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A research team from Israel has found that increased tem­per­a­tures can neg­a­tively affect the olive pro­duc­tion cycle and oil qual­ity.

Unseasonal tem­per­a­ture increases influ­ence var­i­ous stages of the repro­duc­tive growth and devel­op­ment of olives, they said.

Even though the olive is resilient to the envi­ron­men­tal con­di­tions of the Mediterranean basin, the researchers said changes in agri­cul­tural tech­niques and breed­ing will be nec­es­sary to adapt to cli­mate change.

“In warm areas, farm­ers should plant resis­tant cul­ti­vars,” Giora Ben-Ari, a researcher at the Institute of Plant Sciences in Israel’s Agricultural Research Organization, told Olive Oil Times. However, he added that his team was still work­ing to iden­tify the best can­di­dates.

“Second, researchers should try and iden­tify dif­fer­ent agro­nomic solu­tions to lower the envi­ron­men­tal tem­per­a­tures around the foliage, on days with ele­vated tem­per­a­ture,” he added.

“A deep under­stand­ing of the mech­a­nism of the effect of ele­vated tem­per­a­tures on fruit devel­op­ment and oil syn­the­sis, as well as under­stand­ing the mech­a­nisms of resis­tant cul­ti­vars, will enable us to develop agro­nomic strate­gies as well as breed resis­tant cul­ti­vars to pro­duce qual­ity olive oil in warm areas,” Ben-Ari con­tin­ued.

The study looked at dif­fer­ent ways of con­trol­ling high-fruit pro­duc­tiv­ity, oil quan­tity and qual­ity, by test­ing how the olive can with­stand tem­per­a­ture con­di­tions at dif­fer­ent stages of devel­op­ment.

“There have been extremely warm days in pre­vi­ous sum­mers,” Ben-Ari said. ​“The warmest months of the year are July and August, the most impor­tant period for the olive, regard­ing fruit devel­op­ment and oil biosyn­the­sis.”

“Since we found that extremely ele­vated tem­per­a­ture at this period neg­a­tively affects fruit devel­op­ment, oil biosyn­the­sis and oil qual­ity, it is very impor­tant to iden­tify resis­tant olive cul­ti­vars able to pro­duce high oil yields and qual­ity despite the warm tem­per­a­tures we are cur­rently expe­ri­enc­ing, which will be more com­mon in the com­ing years,” he added.

Sudden tem­per­a­ture increases are one of the main abi­otic stres­sors that cause mor­pho­log­i­cal, phys­i­o­log­i­cal, bio­chem­i­cal and mol­e­c­u­lar changes to the olive. An increase of 3 ºC to 4 ºC above the opti­mal tem­per­a­ture causes sig­nif­i­cant dam­age to fruit yield, oil amount and oil qual­ity.

The study con­cluded that the Mediterranean is par­tic­u­larly sus­cep­ti­ble to the future effects of cli­mate change. Calculations have shown that over the next 80 years, there will be an aver­age tem­per­a­ture increase of up to 7 ºC, an aver­age of 0.9 ºC per decade.

Producers also have an added chal­lenge of increas­ing extra vir­gin olive oil pro­duc­tion as demand for high-qual­ity olive oil increases, largely dri­ven by chang­ing lifestyle and diet trends.

“Olive oil serves as a basic nutri­tion source in our diet with many health advan­tages,” Ben-Ari said. ​“Olive oil is rich in healthy monoun­sat­u­rated fats, con­tains sub­stan­tial amounts of antiox­i­dants, has strong anti-inflam­ma­tory prop­er­ties and may help pre­vent strokes and pro­tect against heart dis­eases.”

“Low-qual­ity oil loses all the men­tioned advan­tages and there­fore we should aim to con­sume high-qual­ity olive oil,” he added.

As a result, Ben-Ari said it is essen­tial that olive geneti­cists iden­tify more resis­tant cul­ti­vars. The researchers con­cluded that the olives’ responses to ele­vated tem­per­a­tures are geno­type-depen­dent, so iden­ti­fy­ing the thresh­old tem­per­a­ture for dif­fer­ent geno­types in var­i­ous stages of the olive cycle is cru­cial.

The fatty acids in the oil of each cul­ti­var are bal­anced genet­i­cally. For exam­ple, the oleic acid con­tent is depen­dent on each geno­type and helps deter­mine the heat resis­tance of that cul­ti­var to par­tic­u­lar envi­ron­ments.

“To iden­tify resis­tant cul­ti­vars, we are plan­ning to con­duct a wide screen­ing of many cul­ti­vars and try­ing to iden­tify the resis­tant cul­ti­vars among them,” Ben-Ari said.

“[We also want to] under­stand the mech­a­nism involved in the neg­a­tive effect of high sum­mer tem­per­a­tures, to develop new resis­tant olive cul­ti­vars as well as look­ing for agro­nomic solu­tions to mod­er­ate the neg­a­tive effect on warm days,” he added.

Further stud­ies will iden­tify and com­pare heat sen­si­tiv­ity and heat resis­tance by com­par­ing cul­ti­vars from around the world at dif­fer­ent stages of devel­op­ment. The hope is to iden­tify vari­eties for future breed­ing pro­grams to address the demands and chal­lenges of cli­mate change.

• Agronomy