Ortiz-Barbosa Gabriel S, Torres-Martínez Lorena, Manci Angela, Neal Sierra, Soubra Tarek, Khairi Fizzah, Trinh Jerry, Cardenas Paola, Sachs Joel L
Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, California, 92521.
Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, California, 92521.
Evolution. 2022 Mar;76(3):496-511. doi: 10.1111/evo.14424. Epub 2022 Jan 19.
Modern agriculture intensely selects aboveground plant structures, while often neglecting belowground features, and evolutionary tradeoffs between these traits are predicted to disrupt host control over microbiota. Moreover, drift, inbreeding, and relaxed selection for symbiosis in crops might degrade plant mechanisms that support beneficial microbes. We studied the impact of domestication on the nitrogen-fixing symbiosis between cowpea and root-nodulating Bradyrhizobium. We combined genome-wide analyses with a greenhouse inoculation study to investigate genomic diversity, heritability, and symbiosis trait variation among wild and early-domesticated cowpea genotypes. Cowpeas experienced modest decreases in genome-wide diversity during early domestication. Nonetheless, domesticated cowpeas responded efficiently to variation in symbiotic effectiveness, by forming more root nodules with nitrogen-fixing rhizobia and sanctioning nonfixing strains. Domesticated populations invested a larger proportion of host tissues into root nodules than wild cowpeas. Unlike soybean and wheat, cowpea showed no compelling evidence for degradation of symbiosis during domestication. Domesticated cowpeas experienced a less severe bottleneck than these crops and the low nutrient conditions in Africa where cowpea landraces were developed likely favored plant genotypes that gain substantial benefits from symbiosis. Breeders have largely neglected symbiosis traits, but artificial selection for improved plant responses to microbiota could increase plant performance and sustainability.
现代农业高度注重地上植物结构的选择，却常常忽视地下特征，预计这些性状之间的进化权衡会破坏宿主对微生物群的控制。此外，作物中的共生漂变、近亲繁殖以及对共生选择的放松，可能会削弱支持有益微生物的植物机制。我们研究了驯化对豇豆与根瘤慢生根瘤菌之间固氮共生的影响。我们将全基因组分析与温室接种研究相结合，以调查野生和早期驯化的豇豆基因型之间的基因组多样性、遗传力和共生性状变异。在早期驯化过程中，豇豆的全基因组多样性略有下降。尽管如此，驯化后的豇豆通过与固氮根瘤菌形成更多根瘤并制裁非固氮菌株，对共生有效性的变化做出了有效反应。与野生豇豆相比，驯化群体将更大比例的宿主组织投入到根瘤中。与大豆和小麦不同，豇豆在驯化过程中没有明显的共生退化证据。驯化后的豇豆经历的瓶颈比这些作物要轻，而且在非洲培育豇豆地方品种的低养分条件可能有利于从共生中获得大量益处的植物基因型。育种者在很大程度上忽视了共生性状，但通过人工选择来改善植物对微生物群的反应，可以提高植物性能和可持续性。
