Rootstock-mediated variation in tomato vegetative growth under drought, salinity and soil impedance stresses

There is increasing interest in using novel rootstocks to confer resistance to abiotic stresses in horticultural species, and to understand the physiological mechanism(s) conferring these responses. The same scion (Solanum lycopersicum ‘Boludo F1’, ‘Monsanto’) was grafted onto 144 different rootstocks: six accessions from S. lycopersicum (‘Cerasiforme’) and S. pimpinellifolium, selected for drought tolerance (sourced from AVRDC); nine introgression lines from S. lycopersicum × S. pennellii and × S. habrochaites, selected for high root/shoot ratio, salinity and drought tolerances (sourced from TGRC); and a population of 129 recombinant inbred lines (RILs) derived from a salt sensitive genotype of S. lycopersicum var. cerasiforme and a salt tolerant line from S. pimpinellifolium L. (sourced from IVIA). Plants were grown in greenhouses in hydroponics (salinity stress) or soil (soil drying or high soil mechanical impedance) for 2-5 weeks (during the vegetative stage), and shoot fresh weight (SFW) was recorded at the end of each experiment. Although rootstock effects on SFW were related for the soil drying and impedance assays, no relation was found between SFW under salinity and SFW under the other stresses. Indeed, the best rootstocks for drought stress were different to those that were the best for salinity and high soil impedance. For each abiotic stress, some graft combinations had higher SFW (up to 90% more) than the self-grafted commercial cultivar ‘Boludo F1’. The search for genetic factors contributing to this variation will be the objective of a future study

The grapevine transcription factor WRKY2 influences the lignin pathway and xylem development in tobacco

International audiencePrevious work has shown that transgenic tobacco plants constitutively over-expressing the Vitis vinifera L. transcription factor VvWRKY2 exhibit reduced susceptibility to necrotrophic fungal pathogens, suggesting that this transcription factor plays a role in grapevine response to phytopathogens. The work presented here characterizes the modifications in cell wall structure observed in the stems and petioles of these transgenic plants. Histochemical stainings of stem and petiole cross-sections using phloroglucinol or Maüle reagents revealed a delay in xylem formation, particularly in the petioles, and differences in lignin composition. Evaluation of lignin quantity and quality showed a decrease in the syringyl/guaiacyl ratio in both stem and petioles. Expression analysis using RT-PCR and potato microarrays showed that tobacco plants over-expressing VvWRKY2 exhibited altered expression of genes involved in lignin biosynthesis pathway and cell wall formation. The ability of VvWRKY2 to activate the promoter of the VvC4H gene, which is involved in the lignin biosynthetic pathway, was confirmed by transient transcriptional activation assays in tobacco protoplasts. Moreover, in situ hybridization revealed that VvWRKY2 is specifically expressed in cells undergoing lignification in young grapevine stems. Together, these results confirm that VvWRKY2 plays a role in regulating lignification in grapevine, possibly in response to biotic or abiotic stresses

The Solanum lycopersicum Zinc Finger2 Cysteine-2/Histidine-2 Repressor-Like Transcription Factor Regulates Development and Tolerance to Salinity in Tomato and Arabidopsis(1[W])

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