Genetic variation in pea (Pisum sativum L.) demonstrates the importance of root but not shoot C/N ratios in the control of plant morphology and reveals a unique relationship between shoot length and nodulation intensity

Authors

  • NDIKO N. LUDIDI,

    1. Crop Performance and Improvement Division,
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      Present address: Institute for Plant Biotechnology, Natural Sciences Building Department of Genetics, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.

  • TILL K. PELLNY,

    1. Crop Performance and Improvement Division,
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  • GUY KIDDLE,

    1. Crop Performance and Improvement Division,
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  • CHRISTELLE DUTILLEUL,

    1. Crop Performance and Improvement Division,
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    • Present address: Université Pierre et Marie Curie, UMR7180 CNRS-Paris 6, Physiologie, Cellulaire et Moléculaire des Plantes, Case 156, Le Raphaël, 3 Rue Galilée, F-94200 Ivry-sur-Seine, France.

  • KARIN GROTEN,

    1. Crop Performance and Improvement Division,
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    • Present address: Max-Planck-Institute for Chemical Ecology, Beutenberg Campus, Hans-Knöll-Str. 8, 07745 Jena, Germany.

  • PHILIPPUS D. R. VAN HEERDEN,

    1. Crop Performance and Improvement Division,
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      Present address: School of Environmental Sciences and Development: Section Botany, North-West University, 2520 Potchefstroom, South Africa.

  • SOM DUTT,

    1. Crop Performance and Improvement Division,
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    • Present address: Biotechnology Division, Institute of Himalayan Bioresource Technology, PO Box #6, Palampur-176 061 (HP), India.

  • STEPHEN J. POWERS,

    1. Biomathematics and Bioinformatics Division, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK and
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  • PETER RÖMER,

    1. Südwestsaat GbR, Im Rheinfeld 1-13, 76437 Rastatt, Germany
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  • CHRISTINE H. FOYER

    Corresponding author
    1. Crop Performance and Improvement Division,
      C. H. Foyer. School of Agriculture, Food and Rural Development, Agriculture Building, Newcastle University, Newcastle upon Tyne NE1 7RU, UK. Fax: 0191 2227811; e-mail: christine.foyer@newcastle.ac.uk
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C. H. Foyer. School of Agriculture, Food and Rural Development, Agriculture Building, Newcastle University, Newcastle upon Tyne NE1 7RU, UK. Fax: 0191 2227811; e-mail: christine.foyer@newcastle.ac.uk

ABSTRACT

Nodule numbers are regulated through systemic auto-regulatory signals produced by shoots and roots. The relative effects of shoot and root genotype on nodule numbers together with relationships to organ biomass, carbon (C) and nitrogen (N) status, and related parameters were measured in pea (Pisum sativum) exploiting natural genetic variation in maturity and apparent nodulation intensity. Reciprocal grafting experiments between the early (Athos), intermediate (Phönix) and late (S00182) maturity phenotypes were performed and Pearson's correlation coefficients for the parameters were calculated. No significant correlations were found between shoot C/N ratios and plant morphology parameters, but the root C/N ratio showed a strong correlation with root fresh and dry weights as well as with shoot fresh weight with less significant interactions with leaf number. Hence, the root C/N ratio rather than shoot C/N had a predominant influence on plant morphology when pea plants are grown under conditions of symbiotic nitrogen supply. The only phenotypic characteristic that showed a statistically significant correlation with nodulation intensity was shoot length, which accounted for 68.5% of the variation. A strong linear relationship was demonstrated between shoot length and nodule numbers. Hence, pea nodule numbers are controlled by factors related to shoot extension, but not by shoot or root biomass accumulation, total C or total N. The relationship between shoot length and nodule numbers persisted under field conditions. These results suggest that stem height could be used as a breeding marker for the selection of pea cultivars with high nodule numbers and high seed N contents.

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