Publications des agents du Cirad


Identification de déterminants physiologiques et moléculaires de la tolérance à la contrainte saline et au déficit hydrique de porte-greffes autotétraploïdes d'agrumes

Allario T.. 2009. Corte : Université de Corse, 291 p.. Thèse de doctorat -- Biochimie et biologie moléculaire.

Today, the sustainability of the citrus industry is threatened by the effects of global warming in many geographical semi-arid areas. Many intra-and interspecific crosses between Poncirus, Fortunella and Citrus genera allowed developing new rootstock (RT) increasingly resistant to these new constraints. Citrus spontaneously generate embryos trough partial apomixis that are autotetraploids (4X). Does the use of 4X plants as RT be an alternative to the use of RT designed through breeding? 4X genotypes were shown to be more tolerant to salt stress than their diploids (2X). However, the higher tolerance of 4X vs 2X plants has demonstrated to be dependent on water availability. Rangpur lime (RL), a RT known for its tolerance to water deficit, was chosen as the experimental model plant. 4XRL has a specific morphology and anatomy that could make it more tolerant to abiotic stresses than 2XRL. Transcriptome analysis by DNA microarray and qRT-PCR on leaves has revealed little change in gene expression between 4XRL and 2XRL, suggesting that their phenotypic differences could be more the result of a gene dosage compensation than epigenetic modifications. Stomatal conductance (gs) was lower for 4XRL than for 2XRL, as well for varieties grafted on 4XRL compared to those grafted on 2XRL. Transcriptome studies of the Valencia delta orange grafted on 4XRL and 2XRL revealed many genes involved in water deficit tolerance which were constitutively overexpressed in 4XRL roots. As well, 4XRL RT was more tolerant to water deficit than 2XRL. Abscisic acid contents measured in leaves of the scion and in 4XRL roots were higher than for 2XRL in control condition, which may explain the lower gs values observed in plants grafted on 4XRL. Decreasing in gs of varieties grafted on 4XRL, by limiting the transpiration stream, could limit water absorption and save water from the substrate when occurs a prolonged drought.

Mots-clés : agrume; poncirus trifoliata; fortunella; citrus; tétraploïdie; tolérance au sel; résistance à la sécheresse; porte greffe; espagne; corse; france; Épigénétique; autotétraploïde

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