ASSESSING MORPHOLOGICAL DIVERSITY OF MANGO GERMPLASM FROM THE UPPER ATHI RIVER (UAR) REGION OF EASTERN KENYA

Abstract

Morphological characterization allows for the study of plant variation using visual attributes. Fruits have been the major descriptors for identification of different varieties of fruit crops. However, even in their absence, farmers, breeders and interested stakeholders require to distinguish between varieties. This study aimed at determining diversity in mango germplasm from the UAR and providing useful descriptors for the identification of different mango varieties in the absence of fruits. A total of seventeen IPGRI (2006) descriptors for mango were selected for use in visual assessment of 98 mango accessions from 15 sites of the Upper Athi River (UAR) region of Eastern Kenya. Purposive sampling was used to identify farmers growing diverse varieties of mangoes. Evaluation of descriptors was performed on site and data collected was subjected to multivariate analysis including Principal Component and Cluster (PCA) analysis. Results classified the accessions into two major groups corresponding to indigenous (17.35%) and exotic (82.65%) varieties. The PCA showed the first seven principal components accounting for 82.87% of the total variance. A strong and highly significant correlation was also found between the colors of young leaves, stem circumference, tree height, leaf margin type and fragrance strength. Four leaf descriptor traits namely pulvinus thickness, leaf pubescence, angle of secondary veins to midrib and presence of secondary veins on leaf, were discarded for presenting only one phenotypic class and hence ineffective in distinguishing between mango varieties in the UAR. These results reveal that mango germplasm in the UAR possesses significant diversity and that other morphological traits apart from fruits are useful in determining significant morphological variation that can be incorporated in mango breeding programs in Kenya.