Abstract:

【Objective】 The virulence genes of physiological race of Phytophthora infestans isolates from potato collected from the investigated areas in China were determined and evaluated, which will provide guidelines for resistant breeding and appropriate distribution of resistant varieties. 【Method】 The races of P. infestans isolates were determined by inoculation of detached leaflets of a differential set of potato cultivars carrying the eleven major (R) genes. 【Result】 A total of 30 races were identified among 57 isolates collected from the six provinces of China in 2006-2008 and all of them were complex-races possessing at least two virulence genes and 25 races showed five or more, accounting for 83% in tested strains. In addition, there were three isolates called “super virulence race”, which can overcome all known 11 resistant genes (R1 to R11). 【Conclusion】 The number of races of P. infestans is increacing and its composition is getting more complex in China. Therefore, it is very urgent to explore new resistant germplasm from wild potato relatives and breed horizontal resistant varieties due to all known 11 vertical resistant genes losing resistance to P. infestans in some provinces of China.

Key words: Phytophthora infestans, physiological race, distribution, disease-resistance breeding