Distribution ofArmillaria ostoyaegenets in aPinus resinosa–Pinus banksianaforest

Abstract

Diploid isolates of Armillaria ostoyae were obtained from 278 trees (including stumps, Pinus banksiana seedlings, and hardwood regeneration) and 78 solitary basidiomes on three 50 × 25 m plots (two clearcut and one uncut) in a Pinus resinosa – P. banksiana stand in northern Minnesota. 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. ostoyae genets are closely related and were possibly established by sib-related basidiospores. Analysis of molecular markers of 95 isolates representing the 16 somatic incompatibility groups delineated 16 nuclear and 8 mitochondrial haplotypes. All isolates tested within a somatic incompatibility group were identical for nuclear and mitochondrial haplotypes; a single exception consisted of a somatic incompatibility group with three different nuclear genotypes. The combination of somatic incompatibility and molecular data indicates the presence of at least 18 genets on the site. Large (up to 140-m diameter), spatially continuous genets intermingled with small, recently established genets and older, fragmented genets. The approach identified genetic and ecological processes; these include breeding strategies and pathogenicity. Key words: Armillaria ostoyae, somatic incompatibility, population structure, mitochondria.