PHYSIOLOGICAL SPECIALIZATION OF PUCCINIA-RECONDITA F-SP TRITICI IN CANADA IN 1992

In 1992 leaf rust of wheat (Triticum aestivum) caused by Puccinia recondita f. sp. tritici was first observed during the second week of June in winter wheat fields in southern Manitoba. Lower than normal summer temperatures reduced the development of the disease on spring wheat throughout western Canada in 1992. Wheat cultivars Columbus, Roblin, Pasqua, and Minto remained highly resistant to leaf rust in 1992 and losses in these cultivars were minimal. Moderate servity levels were found in late planted fields of Biggar and Katepwa. A total of 47 virulence phenotypes of the pathogen were detected in Canada using 16 near isogenic Thatcher differential lines. Phenotypes with virulence to resistance genes Lr11 or Lr24 and Lr26 were prevalent in Manitoba and Saskatchewan. The prevalent virulence phenotypes in Ontario, and British Columbia remained relatively unchanged from previous years.