`Understanding Relationship Between Fungus and Climate May Curb Costly Olive Tree Pathogen, Researchers Say - Olive Oil Times

Understanding Relationship Between Fungus and Climate May Curb Costly Olive Tree Pathogen, Researchers Say

Feb. 3, 2021
Paolo DeAndreis

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A coor­di­nated research effort in south­ern Spain has uncov­ered some of the main cli­matic dri­vers behind the spread of a promi­nent Verticillium wilt vec­tor.

The new dis­cov­ery may help Mediterranean olive farm­ers mit­i­gate the impacts of the deadly plant pathogen, which is caused by the Verticillium dahliae fun­gus, in their orchards.

Since V. dahliae thrives in mild tem­per­a­ture con­di­tions, rainy peri­ods must coin­cide with warm ones in order to pro­vide opti­mal con­di­tions for the pathogen to thrive.- IFAPA, 

It has already been proven that the spread­ing of Verticillium wilt in an olive orchard is the result of the inter­ac­tion among the olive tree geno­type, the den­sity of its pres­ence in the soil, the spread­ing mech­a­nisms and other envi­ron­men­tal fac­tors, both biotic and abi­otic,” researchers from the Andalusian Institute for Agricultural and Fisheries Research (IFAPA) said.

While the effects of soil tem­per­a­ture and humid­ity are well known on a local scale, no pre­vi­ous study eval­u­ated which cli­matic fac­tors impact on its pres­ence on a much larger scale,” they added.

See Also: Scientists in Spain Identify Olive Genes Resistant to Common Pathogen

The study, which was pub­lished by the sci­en­tific jour­nal Plos One, focuses on 779 olive groves in the province of Granada, which were selected and sur­veyed for the pres­ence of the Verticillium dahliae.

Granada is home to 183,000 hectares of olive groves, which sig­nif­i­cantly vary in terms of man­age­ment prac­tices, olive cul­ti­vars and envi­ron­men­tal fac­tors.

The olive groves selected for the inves­ti­ga­tion, explained the researchers, cover 2,833 hectares of land with an aver­age olive tree den­sity of 139 olive trees per hectare.

Forty mod­els based on com­pet­ing com­bi­na­tions of cli­matic vari­ables were fit­ted and eval­u­ated using infor­ma­tion-the­o­retic meth­ods,” the sci­en­tists wrote. A model that included a mul­ti­plica­tive com­bi­na­tion of sea­sonal and extreme cli­matic vari­ables was found to be the most viable one.”

More specif­i­cally, the research team dis­cov­ered how an envi­ron­ment under­go­ing minor tem­per­a­ture changes served as the per­fect envi­ron­ment for the fun­gus. They also observed the role of the rain­fall pat­terns in spread­ing the dis­ease.

The sci­en­tists con­sid­ered these two envi­ron­men­tal vari­ables as the most rel­e­vant ones influ­enc­ing the infec­tion.

The isother­mal effect was in turn mod­u­lated by the sea­son­al­ity of rain­fall, and this became less neg­a­tive as sea­son­al­ity increased,” the researchers wrote.

Additionally, in the olive-grow­ing areas sub­jected to a lower tem­per­a­ture dif­fer­en­tial between day and night, the dam­ag­ing fungi tended to be more present. The study also demon­strated that irri­ga­tion reduced the abil­ity of the isother­mal effect to influ­ence the pres­ence of the Verticillium dahliae.

See Also: Native Andalusian Olive Varieties Could Be Wiped Out by 2100, Researchers Warn

Since V. dahliae thrives in mild tem­per­a­ture con­di­tions, rainy peri­ods must coin­cide with warm ones in order to pro­vide opti­mal con­di­tions for the pathogen to thrive,” the researchers wrote.

One impor­tant impli­ca­tion of our study is that appro­pri­ate irri­ga­tion man­age­ment when tem­per­a­ture oscil­la­tion approaches opti­mal con­di­tions for V. dahliae to thrive, may reduce the appear­ance of symp­toms in olive trees,” they added.

The researchers believe that their find­ings will ben­e­fit all olive farm­ers and, most of all, Andalusian olive grow­ers.

The south­ern autonomous com­mu­nity is not only the largest olive oil-pro­duc­ing region in the world – account­ing for more than 1.3 mil­lion tons in the 2020/21 crop year – it is also among the worst affected by the Verticillium wilt. The plant pathogen is one of the main threats to many local high den­sity and super-high-den­sity olive groves.

According to the researchers, the results demon­strate that long-term com­pound cli­matic fac­tors rather than pri­mary vari­ables, such as annual trends, can bet­ter explain the spa­tial pat­terns of Verticillium dahliae occur­rence in Mediterranean Spain.”





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