University of Delaware student Jonathon Cottone knows the tell-tale signs that rice plants are getting sick: the yellowing leaves, the faint football-shaped lesions. Cottone, a junior from Wilmington, Delaware, is working with Harsh Bais, associate professor of plant and soil sciences at UD, on research to help this globally important grain cope with increasing stress.

Recently, the UD team found that when rice plants are subjected to multiple threats -- including increasing concentrations of poisonous arsenic in water and soil, an urgent concern in Southeast Asia, plus a fungal disease called rice blast -- the plants aren't necessarily goners.

Rather, the UD researchers have shown for the first time that a combination of beneficial soil microbes can be applied to the infected plants to boost their natural defenses, combating both problems.

The findings, published in Frontiers in Plant Science, provide new evidence about the potential benefit of "biostacking" -- putting multiple microbes together to protect plants from stress. The research also lends further support for a natural, chemical-free approach to protecting a crop that over half the world's population depends on for food.

A 'health cocktail' for rice plants

"We wanted to see if we could use a combinatorial approach -- a 'cocktail' of organisms -- that would help rice plants with two simultaneous stresses attacking them," Bais said, from his laboratory at the Delaware Biotechnology Institute.

In addition to Bais and Cottone, the team included Venkatachalam Lakshmanan, a former postdoctoral researcher at UD who is now working at the Oklahoma-based Samuel Roberts Noble Foundation.

Previously, the UD team identified two species of bacteria that come to the rescue of rice plants when the plants are under attack. The two microbes naturally inhabit the rhizosphere, the soil around the plant roots.

Pseudomonas chlororaphis EA105 can trigger a system-wide defense against the rice blast fungus, which destroys enough rice to feed an estimated 60 million people each year.

EA105 inhibits formation of the fungus's attack machinery, the appressoria, which acts like a battering ram, putting pressure on a plant leaf until it is punctured.

A second microbe, EA106, mobilizes an iron plaque, or shield, to begin accumulating on the roots of rice plants when arsenic is present, effectively blocking uptake of the poison.

"What's happening in Southeast Asia from high levels of arsenic in water and soil has been called the largest mass poisoning in history," Bais said. "The EA106 microbe has multiple benefits. The iron shield it deploys blocks the arsenic. This iron, absorbed into the rice grain, could help address another big health problem in many developing countries -- iron deficiency."

See more at https://www.sciencedaily.com/releases/2016/11/161118130421.htm