Evidence that Xylella fastidiosa is the causal agent of almond leaf scorch disease in Alicante, mainland Spain (Iberian Peninsula)

Plant Disease ◽  
2021 ◽  
Author(s):  
Ester Marco-Noales ◽  
Silvia Barbé ◽  
Adela Monterde ◽  
Inmaculada Navarro ◽  
Amparo Ferrer ◽  
...  
Keyword(s):  
Xylella Fastidiosa ◽  
Axenic Culture ◽  
Mediterranean Area ◽  
Causal Agent ◽  
Molecular Techniques ◽  
Leaf Scorch ◽  
Molecular Tests ◽  
Outbreak Area ◽  
Almond Trees ◽  
Almond Leaf Scorch

In 2017, Xylella fastidiosa, a quarantine plant pathogenic bacterium in Europe, was detected in almond trees associated to leaf scorch symptoms in Alicante, a Mediterranean area in southeastern mainland Spain. The bacterium was detected by serological and molecular techniques, isolated in axenic culture from diseased almond trees, and identified as X. fastidiosa subsp. multiplex ST6. Inoculation experiments on almond plants in greenhouse trials with a characterized strain of X. fastidiosa subsp. multiplex ST6 isolated in the outbreak area have proved that it was able to multiply and systemically colonize inoculated plants. Disease symptoms characteristic of leaf scorch, as those observed in the field, were observed in the inoculated almond trees after one year. Furthermore, the pathogen was re-isolated and identified by molecular tests. With the fulfillment of the Koch’s postulates we have demonstrated that X. fastidiosa is the causal agent of the almond leaf scorch disease in the Alicante outbreak.

scholarly journals Influence of Inoculation Date on the Colonization of Xylella fastidiosa and the Persistence of Almond Leaf Scorch Disease Among Almond Cultivars

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 158-165 ◽  
Author(s):  
Tiesen Cao ◽  
Joseph H. Connell ◽  
Margot Wilhelm ◽  
Bruce C. Kirkpatrick
Keyword(s):  
Xylella Fastidiosa ◽  
Prunus Dulcis ◽  
Current Season ◽  
Leaf Scorch ◽  
Growing Seasons ◽  
Almond Trees ◽  
Cultivar Susceptibility ◽  
June July ◽  
July August September ◽  
Almond Leaf Scorch

Field grown 2-year-old almond trees (Prunus dulcis cvs. Butte, Carmel, Mission, Ne Plus Ultra, Padre, Peerless, Price, Solano, Sonora, and Thompson) were mechanically inoculated with Xylella fastidiosa in the growing seasons of 2002 and 2003 to study the effect of inoculation date on the movement and colonization of X. fastidiosa and the overwintering persistence of almond leaf scorch disease (ALS) in these cultivars. X. fastidiosa was inoculated into the base of current-season growing shoots in April, May, June, July, August, September, and October. Almond trees inoculated in spring months developed more ALS-symptomatic leaves and more extensive within-plant spread of X. fastidiosa by the end of the current growing season compared with trees inoculated in July, August, September, and October. Trees inoculated in June developed the most severe ALS symptoms during the season in which they were inoculated. Trees inoculated in June and July 2002 had significantly higher disease ratings in 2003 than inoculations made in August and October 2002. Based on disease ratings observed in 2003, 1 year after inoculation, Sonora and Solano were the most ALS susceptible, Mission and Price intermediate, and Carmel, Padre, Ne Plus Ultra, Butte, Peerless, and Thompson were the least susceptible cultivars for allowing X. fastidiosa to overwinter and cause disease the following year. Assessment of all trees in August 2004 indicated that trees inoculated in June and July 2002 had a significantly higher amount of ALS-infected branches than trees inoculated in other months. Butte, Carmel, Padre, and Thompson cultivars had no symptomatic branches, while X. fastidiosa infections persisted or colonized new branches in Sonora, Solano, Peerless, Price, Mission, and Ne Plus Ultra. Based on the 2004 assessment, Sonora was the most susceptible cultivar. Surveys of a diseased orchard in Chico, CA showed large differences in ALS incidence in four almond cultivars. Nonpareil and Peerless had significantly greater incidence of disease than Butte and Carmel over the 2 years surveyed. These data suggest that cultivar susceptibility and the time of X. fastidiosa infection are important factors in determining the persistence of ALS in almond trees.

scholarly journals Phylogenetic inference enables reconstruction of a long-overlooked outbreak of almond leaf scorch disease (Xylella fastidiosa) in Europe

