Xylella-Resilient Groves Are the Future of Apulian Olive Oil

During a two-day event in Lecce and Bari, experts and researchers reviewed sci­en­tific find­ings and dis­cussed the future of olive oil pro­duc­tion in the Xylella fas­tidiosa-stricken region of Puglia.

Sustainably man­aged inten­sive olive groves of resilient cul­ti­vars, empha­siz­ing high-qual­ity pro­duc­tion, emerged as the goal for farm­ers and millers in the south­ern Italian region where there is a grow­ing con­sen­sus that the deadly bac­terium can­not be erad­i­cated.

“This visit is sig­nif­i­cant, as it show­cases a rare exam­ple of vir­tu­ous col­lab­o­ra­tion between researchers and stake­hold­ers who are actively con­tribut­ing to our pro­grams,” said Donato Boscia, a lead­ing plant virol­o­gist at the Institute for Sustainable Plant Protection of the Italian National Research Council (CNR), to Olive Oil Times.

“At this facil­ity, there is a small olive germplasm con­ser­va­tion field, part of an ongo­ing genetic improve­ment pro­gram,” he added. ​“Additionally, there is a green­house funded by dona­tions from Merum mag­a­zine read­ers, a cli­mate cham­ber pro­vided by Unaprol, and a new screen house funded by Save the Olives, the orga­ni­za­tion sup­ported by Helen Mirren.”

Experts believe the new coor­di­nated ini­tia­tive offers hope for safe­guard­ing exist­ing olive groves and cur­tail­ing the fur­ther spread of the pauca sub­species of Xylella fas­tidiosa to unaf­fected ter­ri­to­ries.

Ten years after the emer­gence of the Xylella fas­tidiosa epi­demic, which is widely believed to have trig­gered Olive Quick Decline Syndrome and killed mil­lions of trees, Puglia remains the most sig­nif­i­cant olive oil-pro­duc­ing region in Italy.

“The pres­ence of Xylella in the Apulian ter­ri­tory has reached extreme lev­els of com­plex­ity,” Boscia said. ​“New find­ings in cen­tral Puglia have iden­ti­fied other Xylella sub­species, such as Xylella mul­ti­plex, which is poten­tially dan­ger­ous for viti­cul­ture but not a sig­nif­i­cant issue for olives.”

“However, this com­plex­ity neces­si­tates a mul­ti­fac­eted approach to con­tain­ment and erad­i­ca­tion efforts,” he added.

Farming and pro­ducer orga­ni­za­tions such as Coldiretti, Unaprol and Cai Consorzi Agrari d’Italia have launched a project to assist olive grow­ers in replant­ing Xylella-resis­tant vari­eties.

The goal is to plant around three mil­lion new olive trees, a frac­tion of the 21 mil­lion lost to Xylella. This ini­tia­tive includes pro­vid­ing cer­ti­fied high-qual­ity resis­tant plants, tech­ni­cal sup­port for land prepa­ra­tion and spe­cial­ized agro­nomic and phy­topatho­log­i­cal con­sul­tancy.

“The spread of Xylella has reached a point where erad­i­ca­tion is no longer pos­si­ble. We must learn to coex­ist with it,” said David Granieri, the pres­i­dent of Unaprol.

Boscia high­lighted how exten­sive Xylella-mon­i­tor­ing oper­a­tions have given researchers and stake­hold­ers sig­nif­i­cant knowl­edge about the bac­te­ria.

“This is the result of a sur­veil­lance pro­gram con­ducted by the Puglia region, which is unique world­wide, with over 250,000 analy­ses per year and 250 mon­i­tor­ing sta­tions ded­i­cated to vec­tor mon­i­tor­ing,” he said, refer­ring to the insect pop­u­la­tion, such as spit­tle­bugs, respon­si­ble for spread­ing the bac­te­ria.

“This activ­ity is unsus­tain­able in the long term and pos­si­bly even in the medium term. It is not exportable because you can’t ask other regions or coun­tries to repli­cate it with the same amount of resources,” Boscia added, refer­ring to the grow­ing num­ber of dif­fer­ent strains of Xylella found through­out the Mediterranean.

“Still, those oper­a­tions have pro­vided sub­stan­tial data com­pared to what was known a decade ago,” he noted.

Controlling vec­tor insect pop­u­la­tions goes hand in hand with agri­cul­tural prac­tices and pro­ce­dures that offer hope for the sur­vival of olive trees in affected areas.

