Europe’s LIFE Resilience Project Offers Tools to Mitigate Spread of Xylella

After four years, the European Union-backed LIFE Resilience project has been com­pleted.

Including a broad alliance of researchers, entre­pre­neurs, farm­ers and pub­lic insti­tu­tions, the project has pro­vided olive grow­ers with new tools to stop the spread of Xylella fas­tidiosa, a deadly bac­te­ria that infects olive and almond trees.

One of the pro­jec­t’s most impor­tant results is the ongo­ing test­ing of new Xylella-resis­tant olive tree vari­eties in Italy, Portugal, and Spain.

Other results include the devel­op­ment of new tech­nolo­gies to iden­tify and dis­rupt insect pop­u­la­tions known to be vec­tors of the bac­te­ria, which causes Olive Quick Decline Syndrome, and some farm­ing best prac­tices to pre­vent the spread of Xylella fas­tidiosa sus­tain­ably.

Currently, 18 new olive tree geno­types resis­tant to Xylella fas­tidiosa have been sent for test­ing in the Scorrano area of south­ern Puglia, which is the part of Italy most severely affected by the bac­te­ria.

Project part­ners such as Filippo Berio and Balam Agriculture have also begun test­ing the new geno­types in Tuscany and Spain.

Pedro Valverde Caballero, an agron­o­mist at the University of Córdoba, one of the sci­en­tific part­ners of the project, told Olive Oil Times how sig­nif­i­cant diag­nos­ing and under­stand­ing the spread of Xylella fas­tid­i­ous in Italy has been.

“The bac­terium needs a vec­tor to be trans­mit­ted, which in this case are sev­eral species of insects,” he said.

“The spe­cific case of Italy is a case where a per­fect storm has arisen, an ideal cli­mate for the devel­op­ment of the bac­terium, a very high pop­u­la­tion of the insect vec­tor and a large num­ber of host crops, espe­cially olive trees,” Caballero added.

Xylella fas­tidiosa pauca is the bac­te­r­ial sub­species that causes Olive Quick Decline Syndrome.

“Most of the olive vari­eties present in the area are extremely sus­cep­ti­ble,” Caballero said. ​“We have the seri­ous prob­lem in Puglia, where more than 150,000 hectares of olive trees have already been infected.”

All olive vari­eties assessed or cat­a­loged for sus­cep­ti­bil­ity or resis­tance have been infected by the bac­terium and have symp­toms.

“The dif­fer­ence between the vari­eties cat­a­loged as resis­tant and the sus­cep­ti­ble ones is that the bac­terium devel­ops to a lesser extent in the resis­tant ones and the symp­toms that can be observed are scarce or even neg­li­gi­ble,” Caballero said.

“Whereas in the same grove, if we have sus­cep­ti­ble vari­eties, these are seri­ously affected and even dry up com­pletely,” he added.

Leccino and Fs-17, also known as Favolosa, are the two olive vari­eties that have shown the high­est lev­els of resis­tance to the bac­terium.

“No seri­ous symp­toms were observed in the field plan­ta­tions,” Caballero said. Still, these results might not be suf­fi­cient for olive farm­ers to return affected groves to pro­duc­tion.

“The two vari­eties that are clas­si­fied as resis­tant do not have the best agro­nomic char­ac­ter­is­tics from the point of view of the farmer,” Caballero said. ​“So, it is very impor­tant to develop new resis­tant vari­eties that are bet­ter from an agro­nomic point of view and to work on eval­u­at­ing the resis­tance of olive vari­eties in the global germplasm banks.”

“Fortunately, there is a wide range of olive vari­eties with a mul­ti­tude of dif­fer­ent agro­nomic char­ac­ter­is­tics, and hope­fully, there will also be some with resis­tance to Xylella fas­tidiosa,” he added.

The new vari­eties devel­oped in the project come from crosses between resis­tant vari­eties and oth­ers with good agro­nomic char­ac­ter­is­tics. By mak­ing these crosses, it is expected that some of the off­spring will have resis­tance to the dis­ease.

