Fastidious Xylem-Limited Bacterial Plant Pathogens

Abstract

Numerous bacteria have been isolated from within plants, and many reported from xylem, but only three species of xylem-limited bacteria (XLB) that are fastidious in cultural requirements, are plant pathogens, and exclusively occupy xylem, have been well characterized. Two XLB, Xylella fastidiosa and Pseudomonas syzygii, are transmitted by sucking insects that feed on xylem sap but are not transmitted mechanically from plant to plant. In contrast, Clavibacter xyli is mechanically transmitted to plants by cutting tools. All of these XLB occupy a highly specialized yet diverse ecological niche: the water-conducting systems of an extremely wide range of plant hosts. A variety of detection methods are available as diagnostic aids; each method has advantages and disadvantages; no single method is best for all uses. Molecular and genetic comparisons of strains of XLB lag behind progress being made for many other plant-pathogenic bacteria, but such studies are needed to answer important questions: (a) How do XLB move from cell to cell within plants? (b) What are the physiological and genetic bases of plant host specificity for XLB? (c) Why are only xylem-feeding specialists vectors of X. fastidiosa (and probably P. syzygii), when many leafhoppers feed regularly (but not continuously) on xylem?

Rooting of healthy and CVC-affected 'Valência' sweet orange stem cuttings, through the use of plant regulators

“…This disease is caused by the bacterium, Xylella fastidiosa (Leite Junior and Leite, 1991;Lee et al, 1993;Chang et al,1993;Hartung et al, 1994). There are many important diseases caused by other strains of X. fastidiosa, including Pierce's disease of grapevine (PD) and others (Purcell and Hopkins, 1996). Symptoms include conspicuous variegations on older leaves, with chlorotic areas on the upper side and corresponding light brown lesions on the lower side.…”

Transformação genética de laranja doce (Citrus sinensis L. Osbeck) com o gene cecropin MB39 e avaliação de plantas transgênicas inoculadas com Xylella fastidiosa Wells et al.

“…O termo bactéria limitada ao xilema (XLB) do inglês "xylem-limited bacteria" passou a ser utilizado para referir-se às bactérias parasitas endofíticas que vivem exclusivamente nas células do xilema ou elementos traqueais (PURCELL; HOPKINS, 1996). Este termo descreve as seguintes bactérias patogênicas: Xylella fastidiosa (WELLS et al, 1987), Ralstonia syzygii comb.…”

“…(ROBERTS et al, 1990;VANEECHOUTTE et al, 2004) e Clavibacter xyli (DAVIS et al, 1984). A X. fastidiosa é responsável pela causa de várias doenças em inúmeras espécies de plantas e também coloniza outras plantas sem mostrar sintomas aparentes (PURCELL; HOPKINS, 1996). (HOPKINS, 1989;HOPKINS, 1996).…”

“…A X. fastidiosa é responsável pela causa de várias doenças em inúmeras espécies de plantas e também coloniza outras plantas sem mostrar sintomas aparentes (PURCELL; HOPKINS, 1996). (HOPKINS, 1989;HOPKINS, 1996). No Brasil, três doenças se destacam pela importância econômica: a atrofia dos ramos do cafeeiro (ARC), escaldadura das folhas da ameixeira (EFA) e a clorose variegada dos citros (CVC).…”

“…A transmissão e disseminação da X. fastidiosa entre as plantas cítricas ocorrem por insetos vetores conhecidos como cigarrinhas (Hemíptera: Cicadellidae), que se alimentam nos vasos do xilema das plantas hospedeiras HOPKINS, 1996 (KRÜGNER et al, 2000;YAMAMOTO et al, 2002).…”