Combatting Invisible Worms: Strategies for Tomato Pest Control

The plague of phytoparasitic nematodes is becoming more prevalent in vegetable crops, which is a concern because it is capable of destroying crops, particularly tomato, which is an important product in the Mexican diet and exports, so scientists from the UNAM Institute of Biotechnology (IBt) are looking for microfungi and bacteria capable of protecting these plants.

IBt researcher and project leader, Claudia Martínez Anaya, explained that it causes serious losses in Mexico and around the world, which is why it is considered one of the most harmful since they are tiny worms (less than one millimeter) that live in the soil and are transparent.

"It is like an invisible pest; to a certain extent, farmers see that their crops are starting to go bad, but the cause is not well known." "In Mexico, they are found in vegetables, but around the world, they affect many crops; almost any plant is susceptible to a root-knot nematode pest," she explained.

On its website, the Ministry of Agriculture and Rural Development reports that in 2020 a volume of 3.27 million tons of tomato was obtained, which implies a growth in production of 9.5 percent in the last decade. According to estimates, this product will export 5.50 million tons by 2030, bringing in $6,641 million in profits.

There are several types of nematodes: migratory, injurious, sedentary, and knot nematodes, or galls; the latter is of greater concern to farmers because they settle in the roots and stay there all their lives; they are the cause of the greatest economic losses. The main representative of this type of parasite is the genus Meloidogyne, which has more than 100 species.

For example, in 2019, in Sinaloa, where farmers grow a lot of saladet tomatoes, a variety that was thought to be very resistant to this pest, it was found that more than 80% of the bushes were infected with the Meloidogyne enterolobii variety, which cost farmers a lot of money.

That is why Martínez Anaya, in collaboration with Iran Tapia Vázquez, co-founder of the company ESBiovolt, and experts from the University of Veracruz, is studying a population of M. enterolobii in the laboratory of the Department of Cellular Engineering and Biocatalysis of UNAM's IBt to identify native soil microorganisms (such as fungi and bacteria) that can protect the plants.

They may start an infection, and what can happen is that the wounds they cause when they get inside the plants leave the entrance door open for other organisms. It is well known that occasionally, fungi or bacteria take advantage of this and exacerbate the disease the parasite caused.

Developing Safe and Sustainable Biological Control Strategies

The goal is to come up with ways to get rid of nematodes that don't hurt the environment or the health of people and animals, like some synthetic nematicides do, which are now banned in several countries.

"Part of the work we are doing in the laboratory is to characterize bacteria and fungi that could help us control nematode populations. We were able to identify in the laboratory a fungus that invades the egg mass and kills the nematodes, which tells us that this fungus could be a natural enemy and we are just characterizing it right now," said the researcher.

It is believed that there is a diversity of microorganisms that could be used to control pathogen populations, so in this case the IBt's work is based on native Mexican soils and there is collaboration with experts in bacteria to broaden the combat strategy.

In addition to the above studies with the nematode population, Martnez Anaya is also looking into how the parasite gets into the plant and how the plant senses its presence, or how its proteins help the parasite grow and trick the plant's immune system into not rejecting them.

Plants have mechanisms to defend themselves from different pathogens and there is "a biochemical war" between them and the parasite, with different interactions between molecules of both that need to be understood. This will let them come up with plans to find plants that are naturally resistant to infection or to make them, which is the goal of many labs around the world because it lets them come up with different plans.