HOST PREFERENCE OF 2 GREMMENIELLA-ABIETINA VARIETIES ON BALSAM FIR, JACK PINE, AND BLACK SPRUCE IN EASTERN CANADA

Host preference of Gremmeniella abietina var. balsamea (GAB) originati ng from Picea mariana or Abies balsamea and of the North American race of G. abietina var. abietina (GAA-NA) originating from Pinus banksian a was tested by cross-inoculations on their original host species grow ing in a boreal forest in Quebec. Mycelia of six different isolates (t wo from each host of origin) were inoculated into cortical tissue of c urrent shoots in late autumn and the length of the necrotic area was m easured the next summer. There was evidence of host preference of the isolates. GAB caused more necrosis than GAA on P. mariana and A. balsa mea, whereas it was the opposite situation on P. banksiana. The necrot ic area on P. mariana was longer when caused by GAB originating from P . mariana than when caused by GAB originating from A. balsamea. The re sults are in agreement with the recent morphological, biochemical, and genetic separation of G. abietina into GAA and GAB. The results also support the recent DNA-based differentiation of GAB isolates according to the host genera Picea and Abies. We suggest that the genetic diffe rentiation leading to separate genetic entities within G. abietina cou ld be associated with host specialization.