Morphological, Histological and Molecular Identification of Some Cucurbits in Khartoum State, Sudan.

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Ismail Ahmed Mohammed Ahmed
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This study is an attempt to make a comprehensive systematic study of some Cucurbits in Khartoum State. The study includes a brief description of the study area: location, geology, geomorphology, soil types, climate, water resources and people. Some Cucurbits were studied and systematic interrelationships among them were determined using morphological, histological and molecular identification. In the morphological study, 27 Cucurbit species were collected from the study area belonging to 12 genera. Botanical names, synonyms and vernacular English and Arabic names have been presented. Brief species descriptions of the collected plants have also been provided. The results showed that the species were very similar in the above ground development and root habit, but were extremely diverse in fruit characteristics. In the histological study, similarities were observed in the distribution, tissue differentiation and number of layers of cells and tissues in the root, stem and leaf transverse sections. There were, however, variations in the vascular bundles in the roots where they were found to be bicollateral in Cucumis sativus and Luffa aegyptiaca. In the other species, the bundle consists of four radial arms of primary xylem alternating with four arms of primary phloem. In the molecular study thirteen RAPD primers were used to amplify DNA extracted from the leaves of 10 Cucurbit species using CTAB method. A total of 227 bands were amplified of which 225 showed polymorphism among the 10 accessions. PCR-RAPD analysis showed a number of differences in the size and number of bands among the accessions, which means that there are genetical differences among the studied Cucurbit species. Based on these markers, genetic similarity coefficients were calculated and a dendrogram was constructed. The dendrogram analysis delineated three major clusters. The first cluster consisted of one group which comprised Cucurbita moschata and C. pepo at a level of 38.6 % genetic similarity. The second cluster consisted of four groups. Group I comprised Luffa aegyptiaca at a level of 20.6 % genetic similarity. Group II comprised the closely related species Cucumis melo var reticullatus and C. melo var flexuosus at a level of 62 % genetic similarity. Group III consisted of Cucumis sativus with about 37.8 % genetic similarity to group II. Group IV consisted of Ctenolepis cerasiformis at a level of 26.6 % genetic similarity. The third cluster consisted of two groups. Group I comprised Citrullus lanatus and Colocynyhis vulgaris at a level of 36.2 % genetic similarity. Group II consisted of Coccinia grandis at the level of 19.4 % genetic similarity. The three clusters were similar to each other at a level of 15% genetic similarity. Genetic similarity ranged between 15 to 62 %. This study demonstrates that molecular markers are useful in assessing genetic diversity among Cucurbits.
University of khartoum