Researchers from Brazil complete genetic sequencing of natural enemy fungus of caterpillars

Brazilian scientists have completed the genetic sequencing of a fungus that acts as a natural enemy of caterpillars that attack soy, corn and cotton. The research represents an important step forward in scientific knowledge about the fungus, Metarhizium rileyi, known among soybean producers as the disease of the soybean caterpillar, and opens space for the development of new biological products in the medium and long term.

“This fungus acts as a natural enemy of several caterpillars, such as soybean caterpillar, false medideira, fall armyworm and the cotton leafworm. It infects the caterpillar by contact with the tegument and does not need to be ingested to act naturally as a biological control,” explained Embrapa researcher, Daniel Sosa-Gómez, research leader. The work was developed in Londrina (PR), at the Embrapa Soja laboratories, with the collaboration of the Center for Parasitological Vector Studies of the Universidad Nacional de La Plata in Argentina.

“It is a fungus that occurs in several countries around the world. With sequencing, we can better understand their different breeds and differentiate the strains that are most efficient for use as commercial biological control,” he explained. According to the scientist, by knowing the behavior of each strain, it is possible to associate it with the genetic identity and the variations that occur in each location.

Embrapa Soja has since the 1990s maintained a collection of strains that occur in different parts of the world, such as Argentina, the United States, the Philippines, Japan, Mexico and India. “With the genome sequencing and the crossing of information about the strains that are in our banks, we can better understand those with potential for the development of biological products, just as it is done with inoculants, specifically, as the Bradirhizobium bacteria,” he said.

The sequencing involved advanced techniques of bioinformatics, with the use of specific computational tools for the reconstruction of the complete sequence of the genome and for the capture and interpretation of molecular information related to each gene throughout the genome.

“Basic research takes time because it is based on a large volume of DNA data, which is being reviewed and organized using these tools, based on the knowledge we have, and will facilitate the understanding of the relationships between genes and the particularities of this fungus,” said the researcher. The genome was deposited in the public biological sequence database, GenBank-NCBI-NIH, under accession number, SBHS00000000.

Fungicide resistant

A major challenge for scientists now is to make these biological control fungi survive the application of fungicides in crops. That's because the same products used against the fungus that causes soybean rust can also target the caterpillar's natural enemy. Therefore, the researcher said that for the next years, Embrapa will act in the selection of isolates that tolerate high doses of fungicides, such as those used to control Asian soybean rust.

“Production systems are increasingly complex and we can no longer analyze pest control in isolation,” he said. That is why the knowledge obtained by this research is so important; it is necessary to find alternatives to make production systems more balanced.

“The fungus has an interesting characteristic: it only attacks caterpillars, so it has a very selective performance, which, in general, benefits the balance of production systems,” explained Sosa-Gómez. Scientists believe that by identifying isolates of the fungus Metarhizium that tolerate high doses of fungicides used to control rust, it will be possible to find more balanced solutions for the control of caterpillars. The research may also help identify the genes involved in the mechanisms of fungicide resistance.

The study was published in the journal of the American Society for Microbiology, one of the most respected in the field at the international level, and is signed by researchers, Daniel Sosa-Gómez, Eliseu Binneck from Embrapa Soja, and Cláudia López Lastra from the University La Plata, Buenos Aires, Argentina.

The original Portuguese version of this piece is from Grupo Cultivar.