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Etude physiologique et biochimique de l’effet de la tétraploïdie sur l’adaptation des agrumes aux contraintes environnementales

Abstract : Environmental stresses (cold, excess light, drought, flooding, nutrient excess or deficiency, etc.) can limit crop growth and production and reduce fruit quality. In citrus farming, scion/rootstock combinations are used to improve fruit crop production and quality and increase tolerance to biotic and abiotic stresses. Recently, it was hypothesized that this stress tolerance could be further improved by using polyploid rootstocks. The aim of this study is to test whether doubled diploid genotypes frequently used as citrus rootstocks can improve the tolerance. Different combinations of genotypes were selected and subjected to various natural or imposed environmental stresses frequently observed in orchards. First, response to total nutrient deficiency was studied in different diploid (2x) and doubled diploid (4x) citrus seedlings: Volkamer lemon (Citrus limonia Osb.), Trifoliate orange  Cleopatra mandarin hybrid (Poncirus trifoliata L. Raf. × Citrus reshni Hort. ex Tan.), Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.), Citrumelo 4475 (Citrus paradisi L. Macf. × Poncirus trifoliata L. Raf.). FlhorAG1 (Poncirus trifoliata + and Willow leaf mandarin), an allotetraploid somatic hybrid, was also included in this study. The behavior of FlhorAG1 was then studied under low natural temperature conditions and controlled light stress, and its response was compared to that of its 2x parents, common mandarin (Citrus deliciosa Ten) and Pomeroy Poncirus (Poncirus trifoliata (L.) Raf.), and their 4x counterparts. Finally, response to seasonal temperature fluctuations was studied in clementine grafted on 2x and 4x Carrizo citrange rootstocks. The genotypes were compared at physiological level by determining net photosynthesis (Pnet), stomatal conductance (Gs), chlorophyll fluorescence (Fv/Fm) and chlorophyll content, and then at biochemical level by assessing the activities of the main antioxidant enzymes (including superoxide dismutase, catalase, and ascorbate peroxidase) and the concentrations of hydrogen peroxide (H2O2), malondialdehyde (MDA), ascorbate and glutathione. Depending on the type of experiment, we also measured electrolyte leakage and glutathione, proline and starch content, as well as changes in size and/or density of various structural (stomata) and ultrastructural (cells, chloroplasts, thylakoids, mitochondria, plastoglobuli and starches) components. Based on the results obtained under nutritional stress conditions, FlhorAG1 was classified as tolerant and 4x Citrumelo 4475, 2x and 4x Volkamer lemon as moderately tolerant. The 2x and 4x Carrizo citrange genotypes, 2x and 4x Poncirus Pomeroy x Cleopatra mandarin, and 2x Citrumelo 4475 were assessed as sensitive. Analysis of leaf ultrastructure in 2x and 4x Citrumelo 4475 and Volkamer lemon confirmed greater tolerance of the 4x genotype to nutrient deficiency. FlhorAG1 showed better tolerance to seasonal temperature variations and light stress than its 2x parents and their 4x counterparts. Even though the 2x and 4x forms of Carrizo citrange genotype showed similar sensitivity to nutritional deficiency conditions, use of the 4x rootstock improved scion tolerance at low temperatures.
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Submitted on : Friday, November 12, 2021 - 6:55:31 PM
Last modification on : Monday, November 15, 2021 - 10:25:11 AM


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  • HAL Id : tel-03427045, version 1



Julie Oustric. Etude physiologique et biochimique de l’effet de la tétraploïdie sur l’adaptation des agrumes aux contraintes environnementales. Sciences agricoles. Université Pascal Paoli, 2017. Français. ⟨NNT : 2017CORT0016⟩. ⟨tel-03427045⟩



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