Genetic diversity of pumpkin accessions in Kenya revealed using morphological characters, diversity index, CATPCA and factor analysis

Abstract

Pumpkin is one of the most morphologically variable genera in the entire plant kingdom. In Kenya, its genetic diversity is undocumented and distribution is haphazard. An expedition was done in Kakamega and Nyeri regions in 2012 using purposive sampling and IPGRI descriptors that led to collection of 155 accessions planted and replicated three times in the Chuka University experimentation farm. The character ranges were green to orange for mature fruit rind, speckled to striped secondary fruit rind, smooth to warty fruit surface, and white to yellow internal flesh, and yellow to pink-red inner flesh and outer flesh. Sex type was monoecious, with most flowers being male and flowering early; only 9 accessions had female flowers appearing early. Most accessions had globular fruits and second fruit cycle. All the accessions had fruit vein tracks and peduncles that abscised when overripe. Deep fruit ribbing was in 40, while small blossom scars were in 69 accessions. Shannon diversity index based on qualitative traits ranged 0.49 to 1.79, with average of 0.97. Fruit shape and seed coat surface displayed high and low indices, respectively. Nyeri accessions had the highest diversity index. CATPCA, factor and cluster analysis determined relationships of the accessions based on the dissimilarity of qualitative characters. CATPCA and factor analysis reduced the dimensionality of the characters to 13 PCs and factors, respectively. CATPCA captured 78.3% and factor analysis 72.1% of the total variation. The two methods jointly identified second fruiting cycle, central leaf lobes, leaf pubescence type, leaf glossiness, and plant growth habit, leaf and flower colour contributing most to divergence of the accessions. The communalities were mostly high except for few characters exhibiting high specificity. Configuration by scatter Bi-plot along the first two PC axes grouped 124 accessions into variegated and green-leafed. Cluster analysis identified four groups with 59, 40, 24 and 1 accessions in clusters one, two, three and four, respectively. The green-leafed accessions were grouped in cluster three and four, and the variegated into cluster one and two. The characters with high discrimination can be useful in identifying variation that can be used for direct selection and in assisting breeders in the identification of pumpkin germplasm with desirable traits for inclusion in breeding and improvement programmes.