Effects of soil rhizobia in inducing anti-herbivore defense and altering host plant quality in peas in response to S. lineatus feeding

Primary author: Saumik Basu
Co-author(s): Benjamin Lee; Robert Clark; Clare Casteel; David Crowder
Faculty sponsor: David Crowder

Primary college/unit: Agricultural, Human and Natural Resource Sciences
Campus: Pullman


Soil bacterial mutualists (e.g. soil rhizobia) contribute significantly to improve the performance of legumes against herbivores and pathogens. The additional nitrogen supplied by soil rhizobia during legume-rhizobia symbiosis not only boost host nutritional status, but also induce various defense responses. The performance of various aboveground herbivores has been investigated during legume rhizobia symbiosis. We for the first time investigates the mechanism of various rhizobia-mediated defense induction and nutritional status in peas against S.lineatus, a non-vector chewing herbivore. Our study showed that, soil rhizobia, Rhizobium leguminosarum bv. Viciae confer resistance in peas by reducing defoliation (leaf notches) produced by S. lineatus. Conversely, S. lineatus interfere with legume-rhizobia symbiosis by reducing nodule numbers and biomass in peas. Soil rhizobia induced anti-herbivory in pea is achieved through induction of various defense genes and alteration of host plant quality. Soil rhizobia enhance expression of both jasmonic acid and abscisic acid responses and keep expression of the salicylic acid responsive gene low in peas. Besides phytohormone defense, soil rhizobia also enhance levels of genes associated with physical defense and antioxidant defense pathways in peas and improve host plant quality. Taken together, our results show both mutually-antagonistic interactions between soil rhizobia and S. lineatus herbivorey and in-depth mechanism of soil rhizobia mediated anti-herbivore response in legume.