Strigolactones influence on tomato water use efficiency under drought

Strigolactones are phytohormones that influence many aspects of plant development and physiology, including stomatal movement under irrigated and drought stress conditions. Plants defective in strigolactone biosynthesis and signalling have higher stomatal conductance, especially when irrigated, and thus are worse than the wt at avoiding drought consequences. Also, treatment with the synthetic strigolactone analogue rac-GR24 decreases stomatal conductance and water loss; and tomato (Solanum lycopersicum L.) scions, in which strigolactone content in the shoot is increased by grafting on strigolactone-defective roots, also show lower stomatal conductance and better drought avoidance (our previous work). However, results obtained so far focussed on the physiological and molecular aspects influenced by strigolactones under drought stress, while no information is available on the yield of the crop, and agronomical water use efficiency. In order to investigate this issue, these parameters are being evaluated under well-watered and drought stress conditions, in self-grafted wild-type and strigolactone-depleted tomato plants. Additionally, hetero-grafted plants (wild-type scions on strigolactone-depleted rootstocks, which leads to higher strigolactones in leaves as mentioned above) and self-grafted, strigolactone-treated plants are used to investigate the potentially positive effects of a moderate excess of hormone on water use efficiency and yield.