Changes in yield, growth and photosynthesis in a drought-adapted Mediterranean tomato landrace (Solanum lycopersicum 'Ramellet') when grafted onto commercial rootstocks and Solanum pimpinellifolium

Although grafting has become an effective tool to enhance many traits in horticultural crops, its role in improving the performance of local landraces is yet to be proven. The aim of this work was to assess the performance of the 'Ramellet' tomato, a landrace from the Balearic Islands, when grafted onto different rootstocks. For this purpose, two 'Ramellet' genotypes were grafted on two commercial ('Beaufort' and 'Maxifort') and a wild (Solanum pimpinellifolium) tomato rootstock species, and cultivated in greenhouse under commercial conditions. Plant yield, morphology and photosynthetic traits were measured in all combinations, with non-grafted and self-grafted 'Ramellet' plants used as controls. A significant effect of the rootstock on key parameters related to yield, plant growth and photosynthesis was found in both 'Ramellet' genotypes. Stomatal conductance increased, resulting in a decreased water-use efficiency in both genotypes grafted on the commercial rootstocks. Oppositely, when grafted on S. pimpinellifolium, stomatal conductance decreased and water-use efficiency increased in one of the 'Ramellet' genotypes. Remarkably, there was a significant correlation between water-use efficiency, plant growth and yield. Overall, the results highlight the potential of grafting to alter several physiological traits of local landraces and to provide new clues towards advancing our understanding in the underlying determinants of water-use efficiency and plant yield.