Xylella Arrived in Italy from a Costa Rican Coffee Plant, Researchers Say

A study concluded that the genomes of Xylella fastidiosa in Apulian olive trees descended directly from Costa Rican coffee plants.

Coffee plants in San Jeronimo, Costa Rica
By Francesca Gorini
Mar. 8, 2022 13:17 UTC
Coffee plants in San Jeronimo, Costa Rica

An inter­na­tional team of sci­en­tists has inves­ti­gated the endur­ing ques­tion of how Xylella fas­tidiosa arrived in Europe and adapted to its new envi­ron­ment.

The study, pub­lished in Microbial Genomics, sheds new light on the ori­gin of the Xylella fas­tidiosa bac­te­ria and how the pathogen has evolved, killing mil­lions of olive trees in Puglia.

Our analy­sis sug­gests that the pathogen had arrived in Italy with a sin­gle intro­duc­tion from Costa Rica, con­firm­ing 2008 as the most likely year when Xylella was intro­duced in Italy.- Maria Saponari, Italian National Research Council

While the pres­ence of the bac­terium was orig­i­nally con­firmed in Europe in 2013, there remains very lit­tle infor­ma­tion on the bio­log­i­cal rela­tion­ship between bacteria’s geno­types and host plant species, which is par­tic­u­larly rel­e­vant as Xylella fas­tidiosa con­tin­ues to spread across Europe.

By ana­lyz­ing a pop­u­la­tion of strains from Italian olive trees and closely related genomes from other plant species and loca­tions, researchers have con­cluded that the Italian out­break was caused by a sin­gle cof­fee plant imported from Central America in 2008.

See Also:Researchers Find Another Disease Afflicting Olive Groves in Puglia

The study spanned five years – 2013 to 2017 – dur­ing which sci­en­tists col­lected twig sam­ples from more than 70 trees with Olive Quick Decline Syndrome, the dis­ease caused by Xylella fas­tidiosa, using a new pro­to­col to extract the trees’ DNA.

The genomic sequences of the Xylella fas­tidiosa iso­late affect­ing the olive trees were then com­pared with three cof­fee and ole­an­der iso­lates from Costa Rica, which had been pre­vi­ously sequenced and were pub­licly avail­able.

Previous stud­ies – and numer­ous reports of cof­fee plants infected with Xylella fas­tidiosa imported into Europe from Central America – iden­ti­fied the same bac­terium in some Center America plants. However, there was no sci­en­tific evi­dence of genetic relat­ed­ness among the cof­fee iso­lates from Costa Rica, and the olive tree iso­lates in Puglia.

The data com­par­i­son of the genetic sequences reported in the study demon­strated that the Xylella fas­tidiosa bac­terium from the olive trees is directly related to Central American vari­ants.

The data also sug­gested that the con­ta­gion occurred with the intro­duc­tion of an asymp­to­matic” infected cof­fee plant, prob­a­bly brought to Italy as an orna­men­tal plant.

The study was led by an inter­na­tional team includ­ing sci­en­tists from the United States, France and Italy.

Among the authors, Italian biol­o­gist Maria Saponari of the National Research Council of Italy in Puglia was the first to detect Xyella fas­tidiosa in the nearby Salento region in 2013.


Felling of olive trees in Puglia, Italy (Getty Images)

Previously thought to be restricted to the Americas, the detec­tion of Xylella fas­tidiosa in Europe has raised new con­cerns world­wide due to its highly nox­ious poten­tial,” she said. The first con­firmed report in Europe in 2013 was soon fol­lowed by its pro­gres­sive detec­tion in sev­eral other E.U. coun­tries.”

The pathogen grad­u­ally expanded its geo­graph­i­cal range world­wide as well as its abil­ity to form novel asso­ci­a­tions with host plants,” she added. In this frame, we have used a genomic tool to study the processes dri­ving an emerg­ing bac­te­ria toward a plant dis­ease epi­demic.”

With par­tic­u­lar regard to the spread­ing of the bac­terium across south­ern Puglia, genomic data allowed us to recon­struct the emer­gence of the Olive Quick Decline Syndrome, which led to the death of sev­eral mil­lions of olive trees, with sig­nif­i­cant envi­ron­men­tal, social, polit­i­cal and eco­nomic con­se­quences,” Saponari con­tin­ued.

Our analy­sis sug­gests that the pathogen had arrived in Italy with a sin­gle intro­duc­tion from Costa Rica, con­firm­ing 2008 as the most likely year when Xylella was intro­duced in Italy,” she added. This is con­sis­tent with Apulian farm­ers’ first reports of infected trees in 2010 since the dis­ease incu­ba­tion period can last more than two years.”

Coffee plants are widely used in gar­dens, vil­las, and resorts: their intense green foliage makes them ideal for dec­o­rat­ing out­door areas.

While in colder areas, the plant is almost always kept inside; in Salento, it was most likely kept out­side, thus favor­ing the con­ta­gion,” Saponari said.

To prove that Xylella fas­tidiosa could have been trans­mit­ted from one species to another, the researchers also con­ducted exper­i­ments where they inoc­u­lated the bac­te­ria in cof­fee plants and spread the infec­tion to olive trees in a con­trolled way using spit­tle­bugs, the nat­ural vec­tor for Xylella fas­tidiosa.

Results show that cof­fee plants may rep­re­sent a latent car­rier of the bac­terium,” the researchers con­cluded.

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