Xylella fastidiosa: an examination of a re‐emerging plant pathogen

Abstract

Most X. fastidiosa-related diseases appear as marginal leaf necrosis and scorching of the leaves. In the case of PD, X. fastidiosa can also cause desiccation of berries (termed 'raisining'), irregular periderm development and abnormal abscission of petioles. In olive trees affected with OQDS, leaves exhibit marginal necrosis and defoliation, and overall tree decline occurs. Plants with ALS and OLS also exhibit the characteristic leaf scorch symptoms. Not all X. fastidiosa-related diseases exhibit the typical leaf scorch symptoms. These include CVC and Phony Peach disease, amongst others. In the case of CVC, symptoms include foliar wilt and interveinal chlorosis on the upper surfaces of the leaves (similar to zinc deficiency), which correspond to necrotic, gum-like regions on the undersides of the leaves. Additional symptoms of CVC include defoliation, dieback and hardening of fruits. Plants infected with Phony Peach disease exhibit a denser, more compact canopy (as a result of shortened internodes, darker green leaves and delayed leaf senescence), premature bloom and reduced fruit size. Some occlusions occur in the xylem vessels, but there are no foliar wilting, chlorosis or necrosis symptoms . USEFUL WEBSITES: http://www.piercesdisease.org/; https://pubmlst.org/xfastidiosa/; http://www.xylella.lncc.br/; https://nature.berkeley.edu/xylella/; https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa_en.

Coffee bacterial diseases: a plethora of scientific opportunities

“…The first disease caused by X. fastidiosa was reported in the late 19th century on grapevine in California, USA, and the bacterium properly identified later by Wells et al (1987). Based on phylogenetic studies, the species has been proposed to consist of several distinct subspecies, namely, fastidiosa (causing Pierce's disease of grapevines and leaf scorch of almond), multiplex (leaf scorch of peach, oak and almond), pauca (Xfp; citrus variegated chlorosis and leaf scorch of coffee and olive), sandyi (leaf scorch of oleander), tashke (isolated from Chitalpa tashkenensis) and morus (leaf scorch of mulberry) (Mendonc ßa et al, 2017;Rapicavoli et al, 2017).…”

“…Studies on the molecular mechanisms underlying the pathogenicity of X. fastidiosa toward coffee plants have not been published. The vast majority of knowledge on the pathogenicity of X. fastidiosa has been obtained from strains that cause Pierce's disease and CVC (Mendonc ßa et al, 2017;Rapicavoli et al, 2017). It is presumed that some of those mechanisms are shared among strains that cause disease on different host species.…”

“…Xylella fastidiosa possesses the main bacterial secretion systems, except for the T3SS, which is usually required for pathogenicity (Mendonc ßa et al, 2017;Rapicavoli et al, 2017). The absence of a T3SS could explain why gene-for-gene resistance has not been observed in its host species.…”

Sharpshooters: a review of what moves Xylella fastidiosa

“…fastidiosa have been observed worldwide (Almeida & Nunney ; Bucci ; Rapicavoli et al . ; Sicard et al . ).…”

“…; Baldi & La Porta ; Rapicavoli et al . ), and significant research has been conducted on genetics of this organism since the first genome was sequenced in 2000 (Simpson et al . ).…”