Genetic Diversity of Pierce's Disease Strains and Other Pathotypes of Xylella fastidiosa

Abstract

Strains of Xylella fastidiosa isolated from grape, almond, maple, and oleander were characterized by enterobacterial repetitive intergenic consensus sequence-, repetitive extragenic palindromic element (REP)-, and random amplified polymorphic DNA (RAPD)-PCR; contour-clamped homogeneous electric field (CHEF) gel electrophoresis; plasmid content; and sequencing of the 16S-23S rRNA spacer region. Combining methods gave greater resolution of strain groupings than any single method. Strains isolated from grape with Pierce's disease (PD) from California, Florida, and Georgia showed greater than previously reported genetic variability, including plasmid contents, but formed a cluster based on analysis of RAPD-PCR products, NotI and SpeI genomic DNA fingerprints, and 16S-23S rRNA spacer region sequence. Two groupings of almond leaf scorch (ALS) strains were distinguished by RAPD-PCR and CHEF gel electrophoresis, but some ALS isolates were clustered within the PD group. RAPD-PCR, CHEF gel electrophoresis, and 16S-23S rRNA sequence analysis produced the same groupings of strains, with RAPD-PCR resolving the greatest genetic differences. Oleander strains, phony peach disease (PP), and oak leaf scorch (OLS) strains were distinct from other strains. DNA profiles constructed by REP-PCR analysis were the same or very similar among all grape strains and most almond strains but different among some almond strains and all other strains tested. Eight of 12 ALS strains and 4 of 14 PD strains of X. fastidiosa isolated in California contained plasmids. All oleander strains carried the same-sized plasmid; all OLS strains carried the same-sized plasmid. A plum leaf scald strain contained three plasmids, two of which were the same sizes as those found in PP strains. These findings support a division of X. fastidiosa at the subspecies or pathovar level.Xylella fastidiosa (Wells et al.) (35) is a gram-negative, xylem-inhabiting bacterium that causes Pierce's disease (PD) of grape, phony peach disease (PP), periwinkle wilt, citrus variegated chlorosis, and leaf scorch diseases of almond (almond leaf scorch [ALS]), plum (PLS), elm, maple, oak (OLS), and sycamore (16, 27). All strains of X. fastidiosa are currently classified as one species but differ in important respects in plant host range and pathogenicity. The geographic isolation of the plant diseases caused by X. fastidiosa restricts the easy comparison of the pathological characteristics of the various strains. Previous studies differentiated X. fastidiosa strains on the basis of pathogenicity, nutritional requirements (16), DNA homology (19), structural protein analysis (3), restriction fragment length polymorphisms (RFLPs) (4), and random amplified polymorphic DNA (RAPD)-PCR (1, 6, 9, 25, 27). RFLP and DNA-DNA hybridization studies revealed distinct differences between PD strains and strains that cause PP, PLS, and periwinkle wilt (4, 19). Pooler et al. (25) distinguished five groups of X. fastidiosa using RAPD-PCR: the citrus group, plum-elm group, grape-ragweed group, almond gro...

Microarray Analyses of Xylella fastidiosa Provide Evidence of Coordinated Transcription Control of Laterally Transferred Elements

“…The subdivision of Xf strains into at least two distinct groups is in accord with previous observations (Chen et al 2000;Hendson et al 2001;Mehta and Rosato 2001), but even inside each group, a considerable degree of variation can be observed. The citrus group bears duplicated regions not observed in the coffee strain.…”

“…These results could provide the basis for further epidemiological studies and more efficient control of these phytopathogens (Hendson et al 2001). Thus, the genomes of two other strains isolated from oleander and almond trees were partially sequenced and annotated (http:// www.jgi.doe.gov/jgi_microbial/html), and a fourth strain, isolated from grapevines and responsible for PD in California, has also been sequenced to completion (http://www.lbi.ic.…”

Whole-Genome Analysis of Transporters in the Plant Pathogen Xylella fastidiosa

“…Xylella fastidiosa is a plant-pathogenic bacterium that causes variegated chlorosis in citrus trees and other diseases in a wide range of plant hosts (15,34). The citrus pathogen has an insect as its vector, which takes the parasite from tree to tree while feeding on the xylem.…”

Structural and Biochemical Characterization of Peroxiredoxin Qβ from Xylella fastidiosa

“…Citrus variegated chlorosis is the major problem faced by the Brazilian citrus industry and is responsible for significant losses in orange production (2). X. fastidiosa also imposes severe economic damage for other countries of the American continent because other strains of this bacterium provoke Pierce disease in grapevines, phony peach disease, and leaf scorch diseases in almond and oleander (3). During infection by microorganisms, one of the first plant responses is the production of oxidants, including hydrogen peroxide, organic hydroperoxides, and peroxynitrite (4 -6).…”