Microbe-mediated effects on seed nutritional quality in chickpea
The plant microbiome mediates many aspects of crop phenotype, including yield, reproductive phenology, and potentially crop nutritional quality. Microbes can affect crop nutritional quality affecting root phenotypes, changing nutrient availability in the rhizosphere, and buffering plants against stressors that affect crop quality. In my current USDA-NIFA fellowship project, I am “mining the microbiome” of domestic and wild chickpea relatives, with the objective of finding bacterial species that can be incorporated into chickpea cultivation that will enhance the nutritional quality. I am using seed nutritional phenotyping, metagenomic sequencing technologies, microbial culturing, and informatics to generate hypotheses, and synthetic community approaches to validate these relationships. Preliminary results suggest that chickpea fecundity is higher in the presence of rhizosphere microbes, however the effects seed nutritional quality are to be determined.
Nitrogen deposition and coevolution between legumes and nodulating bacteria
Abundant soil nitrogen may lead to reduced reliance on rhizobia and an eventual transition to antagonistic coevolution instigated by the evolution of less mutualistic bacteria (i.e. those that provide fewer fitness benefits to their host plants). I will use herbarium specimens, an untapped resource for studying coevolution, to accomplish two main objectives: 1) Compare contemporary and historic bacteria, using genomics, to understand how areas of the genome under selection have changed with increasing nitrogen deposition levels. 2) Test how coevolutionary history has changed with nitrogen deposition by reviving historic Medicago lupulina seeds and historic populations of bacteria and using time-shift experiments. I developed methods for this project while on a National Science Foundation-Postdoctoral Fellowship in Biology (PRFB) and have been able to recover historic bacteria and resurrect historic plant genotypes.
Environmental determinants of free-living nitrogen fixing species of bacteria
The negative effects of perpetual nitrogen fertilization in agriculture are becoming abundantly clear over a hundred years after the invention of the Haber-Bosch process. Soils are increasingly becoming acidic while nitrogen demands remain constant. A potential solution to this conundrum is to use free-living nitrogen fixing bacteria (diazotrophs) to increase nitrogen availability in agricultural soils. I am simultaneously describing how diazotrophs vary by habitat and nitrogen availability and working on identifying putative nitrogen fixers, in a culture collection of isolates from switchgrass. Our work suggests that diazotroph diversity decreases with soil nitrogen, indicating that inoculations may not be successful given existing nitrogen fertilization regimes.