Corn: Genes Identified to Help Resist Spigot Diseases

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A research team from INTA Pergamino (Buenos Aires) detected common genes and metabolic pathways associated with the plant’s resistance to Fusarium spp. and corn smut, pathogens with a high productive and sanitary impact on the crop. The finding opens up new opportunities for the genetic improvement of maize.

Fusarium verticillioides, Fusarium graminearum and Ustilago maydis are diseases of the spigot of corn (Zea mays L.) that pose a risk to production. For this reason, a team of specialists from INTA Pergamino focuses on the study of the cereal genome to detect and identify common genes and metabolic pathways that are activated against these three pathogens. In the future, this finding will allow progress in the development of varieties with multiple resistance, capable of sustaining yields and improving the safety of the grain.

Since 2002, Juliana Iglesias, a specialist in plant genetics at INTA, has been advancing in the understanding of the molecular mechanisms that explain the resistance of corn to pathogens with a high productive and health impact. From a large-scale transcriptomic analysis, the research identified common genes associated with defense against spigot diseases that compromise both yield and grain quality.

The team coordinated by Iglesias adds strategic evidence to select candidate genes applicable to future genetic improvement programs. By identifying shared defensive routes against spigot diseases, the research opens the door to designing more resilient maize with greater productive stability.

“With these results, we will be able to identify and study the genes that are activated in the response to multiple diseases to improve disease resistance in corn,” said the INTA biologist.

Andrea Peñas Ballesteros —within the framework of her master’s thesis in Bioinformatics and Systems Biology at the National University of the Northwest of the Province of Buenos Aires (UNNOBA)— focused on the interaction between corn and these three critical pathogens: Fusarium verticillioides and Fusarium graminearum cause rot that affects the filling of the spigot and, in addition, they generate mycotoxins – such as fumonisins and deoxynivalenol – that can enter the food chain. On the other hand, Ustilago maydis – which causes corn smut – severely alters the tissues of the spigot and reduces production, affecting the uniformity and commercial value of the crop.

Unlike traditional studies focused on a single disease, the work addressed multiple resistance through a meta-analysis of high-quality transcriptomic data from public databases. The objective was to identify genes and biological processes that are commonly activated against pathogens with different infection styles and strategies.

The work takes on greater importance when understanding that maize DNA is made up of 32,000 genes inserted into 10 chromosomes. This confirms how complex the cereal genome is, because 85% of its genomic sequences are repeated multiple times.

Based on these data, candidate genes are being prioritised using a machine learning algorithm and, at the same time, they are being compared with previous Genome-Wide Association Study (GWAS) studies. Iglesias indicated that “an estimated 400 genes that could be associated with multiple resistance were classified and are being evaluated in functional field studies.”

Resistant genotypes presented a more effective and balanced defense response between defense and primary metabolism, maintaining cellular integrity and limiting infection. And susceptible genotypes showed a less effective response, with a metabolic conflict that prioritizes defense at the expense of growth and physiological stability.

The meta-analysis allowed to simultaneously compile, standardize and compare the responses of maize crops to these three pathogens with markedly differentiated pathogenesis styles.

“The analysis allowed us to obtain a comprehensive view of the defensive mechanisms of corn, beyond the punctual response to a pathogen,” explained Iglesias, who supervised the Peñas Ballesteros’s thesis together with Agustín Baricalla, a bioinformatician and geneticist at CONICET. In this sense, the results provide key information on the so-called resistance hotspots: regions of the genome where genes that confer simultaneous resistance to several diseases are concentrated.

“This finding opens up new opportunities for the genetic improvement of maize,” said Iglesias, while pointed out that “the precise knowledge of which genes are activated and how they interact against different pathogens allows us to accelerate breeding programs through the understanding of maize-pathogen interaction and selection assisted by molecular markers or even gene editing. A strategy that reduces time and costs.”