The team has uncovered a new metabolic pathway that can be disrupted to preventing many known plant fungi from invading the host plant. 
 - University of the State of ParanĂ¡ photo -























Published Wednesday, September 23, 2020

International News

Plants can be protected from
fungal infection, say researchers



  
By the A.M. Costa Rica wire services

Widespread fungal disease in plants can be controlled with a commercially available chemical primarily used in medicine until recently, scientists from Martin Luther University Halle-Wittenberg (MLU) and the University of the State of ParanĂ¡ in Brazil said on Tuesday.

The team has uncovered a new metabolic pathway that can be disrupted with this chemical, preventing many known plant fungi from invading the host plant. 

The fungus Colletotrichum graminicola is prevalent around the world. It infects maize, causing anthracnose, a disease that causes plant leaves to turn yellow at first and then ultimately to succumb to toxins.

The fungus multiplies through spores that initially land on the surface of the plant. There they find rather inhospitable conditions, lacking most of the nutrients that fungi need to develop, in particular nitrogen.

"The only option they have is to break down some of their own nitrogen-containing molecules, for instance purines, the building blocks of DNA or RNA," plant pathologist Professor Holger Deising from MLU said.

The researchers on Deising's team have found a way to impede this transitional phase which the fungus relies on. To do this, the team administered acetohydroxamic acid onto the plants, a substance also used to treat harmful bacteria in the human stomach, and which is known to inhibit the breakdown of urea. "The acid prevents the harmful fungi from penetrating into the plants and from becoming infectious," Deising said.

The team also tested whether the findings from C. graminicola and maize could be transferred to other plants and fungi. The acid was also found to be effective against numerous other pathogens which cause, for example, powdery mildew in cereal crops, late blight in potatoes, as well as corn and bean rust. "We have been able to develop a completely new approach to pathogen control that uses an existing active ingredient and thus can be quickly used commercially," Deising said.

The scientists conducted extensive experiments in order to come to their conclusions. They wanted to understand the molecular details of how the fungus manages to obtain nitrogen at the onset of the infection. First, they generated a series of random mutations in the genome of the fungus C. graminicola. "Then we inoculated the different fungal mutants onto the plants to see which ones were no longer infectious," Deising said.

One of these mutants had a defect in the purine degradation pathway. In order to check whether the mutants' failure to infect the plant was actually caused by a lack of nitrogen, the researchers then applied nitrogen to the plants. "Once nitrogen was added, even the harmless mutants became infectious again," Deising said.

The team was able to induce the same defect they had observed in the mutants in wildtype fungi by applying acetohydroxamic acid because it blocks the purine degradation pathway, too.





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Could be this study the first step to allow the production of less toxic fungicides in plantations? We would like to know your thoughts on this story. Send your comments to news@amcostarica.com