The bacteria living in your soil and depending on wheat and barley roots to survive may be lending the plants a helping hand in return.
Scientists are looking into the possibility that the bacteria can biologically control root-rot fungi — a pest that causes crop yield losses of 10 to 30 per cent each year in the U.S. Pacific Northwest and elsewhere.
These beneficial bacteria are known as Pseudomonas. There are 11 strains of this bacteria that hinder the growth of Pythium and Rhizoctonia fungi, fungi known to cause diseases in wheat and barley. These diseases are hard to control. There are no resistant wheat or barley varieties, fungicides aren’t effective and control with rotations is challenging due to the pathogens’ broad plant-host range.
Pseudomonas bacteria secrete enzymes and biochemicals that keep fungal rivals at bay. Some strains can trigger immune-system response in plants. Other bacteria make hormone-like matter that stimulate root and shoot growth in host plants.
Dr. Patricia Okubara, a scientist with the USDA Agricultural Research Service in Washington, is researching plant defense responses to pathogens, pathogen diagnostics, and control of soilborne pathogens of wheat and barley. Basically, she says, “I study root disease problems of wheat.”
Okubara has been surveying the root-rot pathogens Rhizoctonia and Pythium. Pseudomonas may be one answer to controlling these fungal diseases “Commercial potential of the new strains of Pseudomonas is being examined in collaboration with Dr. Christopher Taylor at Ohio State University, Wooster, Ohia, and scientists at a small U.S. agro-products company,” said Okubara. She is unaware of any Canadian research being done on cereal root-rot pathogens.
“Certain strains of bacteria can directly benefit the plant if they produce growth-promoting plant hormones that stimulate root or shoot growth,” Okubara says. Plants can reap these benefits even without the presence of a pathogen.
This won’t be simple. “Control of soilborne pathogens by introduced biocontrol bacteria — bacteria added as a seed treatment or in fertilizer — in large-acreage production systems is expected to be difficult to achieve.”
Difficult, but not impossible. She says, “There are cases of naturally occurring biological control of soilborne pathogens in the field through a process called disease suppression. In these cases, beneficial microbes that antagonize or suppress the pathogen arise naturally, control the pathogen, and increase crop health and yield.
“But enhancing the efficacy of introduced biocontrol strains, not necessarily native to the soil into which they’re being introduced, is still in its infancy. †