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    Researchers digitalize path of the greatest enemy of potatoes

With the rainy season, Colombian potato growers begin to become concerned as the increased soil moisture favors the appearance of pests and diseases including late blight or potato blight, considered as the cancer of this tubercle.

The economic impact this pathogen produces is considered serious due to the socio-economic consequences it brings, besides the great production losses in different parts of the world. Calculations estimate that its presence can damage up to 80% of a crop in every production cycle, entailing a loss of approximately US $5,000 million a year.

Air is the first abettor of Phytophthora infestans (Mont.) –an organism of the Oomycetes group, close to fungi and algae, the cause of late blight– as it helps the pathogen to spread throughout the territory, including the Provinces of Cundinamarca, Boyacá, and Nariño, which represent 80% of the potato crops in Colombia and production leaders in the country.

Just a few raindrops are enough for mobile spores or zoospores –in charge of initiating infection– land on plant leaves. Then if there is water on the surface of the potato leaves, the spores can penetrate the stoma and begin the infection process.

“After a few days, the leaves begin to show round stains which change from brown to black and then expand throughout the plant until they reach the stalks and tubercles, and the skin begins to fade”, says Professor Carlos Ñústez of the Universidad Nacional de Colombia (UNal) in Bogotá Faculty of Agrarian Sciences

The natural development of the common potato while being attacked by late blight has been “translated” to computer language, in other words, the process consisted of rebuilding the metabolism of the plant, i.e. the biochemical reactions which determine the behavior of attacked cells.

The computer model allows verifying the hypothesis of how the infection mechanism is and also carry out laboratory predictions which will save time during research.

The creator of the model was UNal- Bogotá Engineering Faculty, Bioinformatics Engineering M.Sc. Kelly Botero Orozco, who claims, “The tool could be used by Phytopathologists to create comprehensive disease management strategies, beyond the use of fungicides, to restrain the propagation of blight. This could have a major impact if they work with institutions that are in direct contact with farmers and therefore carry out an adequate technological transference.”

Applicable in the real world

To develop the model, Botero used the appearance and behavior of the plant through a metabolic network which integrates genomic and biochemical information. Later, in order to evidence chemical reactions altered in the plant by infection of Phytophthora infestans, she combined genome data taken 24 hours from the development of the disease.

Considering when the potato is infected it has trouble capturing solar light, they determined three pathogen post-inoculation moments at 0, 1, and 3 days and analyzed the metabolic affected paths, mainly those linked to photosynthesis, such as light reactions, carbon fixation, and photorespiration.

To this respect, Botero added, “Previous research reports a possible reduction of the capacity of the infected plant to perform photosynthesis, although the ways how the metabolic mechanisms transform has not been yet understood”.

In this sense, something essential for the development of computer models is that they can be applied to the real world for predictions to have a high trust level and to transfer them to biological tests.

The results of the research mirror that observed in the field, in other words, that effectively during the disease the photosynthetic capacity is reduced, as evidenced by photosynthetic light reaction and carbon fixation. The model also predicts that this reduction may be linked to a rapid defense mechanism to produce hydrogen peroxide, through photorespiration.

However, in the battle between the plant and the blight, the plant ends up being defeated: “We observed that the plant reduces its capability to store energy reserves –through starch– so as to synthesize leaf biomass”, said Botero.

The model reduces associated costs

The Director of the UNal Bioinformatics and Computational Biology Center, Professor Andrés Pinzón, says that computer models are tools that never cease to be improved, although the model proposed by Botero has a 70% prediction level, which is highly effective.

He also highlighted that the development of said technological tools is a trend which is becoming a stronger tool in scientific research, as they reduce the costs associated to laboratory testing and in most cases allow directing research to “targets” or processes which have greater a likelihood of impacting or providing answers to research questions.

“Its development is not an easy task and requires a joint effort between the computer and the field laboratories; for instance in this case we worked jointly with the Universidad de los Andes Laboratory of Mycology and Phytopathology and the Bioinformatics and Computational Biology Center (BIOS for its Spanish acronym)”, said the researcher.

In this sense, having rebuilt the computer reality of the potato which it is attacked by late blight, is great news for Colombian and world agriculture, as now we have a technological resource which allows deepening research of one of the most aggressive plant diseases, such as late blight.