Interacting effects of arbuscular mycorrhizae fungi in rice: Do AMF interactions change the resistance of rice plants to pests?

Rice, Oryza sativa, in Louisiana faces hardships from both above-ground (AG) and below-ground (BG) stressors and rice plants defend themselves against harmful insects and pathogens in many ways. Interactions between plants and herbivores and between plants-arbuscular mycorrhizal fungi (AMF) are ubiquitous in terrestrial ecosystems and may be interconnected by complex regulatory networks via a shared host plant. Arbuscular Mycorrhizal Fungi (AMF) are symbiotic associations in many plant roots thought to play a central role in plant nutrition, growth and fitness. Previous studies suggest that AMF colonization makes rice more susceptible to insect and pathogen attack. We hypothesize that the interaction of AMF with rice roots activates responses that change the resistance of rice to pests. Our aims are to investigate if AMF colonization increases nutrient uptake by rice, thereby making rice plants more susceptible to pests. We showed that growth rates of fall armyworm (FAW) larvae were higher on rice plants treated with AMF and nutritional analyses of root and shoot tissues indicated no significant difference in the concentration of nutrients in mycorrhizae-colonized plants, suggesting that the observed difference in plant resistance were due to changes in defense-related pathways. In addition, we showed that root colonization by AMF is accompanied by the expression of genes that play a regulatory role in host defense responses. These results suggest that AMF colonization influences processes in the root system of rice making them more susceptible to insect attack. Understating interactions among above- and below-ground organisms may help in developing novel methods for managing pests of rice.