Assessment of Morphological, Nutritional and Cytological Characteristics of Some Nigerian Cucurbita Species

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Abstract

Two field experiments were conducted in 2007 and 2008 cropping seasons at the Department of Crop Science research farm, University of Nigeria, Nsukka, to characterize some Nigeria cucurbita genotypes with respect to morphology, nutrient composition and the cytology. The results obtained showed that Shannon diversity index (Hs) was 4.136 which suggests high level of diversity among the Nigerian cucurbita species evaluated. Cucurbita moschata had the highest Shannon diversity index of 1.559 followed by C. maxima (1.474) and C. pepo (1.103) thereby revealing C. moschata as the most diverse. The mature fruit colour, seed colour, immature fruit colour, leafiness, petiole colour recorded high Hs values vis-a-vis the other qualitative descriptors. This is an indication that the above traits contributed meaningfully to the observed diversity in the species. The evenness of C. pepo, C. Maxima and C. moschata were 0.187, 0.250 and 0.265, respectively, suggesting uneven species distribution in the Nigerian agro-ecologies. The genotypes differed significantly (P<0.05) in all the agronomic and yield traits measured. The only exception was in weight of healthy fruits. The planting season had significant effects (p<0.05) on all the floral and agronomic traits measured with the exception of number of leaves per plant, girth size, vine length, weight of healthy fruits and 100-seed weight. The interaction of genotype and planting season also had significant effects on days to 50% emergence, number of healthy fruits, number of damaged fruits, 100-seed weight and seed length. The principal component analysis of the agronomic and yield traits showed that the first three components accounted for 72.20% and 74.75% of the total variation in the 2007 and 2008 plantings, respectively. The traits representing the genotypes along the first principal axis were 100-seed weight and weight of healthy fruits for the 2007 planting and, number of damaged fruits, seed length and 100-seed weight in the 2008 planting. Genotypes were differentiated on the basis of days to 50% flowering, fruit diameter, girth size, number of damaged fruits, number of healthy fruits and vine length in the 2007 planting and, days to 50% emergence, number of fruits per plant, number of healthy fruits, number of leaves and weight of healthy fruits in the 2008 planting along the second principal axis. The hierarchical cluster analysis and cluster plot revealed that the 10 cucurbita genotypes were grouped into two clusters with Akwa-01 alienated from the clusters in the 2007 and 2008 planting seasons. The coefficients of similarity between the clusters were 0.86 and 0.89 for the 2007 and 2008 plantings, respectively. The members of cluster I genotypes at both planting seasons are very promising in the production of male and female flowers, ability to sustain larger and healthier fruits. However, genotypes in cluster II are prolific in terms of leaf production and are suceptible to fruit damage. The correlation coefficient for weight of healthy fruits was highly significant and positive with number of seeds per fruit (r = 0.339**) and days to 50% flowering (r = 0.494**) indicating that increase in these traits will ultimately increase weight of healthy fruits. The number of male flowers had significant positive relationships with seed length, number of seeds per fruit, fruit length, fruit diameter, number of fruits per plant and number of female flowers indicating that the above traits are influenced linearlly by the number of male flowers. However, days to 50% emergence was negatively correlated with seed length (r = -0.560**), fruit length (r = -0.557**), fruit diameter (r = -0.371**), number of fruits per plant (r = -0.430**), number of female flowers (r = -0.543**) and number of male flowers (r = -0.457**). The chemical composition and nutritional profile differed significantly (p<0.05) among the genotypes in the proximate, mineral, phytochemical and the anti-nutrient analyses. The results revealed that Pumpkin fruits are very rich in crude protein, minerals (calcium, phosphorus, sodium and iron), phytonutrients (lycopene, ascorbic acid and β-carotene) and crude fibre but low in crude fat, phytate, tannin and moisture content. The result of the cytological work established a diploid chromosome number of 2n=40 for Cucurbita species at the metaphase stage.

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