Analyses of the 16S-23S intergenic region of the phytoplasma causing the sugarcane white leaf disease in Yunnan Province, China

Sugarcane white leaf (SCWL) is an important disease caused by a phytoplasma. In Baoshan, Yunnan, China, SCWL was firstly observed in 2012, and has extended its area of occurrence to 600 hm² . Up to 52% of the plants may become diseased in a field and even complete loss of cane yield may result in the heavily infected fields, posing a serious threat to Yunnan sugar industry. To ascertain the causal agent of suspected SCWL disease in Yunnan, nested PCR using two sets of phytoplasma primer pairs (MOLX/MLOY and P1/ P2) was used to successfully amplify a genomic region of the 16S ribosomal DNA (16S rDNA) from 36 suspected SCWL samples. On the basis of sequencing, phylogenetic analysis and nucleotide alignments of 17 nested PCR products randomly selected from positive samples, identical fragments of 210bp in length were obtained that could be clustered into the 6Sr group XI (Rice Yellow Dwarf group) and shared 100% identity with the 16S-23S intergenic spacer region (ISR) of a member of this group, the SCWL phytoplasma (GenBank: HQ917068), and 99.52% with Sugarcane grassy shoot phytoplasma, of the same group. These results indicate that the SCWL disease in Baoshan is caused by a phytoplasma of the 6Sr group XI.