Resistance of Pinus contorta to the European race of Gremmeniella abietina
Pinus contorta seedlings, together with Pinus resinosa and Pinus banksiana seedlings, were planted adjacent to 25-year-old red pine trees infected by the European (EU) race of Gremmeniella abietina. Resistance to this race was assessed over 5 years. All P. resinosa seedlings were dead after that period while 65% of P. contorta and 86% of P. banksiana seedlings appeared resistant to the disease. The tip blight that occurred on P. contorta was slightly longer than that observed on P. banksiana. In microscopy, one, two, or even more suberized boundaries were seen to be initiated near the surface of the shoot at the base of healthy needles where they extended downward in the direction of the vascular cambium. Suberized boundaries occasionally crossed the xylem and joined together in the pith region to form continuous barriers around necrotic tissues. However, in most cases, these suberized barriers were not continuous across the shoot and compartmentalization was then completed by other barriers mainly constituted of parenchyma cells and xylem tracheids that accumulated phenolic compounds. Meristematic-like cells were observed adjacent to the necrophylactic periderm. Tissue regeneration, restoration of cambial activities and formation of traumatic resin canals also seemed to be associated with the defence system of P. contorta against the EU race of G. abietina.
Document Type: Research Article
Affiliations: 1: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., PO Box 3800, Sainte-Foy, Québec, G1V 4C7, Canada., Email: [email protected] 2: Centre de recherche en biologie forestière, Faculté de foresterie et de géomatique, Université Laval, Sainte-Foy, Québec, Canada 3: Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada
Publication date: 2006-04-01