AbstractExperiments were conducted in the greenhouse to elucidate the histopathological effects of a possible interrelationship between the nematodes Meloidogyne incognita and Pratylenchus coffeae and the fungus Fusarium oxysporum f. sp. dioscoreae on yam (Dioscorea rotundata cv Habanero). Separate and combined inoculations were made with the fungus and the nematodes. Longitudinal and transverse sections of root tissues collected at 14, 42 and 72 days after inoculation showed that colonization by the fungus occurred indiscriminately, either inter- or intracellularly. Colonization in the stem was restricted to the vascular system, where abundant proliferation of hyphae was observed, mainly in the nodal tissues. Apparently, the root-knot nematode (M. incognita), as well as the fungus, colonized different sectors of the tissues invaded. However, abundant and vigorous hyphae were present in sections of tissues modified by M. incognita. It may be concluded from these studies that a positive Meloidogyne-Fusarium interaction occurs in yam. The lesion nematode (P. coffeae) was sometimes observed together with the fungus within the same tissues. However, this association did not appear to considerably accelerate the severity and/or the incidence of wilt caused by Fusarium.
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