Molecular detection and prevalence of Xanthomonas albilineans, the causal agent of sugarcane leaf scald, in China

Leaf scald caused by Xanthomonas albilineans (Ashby) Downson is a destructive disease of sugarcane that can cause severe economic losses. During 2013-2017, 357 sugarcane leaf samples were collected from four provinces in China: 141 samples were taken from plants showing symptoms attributed to leaf scald and 216 were taken from asymptomatic plants. A previously described PCR protocol and PCR primers (XAF1/XAR1) targeting a putative ATP (adenosine triphosphate)-biding cassette (ABC) transporter gene (XALc_1791) were used to detect X. albilineans in these leaf samples. The pathogen was detected in 73% and 17% of symptomatic and asymptomatic leaf samples, respectively. The PCR-amplified fragments (608 bp) from 140 Xa-positive samples were cloned and sequenced. A total of 241 XALc gene sequences were obtained and compared to 13 sequences of X. albilineans isolates retrieved from GenBank. The isolates from China had 99.1-100% sequence identity with one another and 99.5-100% with four strains from the French West Indies (GPE PC73, GPE PC17, GPE PC86, and MTQ032) and one from Florida/USA (XaFLO7-1). Our findings show that X. albilineans causes leaf scald of sugarcane in Guangxi, Guangdong, Hainan, and Fujian provinces, suggesting that this disease could be a potential threat to the sugarcane industry in China.