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A team of Spanish sci­en­tists have iden­ti­fied genetic vari­a­tions that allow some olive tree vari­eties to resist Verticillium wilt, a dis­ease for which there is no cure.

Their find­ings could pave the way for the intro­duc­tion of new olive cul­ti­vars that are able to resist the fun­gus that causes the dis­ease while pre­serv­ing their pro­duc­tive capacity.

Frantoio, Changlot Real and Empeltre are among the vari­eties that dis­play resis­tance to the disease.

Verticillium wilt causes the dete­ri­o­ra­tion of the vas­cu­lar sys­tem in a tree, with severe con­se­quences such as fruit and leaf drops. Over time, many of the affected trees die as a result of the infection.

Researchers at the Andalusian Institute for Agricultural and Fisheries Research (IFAPA) have found a set of genes that seem to act together as a response to the pathogen.

In their study, which was pub­lished in Scientia Horticolturae, researchers ana­lyzed 77 dif­fer­ent geno­types from cul­ti­vated and wild sub­species of the olive, includ­ing Olea europaea, guanchica and cerasiforis.

They found that genes such as TLP1 and PFN2 have shown genetic vari­a­tions that could be vital to develop future cul­ti­vars that are able to resist the pathogen.

As stated in the research paper, they are con­sid­ered the first mark­ers ​“asso­ci­ated with Verticillium wilt resis­tance genes in olives and can con­tribute to estab­lish a set of valu­able mark­ers for the man­age­ment of germplasm col­lec­tions and selec­tion process in breed­ing programs.”

Alicia Serrano Gómez, one of the authors of the study and researcher at IFAPA, told the Andalusian Desqbre Foundation that the results hint ​“at the need to give birth to a wide col­lec­tion of geno­types, from mul­ti­ple sources and with well-evi­denced reac­tions to the Verticillium wilt, with which to con­firm the use­ful­ness of the [observed] genetic variations.”

Those responses might include phys­i­cal bar­ri­ers such as lignin, which pre­vents the fun­gus from invad­ing the cells of the plant, or bioac­tive com­pounds such as phe­nols that inhibit the growth of the pathogen.

“The prob­lem is that most of the grown cul­ti­vars nowa­days are very vul­ner­a­ble to this dis­ease,” Serrano told Olive Oil Times in a January 2020 inter­view. ​“And those that are a lit­tle more resis­tant are not inter­est­ing from an agro­nomic point of view.”

No treat­ment is cur­rently avail­able to pre­vent the fungi that causes the dis­ease from attack­ing the roots and the tis­sues, which are respon­si­ble for trans­port­ing nutri­ents through­out the olive tree.

The fungi can eas­ily be found on cul­ti­vated lands and are eas­ily spread fur­ther by means of irri­ga­tion or crop resid­u­als. That is why sci­en­tists believe that farm­ers will have to adapt to the new prac­tices that are being inves­ti­gated by the researchers.

“The high per­sis­tence of this fun­gus in the soil and the reduced num­ber of resis­tant [olive tree] vari­eties make it nec­es­sary to develop new vari­eties that meet the char­ac­ter­is­tics of repli­ca­tion and pro­duc­tiv­ity desir­able for the sus­tain­abil­ity of the crop,” Serrano said.

• Scientia Horticolturae
• Fundación Desqbre
• Cordopolis