“Many native olive trees have been killed, but some have sur­vived. If they are not severely affected, we must try to keep them alive until research enables their recov­ery,” said Giuseppe Lima, plant pathol­o­gist and pro­fes­sor at the University of Molise.

A vet­eran plant pathol­ogy researcher, Lima now coor­di­nates the mul­ti­dis­ci­pli­nary research ini­tia­tive Integroliv, which aims to coun­ter­act the effects of Xylella on olive grow­ing in affected areas sus­tain­ably.

“To effec­tively counter such an insid­i­ous enemy, spe­cific, sin­gle inter­ven­tions in the region are insuf­fi­cient,” he said. ​“Combining dif­fer­ent approaches in com­plex pro­to­cols is cru­cial to max­i­mize their effec­tive­ness.”

“The new col­lab­o­ra­tion model is open to every­one,” Lima added. ​“Our approach aims to be a model of inves­ti­ga­tion and work, as we can­not expect a sin­gle project to encom­pass all pos­si­ble com­pe­ten­cies and solu­tions.”

“This approach ensures that new knowl­edge and tech­niques can be inte­grated into ongo­ing efforts to com­bat Xylella as they emerge,” he con­tin­ued.

Several nation­ally-funded research projects, such as the Reach-Xy and Omibreed projects, aim to uncover what is behind Xylella’s genetic resilience, enhance biose­cu­rity infra­struc­ture, con­trol vec­tors and pro­mote sus­tain­able water use in olive groves.

Other con­tri­bu­tions at the event included the 1LiveXylella project, which is devel­op­ing inno­v­a­tive tech­nolo­gies for Xylella diag­no­sis, and the SOS project, which focused on reduc­ing the insect vec­tor pop­u­la­tion.

“This event is a tes­ta­ment to the col­lab­o­ra­tive spirit of the sci­en­tific com­mu­nity and local stake­hold­ers in Puglia,” Lima said. ​“It brings together exper­tise from across Europe to tackle a com­mon chal­lenge.”

He added that the new olive trees in Xylella-affected areas, cur­rently rep­re­sented by non-native vari­eties, must fol­low mod­ern, ratio­nal agro­nomic man­age­ment mod­els to ensure their suc­cess.

These mod­els will be based on four olive cul­ti­vars demon­strat­ing high resis­tance to Xylella fas­tidiosa: Leccino, Lecciana, FS17 and Leccio del Corno.

“These vari­eties are resis­tant and tol­er­ant but not immune,” Lima said. ​“This means we can­not be mis­led into think­ing that, as in the past, we can sim­ply plant olives and rely on good for­tune.”

Continuous field man­age­ment and mon­i­tor­ing will keep new semi-inten­sive and inten­sive olive plan­ta­tions in good health and pro­duc­tiv­ity.

“In these new forms of inten­sive and semi-inten­sive olive grow­ing, phy­tosan­i­tary prob­lems will increase, requir­ing more fer­til­iz­ers and phy­tophar­ma­ceu­ti­cals than tra­di­tional meth­ods,” Lima warned.

“The pro­to­cols [being devel­oped] aim to coun­ter­act Xylella and other pathogens to keep the trees of both native and new vari­eties in good health and pro­duc­tiv­ity,” he added.

According to Lima, the dev­as­ta­tion caused by Xylella has harmed the Apulian land­scape and iden­tity. However, a new future can emerge from this adver­sity, char­ac­ter­ized by higher-qual­ity olive oil than in the past.

“In the Salento area, olives from those huge, mag­nif­i­cent trees were often tra­di­tion­ally col­lected from the ground, result­ing in high acid­ity lev­els in the lam­pante oil,” Lima said.

“Tomorrow, with mod­ern olive grow­ing and the plant­ing of ratio­nal, semi-inten­sive orchards, things can change,” he added.

In his view, the new groves will be able to con­sider the socio-eco­nomic aspects of mod­ern olive grow­ing, where a work­force can be hard to find and prod­uct qual­ity becomes an essen­tial equire­ment.

“Such mod­ern olive grow­ing will cer­tainly lead to the pro­duc­tion of bet­ter qual­ity oil,” Lima said. ​“We are mov­ing towards new forms of olive grow­ing, which could bring more income to olive oil com­pa­nies while con­tribut­ing to the restora­tion of olive grow­ing and the envi­ron­ment in areas affected by Xylella.”