Random amplified polymorphic DNA variability among geographic isolates of western gall rust fungus in Canada

Geographic variability among western gall rust (WGR) fungus (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was studied by random amplified poly morphic DNA (RAPD). Samples were taken from lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) host at four locations in British C olumbia and Alberta and from jack pine (Pinus banksiana Lamb.) host at nine locations in Alberta. Saskatchewan, Manitoba, and Ontario. Of 90 random ol igonucleotide primers screened, 9 were chosen for analysis. These nine prim ers consistently amplified 41 sharp and reproducible RAPDs (fragments) of t he WGR fungal isolates over several independent runs. Eighteen of the 41 RA PDs were polymorphic (showing the presence of both marker and null phenotyp es), of which 15 could discriminate WGR isolates of lodgepole pine hosts fr om jack pine ones. Of these 15 RAPDs, five were unique to isolates of lodge pole and five to jack pine. The remaining five RAPDs were significantly het erogeneous in the RAPD frequency between WGR isolates of the two host origi ns. The RAPD pattern of WGR isolates from lodgepole pine was uniform. Howev er, isolates from jack pine differed significantly in the frequency of four RAPDs among locations. with an east-west trend of decreasing similarity in RAPD. Analysis of molecular variance apportioned 76.3, 14.4, and 9.3% of t he total RAPD variability to differences among hosts, to differences among locations within hosts. and to differences within locations, respectively. The large differentiation between WGR fungal isolates sampled in lodgepole pine and jack pine hosts might suggest that selective pressure for host spe cificity in sampled populations was strong.