Grafting raises the salt tolerance of tomato through limiting the transport of sodium and chloride to the shoot

Abstract

With the aim of determining whether grafting could improve salinity tolerance of tomato (Lycopersicon esculentum Mill.), and what characteristics of the rootstock were required to increase the salt tolerance of the shoot, a commercial tomato hybrid (cv. Jaguar) was grafted onto the roots of several tomato genotypes with different potentials to exclude saline ions. The rootstock effect was assessed by growing plants at different NaCl concentrations (0, 25, 50, and 75 mM NaCl) under greenhouse conditions, and by determining the fruit yield and the leaf physiological changes induced by the rootstock after 60 d and 90 d of salt treatment. The grafting process itself did not affect the fruit yield, as non-grafted plants of cv. Jaguar and those grafted onto their own root showed the same yield over time under non-saline conditions. However, grafting raised fruit yield in Jaguar on most rootstocks, although the positive effect induced by the rootstock was lower at 25 mM NaCl than at 50 and 75 mM NaCl. At these higher levels, the plants grafted onto Radja, Pera and the hybrid VolgogradskijxPera increased their yields by approximately 80%, with respect to the Jaguar plants. The tolerance induced by the rootstock in the shoot was related to ionic rather than osmotic stress caused by salinity, as the differential fruit yield responses among graft combinations were mainly related to the different abilities of rootstocks to regulate the transport of saline ions. This was corroborated by the high negative correlation found between fruit yield and the leaf Na(+) or Cl(-) concentrations in salt-treated plants after 90 d of salt treatment. In conclusion, grafting provides an alternative way to enhance salt tolerance, determined as fruit yield, in the tomato, and evidence is reported that the rootstock is able to reduce ionic stress.

Differences in Root Growth and Permeability in the Grafted Combinations of Dutch Tomato Cultivars (Starbuck and Maxifort) and Japanese Cultivars (Reiyo, Receive, and Magnet)

“…In particular, increased salinity tolerance improves fruit yield of grafted tomato [8] [14]. Higher yield of grafted plants has been also observed in watermelon (Citrullus lanatus) [15] and in melon (Cucumismelo) [16] [17].…”

“…Grafting is widely established in agriculture and provides practical advantages for vegetable production by increasing resistance to soilborne pathogens [1]- [4], tolerance to low root-zone temperatures [5]- [7], salinity tolerance [8]- [10], and endogenous hormone production [11]- [13]. In particular, increased salinity tolerance improves fruit yield of grafted tomato [8] [14].…”

Salt-tolerant rootstock increases yield of pepper under salinity through maintenance of photosynthetic performance and sinks strength

“…Tomato and melon are the two commonest herbaceous species in which the grafting practice has been efficiently applied to obtain salt-tolerant plants (Estañ et al, 2005, Edelstein et al, 2011, Orsini et al, 2013. In melon, the favorable effects of grafting on plant growth cannot be ascribed to a more efficient exclusion of Na + or enhanced nutrient uptake but they were associated with a more efficient control of stomatal functions (changes in stomatal index and water relations), which may indicate that the rootstock may alter hormonal signalling between root and shoot (Orsini et al, 2013).…”

Some rootstocks improve pepper tolerance to mild salinity through ionic regulation

“…This increased tolerance of grafted plants is generally associated with their capacity to exclude or retain and/or accumulate toxic ions, Na + and Cl -in rootstock roots, thus limiting their transport to leaves rather than through the synthesis of osmotically active metabolites or the induction of antioxidant systems [6][7][8].…”