Research identifies genetic signature of sugarcane resistant to orange rust

Scientific Initiation (IC) research developed at the Araras Campus of the Federal University of São Carlos (UFSCar) identified a molecular marker - a kind of genetic signature - of sugarcane cultivars resistant to orange rust, an important disease in this crop, caused by fungus that spreads through the air. Therefore, the study indicated that this could be an important molecular tool in the search for new cultivars resistant to the disease.

The work was carried out by Ícaro Fier, graduated in Biotechnology from UFSCar, under the guidance of Monalisa Sampaio Carneiro, professor at the Department of Biotechnology and Plant and Animal Production (DBPVA-Ar) of the Institution.

"Firstly, we evaluated, in the field, the resistance to orange rust of these cultivars. Then, we checked the frequency of the G1 marker among the cultivars, to analyze whether this marker helps in an even greater resistance to this rust", summarizes Carneiro.

The research found that the molecular marker G1, previously tested only on sugarcane cultivars originating in the United States, is also a resistance factor to orange rust in 10 of the 24 Brazilian cultivars tested. This is the first study in the country that analyzes the marker in Brazilian cultivars.

The results showed that the efficiency of the G1 marker in predicting resistance was 71,43%. Furthermore, on average, the reduction in disease severity was 35% when the G1 marker was present.

Orange rust is caused by the fungus Puccinia kuehnii and affects the leaves, which are full of orange spots. The disease impairs photosynthesis and therefore reduces sugarcane productivity. Unlike bacteria, for example, in which it is possible to have greater control of the environment to avoid proliferation, the fungus is easily spread through the air - hence the importance of creating cultivars resistant to it.

The integration of field data with the G1 marker allowed the identification of sugarcane cultivars resistant to orange rust, with this resistance being promoted, in part, by the genes to which the G1 marker is linked. Resistant cultivars with the presence of the G1 marker can be used in the breeding process to carry out new crosses and, thus, obtain cultivars that also combine this type of resistance to orange rust, creating what scientists call durable resistance.

"This durable resistance is one of the objectives of our genetic improvement program - the largest in the country -, as it aims to release cultivars resistant to the main sugarcane diseases, thus having greater commercial durability and good conditions productivity", says the UFSCar professor.

Another advantage: more resistant cultivars reduce the use of chemical products to combat diseases - something harmful to the sugarcane itself and the environment.

The research was developed within the scope of the Plant Biotechnology Study Group (GEBPlant), coordinated by Carneiro, with support from the UFSCar Genetic Improvement Program for Sugarcane (PMGCA), based at the Center for Agricultural Sciences (CCA) , on the Araras Campus.

Awards and recognition

Part of the study generated the publication "Field resistance and molecular detection of the orange rust resistance gene linked to G1 marker in Brazilian cultivars of sugarcane" (https://doi.org/10.1590/0100-5405/221803), which won the Summa Phytopathologica Award, as the best article published in 2020 in the journal of the same name.

In addition to Fier and Carneiro, the text was co-authored by Hermann Paulo Hoffmannn - as well as Carneiro, professor at DBPVA-Ar -, as well as Thiago Willian Almeida Balsalobre and Roberto Giacomini Chapola, researchers at PMGCA and members of the Interuniversity Network for the Development of the Sector Sugar energy (RIDESA).

Fier, now a doctoral student in the Postgraduate Program in Genetics and Molecular Biology at the State University of Campinas (Unicamp), comments that the award gave him personal encouragement, in addition to confirming the importance of the work that scientists carry out on a daily basis.

"As a professional in the field, I see Biotechnology as a rationale that allows us to create technologies applicable in different areas. In Agronomy, for example, it can enhance the development of cultivars that are more adapted to current needs. The period I spent at GEBPlan helped to structure my knowledge base that propelled me into my academic career. Today, as a doctoral student at Unicamp, I am happy to know that our efforts have borne fruit", points out the student.