DISTRIBUTION OF ARMILLARIA-OSTOYAE GENETS IN A PINUS-RESINOSA PINUS-BANKSIANA FOREST

Diploid isolates of Armillaria ostoyae were obtained from 278 trees (i ncluding stumps, Pinus banksiana seedlings, and hardwood regeneration) and 78 solitary basidiomes on three 50 x 25 m plots (two clearcut and one uncut) in a Pinus resinosa - P. banksiana stand in northern Minne sota. Based on pairings among 439 isolates, 16 somatic incompatibility groups of A. ostoyae were distinguished on the three plots. Analysis of nuclear and mitochondrial markers suggests that many of the A. osto yae genets are closely related and were possibly established by sib-re lated basidiospores. Analysis of molecular markers of 95 isolates repr esenting the 16 somatic incompatibility groups delineated 16 nuclear a nd 8 mitochondrial haplotypes. All isolates tested within a somatic in compatibility group were identical for nuclear and mitochondrial haplo types; a single exception consisted of a somatic incompatibility group with three different nuclear genotypes. The combination of somatic in compatibility and molecular data indicates the presence of at least 18 genets on the site. Large (up to 140-m diameter), spatially continuou s genets intermingled with small, recently established genets and olde r, fragmented genets. The approach identified genetic and ecological p rocesses; these include breeding strategies and pathogenicity.