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Eduardo Moralejo ◽  
Margarita Gomila ◽  
Marina Montesinos ◽  
David Borràs ◽  
Aura Pascual ◽  
...  
Keyword(s):  
Fungal Pathogens ◽  
Xylella Fastidiosa ◽  
Epidemiological Data ◽  
Phylogenetic Inference ◽  
Posterior Density ◽  
Leaf Scorch ◽  
Almond Trees ◽  
Bayesian Phylogenetic Inference ◽  
Highest Posterior Density ◽  
Almond Leaf Scorch

Abstract The recent introductions of the bacterium Xylella fastidiosa (Xf) into Europe are linked to the international plant trade. However, both how and when these entries occurred remains poorly understood. Here, we show how almond scorch leaf disease, which affects ~79% of almond trees in Majorca (Spain) and was previously attributed to fungal pathogens, was in fact triggered by the introduction of Xf around 1993 and subsequently spread to grapevines (Pierceʼs disease). We reconstructed the progression of almond leaf scorch disease by using broad phylogenetic evidence supported by epidemiological data. Bayesian phylogenetic inference predicted that both Xf subspecies found in Majorca, fastidiosa ST1 (95% highest posterior density, HPD: 1990–1997) and multiplex ST81 (95% HPD: 1991–1998), shared their most recent common ancestors with Californian Xf populations associated with almonds and grapevines. Consistent with this chronology, Xf-DNA infections were identified in tree rings dating to 1998. Our findings uncover a previously unknown scenario in Europe and reveal how Pierce’s disease reached the continent.

A New Sharpshooter Threatens Both Crops and Ornamentals

2000 ◽  
Vol 1 (1) ◽  
pp. 4 ◽  
Author(s):  
Matthew J. Blua ◽  
Phil A. Phillips ◽  
Richard A. Redak
Keyword(s):  
Host Range ◽  
Potential Distribution ◽  
Xylella Fastidiosa ◽  
New Disease ◽  
Leaf Scorch ◽  
Economic Problems ◽  
The Future ◽  
Different Strains ◽  
Large Host ◽  
Almond Leaf Scorch

The glassy-winged sharpshooter (Homalodisca coagulate), an insect that has recently invaded California, and the smoke tree sharpshooter (Homalodisca lacerta) are creating serious new economic problems in both agricultural and ornamental plantings. The greatest threats surround their ability to spread the plantpathogenic bacterium Xylella fastidiosa, which induces Pierce's disease in grapevines, almond leaf scorch disease, and a new disease known as oleander leaf scorch. Because of the potential distribution and large host range of the glassywinged sharpshooter, other diseases caused by different strains of X. fastidiosa may have an even greater impact on the state's agricultural and ornamental landscape industries in the future. Posted 27 June 2000.

scholarly journals Almond Leaf Scorch Disease Development on Almond Branches High-Grafted on Peach Rootstock

Plant Disease ◽  
2013 ◽  
Vol 97 (2) ◽  
pp. 277-281 ◽  
Author(s):  
Tiesen Cao ◽  
Theodore M. DeJong ◽  
Bruce C. Kirkpatrick
Keyword(s):  
Xylella Fastidiosa ◽  
Average Distance ◽  
Winter Season ◽  
Growing Season ◽  
Prunus Dulcis ◽  
Leaf Scorch ◽  
Second Year ◽  
Peach Rootstocks ◽  
Almond Leaf Scorch ◽  
Made In

Development of almond leaf scorch (ALS) disease was monitored on young almond (Prunus dulcis ‘NePlus’ and ‘Peerless’) shoots produced from almond scion wood that was high-grafted on peach rootstocks (P. persica ‘Queencrest/Nemaguard’), after the almond shoots were mechanically inoculated with Xylella fastidiosa. The objective of this study was to evaluate the potential movement of X. fastidiosa through almond–peach graft unions. ALS symptoms developed on both X. fastidiosa-inoculated and uninoculated almond shoots that were high-grafted on different peach limbs of the same tree in September following inoculations with X. fastidiosa made in June and July 2002, respectively, when the average distance in peach rootstock between the two almond–peach graft unions was 30.5 cm or shorter. No ALS symptoms were observed on uninoculated almond shoots late in the growing season of the second year. The incidence of ALS-affected leaves on shoots inoculated with X. fastidiosa decreased in the second year on the inoculated shoots of Peerless as determined by the number of inoculated shoots showing ALS symptoms in 2002 versus 2003. No visible ALS symptoms were observed in NePlus late in the growing season of the second year, suggesting that survival of X. fastidiosa in NePlus was less than in Peerless. These data demonstrate that movement of X. fastidiosa through two almond–peach graft unions was possible during the year of inoculation when the peach rootstock stem distance between the two almond–peach graft unions was minimal. However, X. fastidiosa may not survive the winter season or survived so poorly as not to be able to produce ALS symptoms in the second growing season on the uninoculated shoots that previously showed ALS symptoms in the fall of the year when an adjacent shoot was inoculated. The results suggest that high-grafting almond scion wood on multiple peach rootstock limbs may provide a means to limit movement of X. fastidiosa from one almond limb to another on the same tree.

