A STUDY OF THE LIFE CYCLE OF NEOCOSMOSPORA AFRICANA (VON ARX)

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Date
2014-07-11
Authors
ONUORAH, OKAY MARTINS OREFO
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Abstract
The life cycle of Neocosmospora africana was studied from single spores. These unisporous cultures developed to yield mature perithecia. The fungus was found to be homothallic. Media containing different carbon sources were tested for the ability of the fungus to maintain growth on them. All carbon sources tested supported the growth and sporulation of the fungus. Of the different nitrogen sources tested, vegetative growth was obtained on all while sporulation occurred on all media except the one containing ammonium sulphate as a result of changes in hydrogen-ion concentration despite the heavy buffering of the medium. Reproductive morphogenesis of the fungus was studied from surface static cultures on liquid glucose asparagine medium. Production of conidia occurred following the establishment of the mycelium. Development of perithecia in the same culture occurred much later following decline in growth rate and nutrient depletion. The ascogonium was found to be a coiled hyphal branch. The uninucleate and binucleate cells of the ascogonium become surrounded by hyphal cells that develop from adjacent stalk cells. Growth of the perithecium is caused by the divisions and enlargement of cells of hyphae surrounding the ascogonium. Meristematic cells in the apical region of the young perithecium give rise to an ostiole lined by periphyses. The centrum comprises the ascogonium and its descendant structures. The asci and evanescent paraphyses are borne on a slightly convex hymenium restricted to the basal central part of the centrum. The perithecial cavity increases from the deliquescence of the inner pseudoparenchymatous walls. The asci develop from the ascogenous system without crozier formation. Asci are double walled, cylindrical structures and are characteristically 8 - spored. Two successive mitoses in each ascospore followed by cell divii3ion synchronise with the maturation of the spores.
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A Thesis presented for the degree of Master of Science in Botany in the Department of Biological Sciences of Ahmadu Bello University, Zaria. by OKAY MARTINS OREFO ONUORAH^ B.Sc. (Hons.)
Keywords
LIFE CYCLE,, NEOCOSMOSPORA,, AFRICANA,, (VON ARX),
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