Early stage of disease in fig roots induced by Xiphinema index

Abstract

The ectoparasite nematode, Xiphinema index Thorne et Allen, is one of several species that damage root tips by forming galls. Previous studies indicated that the host range of these species is restricted to a few plants, which support a rapid population increase (Weischer and Wyss, 1976; Prota et al., 1977; Wyss, 1978). Direct observations on the feeding behaviour of X. index, in agar culture (Fisher and Raski, 1967; Cohn, 1970; Cotten, 1973), revealed that the activities of the nematode, on the host roots, consisted in exploration, cell wall perforation with the stylet, salivation and ingestion of the cell cytoplasm and, finally, withdrawal of the stylet from the feeding site (Wyss, 1977a, 1977b). In response, the root-tips progressively swell and gradually transform into a terminal gall. Galls are strongly attractive to feeding nematodes which often aggregate at single sites (Weischer and Wyss, 1976). Sections of galled root-tips showed modified cells, with high metabolic activities, expressed in hypertrophied and lobed nuclei and in density of the cytoplasm, rich in mitochondria and rough endoplasmic reticulum. Multinucleate cells were observed (Wyss, 1980) contiguous with the cortical cells, which were collapsed by nematode feeding. In the present study we report the results of cytochemical response during the initial attack of X. index and a sequential description of structural phenomena that occur in cells of parasitized fig (Ficus carica L.) root tips, after removal of the nematode.