scholarly journals Differential Susceptibility of Prunus Germplasm (Subgenus Amygdalus) to a California Isolate of Xylella fastidiosa

HortScience ◽  
2009 ◽  
Vol 44 (7) ◽  
pp. 1928-1931 ◽  
Author(s):  
Craig A. Ledbetter ◽  
Elizabeth E. Rogers
Keyword(s):  
First Generation ◽  
Prunus Persica ◽  
Xylella Fastidiosa ◽  
Differential Susceptibility ◽  
Inoculum Sources ◽  
Disease Symptoms ◽  
Leaf Scorch ◽  
Bacterial Titer ◽  
Almond Trees ◽  
Polymerase Chain

Seedling peach (Prunus persica Batsch) and clonal peach–almond hybrids are popular rootstock choices for commercial almond growers in California. In this study, clonal replicates of peach and almond [P. dulcis (Mill.) D.A. Webb] rootstock germplasm and a first-generation peach–almond hybrid created from them were challenged with Xylella fastidiosa isolate M23. Clonal replicates were needle-inoculated with M23 and maintained in a greenhouse environment for a growing season. Typical almond leaf scorch disease symptoms began to develop on M23-inoculated almonds 11 weeks after inoculation. No leaf scorch symptoms were observed on M23-inoculated peach or peach–almond hybrids. Quantitative real-time polymerase chain reaction revealed consistent levels of X. fastidiosa DNA among inoculated almond replicates, whereas X. fastidiosa DNA was undetectable in replicates of peach–almond hybrids. A trace level of X. fastidiosa DNA was detected in a single peach replicate, and statistical analysis demonstrated that this level differed significantly (P < 0.001) from that detected in almond replicates. Selected almonds were further sampled sequentially along their meristematic axes to examine bacterial titer throughout the trees. Selected almond trees differed significantly (P = 0.036) in bacterial titer, but no significant differences were noted in levels of X. fastidiosa from different vertical sections of the main growth axes. The results suggest that peach and peach–almond hybrid rootstock germplasm used by commercial almond tree nurseries in California are not primary inoculum sources for X. fastidiosa-induced diseases.

scholarly journals Multilocus Simple Sequence Repeat Markers for Differentiating Strains and Evaluating Genetic Diversity of Xylella fastidiosa

2005 ◽  
Vol 71 (8) ◽  
pp. 4888-4892 ◽  
Author(s):  
Hong Lin ◽  
Edwin L. Civerolo ◽  
Rong Hu ◽  
Samuel Barros ◽  
Marta Francis ◽  
...  
Keyword(s):  
Simple Sequence Repeat ◽  
Xylella Fastidiosa ◽  
Sequence Repeat ◽  
Leaf Scorch ◽  
Genome Wide ◽  
A Genome ◽  
Genome Wide Search ◽  
Ssr Loci ◽  
Simple Sequence ◽  
Almond Leaf Scorch

ABSTRACT A genome-wide search was performed to identify simple sequence repeat (SSR) loci among the available sequence databases from four strains of Xylella fastidiosa (strains causing Pierce's disease, citrus variegated chlorosis, almond leaf scorch, and oleander leaf scorch). Thirty-four SSR loci were selected for SSR primer design and were validated in PCR experiments. These multilocus SSR primers, distributed across the X. fastidiosa genome, clearly differentiated and clustered X. fastidiosa strains collected from grape, almond, citrus, and oleander. They are well suited for differentiating strains and studying X. fastidiosa epidemiology and population genetics.

scholarly journals Coffee Leaf Scorch Bacterium: Axenic Culture, Pathogenicity, and Comparison with Xylella fastidiosa of Citrus

Plant Disease ◽  
1998 ◽  
Vol 82 (1) ◽  
pp. 94-97 ◽  
Author(s):  
J. E. O. de Lima ◽  
V. S. Miranda ◽  
J. S. Hartung ◽  
R. H. Brlansky ◽  
A. Coutinho ◽  
...  
Keyword(s):  
Shoot Growth ◽  
Xylella Fastidiosa ◽  
Polymerase Chain Reaction Amplification ◽  
Axenic Culture ◽  
Enzyme Linked Immunosorbent Assay ◽  
Leaf Scorch ◽  
Mature Leaves ◽  
Reaction Amplification ◽  
Polymerase Chain ◽  
Cultured Bacteria

