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Report, 1978

Ultrastructural studies of resistance mechanisms in Pinus sylvestris L. against Melampsora pinitorqua (Braun) Rostr. (pine twisting rust)

Jonsson, Alena; Holmvall, Monica; Walles, Björn


Seedlings of Pinus sylvestris infected by Melampsora pinitorqua have been studied with regard to the ultrastructure of host and parasite. Septated and branched intercellular hyphae of the pycnial stage occurred mostly in the cortex but also in phloem and xylem. The haustoria, separated from their mother cells by septa, were elongated and sometimes coiled. In a few cases a papilla-shaped collar was observed at the penetration site. Cisternae of endoplasmic reticulum and organelles of the host cell were frequently observed accumulated around the haustoria. The haustorial sheath bordered by the invaginated host plasmalemma varied in thickness and structure. In young haustoria it was thin and filled with homogeneous material of moderate electron density. The sheath membrane was smooth. Those haustorial sheaths that probably represented later stages were thick and contained a lot of electron-dense grains. The associated sheath membranes were convoluted. Some haustoria were trapped in encasements, possibly originating from deposition of macromolecules in the sheath. These encasements could attain a considerable thickness and sometimes several zones of varying appearance were discernible. The encased haustoria were often more or less degenerated. The high frequency of necrotic host cells observed might indicate another type of defence reaction. Sometimes they contained dead haustoria.


resistance mechanisms; Pinus sylvestris L.; Melampsora pinitorqua (Braun) Rostr.; pine twisting rust

Published in

Studia Forestalia Suecica
ISBN: 91-38-04241-X
Publisher: College of Forestry, Swedish University of Agricultural Sciences

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