title: Bacillus thuringiensis suppresses bacterial wilt disease caused by Ralstonia solanacearum with systemic induction of defense-related gene expression in tomato.
abstract: Bacillus thuringiensis is a naturally abundant Gram-positive bacterium and a well-known, effective bio-insecticide. Recently, B. thuringiensis has attracted considerable attention as a potential biological control agent for the suppression of plant diseases. In this study, the bacterial wilt disease-suppressing activity of B. thuringiensis was examined in tomato plants. Treatment of tomato roots with B. thuringiensis culture followed by challenge inoculation with Ralstonia solanacearum suppressed the development of wilt symptoms to less than one third of the control. This disease suppression in tomato plants was reproduced by pretreating their roots with a cell-free filtrate (CF) that had been fractionated from B. thuringiensis culture by centrifugation and filtration. In tomato plants challenge-inoculated with R. solanacearum after pretreatment with CF, the growth of R. solanacearum in stem tissues clearly decreased, and expression of defense-related genes such as PR-1, acidic chitinase, and β-1,3-glucanase was induced in stem and leaf tissues. Furthermore, the stem tissues of tomato plants with their roots were pretreated with CF exhibited resistance against direct inoculation with R. solanacearum. Taken together, these results suggest that treatment of tomato roots with the CF of B. thuringiensis systemically suppresses bacterial wilt through systemic activation of the plant defense system.
authors.affiliation: Gifu University, Gifu, Japan. hyakumac@gifu-u.ac.jp
authors.forename: Mitsuro
authors.initials: M
authors.lastname: Hyakumachi
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Nishimura
authors.forename: Tatsuyuki
authors.initials: T
authors.lastname: Arakawa
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Asano
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yoshida
authors.forename: Seiya
authors.initials: S
authors.lastname: Tsushima
authors.forename: Hideki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D001413:Bacillus thuringiensis / Q000502:physiology*; D002688:Chitinases / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D043326:Glucan 1,3-beta-Glucosidase / Q000235:genetics / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000201:enzymology / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology; D018547:Plant Stems / Q000201:enzymology / Q000382:microbiology; D043368:Ralstonia solanacearum / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D010940:Plant Proteins; D002688:Chitinases; D043326:Glucan 1,3-beta-Glucosidase