The roots of maize defend against phytopathogens by releasing a pesticide that also attracts a beneficial microbe that preys on the target pest.

Introduction

Plant roots are surrounded by tens of thousands of species of microbes that collectively make up what is called the rhizosphere. Some of these microbes are phytopathogens that have damaging effects on plants. Others benefit the plant through promoting nutrient uptake, nitrogen fixation, and pathogenic defense systems. Of the rhizosphere microbes that aid in immunity, some function by out-competing pathogens for nutrients, while others actively secrete antibiotics or induce an immune response in the plant.

The Strategy

It has been recently documented that maize is capable of attracting beneficial bacteria to its rhizosphere to promote health. Early stage maize seedlings are especially vulnerable to harm from phytopathogens.

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Early stage maize seedlings are especially vulnerable to harm from phytopathogens.

They have long been known to secrete a chemical called DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one) from their roots. This compound is a potent biocide that eliminates harmful bacteria, insects, and other plants. Remarkably, a beneficial bacterium called Pseudomonas putida is attracted to DIMBOA and can detoxify it. Once within the rhizosphere or the maize seedling, the bacteria can out-compete phytopathogens for the limited nutrient supply. In this way, maize plants are able to recruit microbial allies to their roots in order to prevent the growth of phytopathogens.

The Potential

To protect our food crops, we often apply pesticides that are harmful to other organisms and the environment. With maize, we see an example of a plant altering the chemical and biological properties of soil to suit its needs. By continuing to study how corn accomplishes this as well as identifying other plants that can affect soil properties, we may be able to plant plants as “pesticides” instead of using harsh chemicals.

Last Updated March 23, 2020