Epidemiology of wheat rusts in the western hemisphere

Shortly after the turn of the century, devastating wheat rust epidemics in the Great Plains of North America (Northern Mexico, the Plains of the U.S.A. and the Prairie Provinces of Canada), prompted the study of physiologic specialization in stem and leaf rust, the breeding of resistant varieties, and the epidemiology and aerobiology of these rust diseases. No comparable area of the world has been studied so precisely and 50 years data have been systematically presented for the aerobiology and epidemiology of these organisms in this region. In the present paper, additional evidence is provided to support the hypothesis that this region forms a single epidemiological zone for these two diseases. Five other major geographical epidemiological zones are delineated in the Western Hemisphere: three in North America and two in South America. Evidence for their existence is based on data available for virulence patterns of the three species viz Puccinia graminis tritici, Puccinia recondita and Puccinia striiformis, either of one or a combination of species. Epidemics, virulence surveys, virulence patterns on varieties in Five. International Spring Wheat Yield Nurseries and two years of the International Stripe Rust Nursery, have been used to provide supporting data indicative of regional groupings. On the basis of available evidence it appears that the following epidemiological zones for rust exist: 1. The Great Plains of North America. 2. The Pacific Northwest (California, Oregon, Washington)The Eastern United States and Canada (areas east of the Alleghanys in the U.S. and the Laurentian Shield in Canada). 4. Southern Mexico and Guatemala. 5. The Andean Countries of Colombia, Ecuador, Peru and Chile (there is evidence of sub-epidemiological zones in this region). 6. Southern Brazil, Argentina, Paraguay and Uruguay. While corre!ctions are high for virulence patterns within these areas, there are indications of occasional interchange of virulence types between the zones. This is likely to occur where the zones come into close proximity, there are gaps in mountain ranges or a narrowing of desert barriers occurs.

Bibliographic Details

Main Authors:	Rajaram, S., Campos Vela, A.
Format:	Report biblioteca
Language:	English
Published:	CIMMYT 1974
Subjects:	AGRICULTURAL SCIENCES AND BIOTECHNOLOGY, WHEAT, RUSTS, PLANT BREEDING, DISEASE RESISTANCE, PUCCINIA, PLANT NURSERIES, FIELD EXPERIMENTATION,
Online Access:	https://hdl.handle.net/10883/19414
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