Occurrence of Kabatina juniperi in Ontario and genetic analysis using RAPDmarkers

A survey conducted in 1992 and 1993 revealed that the major cause of junipe r twig blight in Ontario was Kabatina Juniperi. Phomopsis juniperovora was found in 3 of 26 samples received in 1992 and in none of 23 samples in 1993 . Analysis of acervuli of K. juniperi collected from spring 1997 through sp ring 1999 showed that spore production was high in spring, was lower in the summer, and gradually declined in the fall to very low levels in winter. U sing RAPD markers, we found molecular variation between K. juniperi isolate s from five locations within a 50 km radius. RAPD analysis of 24 isolates f rom five different cultivars of Juniperus scopulorum did not reveal host sp ecialization. Among 49 isolates sampled from two adjacent rows of J. scopul orum 'Grey Gleam', there were 36 different RAPD haplotypes. Genetic diversi ty analysis of this population showed significant gametic linkage disequili brium between putative RAPD loci and indicated that asexual propagules such as conidia are the major form of dispersal of this pathogen. A practical i mplication of this work is that pruning operations should be timed so that they do not coincide with peak spore production.