The Evolution of Alleles Conferring Symbiotic Specialization in Legumes

点击翻译按钮获取中文摘要

9707697 Parker The symbiosis between legume plants and bacteria that form nodules on their roots (rhizobia) is globally important in providing a key nutrient (nitrogen) for both natural ecosystems and agriculture. However, the ecology and evolution of legume-rhizobial interactions remain very poorly understood. In particular, legumes are commonly found to be genetically variable in their capacity to interact with different bacterial genotypes. The plant genes affecting this mutualism typically cause differences in symbiotic specialization: some plants can only interact successfully with a limited number of rhizobial strains, while other plants achieve successful symbiosis with a wide range of bacterial partners. Because rhizobia benefit plants by providing an important nutrient, plants with restricted symbiotic abilities should be at a disadvantage. Nevertheless, genes that cause symbiotic specialization are widely prevalent in legume populations, suggesting that there are other evolutionary processes that compensate for any natural selection against them. The nature of such processes is currently unknown, so the primary objective of this research is to experimentally test a series of hypotheses about why symbiotic specialization has evolved to be common in natural populations of legumes. The main significance of this research is that it will reveal the fitness benefits and costs for legume plants associated with being specialized or promiscuous toward bacterial symbionts. Genes that affect rhizobial specificity are also of interest in efforts to improve the productivity of agriculturally-significant legumes (such as soybeans, peas, beans, alfalfa, etc.). Thus, the results of this project should also provide an important comparative perspective for an improved understanding of legume-rhizobial interactions in agroecosystems as well.