Chapter 5 - Diversity, distribution, and status of phytoplasma diseases in Vietnam

Abstract

Several phytoplasma diseases: such as cassava witches broom (CaWB), sugarcane grassy shoot (SCGS), sugarcane white leaf (SCWL), sugarcane yellow leaf (SCYL), rice orange leaf (ROL), maize bushy stunt (MBS), sesame phyllody (SP), and cinnamon witches broom (CinWB) were detected in Vietnam. The CaWBD-infected plants showed small shoots with the discoloration of stems and roots, and the association of “Candidatus Phytoplasma asteris” was confirmed. SCGSD and SCYLD have been detected in Nghe An province in the north–central coast of Vietnam. However, SCWLD was reported in Dong Nai, Binh Duong, Tay Ninh, and Khanh Hoa provinces in the south of Vietnam. It was confirmed that the phytoplasma strains identified from the SCGSD- and SCWLD-infected plants are members of the 16SrXI group; meanwhile, the phytoplasma associated with SCYLD belongs to the 16SrXII (stolbur group). Both SCGSD and SCWL were transmitted via vegetable propagation, but no insect vector has been confirmed. The ROLD has been detected in the south of Vietnam, and 16SrI phytoplasma group has been identified as associated with ROLD. MBSD was the only phytoplasma disease that has been detected in maize in Quang Ngai province of Vietnam caused by “Candidatus Phytoplasma asteris.” SPD was detected in sesame-growing areas surrounding Hanoi city in the north of Vietnam, and 16SrII group has been identified. Interestingly, it was reported that two phytoplasma strains belonging to 16SrI and 16SrII groups have been detected based on loop-mediated isothermal amplification (LAMP). Another phytoplasma strain belonging to the 16SrXIV group has been shown associated with CinWBD in Quang Ngai province. Further studies are required to identify the insect vectors and other natural reservoirs of the above phytoplasma strains reported in Vietnam for their effective management.