Long-Distance Spread and Interregional Epidemics of Wheat Stripe Rust in China

Abstract

China, one of the largest wheat producing and consuming countries, produces over 90 million metric tons of wheat annually, or approximately 17% of the world’s wheat. According to the China Statistical Yearbook 2004, the total area under winter and spring wheat was 21.6 million hectares. As a food crop, wheat ranks second to rice in China. Wheat is grown at different geographical regions with various elevation and climate (Fig. 1). Winter wheat is mainly grown between 22 and 42°N latitude and between 75 and 97°E longitude, and spring wheat is mainly grown north of 42°N and in high altitude mountain regions in the western and southern parts of China, but the hectarage is relatively limited. Wheat is produced in 34 provinces of China (Fig. 2). The eight major winter wheat growing provinces are located in north-central (Hebei and Henan provinces), northwestern (Gansu and Shaanxi provinces), east-central (Shandong Province), southeastern (Jiangsu and Anhui provinces), and southwestern (Sichuan Province) China. Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks. & Henn., has been the most destructive wheat disease (Fig. 3). The epidemics of 1950, 1964, 1990, and 2002 caused yield losses up to 6.0, 3.0, 1.8, and 1.3 million metric tons, respectively (7,13). Wheat stripe rust is a worldwide destructive disease causing severe yield losses, especially in North America, Europe, and Asia (3,8,15). It also was introduced into Australia in 1979 (9) and into New Zealand in 1980 (12). In China, stripe rust exhibits a unique system which involves diverse and complicated cropping systems, geographic and climatic conditions, and pathogen life cycle features. Pandemics of the disease across various regions occasionally occur in China. The unique administrative system of this country made it feasible to conduct extensive across-regions cooperative research on long-distance disease spread. This report summarizes the China studies on longdistance disease spread and the complex regional classification of stripe rust epidemics.