Relative growth rate correlates negatively with pathogen resistance in radish: the role of plant chemistry

Authors

  • E. HOFFLAND,

    1. Department of Plant Ecology and Evolutionary Biology. Utrecht University; P.O.Box 80084, 3508 TB Utrecht, The Netherlands
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      Ellis Hoffland, Department of Soil Science and Plant Nutrition. Wageningen Agricultural Univrsity. P.O.Box 8005, 6700 EC Wageningen. The Netherlands.

  • G. J. NIEMANN,

    Corresponding author
    1. Department of Plant Ecology and Evolutionary Biology. Utrecht University; P.O.Box 80084, 3508 TB Utrecht, The Netherlands
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  • J. A. VAN PELT,

    1. Department of Plant Ecology and Evolutionary Biology. Utrecht University; P.O.Box 80084, 3508 TB Utrecht, The Netherlands
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  • J. B. M. PUREVEEN,

    1. FOM Institute for Atomic and Molecular Physics, P.O.Box 41883. 1009 DB Amsterdam, The Netherlands
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  • G. B. EIJKEL,

    1. FOM Institute for Atomic and Molecular Physics, P.O.Box 41883. 1009 DB Amsterdam, The Netherlands
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  • J. J. BOON,

    1. FOM Institute for Atomic and Molecular Physics, P.O.Box 41883. 1009 DB Amsterdam, The Netherlands
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  • H. LAMBERS

    1. Department of Plant Ecology and Evolutionary Biology. Utrecht University; P.O.Box 80084, 3508 TB Utrecht, The Netherlands
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Gerard J. Niemann, Department of Plant Ecology and Evolutionary Biology, Utrecht University. P.O.Box 80084,3508 TB Utrecht, The Netherlands

ABSTRACT

Plant growth rate has frequently been associated with herbivore defence: a large investment in quantitative defence compounds occurs at the expense of growth. We tested whether such a relationship also holds for growth rate and pathogen resistance. For 15 radish (Raphanus sativus L.) cultivars, we determined the potential growth rate and the resistance to fungal wilt disease caused by Fusarium oxysporum. We subsequently aimed to explain a putative negative relationship between growth rate and resistance based on plant chemical composition. Both growth rate and resistance level varied greatly among cultivars. Moreover, there was a strong negative correlation between growth rate and resistance, i.e. there are costs associated with a high resistance level. Roots of slow-growing, resistant cultivars have a higher biomass density. Using pyrolysis mass spectrometry. we part1y explained variation in both growth rate and resistance in terms of the same change in chemical composition. Leaves of slow-growing, resistant cultivars contained more cell wall material. Surprisingly, roots of slow-growing, highly resistant cultivars contained significantly less cell wall material, and more cytoplasmic elements (proteins). We speculate that this higher protein concentration is related to high construction and turn-over costs and high metabolic activity. The latter in turn is thought to be responsible for a rapid and adequate resistance reaction, in which phenols may be involved.

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