Cytological changes induced by the stem nematode Ditylenchus dipsaci in strawberry leaves


  • T. Bleve-Zacheo
  • G. Zacheo
  • M. T. Melillo
  • F. Lamberti
  • O. Arrigoni


The stem nematode, Ditylenchus dipsaci (KUhn) Filipjev, causes swellings and growth malformation on stems and leaves of various susceptible hosts in which the chlorophyllic parenchyma cells are hypertrophied or destroyed (Rhode, 1972). Watson et al. (1979) report that at the feeding site the nematode induces cell separation because of the dissolution of the middle lamella which according to Seinhorst (1957), is a process necessary for the development of the parasite. Hussey and Krusberg (1968, 1970) found that D. dipsaci attacks the embryonic leaves of shoot apices of resistant pea varieties by penetrating directly through the epidermis and induces formation of cavities in the parenchymatous mesophyll tissue only 48 hr after inoculation. They observed thickening of the cortical cell walls of the invaded tissues and an intense peroxidase activity, associated with the trophic activity of the nematode. Dropkin (1963), Krusberg (1960, 1967) and Riedel and May (1971) suggested that pectolytic enzymes are secreted by D. dipsaci within the plant tissue and that these are primarily responsible for cell separation during the early stages of the nematode infestation. Campbell and Griffin (1973) observed « white flagging» associated with D. dipsaci in alfalfa leaves and noted a progressive reduction in the lamellar structure of the chloroplasts followed by a decrease in pigmentation. The object of the present investigation was to study the changes induced by D. dipsaci in strawberry (Fragaria vesca L.) leaves.