Electron microscopy of elm infected with Ceratocystis ulmi (Buism) C Moreau

Electron microscopy of host tissue deterioration in Dutch elm disease

“…I correlated my research closely with the previous electron microscope study of early diseased elm tissue (MacDonald, 1970). Thus the two studies compliment each other; mine beginning at the point where the previous study ended.…”

“…Vascular discoloration has, similarly, been observed following invasion by C, ulmi (Schwarz, 1922;Wollenweber, 1927;Buisman, 1933;Clinton and McCormick, 1936;Kerling, 1955;Ouellette, 1962;Tchernoff, 1965;Gagnon, 19679', b;MacDonald, 1970).…”

“…The protoplasm became granular and the cellular contents, yellow and then brown. During the period before external symptom expression, discoloration appeared to be limited to living xylem cells having vacuoles containing tannin-like bodies, and discolored intertracheary pit "membranes" (MacDonald, 1970). Gagnon (1967b) suggested that when solutions such as ethanol and buffers of different concentrations were Injected into seedlings of U. americana, the results were similar to those produced when elms were inoculated with C_.…”

“…Many studies (Boyer and Isaac, 1964;Dufrenoy, 1932Dufrenoy, , 1936Bailey, 1954;Bosshard, 1968;Esau, 1963;Wardrop and Cronshaw, I962) have indicated that polyphenols and tannins were formed within vacuoles. A recent fine--^ structural study on diseased elm tissue showed phenolic compounds in vacuoles of xylem parenchyma,'âihd expanded tyloses (MacDonald, 1970).…”

“…Much literature is available on host tissue reactions in vascular wilt diseases (Dimond, 1955;Becknvan, 1964;Dimond, 1967;MacDonald, 1970). However, I will confine this review to the issues directly related to ny study objectives.…”