Attracts beneficial bacteria | Healthy roots could reduce the need for chemicals
LINDELL BEACH, B.C. — Research has shown for the first time that corn can attract beneficial bacteria to their root environment, basically through the power of perfume.
Scientists have discovered that one of a variety of chemicals put out by corn roots produces aromatic toxins to attract a certain competitive bacteria to the root system.
The bacteria helps detoxify the soil, competes with harmful compounds in the root system and stimulates the availability of growth-enhancing iron and phosphorus.
Andrew Neal of Rothamsted Research, who co-led the study, said the research into these root chemicals called benzoxazinoids (BXs) could have significant on-farm repercussions.
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“Ensuring that roots of crops form strong relationships with beneficial soil bacteria could indeed reduce the need for regular chemical applications, and because treating roots is difficult in the field, (the research results) may provide a better approach to promoting root health.”
The BXs appear to stimulate genes that control the movement of bacterial cells by what researchers call chemotaxis, or movement in re-sponse to a chemical.
The study was published in April in the open access journal PLoS One and was conducted by researchers at Rothamsted Research in Hertfordshire, United Kingdom, and the University of Sheffield’s animal and plant sciences department.
Neal said the chemicals given off by the BXs are able to attract one particular soil bacterium, called Psudomonas putida. It moves toward the plant to locate the roots.
BX chemicals, once released by the roots into the soil, break down quickly with a half-life of less than 24 hours. The P. putida increases that breakdown process, using the BX molecules as an energy source.
By taking advantage of the energy-rich niche in the root ecosystem, the bacteria can exploit a beneficial environment unavailable to bacteria that aren’t able to detoxify BX.
It is a symbiotic relationship. Corn produces BXs as a chemical defence, and the P. putida bacterium has evolved a system that allows it to locate roots by cueing on the BX chemical.
There are advantages to both the plant and the bacteria, and researchers are exploring the soil ecosystem to see how the bacterial behaviour can be managed to improve crop health and production yield.
“BXs contain nitrogen, and so P. putida may exploit the compound as an N source,” Neal said.
However, there is an emerging threat to this co-operative soil-based community. Commercial grass crops are losing the ability to produce BXs, which puts their root ecosystems at risk.
“BX production is common in the grasses, but many of the elite cereals that are now grown intensively have lost the capacity to produce BXs,” said Neal. “This has happened because the varieties now in use were selected specifically because of an increased yield, a good thing in itself, but other positive attributes were lost, or lessened. So, there are some wheat varieties that produce BXs, but we are not sure whether the BXs are exuded from their roots, and anyway they are not widely grown.
“Of the agricultural crops, BXs are only found in grasses (like) wheat and (corn).”
Ongoing research is focusing on how to enhance the ability of BX chemicals to aid in the fight against soil-borne pests.
Neal said they know that bacteria such as P. putida significantly influence plant growth. They can compete for space on the root surface with plant pathogens and produce antibiotics, which are certain to improve plant health. As well, the stimulation of essential nutrients such as iron and phosphorus also helps plants grow substantially.
The long-range aim of the research is to reintroduce the appropriate genes from ancestral wheat and corn varieties into elite crop varieties that are intensively cultivated.
