Status of groundnut bacterial wilt research in China.
This disease has been reported from 16 provinces in China and the area under groundnut cultivation naturally infested with the pathogen is estimated at >200 000 ha. Annual incidence ranges from 4 to 8% on resistant cultivars and the annual loss in pod yield is estimated at c. 36 000 t. The pathogen in China is race 1 of Pseudomonas solanacearum, and biovars 3 and 4 have been identified. Pathogenicity varies greatly with the region, the disease generally being more serious in southern provinces. Rotation of groundnut with rice for 1-2 yr provides the best cultural control. Rotation with other nonhost crops such as maize, wheat, sorghum and sugarcane for 2-5 yr is also effective. The use of wilt-resistant cultivars is the most important control measure in China and those grown at present include E Hua 5, Gui You 28, Lu Hua 3, Yue You 92, Yue You 256 and Zhonghua 2. Some of the 55 highly resistant germplasms identified have been used in breeding programmes. Research has also been conducted on the genetics and mechanisms of resistance, and on the molecular basis of virulence and pathogenicity of P. solanacearum, seed transmission, and biological control.