Researchers decode the complete genome of the fungus responsible for Cercospora leaf spot in olive trees
Collaboration between the UCO's Agronomy and Genetics departments was key to sequencing the genome of this pathogen, which is responsible for losses of up to €50 million per year.
Cercospora leaf spot is an olive tree disease that causes defoliation and lower yields. It is caused by the fungus Pseudocercospora cladosporioides, which affects only the olive and wild olive trees. Chlorotic spots appear on the upper surfaces of the leaves, and on their undersides, in a tell-take leaden color caused by the fungus’s fruiting bodies. The introduction of vulnerable varieties in Spain, such as 'Frantoio' , and the reduced use of copper as a preventive treatment, are making this disease increasingly prevalent.
To understand how this pathogen works and to make progress in developing resistant varieties, it is essential to know its genome, which is, essentially, its complete instruction manual. However, this milestone had not been achieved until now due to the difficulty of isolating the fungus outside its host and growing it under laboratory conditions to obtain high-quality DNA and RNA. Now, thanks to collaboration between research teams in the Departments of Agronomy and Genetics at the University of Cordoba, the complete genome of the fungus P. seudocercospora cladosporioides has been sequenced and made openly available to the research community.
"The main challenge was to obtain high-quality DNA and RNA, and to do that, the key was to develop a precise isolation protocol," explained Juan Moral, the researcher who led the phytopathology component of the project.
Once this high-quality genetic material had been obtained, it was time for bioinformatics. By combining short- and long-read DNA sequencing technologies, a 53-Mb genome assembly was generated, identifying over 14,000 genes.
Based on the genome annotation (the process of identifying and understanding the genes), it was possible to gain a deeper understanding of the fungus's infection mechanisms and its interaction with its host. According to researcher José V. Die, who led the genetic component of the work, "one of the most interesting results we have obtained from genome annotation is the identification of 491 genes that are exclusively involved in degrading the cell wall of the olive tree , the fungus’s primary attack mechanism, degrading the olive tree’s most important defense component." Another element identified was a set of effector proteins (434) that act "as inhibitors of the olive tree's resistance mechanisms."
"With this result, we now have a key tool for breeding programs aimed at developing varieties resistant to olive anthracnose and for further studying fungus–olive tree interactions," concluded Cristina Estudillo, the lead author of the study.
Stronger Together
The complete genome sequencing of Pseudocercospora cladosporioides would not have been possible without the synergy between geneticists and plant pathologists. The challenge required specific knowledge of the fungus and the protocols for growing it, as well as of the disease in addition to expertise in bioinformatics and genetics. This collaboration, which enabled Cristina Estudillo's thesis to benefit from the scientific support of both disciplines, stems from research excellence programs, such as the Ramón y Cajal call, as well as from predoctoral research training contracts (FPI). These types of calls, along with European projects like Gen4olive, which gave rise to this study, foster synergies and collaboration to address scientific problems requiring multidisciplinary approaches. Thanks to all these efforts, the research community now has a reference genome for this fungus, which will enable it to monitor the pathogen’s evolution and develop better tools for surveillance and early detection.
Reference
Estudillo, C., Tercero-Alcázar, C., Orduña, L., et al. 2026. “The Genome of Pseudocercospora cladosporioides : A Step Toward Understanding Olive Cercosporiosis.” Plant Pathology 75: e70130. https://doi.org/10.1111/ppa.70130.
Plant Pathology
Computational simulation/modeling
Not applicable
The Genome of Pseudocercospora cladosporioides: A Step Toward Understanding Olive Cercosporiosis
10-Feb-2026