Burkholderia gladioli causes bacterial internal browning in sweetpotato of China

Abstract

A new bacterial disease of sweetpotato was recently identified in Puning, Guangdong Province, China and is referred to bacterial internal browning of sweetpotato in this paper. One-third of the tubers of sweetpotato were infected in the field. These tubers in the field with bacterial inner brown displayed yellowing on the skin that turned into slightly roughened and cracked surface with progress in disease. Cross-sections of these roots revealed a yellowish brown or dark brown circle in the vascular cambium. Pathogenicity tests were conducted on different organs of two sweetpotato cultivars and revealed that the isolated bacteria are pathogenic on stems and roots. We confirmed the causal agent as Burkholderia gladioli based on biochemical and physiological characterization, carbon source utilization, and sequence analysis of partial 16S rDNA and 16S–23S rDNA internal transcribed spacer (ITS) region. To our knowledge, it is the first report on the occurrence of B. gladioli in sweetpotato as a pathogen.