Chapter 8 - Updates on phytoplasma diseases associated with sugarcane in Asia

Abstract

Five phytoplasma diseases have been identified in sugarcane: grassy shoot, green grassy shoot, white leaf, leaf yellows, and Ramu stunt. However, sugarcane (Saccharum sp. hybrids) is susceptible to many diseases like red rot, smut, wilt, grassy shoot, and yellow leaf. Among these, sugarcane grassy shoot (SCGS) is the most destructive due to the complete loss of millable canes of the affected clump. The 16S rRNA gene sequences showed that new phytoplasma strains in 16SrXI-D and -F subgroups are associated with SCGS disease. Although SCGS and sugarcane white leaf (SCWL) diseases show different symptoms, the 16S rRNA gene and less conserved genes-based analysis revealed the association of a similar phytoplasma with the diseases. The sugarcane yellow leaf (SCYL) disease is associated with mixed infection of SCYL virus and various phytoplasma species in Mauritius and India. The quantitative PCR assays have been standardized for SCGS phytoplasma detection, which can quantify its lowest possible titer. The whole-genome sequence of the SCGS phytoplasma allowed to classify ‘Ca. Phytoplasma sacchari’. Several sap-sucking insects such as Deltocephalus vulgaris, Cofana unimaculata, Matsumura tettixhiroglyphicus, Yamatotettix flavovittatus, and Maiestas portica have been identified as vectors transmitting the SCGS phytoplasma. At present, the disease is managed through heat therapy and meristem tip-based tissue culture techniques with moderate success. The latest update on SCGS disease has been presented and discussed in this chapter.