Bacillus pumilus, a Novel Ginger Rhizome Rot Pathogen in China

Abstract

Ginger rhizome rot is a major factor limiting the yield and marketability of ginger in Shandong Province, China. In order to identify the pathogen causing ginger rhizome rot, evaluate its pathogenicity, and explore its pathogenesis, diseased ginger rhizomes and surrounding soils were collected. A gram-positive, spore-forming, rod-shaped bacterium, designated GR8, was frequently isolated from the ginger rhizome samples. The bacterium was identified as Bacillus pumilus based on physio-biochemical and molecular biology characteristics. Pathogenicity studies with GR8 showed that it could cause disease of the tested rhizomes slices and the entire rhizome when wounded but no disease occurred when the rhizome was not wounded. Preliminary pathogenicity studies demonstrated that cell-free cultures of GR8 could not cause any disease symptoms, whereas the bacterial suspensions caused severe symptoms. The pathology studies revealed that infection of GR8 could cause starch grains to shrink from normal size, and destroy the parenchyma cells by invading and propagating in them. This is the first report of B. pumilus causing ginger rhizome rot.

Effects of Actin-Like Proteins Encoded by Two Bacillus pumilus Phages on Unstable Lysogeny, Revealed by Genomic Analysis

“…B. pumilus strain GR8, a ginger rhizome rot-causing pathogen, was isolated at our laboratory (14) and was cultured in Luria-Bertani (LB) broth at 30°C. Soil samples were collected from Shandong Province, China, where ginger rhizome rot disease is prevalent.…”

“…The LaiWu Big ginger rhizome initiated from sterile tissue culture was cut into 3-mm slices and placed onto sterile, moistened filter-paper in a petri dish and inoculated with 100 l of 10 8 CFU/ml, log-phase, bacterial suspension along with 100 l of phage suspension at different concentrations. After incubation at 30°C for 24 h, disease severity ratings were evaluated as previous standards, where 1 denotes healthy tissue, 2 denotes slight (up to 20%) rot (slight discoloration), 3 denotes moderate (up to 50%) rot (discoloration and tissue breakdown), 4 denotes severe rot (50 to 75% of slice is affected), and 5 denotes complete rot (up to the entire slice is affected) (14). Sterile water served as negative control, while bacterial suspension alone added to the ginger rhizome slice was used as positive control.…”

“…B. pumilus also causes some human disease (10), such as acting as a bloodstream pathogen during infancy (11). B. pumilus strain GR8 isolated from Shandong Province of China was identified as an opportunistic pathogen of the ginger rhizome rot disease (14) and causes serious losses of ginger production in Shandong Province. Due to the ability of phages and phage-derived endolysin in controlling bacterial pathogens, phages are regarded as potential agents for plant disease control.…”

“…In this study, we characterized two newly isolated myoviruses, Bp8p-C and Bp8p-T, infecting B. pumilus GR8, the pathogen causing ginger rhizome rot disease (14), by physiological analysis, genome sequencing, and structural proteomic analysis. Further, we clarified the effect of actin-like plasmid segregation-associated protein on phage lysogeny and revealed a direct relationship between the actin-like protein of the plasmid segregation system and the lysogenic ability of phage.…”

Chitosan and oligochitosan enhance ginger (Zingiber officinale Roscoe) resistance to rhizome rot caused by Fusarium oxysporum in storage

“…Ginger, however, is subject to various fungal and bacterial pathogens that can cause diseases at different growth stages (Le, Smith, Hudler, & Aitken, 2014;Peng, Yuan, & Gao, 2013;Prasath et al, 2014;Shanmugam, Thakur et al, 2013). Among fungal pathogens, Fusarium oxysporum is especially a major problem in the production of ginger.…”