Histopathology of the root-knot nematodes and interaction of Meloidogyne javanica and Fusarium sp. and Thielaviopsis paradoxa on date palm, Phoinex dactylifera seedlings

Abstract

The pathological effects of Meloidogyne javanica and M.incognita on seedlings obtained by germinating seeds of Khistawi,Zahdi and Braim date palm cultivars and the interaction of M.javanica , Fusarium sp., and Thielaviopsis paradoxa on two date palm cultivars was studied. M. incognita caused more reduction in seedlings immergence of cv.Khastawi and cv.Braim than M.javanica. M.incognita produced significantly more galls on the root of both cultivars compared with those caused by M.javanica. The different nematode inoculum densities used in this study caused no significant differences in seedlings shoot height or root length compared with that in the control. Combined treatments of Fusarium sp.,T. paradoxa and M.javanica caused increased percentages of root necrosis in cv. Zahdi and cv. Braim compared with necrosis caused by inoculation with any one of these pathogens alone. M.javanica-T.paradoxa combined inoculation cause the greatest root necrosis on both cultivars when seedlings were inoculated with the nematodes 3 weeks prior to fungal inoculation. Nematode infection caused marked disorganization of root anatomy. Characteristic nematode induced feeding giant cells were observed in only the stealer tissues and in close association with xylem vessels. Several normal size females each associated with 3-6 giant, multinucleate cells and large egg masses were often observed in relatively small areas of root tissue.