Genetic variation for root architecture, nutrient uptake and mycorrhizal colonisation in Medicago truncatula accessions
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Sustainable agriculture strives for healthy, high yielding plants with minimal agronomic inputs. Genetic solutions to increase nutrient uptake are desirable because they provide ongoing improvements. To achieve this it is necessary to identify genes involved in uptake and translocation of nutrients. We selected Medicago truncatula L. as a model because of its: i) close genetic relationship to food legumes, ii) use as a pasture legume in southern Australia and iii) availability of mapping populations generated from genetically diverse accessions. We discovered statistically significant differences between eight accessions for: root architecture in growth pouches, % root colonisation with the arbuscular mycorrhizal (AM) fungus Glomus intraradices, and plant tissue concentration of most macro- and micronutrients. Mycorrhizal colonisation had a significant effect on P concentration in roots but not shoots, Mg concentration in both roots and shoots, and the concentration of various micronutrients in shoots including Fe, Ca, but not Zn. Comparison of micronutrient uptake between root and shoot tissues showed that some M. truncatula accessions were more efficient at mobilisation of nutrients from roots to shoots. We are now in a position to use existing mapping populations of M. truncatula to identify quantitative trait loci important for human health and sustainable agriculture.
KeywordsRoot architecture Micronutrient Arbuscular mycorrhizal fungi Legume Low-input cropping Zinc
We gratefully thank Simon Ellwood and Richard Oliver for providing information on the availability of M. truncatula mapping populations. Accessions DZA045 and F83005 were kindly provided by David Bird. Expert technical assistance was provided by Eric Craft (nutrient analysis) and Jean-Patrick Toussaint (AM colonisation). Kathy Crowley provided access to and assistance with WinRHIZO. We thank Evelina Facelli for statistical advice and gratefully acknowledge Sally Smith, Andrew Smith and James Stangoulis for valuable discussions and critical comments on the manuscript. Financial assistance was provided by the AW Howard Memorial Trust Inc. for a travel grant (to CJS) and the U.S. National Science Foundation (DBI-0421676 to M.J.H).
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