Doctoral Degrees (Viticulture and Oenology)

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An anatomical and experimental study on changes induced by Meloidogyne hapla Chitwood, 1949 in Vitis roots
(Stellenbosch : Stellenbosch University, 1971) Joubert, D. J. (Daniel Jakobus); Orffer, C. J.; De Vos, M. P.; Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology and Institute for Wine Biotechnology .
ENGLISH ABSTRACT: The object of this anatomical study was to collect scientific data on the effect of Metoidogyne hapta Chitwood, 1949, on the roots of the following grapevine cultivars viz: Vitis vinifePa L. cvs. Steen and White French and the root-stocks, Jacquez, 1202 C, 99 R, Salt.Creek and Dogridge. These cultivars differed widely in their resistance to M. hapta attacks. In the roots of Steen, White French, Jacquez and 1202 C the formation of multinucleate syncytia by the destruction of the walls of groups of cells often occurred. In Salt Creek, Dogridge and 99 R roots, syncytia were observed in the stele only. The formation o,f abnormal xylem as a result of nematodal activities was a common occurrence. In the roots of these latter three cultivars, M. hapta could not complete its life cycle. Salt Creek, Dogridge, 99 R and often Steen formed a wound periderm which prevented the nematodes from reaching the xylem. Histological changes were often induced in advance of the invading nematodes.