MOLECULAR COMPARISON AND DIFFERENTIATION OF ERWINIA STRAINS CAUSING FIRE BLIGHT AND ASIAN PEAR BLIGHT
In contrast to fire blight, Asian pear blight mainly affects pear fruit trees. The disease, caused by Erwinia pyrifoliae, was first documented in 1995 for Korea; strains resembling E. pyrifoliae were also isolated from necrotic pear trees in Japan. Unlike E. amylovora, these pear pathogenic strains do not synthesize levan, but also form mucoid colonies on MM2Cu medium. PCR and additional assays such as sequence analysis of the hrpN genes showed a close relationship of Erwinia strains from Japan and E. pyrifoliae, but only a distant relationship to E. amylovora. Strains were differentiated by PFGE analysis after digests with rare cutting enzymes. E. pyrifoliae strains showed three different patterns, and Erwinia strains from Japan were even more diverse. With an XbaI digest E. amylovora strains from Central Europe and the Mediterranean region were grouped into mainly four patterns tracing spread of fire blight in the affected countries. The PFGE patterns of European and Mediterranean isolates are highly conserved and have been constant for many years. The Asian pear pathogens are more divergent, and from a population of diseased plant tissue, E. pyrifoliae strains were isolated with a mutation in hrpL.
Jock, S., Kim, W.-S. and Geider, K. (2002). MOLECULAR COMPARISON AND DIFFERENTIATION OF ERWINIA STRAINS CAUSING FIRE BLIGHT AND ASIAN PEAR BLIGHT. Acta Hortic. 590, 423-427
Asian pear pathogens, PCR, PFGE analysis, sequence alignments, HR