Ultrastructural studies of resistance mechanisms in Pinus sylvestris L. against Melampsora pinitorqua (Braun) Rostr. (pine twisting rust)
Jonsson, A.; Holmvall, M.; Walles, B.
Studia Forestalia Suecica 145: 28
Intercellular hyphae of the pycnial state of M. pinitorqua occurred mostly in the stem cortex of pine seedlings, but also in the phloem and xylem. Haustoria were elongated, sometimes coiled, and some had a papilla-shaped collar at the penetration site. The haustorial sheath was thin in young haustoria, with age becoming thick, containing electron-dense granules and with convoluted membranes. Some haustoria became encased and degenerated.