Distribution, phylogeny, and pathogenicity of Xanthomonas albilineans causing sugarcane leaf scald in Mexico

Disease outbreaks attributed to leaf scald of sugarcane caused by Xanthomonas albilineans were recently reported in southern Mexico. In this study, the distribution of leaf scald was investigated in the main sugarcane producingstates in Mexico. The disease was found in eight of 14 sugarcane-growing states and in 12 of 31 fields. In contaminated fields, incidence of leaf scald based on symptomatic plants ranged from 3 to 15%. The causal agent was identified by phylogenetic reconstruction using a single concatenated sequence of four genes (16S rRNA, fusA, leuS, and rpiA). Twelve X. albilineans isolates from different locations in Mexico produced disease symptoms after inoculation into stalks of susceptible variety Mex 69-290. Microscopic examination of infected stalks revealed structural changes within vascular and non-vascular tissues. These alterations reflected acute disease development and highlighted the importance of selecting varieties resistant to X. albilineans in breeding programs in Mexico.