Bacterial blight of Brachiaria caused by Burkholderia glumae in Colombia

A new disease of Brachiaria was observed in 2009 at the CIAT experiment station in Palmira, Colombia, on plants of B. humidicola (CIAT accession no.16888). In 2016, the disease was observed on multiple genotypes of B. humidicola, Brachiaria hybrid cv. Mulato II, and Brachiaria hybrid Cayman. Symptoms included chlorosis along the midribs and yellowing on flag-leaf margins, followed by wilting and necrosis of foliage. Bacteria isolated from the lesions were cream-colored and produced a yellow, diffusible, non-fluorescent pigment on King´s medium B. Thirty-two bacterial strains fitting this description were pathogenic on Brachiaria spp. and were identified as Burkholderia glumae by PCR and sequence analysis of 16S rDNA. Real-time PCR was the most sensitive and accurate method evaluated for identifying the pathogen. B. glumae 88b, a highly-virulent strain identified in this study, was inoculated to ten Brachiaria genotypes including B. decumbens, B. brizantha ‘Marandú, B. brizantha ‘Toledo’, B. ruziziensis, B. brizantha ‘Piata’ and Brachiaria hybrids CIAT 36061, CIAT 36062, CIAT 36087, BR02/1752, and BR02/1794. B. glumae 88b was pathogenic on nine of the Brachiaria genotypes; interestingly, CIAT 36062 was resistant to strain 88b. This knowledge of B. glumae would help to develop bacterial blight disease management.