Exploring the genetic diversity of sugarcane white leaf phytoplasma in Thailand, Laos and Vietnam by multilocus sequence typing

The sugarcane production in South-east Asia is suffering significant losses caused by the sugarcane white leaf disease (SCWLD), up to 10% of the total sugarcane production every year. In this study, we aimed to reveal the current status of the genetic diversity of phytoplasmas (Candidatus phytoplasma) related to the SCWLD in Thailand, Laos and Vietnam. We also compared phytoplasmas found in sugarcane with the ones found in different field grass species in order to determine if some grass species could play a role of pathogen reservoir in sugarcane fields.This work was conducted on samples collected in 7 provinces of Thailand, 2 provinces of Laos and 2 provinces of Vietnam, with a minimum of 3 locations investigated per province (47 locations in total). For each location, samples of cane leaves and field grass species with SCWLD symptoms were collected. In total, 192 samples were collected including 138 samples of sugarcane and 54 samples of other species (mainly field grass species). Also, for each location, the disease incidence was recorded by both field observations and by nested PCR in order to determinate if the genetic diversity could explain the observed variance in the pathogen virulence.The classification of phytoplasma strains was realized by multi-locus sequence typing (MLST) using 3 housekeeping genes: 16SrRNA, secA, and leuS.