Incidence of sugarcane ratoon stunting disease in the major cane-growing regions of China

• We surveyed the occurrence of RSD in the main cane-growing areas of China.
• We found RSD in all 21 cane-growing regions and 33 of the 35 cultivars in the survey.
• We found five cultivars with low RSD incidence under natural condition.
• Lxx detected in China is consistent with the species of bacteria known to cause RSD.
• This study shows the need for effective RSD control measures in China.

Ratoon stunting disease (RSD), caused by Leifsonia xyli subsp. xyli (Lxx), is one of the most important diseases that limits sugarcane production worldwide. A scientific understanding of the distribution, occurrence, and damage of RSD in cane-growing areas will provide basal information for the application of effective RSD control strategies. In the present study, the occurrence and distribution of RSD were surveyed in the 21 cane-growing regions of Yunnan and Guangxi Provinces of China from 1270 samples using a PCR-based assay. The results showed that 949 samples (74.7% out of 1270) were positive for the presence of RSD. In Yunnan and Guangxi provinces, RSD was detected in all 21 cane-growing areas at rates of 65.5–88% and in the 33 main cultivars at rates of 48.9–100%. The results also showed that plant crop and ratoons from both irrigated and rainfed fields were infected with RSD. Thus, RSD has become an established disease that seriously restricts the development of the cane-sugar industry in China due to cane yield loss, a shortened ratoon period, and cultivar degeneration. Effective control of RSD presents a major challenge to the further development of the sugarcane industry in China. The results of our survey indicated that under the field condition, the main cultivars grown over large areas, including Guitang 94-119, Yuetang 93-159, Yuetang 00-236, and Guitang 11 showed high RSD incidence rates, suggesting that the focus on these cultivars should be the production, propagation, application and extension of healthy, bacteria-free seedlings. Relatively low RSD incidence rates were found in the cultivars Liucheng 03-1137, Liucheng 05-136, Yuanlin 1, ROC22, and F95-8899. Further research is required to determine if these cultivars are resistant and can be used to reduce the incidence of the disease and for breeding RSD resistant sugarcane cultivars. Sequencing of 100 PCR products selected randomly from sugarcane samples that tested positive for RSD showed that all 100 sequences were identical and highly homologous to the previously published Lxx 16S–23S spacer region in GenBank (99.54–100% similarity).