Researchers Identify Olive Genes Associated with Fruit Weight

Researchers in Spain have iden­ti­fied nine genes that they said showed a ​“high sta­tis­ti­cally sig­nif­i­cant cor­re­la­tion” with fruit weight.

Historically, fruit weight was the most sig­nif­i­cant trait sought by farm­ers when iden­ti­fy­ing which wild olive cul­ti­vars to domes­ti­cate, along with oil con­tent and abil­ity to grow in anthro­pogenic envi­ron­ments.

“Larger fruit size is extremely impor­tant in cul­ti­vated olive trees to facil­i­tate har­vest­ing,” researchers from the University of Jaén and the Institute of Agricultural and Fisheries Research and Training (Ifapa) wrote in the study pub­lished in Plants.

“Therefore, fruit size in tra­di­tional olive cul­ti­vars is much big­ger than in wild ones,” they added. ​“However, as the long juve­nile period is a main hin­drance in clas­sic breed­ing approaches, obtain­ing genetic mark­ers to be used in breed­ing pro­grams for this trait is a highly desir­able tool.”

According to the researchers, this was the first study iden­ti­fy­ing indi­vid­ual genes linked with olive weight. The Discover Foundation, an Andalusian gov­ern­ment research sup­port group that funded the study, hailed the find­ings as a sig­nif­i­cant advance­ment in under­stand­ing the genet­ics of olive fruit devel­op­ment.

The researchers used data from the genomes of 40 cul­ti­vated olive vari­eties and ten wild olive tree species, which they had pre­vi­ously sequenced, select­ing rep­re­sen­ta­tive sam­ples of each vari­ety with olives of dif­fer­ent weights.

They said the 40 cul­ti­vated olive vari­eties rep­re­sent more than 90 per­cent of the genetic vari­abil­ity of domes­ti­cated olive tree vari­eties. They added that the ten wild vari­eties sequenced rep­re­sented a broad geo­graph­i­cal sam­ple of non-domes­ti­cated olive trees.

The researchers extracted DNA from the 50 spec­i­mens using a genome-wide asso­ci­a­tion study analy­sis, which they said was sim­i­lar to ​“read­ing” and assem­bling DNA as if it were a detailed instruc­tion man­ual.

By doing this, they found 113 genetic mark­ers grouped into sev­eral clus­ters. The researchers then ran a sta­tis­ti­cal analy­sis to detect cor­re­la­tions between the clus­ters of genetic mark­ers and cross-ref­er­enced between the olive sam­ples.

As a result, they deter­mined that 18 of 31 mark­ers clus­tered into nine groups were linked with fruit size and weight, sug­gest­ing nine genes are involved in deter­min­ing fruit size.

“Checking spe­cific genetic mark­ers, such as those that deter­mine the weight of the olive, facil­i­tates the selec­tion of trees with ben­e­fi­cial char­ac­ter­is­tics, thus speed­ing up the genetic improve­ment process,” said Francisco Luque, a researcher from the University of Jaén and co-author of the study. ​“It is like open­ing a man­ual for each tree that tells us its qual­i­ties.”

“For exam­ple, if a very young olive tree is ana­lyzed and it is con­cluded through a genetic analy­sis that the fruit will have a mediocre weight, the deci­sion could be made to dis­card it and use resources on a spec­i­men whose genetic mark­ers indi­cate that the olive will weigh more,” he added.

The researchers now plan to use a sim­i­lar method to iden­tify the genetic mark­ers and genes that influ­ence the pro­duc­tion of polyphe­nols in dif­fer­ent olive vari­eties. They believe this will help farm­ers pro­duce olives with greater organolep­tic value and health ben­e­fits.

“We want to iden­tify the genes respon­si­ble for the pro­duc­tion of dif­fer­ent polyphe­nols and between dif­fer­ent vari­eties of olive trees and deter­mine why some fruits have a greater amount of these mol­e­cules than oth­ers,” Luque said.

• Discovery Foundation