found to be triploid, triploid, triploid, diploid and triploid. All these bananas were recently introduced into Rwanda, while the endemic Highland bananas were triploid. The genomic group and genetic similarities of 49 accessions were investigated using Random Amplified Polymorphic DNA markers. The genomic group of bananas assessed were established using OPA-18 (PILLAY et al., 2000) and OPG-17 primers. These primers showed bands 441 and 443 base pairs (bp) respectively for the accessions having only the B genome. Whilst they were absent for the accessions " having an A genome. The genetic similarity was estimated via a Simple Matching coefficient which showed the lowest value 0.46 measured between 'Ingumba' and 'Ishika 'and the highest value of 0.85 between 'Kirayenda' and 'Inyabukuwe'. The data of matrix of coefficient of similarity was subjected to cluster analysis with unweighted pair group method with arithmetic average (UPGMA). Each accession was clearly separated demonstrating the usefulness of RAPDs in analysis of genetic diversity. The results of this study are very important to the Curator of the banana germplasm collection in Eastern Central Africa and for the future breeding of this crop.