Efficient somatic embryogenesis from meristematic explants in grapevine (Vitis vinifera L.) cv. Chardonnay: an improved protocol

International audienceSomatic embryogenesis (SE) has great importance for propagation and transformation of woody perennial plants. In Vitis vinifera L., the most cultivated grape species, somatic embryos are generally obtained from floral organs (stamens, ovaries, whole flowers) not easily available. Moreover, the efficiency of SE induction from reproductive organs greatly depends on the physiological state of explants which is hardly controlled. We report here on a culture system for the efficient and reproducible induction of SE and the production of good quality embryos, based on the use of nodal explants excised from in vitro grown plantlets easily obtained all year round. This method involves a first culture step on a callus inducing medium (CIM) containing unusually elevated concentrations of auxin and cytokinin. SE efficiencies from 10.3 to 20.2 % were reproducibly attained with a combination of 18 μM of 2,4-dichlorophenoxyacetic acid (2,4-D) and 9 μM of 6-benzylaminopurine (BAP) in CIM. Callus formation and embryogenesis induction were preferentially observed in the bud region. Moreover, we showed that internodal stem segments, petioles and leaf fragments were not amenable to SE under the same conditions, strongly suggesting that axillary meristems are involved in the embryogenic response. In addition, we verified that high concentrations of 2,4-D and BAP in CIM did not affect the viability of embryos further generated, nor hamper their regeneration into whole plants

Reponse stomatique du Pin maritime (Pinus pinaster Ait.) a la secheresse : examen de quelques donnees experimentales a partir des hypotheses de controle direct et de retrocontrole de la conductance foliaire par la secheresse

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Genetic control of organogenesis in cotyledons of sunflower (Helianthus annuus)

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Arbuscular mycorrhizal symbiosis stimulates key genes of the phenylpropanoid biosynthesis and stilbenoid production in grapevine leaves in response to downy mildew and grey mould infection

International audienceGrapevine (Vitis spp) is susceptible to serious fungal diseases usually controlled by chemical treatments. Arbuscular mycorrhizal fungi (AMF) are obligate plant symbionts which can stimulate plant defences. We investigated the effect of mycorrhization on grapevine stilbenoid defences. Vitis vinifera cvs Chasselas, Pinot noir and the interspecific hybrid Divico, on the rootstock 41B, were mycorrhized with Rhizophagus irregularis before leaf infection by Plasmopara viticola or Botrytis cinerea. Gene expression analysis showed an up-regulation of PAL, STS, and ROMT, involved in the stilbenoid biosynthesis pathway, in plant leaves, 48 h after pathogen inoculation. This defense response could be potentiated under AMF colonization, with an intensity level depending on the gene, the plant cultivar and/or the pathogen. We also showed that higher amounts of active forms of stilbenoids (i.e trans-form of resveratrol, ε- and δ-viniferins and pterostilbene) were produced in mycorrhized plants of the three genotypes in comparison with non-mycorrhized ones, 10 days post-inoculation with either pathogen. These results support the hypothesis that AMF root colonization enhances defence reactions against a biotrophic and a necrotrophic pathogen, in the aerial parts of grapevine