This project began as a literature review as part of directed research in my mentor's [ Dr. Lorena Torres-Martinez ] lab studying plant-microbe interactions. After being accepted into the SURF program, this experiment has come to life during the summer!
Legumes such as Trifolium repens (white clover) are cover crops that are continuously rotated with regular crops to help farmers maintain soil health. Legumes form a highly specific mutualistic interaction with soil bacteria called rhizobia, where in exchange for carbohydrates the rhizobia fix atmospheric nitrogen for the plant. To promote this interaction agricultural companies sell pre-inoculated seeds of white clover to local farmers. However, indigenous rhizobia exist naturally in the soil and provide competition for commercial inoculants, which can be exacerbated by stressful environmental conditions such as saltwater intrusion that increase soil salinity. Here we implemented a manipulative experiment to investigate the effects of saltwater intrusion on the symbiosis of white cover with native and pre-inoculated rhizobia. We isolated native rhizobia from local non-agricultural soils and exposed sterile white clover seedlings to single and co-inoculations of a native rhizobia and a commercial rhizobia strain under normal watering conditions and saltwater intrusion (~12ppt). We found that under saltwater intrusion, white clover had higher growth benefits and higher performance when partnered with indigenous rhizobia instead of the commercial strain. The results of this study will shed light on possible methods of improving cover crop resistance to saltwater intrusion not only for clover but also for other legumes and native plants that rely on endogenous rhizobia.