Identification and characterization of Xanthomonas albilineans causing sugarcane leaf scald in China using multilocus sequence analysis

Xanthomonas albilineans is the causal agent of leaf scald, a disease that can cause considerable damage to sugarcane industries. This study analysed the phylogenetic relationship of 14 samples of X. albilineans from China and 13 reference strains retrieved from the GenBank database by multilocus sequence analysis (MLSA). To reach this goal, five housekeeping genes of X. albilineans were amplified from diseased leaves and sequenced: gyrB, abc, rpoD, atpD and glnA. Based on the concatenated sequence of these genes (4473 nt), the 14 samples of X. albilineans from China had 99.9–100% sequence identity with one another and with five strains of the pathogen from the French West Indies and the USA (Florida). The 27 samples or strains of X. albilineans were distributed in two distinct clades in the MLSA‐based phylogenetic tree. Clade 1 was formed by four strains of the pathogen from Fiji, Papua New Guinea and the USA. All the other strains from worldwide locations, including the 14 samples from China, were grouped in clade 2. This latter clade included all strains of the pathogen that were associated with outbreaks of leaf scald that have occurred over the last two decades, especially in the Caribbean islands and the USA. The very low diversity of X. albilineans in four Chinese provinces suggests recent spread of a single strain (from genetic group PFGE‐B) of the leaf scald pathogen within China