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.
