GENOMIC APPROACHES TO IMPROVING TRANSPORT AND DETOXIFICATION OF SELECTED MINERAL ELEMENTS IN CROP PLANTS
Location: Plant, Soil and Nutrition Research
Title: Genetic variation for root architecture, nutrient uptake and mycorrhizal colonisation in Medicago truncatula accessions
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 25, 2010
Publication Date: June 26, 2010
Citation: Shulz, C., Kochian, L.V., Harrison, M. 2010. Genetic variation for root architecture, nutrient uptake and mycorrhizal colonisation in Medicago truncatula accessions. Plant and Soil Journal. Available: http://www.springerlink.com//index/73J4KLH3M3607430.pdf.
Interpretive Summary: Identifying plant genes that control the efficient uptake and translocation of nutrients is needed for the development of new plant cultivars that require less agronomic inputs such as fertilizers. Many of the world’s cropping soils have low fertility and both macro (N, P, K) and micronutrients (Fe, Zn) need to be added. Micronutrient deficiencies are important to both agriculture and human health. Recent estimates show that over 60% of the world’s population suffer from micronutrient malnutrition. Improvements in the uptake of micronutrients by plants will provide economic, environmental and social benefits. Root traits are becoming a major focus for this type of research because of their primary role in nutrient acquisition and other important agronomic traits such as drought tolerance. Root system architecture (RSA) describes the spatial arrangement of roots in the soil. To expand our previous work in this area using the model legume species, M. truncatula, and develop a universal resource for uncovering genetic traits for nutrient acquisition, we selected eight diverse M. truncatula accessions and used growth pouch and pot based experiments to examine root architecture, mycorrhizal colonisation and nutrient uptake. We found significant differences in root architecture that impacted the ability of the accessions to acquire macro and micronutrients, and played a role in the efficiency to transport these nutrients to the shoot. This work sets the stage for genetic mapping of root architecture traits that then can be used for the breeding for lines better suited for sustainable agriculture.
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 maco- 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.