The effect of domestication on the legume-rhizobia mutualism

Link To Share This Poster: https://cdmcd.co/Yk3dpx
Live Discussion Link: https://cdmcd.co/3wqGm7

Niall Millar, School of Biological Sciences, Washington state university, Vancouver, WA, Stephanie Porter, School of Biological Sciences, Washington State University, Vancouver, Vancouver, WA and Jonah Piovia-Scott, Biological Sciences, Washington State University, Vancouver, Vancouver, WA

Background/Question/Methods
Domestication has greatly improved plants for human use, but can also have unintended consequences. Genetic drift under crops’ small effective population sizes, tradeoffs between agronomic and less-visible traits, and the relaxation of selection can allow deleterious mutations and undetected changes in phenotypes to accumulate. We ask whether domestication has reduced the benefits that legumes receive from the rhizobial mutualism, and whether legume crops have evolved a greater tendency to cease the mutualism in response to nitrogen fertilisation. We compared the growth of wild and domesticated chickpeas, lentils, peas, peanuts, and soybeans across six levels of nitrogen fertilisation, with or without rhizobia.
Results/Conclusions
We find that at low levels of nitrogen addition, wild soybeans receive a greater benefit from rhizobia than do domesticated soybeans, and that domesticated chickpeas cease nodulation a lower level of nitrogen addition than do wild chickpeas, though we do not detect such changes in other crops. Thus, disruption of the rhizobial mutualism is a possible, but not necessary, consequence of domestication. The lower growth benefit received by domesticated soybean, and the greater nitrogen sensitivity of domesticated chickpea, could result from adaptation to a higher-nitrogen environment than was experienced by their wild relatives. These instances of symbiotic disruption elucidate ways in which mutualism may shift in response to human induced selection and may offer targets for improvement in crop breeding.