HOST RESPONSE TO SARISODERA-HYDROPHILA WOUTS AND SHER, 1971

  • 1 January 1983
    • journal article
    • research article
    • Vol. 15  (2) , 259-268
Abstract
The histopathology of 2 populations of S. hydrophila Wouts and Sher was examined on Salix lasiolepsis Benth. (willow), Populus fremontii Wats. (cottonwood), and Lyonothamnus floribundus Gray (ironwood) using light microscopy as well as scanning and transmission electron microscopy. S. hydrophila induces formation of a single uninucleate hypertrophied cell (giant cell) which varies only slightly among the 3 hosts. The giant cell is enclosed by the root stele and contacts phloem, vascular cambium and xylem. The single hypertrophied nucleus of the giant cell is ameboid or lobulate in shape, generally with a single nucleolus. The cell is characterized by a wall which is separated into 2 distinct regions about 2 .mu.m and 13 .mu.m thick; the thicker region occurs adjacent to the nematode head. Cell wall ingrowths, such as those associated with host responses to certain other plant-parasite nematodes, were not observed in giant cells induced by S. hydrophila. However, a high frequency of pit fields with plasmodesmata occurred in the thinner portion of the cell wall which is adjacent to vascular elements. Roots of the 3 hosts simultaneously infected with S. hydrophila and Meloidogyne sp. resulted in adjacent responses characteristic of each nematode, supporting the view that the specific type of host response is a function of the nematode rather than the host. The varying expressions of host responses among Heteroderoidea may be useful in testing congruency with existing interpretations of phylogeny.