Molecular and Symptom Analysis Reveal the Presence of New Phytoplasmas Associated with Sugarcane Grassy Shoot Disease in India

Abstract

A total of 240 sugarcane (Saccharum officinarum) plants showing phenotypic symptoms of sugarcane grassy shoot (SCGS) disease were collected from three states of India, Maharashtra, Karnataka, and Uttar Pradesh. Phytoplasmas were detected in all symptomatic samples by the polymerase chain reaction (PCR) amplification of phytoplasma-specific 16S rRNA gene and 16S-23S rRNA spacer region (SR) sequences. No amplification was observed when DNA from asymptomatic plant samples was used as a template. Sixteen samples were selected on the basis of phenotypic symptoms and geographic location, and cloning and sequencing of the 16S rRNA and spacer regions were performed. Multiple sequence alignments of the 16S rRNA sequences revealed that they share very high sequence similarity with phytoplasmas of rice yellow dwarf, 16SrXI. However, the 16S-23S rRNA SR sequence analysis revealed that while the majority of phytoplasmas shared very high (>99%) sequence similarity with previously reported sugarcane phytoplasmas, two of them, namely BV2 (DQ380342) and VD7 (DQ380343), shared relatively low sequence similarity (79 and 84%, respectively). Therefore, these two phytoplasmas may be previously unreported ones that cause significant yield losses in sugarcane in India.