Plant-Eating Nematodes and the Key to Fighting Them

Plant roots interact with many bacteria, fungi, and microscopic organisms within the soil that can impact how well the plants grow. Some of these microscopic organisms are animals called nematodes, and they are an especially important part of the life in the soil. Nematodes can be good, bad, and neutral for plants. Some scientists called nematologists study nematodes and how to prevent the bad ones from damaging important crops, like carrots. Nematologists and other scientists partner up to help farmers manage these pests and grow healthy crops.


Figure Figure
A male root-eating nematode of the Pratylenchus species, collected from carrot roots. For scale, µm is times smaller than mm and is roughly the width of a human hair! plant world. These dangerous nematodes feed on plant roots, which NEMATODE A group of animals (Phylum: Nematoda) that have a worm-like shape that is long and cylindrical. They can be found on all seven continents (even Antarctica!), as well as in oceans and lakes. ultimately damages the plant and severely impacts plant growth. While feeding, nematodes create wounds on the roots, which can leave the plant's roots vulnerable to infection by other disease-causing organisms in the soil [ ]. Nematodes that damage plant roots are often called parasites.

PARASITES
An organism that relies on another host organism to steal food and nutrients.

PLANT-EATING NEMATODES: A THREAT TO ROOT CROPS
Some garden plants have roots that we eat, like carrots, beets, parsnips, and potatoes. Nematodes can damage these important food crops along with many others. Nematodes possess a straw-like mouth part that injects a mixture of enzymes into the plant, which breaks down the ENZYMES Biological molecules that induce chemical reactions within cells. plant cells into a plant-cell soup. After the cells are broken down, the nematodes eat up this soup [ ]. When nematodes feed on carrot roots during the early stages of the plant's life, this can cause serious damage or even the plant's death. When some plant-parasitic nematodes feed on carrots and parsnips early in the growing season, they damage the roots so much that farmers cannot sell them. If certain nematodes of the genus Pratylenchus feed on very young carrots, the root damage causes the carrots to develop forked roots (Figure ). When there are many of plant-parasitic nematodes in the soil, large crop losses can result.
Nematologists are scientists who study nematodes. Nematologists  the e ectiveness of products that can kill dangerous nematodes, to find the best ways to combat these pests. Nematodes that eat root vegetables are particularly di cult to manage because sometimes farmers cannot see the symptoms of nematode infestation until the end of the season, when the roots are harvested.

HOW IS A NEMATODE INFESTATION DIAGNOSED?
Unlike insect pests, nematodes cannot be seen by the naked eye, so confirming a nematode infestation requires laboratory testing. If a farmer is concerned that he has plant-parasitic nematode damage, he can send a soil sample collected from his field to a nematology laboratory. In the laboratory, the soil is mixed with water and shaken through mesh sieves, in a process like sifting flour. The goal is to remove any large chunks of sand or other debris from the soil and capture only the nematodes. The mixture is transferred to tubes, which are put into a centrifuge-a large machine that spins extremely quickly to collect denser particles at the bottom of the tubes. The nematodes float in the water while heavier sand and mud particles stay in the bottom of the tube. Then, a sugar solution is added to the tube that causes the nematodes to float to the top of the tube. Scientists can collect the tiny animals and view them under a light microscope and identify which species of nematodes are in the farmer's field. {Jenskins} However, some species of nematodes look so much like other species that they need to be identified by analyzing their DNA.

DNA
The instructions required to make up cells that is stored in every organism.

HOW CAN FARMERS MANAGE NEMATODES?
Nematologists and other scientists work together to tackle the issues that farmers face with nematodes. There are some chemicals, called nematicides, that are currently used to treat nematode infestations.

NEMATICIDE
A substance or organism that is e ective at killing nematodes.
These chemicals are toxic to nematodes but can also be dangerous for the person applying them, and they are also expensive. Nematologists are researching other e ective ways for farmers to manage these pests. Some types of bacteria and fungi [ ] present in soil have BACTERIA A group of organisms that are prokaryotic, meaning that they lack a nucleus and only have one cell.

FUNGI
A group of organisms that are eukaryotic (cells contain a nucleus) and feed on organic matter. This group includes mushrooms and yeasts that we eat, as well as mildews and molds.
nematocidal qualities, meaning they can kill or inhibit nematodes, and some are so specialized that they only attack the bad nematodes [ ]. Many current studies are trying to identify and grow these beneficial species, so they can be applied to farmers' fields to lower the populations of bad nematodes in the soil. The most desirable nematicide would only be harmful to plant-parasitic nematodes, to ensure that soil resources and other helpful microscopic organisms in the soil are protected.

FUNGI AND BACTERIA: A POTENTIAL KEY TO FIGHTING PLANT-PARASITIC NEMATODES
Plant-parasitic soil nematodes are dangerous pests that can damage plant roots and cause farmers to lose a lot of money due to unsellable crops. Thus, it is important to find e ective ways to manage plant-parasitic nematodes. Ideally, these treatments should be safe for the environment and other soil-living species and should also be easily a ordable for the farmer. This is a considerable challenge for nematologists, but the future is bright! The potential key solution is finding types of soil fungi or bacteria that can control plant-parasitic nematodes to develop new, e ective, and environmentally friendly products for farmers to use. In addition, using nematode DNA to identify the di erent species of nematodes in soil has helped to advance the field of nematology. Sometimes molecular science like DNA analysis can be expensive but, by working together, scientists can make advances in molecular techniques that will make the process cheaper for future scientists and farmers. These techniques will pave the way for teams of nematologists and their partner scientists to help find the best ways to control these harmful pests. . doi: . /frym. .

CONFLICT OF INTEREST:
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
COPYRIGHT © Darling, Quintanilla-Tornel and Chung. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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HENRY CHUNG
Henry is a biologist working at Michigan State University. He is fascinated by how life works at the molecular level. Henry studies insects and nematodes to understand how these organisms can adapt to di erent environments or feed on di erent host plants.