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In other parts of the world, soil-borne arbuscular mycorrhizal fungi are helpful to some crops, improving the uptake of nitrogen and phosphorous and providing other benefits.
For her doctoral dissertation, Lina Bernaola, a graduate student in the LSU Department of Entomology, has been studying whether arbuscular mycorrhizal fungi (AMF) can help rice plants with insect resistance and improved rice growth.
However, the effects of these fungi have varied depending on the species of AMF, the crop species and soil conditions. Bernaola said this is the first time the AMF has been tested in rice in the southern U.S.
Bernaola first tested the effect of AMF in rice resistance to the rice water weevil and fall armyworm as well as the sheath blight pathogen. In all of these she found that rice plants inoculated with AMF were more susceptible to these pests in this test. However, the nutritional analysis (nitrogen and phosphorous) of root and shoot tissues indicated no major changes in the concentration of nutrients that can explain this susceptibility.
She also tested if the effect of AMF is soil dependent. The results in rice were mixed, she said. In a test at the H. Rouse Caffey Rice Research Station near Crowley, inoculation with mycorrhizae showed inoculated plants benefitted from some insect resistance, but in a test near Mamou they showed no advantage. Bernaola said that could be explained because the soil near Mamou lacks phosphorous, which mycorrhizae needs to thrive.
In addition, she demonstrated that all rice-producing areas in the southern U.S. have the natural presence of this fungi, which can be used for future research. Bernaola also showed AMF used on rice in field experiments provided tolerance against weevils after the insects fed on the plants. The three years of trials have been limited to CL111, but she said more variety testing needs to be done.
She said a rice plant’s increased nutrient uptake from mycorrhizae results in more biomass, which could help with the production of more panicles to compensate for the losses from insects. Even though mycorrhizal fungi did not translate to increased insect resistance in this study, the increased yields from the tolerance experiment open a new window to keep working on the effects of this fungi on rice plants.
“I believe mycorrhizae can be incorporated into integrated pest management, but more studies need to be done because my research shows the complexity of these interactions,” Bernaola said. “Soil microbes are an important component for sustainable agriculture that need to be exploited.”
She also is looking at identifying genes in rice that activate chemical responses to pathogens and insects.
