A new phytoplasma strain associated with the sugarcane white leafdisease in Vietnam

Sugarcane white leaf (SCWL) disease is one of the most important diseases of sugarcane in Vietnam. The presence of phytoplasmas in phloem tubes of infected plants was confirmed by DAPI staining. A nested PCR assay using R16mF2/R16mR1 and R16F2n/R16R2 primer pairs amplified products with approximate length of 1,250 bp from the symptomatic sugarcane samples. The sequence analysis indicated that the phytoplasma strains from Khanh Hoa province shared 100% sequence identity with previously sequenced SCWL phytoplasma strains that were related to ‘Candidatus Phytoplasma oryzae’ (16SrXI). The virtual RFLP patterns of a 1,127 bp sequence obtained with the restriction enzymes BfaI, BstUI, EcoRI, HaeIII, HinfI, HpaI, RsaI and TaqI indicate that this SCWL-associated phytoplasma from Vietnam is a different strain from those in the 16SrXI described ribosomal subgroups. The two insect species, Matsumuratettix hiroglyphicus and Yamatotettix flavovittatus, identified as the vectors of SCWL in Thailand, were identified and found to be infected also in the SCWL symptomatic fields in Vietnam. The transmission experiments from SCWL-infected leafhoppers to healthy sugarcane and to insect feeding medium failed, suggesting that the infected planting material is the major transmission manner of SCWL disease in Vietnam.