AOBPreview published online on February 27, 2009
Annals of Botany, doi:10.1093/aob/mcp040
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Using a model-based framework for analysing genetic diversity during germination and heterotrophic growth of Medicago truncatula
1 INRA et Agrocampus Ouest, UMR 1191 Physiologie Moléculaire des Semences, 16 bd Lavoisier, F-49045 Angers, France
2 GEVES Station Nationale d'Essais des Semences, rue Georges Morel, F-49071 Beaucouzé, France
3 INP-ENSAT Laboratoire Symbioses et Pathologies des Plantes (SP2), Avenue de l'Agrobiopole, F-31326 Castanet, Tolosan cedex, France
4 INRA UMR 1097 – Diversité et Adaptation des Plantes Cultivées, Domaine de Melgueil, F-34130 Mauguio, France
* For correspondence. E-mail durr{at}angers.inra.fr
Received: 17 November 2008 Returned for revision: 8 December 2008 Accepted: 13 January 2009
Background and Aims: The framework provided by an emergence model was used: (1) for phenotyping germination and heterotrophic growth of Medicago truncatula in relation to two major environmental factors, temperature and water potential; and (2) to evaluate the extent of genetic differences in emergence-model parameters.
Methods: Eight cultivars and natural accessions of M. trunculata were studied. Germination was recorded from 5 to 30 °C and from 0 to –0·75 MPa, and seedling growth from 10 to 20 °C.
Key Results: Thermal time to reach 50 % germination was very short (15 °Cd) and almost stable between genotypes, while base temperature (2–3 °C) and base water potential for germination (–0·7 to –1·3 MPa) varied between genotypes. Only 35 °Cd after germination were required to reach 30 mm hypocotyl length with significant differences among genotypes. Base temperature for elongation varied from 5·5 to 7·5 °C. Low temperatures induced a general shortening of the seedling, with some genotypes more responsive than others. No relationship with initial seed mass or seed reserve distribution was observed, which might have explained differences between genotypes and the effects of low temperatures.
Conclusions: The study provides a set of reference values for M. trunculata users. The use of the ecophysiological model allows comparison of these values between such non-crop species and other crops. It has enabled phenotypic variability in response to environmental conditions related to the emergence process to be identified. The model will allow simulation of emergence differences between genotypes in a range of environments using these parameter values. Genomic tools available for the model species M. trunculata will make it possible to analyse the genetic and molecular determinants of these differences.
Key words: Core collection, emergence, Medicago truncatula, modelling, seed, temperature, water potential