THE AUTHORS 



GERAL I. MCDONALD is principal plant pathologist at the 

 Intermountain Research Station's Root Diseases and Soil 

 Biology of Northern Rocky Mountain Forests research work 

 unit in Moscow, ID. He received his B.S. degree in forest 

 management in 1963 and Ph.D degree in plant pathology 

 in 1969 from Washington State University. Since joining 

 the Station in 1966, he has investigated the epidemiology 

 and genetic interaction of the blister rust organism and its 

 hosts. He is now investigating the ecological genetics of 

 conifer interaction with Armillaria-caused root rots. 



NEIL E. MARTIN is research plant pathologist with the 

 Intermountain Research Station's Root Diseases and Soil 

 Biology of Northern Rocky Mountain Forests research work 

 unit in Moscow, ID. He received his B.S. degree in botany 

 (1961) from Iowa State University, M.S. degree in plant 

 pathology (1964) from South Dakota State University, and 

 Ph.D. degree in plant pathology (1972) from Washington 

 State University. Since joining the Station in 1966, he has 

 researched blister rust, dwarf mistletoe, and root rots. 



RESEARCH SUMMARY 



A method for segregating a large population of Armillaria 

 spp. isolates into clones is described. The method in- 

 cludes statistical analysis as a part of clonal definition. 

 Four kinds of errors were investigated: readers could 

 either (1) agree to or (2) disagree with theory, or disagree 

 when (3) compatibility was expected or (4) when incom- 

 patibility was expected. All four errors occurred about 4 

 percent of the time. The error rate was high enough to 

 require statistical tests of delineation efficiency. 



A population of 394 isolates was reduced to 177 clones. 

 Traits common to the clones allowed further condensation 

 into four groups. Ecological behavior (host affinity - 

 rhizomorph production) of these groups suggests that the 

 Northern Rockies may support four Armillaria spp. In addi- 

 tion, certain cases of isolates showing compatibility over 

 extended geographic distances suggest the population 

 may contain haploid isolates. The large number of 

 multiple-membered clones is a valuable research resource 

 that will advance the technology of species identification 

 within the genus Armillaria. 



January 1988 



Intermountain Research Station 

 324 25th Street 

 Ogden, UT 84401 



