First Report of Burkholderia gladioli Causing Bacterial Leaf Streak of Fresh-consumption Sugarcane in Fujian Province, China

Fresh-consumption sugarcane (Saccharum officinarum L.) is consumed directly as chewing cane or juice. In April 2025, streaks were observed on leaves of fresh-consumption sugarcane seedlings (cv. Guangdong Huangpi) in Xianyou County, Fujian, China (25.40°N, 118.30°E), with the affected area totaling approximately 30 ha. A field survey of 500 plants across 10 plots estimated a mean disease incidence of 5%. Initial symptoms appeared as small, water-soaked red spots on leaves, which later developed into characteristic reddish-brown to rust-red irregular streaks along the veins. Some lesions coalesced into band-like patterns interspersed with narrow green tissue. Severely infected leaves showed extensive reddish-brown discoloration. These symptoms are distinct from the narrow red stripes with yellow halos (red stripe disease caused by Paracidovorax avenae) and the white "pencil-line" streaks (leaf scald caused by Xanthomonas albilineans). Symptomatic tissues were surface-sterilized with 75% ethanol (twice, 30 s each), rinsed, ground, suspended in sterile water, and spread onto nutrient agar. After 36 h at 28℃, the predominant colony type was purified and designated XYC6. Colonies were yellow, convex, circular, translucent, and shiny, with yellow pigment diffusing into the medium. Genomic DNA was extracted by the CTAB method. The 16S rRNA gene was amplified with universal primers 27F/1492R (Lane 1991), and the gyrB and atpD genes with primers described by Spilker et al. (2009). BLASTn analysis of 16S rRNA (PX457296), gyrB (PX767546) and atpD (PX767548) sequences showed 99.71%, 99.19%, and 99.87% identity (all with 100% coverage) with Burkholderia gladioli strain BBB-01, respectively. Multilocus sequence analysis of concatenated sequences further supported the identification of strain XYC6 as B. gladioli. Whole-genome sequencing data (PacBio) were deposited in NCBI under BioProject PRJNA1328369. Average nucleotide identity analysis showed that XYC6 shared 97.78 to 97.84% ANI values with B. gladioli strains, exceeding the suggested 95% species threshold. Phylogenomic analysis based on whole-genome sequences clustered XYC6 with three B. gladioli strains, collectively verifying its taxonomic status. Pathogenicity was confirmed on 4-week-old sugarcane (cv. Guangdong Huangpi) using two inoculation methods, with three independent biological replicates per treatment (15 plants per replicate). For wound inoculation, leaves were lightly scratched with a sterile needle and the area was wrapped with sterile cotton soaked in 200 μL of XYC6 cell suspension (10 8 CFU/mL) to maintain local humidity. For non-wound inoculation, sterile cotton saturated with 200 μL of the same suspension was placed onto intact leaves for 48 h to allow bacterial ingress through natural openings. Control plants were treated similarly with sterile water. All plants were cultured in a chamber at 28℃ with 60% RH and a 16-h light/8-h dark photoperiod. Water-soaking lesions appeared after 2 d and later developed into reddish-brown streaks identical to field symptoms; control plants remained asymptomatic. Strains were reisolated from these lesions, and their identity to XYC6 was confirmed by PCR amplification and sequencing, thus fulfilling Koch’s postulates. Although B. gladioli has been reported as a biocontrol agent in sugarcane (Cui et al. 2020), strain XYC6 identified in this study caused bacterial leaf streak symptoms on fresh-consumption sugarcane.