“These new vari­eties are cur­rently planted in affected fields in Scorrano and, in this way, we can eval­u­ate resis­tance at field level,” Caballero said. ​“In turn, these new vari­eties, pre-selec­tions, also are being eval­u­ated in a lab­o­ra­tory in Puglia, under con­trolled con­di­tions.”

“Currently, we know that sev­eral inter­na­tional and national projects are mak­ing great efforts in this direc­tion,” he added. ​“Between the vari­eties devel­oped through breed­ing pro­grams and the eval­u­a­tions of the vari­eties in the germplasm banks, we can all do our bit to solve this great prob­lem.”

Developing fully resis­tant olive tree vari­eties which are also bear­ers of good agro­nomic char­ac­ter­is­tics is con­sid­ered cru­cial for the sus­tain­abil­ity of the fight against Xylella fas­tidiosa.

“The use of resis­tant vari­eties is one of the most sus­tain­able mea­sures as it is the most eco­nom­i­cal and envi­ron­men­tally friendly, based on the nat­ural resis­tance of the host vari­ety to the pathogen,” Caballero said.

The project has also led to the devel­op­ment of a con­trol sys­tem to mon­i­tor and cur­tail the vec­tor insect pop­u­la­tion.

Researchers at the Italian National Research Council (CNR) devel­oped a series of tools for mea­sur­ing the impact of the insects and trap­ping the spit­tle­bug in the groves. Automatic traps were tested to ver­ify the pres­ence of the olive fruit fly.

Due to satel­lite imag­ing tech­nolo­gies, researchers were also able to map the dif­fer­ent affected areas and ver­ify the con­di­tions and agro­nomic needs of the observed groves.

New tools against Xylella fas­tidiosa devel­oped by the project include light detec­tion and sens­ing drones capa­ble of ver­i­fy­ing plant growth in the fields. In addi­tion, pre­ci­sion agri­cul­ture tech­nolo­gies have also been devel­oped to enhance olive grove man­age­ment and the effi­cacy of nat­ural chem­i­cal prod­ucts.

Teresa Carrillo, LIFE Resilience project direc­tor and Balam Agriculture researcher, said the use of good prac­tices by the pro­jec­t’s part­ner has encour­aged crop bio­di­ver­sity and improved plant health on farms, con­tribut­ing to more sus­tain­able prod­ucts.

In a recent inter­view with Olive Oil Times, Vasco Abreu, com­mer­cial direc­tor of Nutripado and part­ner of the project, noted how rel­e­vant good prac­tices such as main­tain­ing cover crops and fos­ter­ing bio­di­ver­sity in the groves are prov­ing to be.

“In almond and olive fields, the veg­e­ta­tion cover in between rows can be adopted by grow­ing legu­mi­nous and other mixed plants that main­tain mois­ture in the soil and offer nutri­tion to a series of ben­e­fi­cial microbes, which fix nec­es­sary ele­ments in the soil,” he said.

“Applying this approach also means that farm­ing might also cap­ture car­bon, as the legu­mi­nous plant cover can sequester up to eight tons of car­bon per hectare,” Abreu added. ​“They also sequester nitro­gen, which enhances the fer­til­ity of the soil.”

Pedro Fevereiro, the exec­u­tive direc­tor of Innovaplant Protect, told Olive Oil Times that ​“this project can effec­tively reduce the vec­tor insect pop­u­la­tion by adopt­ing struc­tures, such as bushes, flow­ers or other veg­etable cov­ers.”

“Biodiversity can also help tackle cli­mate change by reduc­ing fer­til­izer use and bring­ing farm­ers to more nature-friendly solu­tions,” he added. ​“It can also reduce water usage or pes­ti­cides.”

The best prac­tices for olive, almond and other woody crops such as vines and cit­rus are replic­a­ble and can be expanded.

As a result, the Spanish Association of Young Farmers and Ranchers (Asaja) con­firmed that the dis­sem­i­na­tion of this new set of sus­tain­able prac­tices has already started among its mem­bers.