Symptoms of coffee leaf scorch (CLS) appear on young flushes of field plants as large marginal and apical scorched areas on recently mature leaves. Affected leaves drop, shoot growth is stunted, and apical leaves are small and chlorotic. Symptoms may progress to shoot dieback. Only scorched leaves which could not be related to other known agents consistently contained bacteria and bacterial agglomerates when observed with light microscopy. Only plants with these symptoms were positive in enzyme-linked immunosorbent assay (ELISA) tests using antiserum to Xylella fastidiosa Wells et al. The bacterium Xylella fastidiosa Wells et al. was isolated in November 1995 from coffee (Coffea arabica) leaves with scorch symptoms on supplemented periwinkle wilt medium. Colonies were circular, dome-shaped, white, and 0.5 to 1.5 mm in diameter. Two of 10 young coffee seedlings stem-inoculated with a suspension of the isolated X. fastidiosa in January 1996 showed leaf scorch symptoms 3 to 5 months later, contained bacteria in xylem extracts, and reacted positively in ELISA using antiserum to the citrus variegated chlorosis (CVC) strain of X. fastidiosa. ELISA-positive bacteria were reisolated from this plant. None of the symptomless plants, including controls, revealed bacteria on microscopic examinations, ELISA, or isolation attempts. Antisera developed against cultured bacteria from both CLS and CVC plants reacted positively against plant extracts of both diseases in dot immunobinding assays (DIBA). The level of detection was about 5 × 105 bacteria ml-1 for both homologous and heterologous reactions. The polymerase chain reaction amplification products produced by CLS and CVC strains of X. fastidiosa were indistinguishable. Geographical distribution of these strains is not the same. CLS is widespread and usually occurs if coffee is adjacent to CVC-affected citrus. However, CVC does not always occur when citrus is grown adjacent to CLS-affected coffee. The bacteria are closely related, if not identical.

scholarly journals Glassy-Winged Sharpshooters Expected to Increase Plant Disease

2000 ◽  
Vol 1 (1) ◽  
pp. 3 ◽  
Author(s):  
Alexander H. Purcell ◽  
Stuart R. Saunders
Keyword(s):  
Plant Disease ◽  
Plant Diseases ◽  
Pierce's Disease ◽  
Leaf Scorch ◽  
Pierce’S Disease ◽  
Almond Trees ◽  
Citrus Orchards ◽  
Almond Orchards ◽  
A Minor ◽  
Almond Leaf Scorch

As it moves through California, the new pest known as glassy-winged sharpshooter (GWSS) may significantly increase the spread of plant diseases caused by the bacterium Xylella fastidiosa. The bacterium causes Pierce's disease of grapevines, almond leaf scorch and the newly recognized oleander leaf scorch disease. Currently, almond leaf scorch is a minor problem for California's almonds, but if GWSS becomes established in significant numbers in or near almond orchards, it might increase the incidence of almond leaf scorch. Our studies show that GWSS and two other sharpshooter species can transmit X. fastidiosa from diseased oleanders to healthy oleanders. GWSS also can transmit Pierce's disease strains of the bacterium from grapevine to grapevine and to almond trees. The oleander strain of the bacterium did not infect grapevines, but the ability of GWSS to transmit Pierce's disease strains may increase the spread of this lethal grapevine disease in vineyards bordering citrus orchards or other habitats where invading GWSS may establish permanent populations. Posted 27 December 2000.

scholarly journals Population Structure of Xylella fastidiosa Associated with Almond Leaf Scorch Disease in the San Joaquin Valley of California

2015 ◽  
Vol 105 (6) ◽  
pp. 825-832 ◽  
Author(s):  
Hong Lin ◽  
Md Sajedul Islam ◽  
Juan C. Cabrera-La Rosa ◽  
Edwin L. Civerolo ◽  
Russell L. Groves
Keyword(s):  
Population Structure ◽  
Driving Forces ◽  
Xylella Fastidiosa ◽  
Prunus Dulcis ◽  
San Joaquin Valley ◽  
Leaf Scorch ◽  
Ssr Analysis ◽  
Cultivar Selection ◽  
Genetic Clusters ◽  
Almond Leaf Scorch

Xylella fastidiosa causes disease in many commercial crops, including almond leaf scorch (ALS) disease in susceptible almond (Prunus dulcis). In this study, genetic diversity and population structure of X. fastidiosa associated with ALS disease were evaluated. Isolates obtained from two almond orchards in Fresno and Kern County in the San Joaquin Valley of California were analyzed for two successive years. Multilocus simple-sequence repeat (SSR) analysis revealed two major genetic clusters that were associated with two host cultivars, ‘Sonora’ and ‘Nonpareil’, respectively, regardless of the year of study or location of the orchard. These relationships suggest that host cultivar selection and adaptation are major driving forces shaping ALS X. fastidiosa population structure in the San Joaquin Valley. This finding will provide insight into understanding pathogen adaptation and host selection in the context of ALS disease dynamics.

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