In vegetables, tolerance to drought can be improved by grafting commercial varieties onto drought tolerant rootstocks. Grafting has emerged as a tool that copes with drought stress. In previous results, the A25 pepper rootstock accession showed good tolerance to drought in fruit production terms compared with non-grafted plants and other rootstocks. The aim of this work was to study if short-term exposure to drought in grafted plants using A25 as a rootstock would show tolerance to drought now. To fulfill this objective, some physiological processes involved in roots (rootstock) and leaves (scion) of grafted pepper plants were analyzed. Pepper plants not grafted (A), self-grafted (A/A), and grafted onto a tolerant pepper rootstock A25 (A/A25) were grown under severe water stress induced by PEG addition (-0.55 MPa) or under control conditions for 7 days in hydroponic pure solution. According to our results, water stress severity was alleviated by using the A25 rootstock in grafted plants (A/A25), which indicated that mechanisms stimulated by roots are essential to withstand stress. A/A25 had a bigger root biomass compared with plants A and A/A that resulted in better water absorption, water retention capacity and a sustained CO2 assimilation rate. Consequently, plants A/A25 had a better carbon balance, supported by greater nitrate reductase activity located mainly in leaves. In the non-grafted and self-grafted plants, the photosynthesis rate lowered due to stomatal closure, which limited transpiration. Consequently, part of NO3- uptake was reduced in roots. This condition limited water uptake and CO2 fixation in plants A and A/A under drought stress, and accelerated oxidative damage by producing reactive oxygen species (ROS) and H2O2, which were highest in their leaves, indicating great sensitivity to drought stress and induced membrane lipid peroxidation. However, drought deleterious effects were slightly marked in plants A compared to A/A. To conclude, the A25 rootstock protects the scion against oxidative stress, which is provoked by drought, and shows better C and N balances that enabled the biomass to be maintained under water stress for short-term exposure, with higher yields in the field.

New sources of water stress and salinity tolerances are needed for crops grown in marginal lands. Pepper is considered one of the most important crops in the world. Many varieties belong to the genus Capsicum spp., and display wide variability in tolerance/ sensitivity terms in response to drought and salinity stress. The objective was to screen seven salt/drought-tolerant pepper accessions to breed new cultivars that could overcome abiotic stresses, or be used as new crops in land with water and salinity stress. Fast and effective physiological traits were measured to achieve the objective. The present study showed wide variability of the seven pepper accessions in response to both stresses. Photosynthesis, stomatal conductance and transpiration reduced mainly under salinity due to stomatal and non-stomatal (Na + accumulation) constraints and, to a lesser extent, in the accessions grown under water stress. A positive relationship between CO 2 fixation and fresh weight generation was observed for both stresses. Decreases in Ψ s and Ψ w and increased proline were observed only when accessions were grown under salinity. However, these factors were not enough to alleviate salt effects and an inverse relation was noted between plant salt tolerance and proline accumulation. Under water stress, A31 was the least affected and A34 showed the best tolerance to salinity in terms of photosynthesis and biomass.Additional keywords: osmotic potential; photosynthesis; proline; salinity ions; water potential. Abbreviations used: A N (maximum net CO 2 fixation rate); A N /C i (instantaneous carboxylation efficiency); C i (substomatal CO 2 concentration); DW (dry weight); E (transpiration); ETc (evapotranspiration); FW (fresh weight); g s (stomatal conductance to water vapour); Ψ s (osmotic potential); Ψ w (water potential).

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

In this study, hybrid pepper rootstock NIBER® is tested for its ability to overcome water stress situations under soil conditions. The impact of deficit irrigation (DI) on yield and fruit quality, irrigation water use efficiency is evaluated, and consequently, the agronomic impact of employing water-stress tolerant rootstock is compared to ungrafted pepper plants. For this purpose, plants of the California-type sweet pepper ‘Maestral F1’ grafted onto NIBER® underwent a sustained DI regime during seasons 2018 and 2019 and were compared to their respective controls. Plants were drip-fertirrigated, and volumetric soil water content was continuously monitored by capacitance sensors. Gas exchange and leaf water potential measurements were taken early in the morning and midday 58, 79, and 114 days after transplanting. Plant and fruit dry biomass, marketable quality, blossom-end rot incidence and harvest index were also determined. For consecutive years, our results confirmed that grafting a pepper cultivar onto an appropriate rootstock (NIBER® in this case) as part of a DI strategy can overcome the negative effects of sustained water stress conditions. The plant biomass production and fruit yields of grafted plants were less affected by DI due to less sensitivity to water stress. This can be attributed to a less marked reduction in shoot dry weight in the grafted plants, which allowed greater whole photosynthesis by maintaining sink activity compared to ungrafted plants.

Solanum pimpinellifolium and Solanum lycopersicum var. cerasiforme represent a valuable tool for tomato breeding, particularly for tolerance to abiotic stresses. Water stress and salinity are major constraints to tomato’s cultivation, and for which limited genetic variability has been reported within the cultivated species. We evaluated four accessions of S. pimpinellifolium and four of S. l. var. cerasiforme for their adaptation to water deficit and salinity. The CO2 assimilation rate, stomatal conductance, substomatal CO2 concentration, transpiration rate, and leaf chlorophyll concentration were evaluated, as well as morphological and agronomic traits. The accessions showed a remarkable inter- and intra-species response variability to both stresses. Two S. pimpinellifolium accessions and one S. l. var. cerasiforme showed unaltered physiological parameters, thus indicating a good adaptation to water deficit. Two S. l. var. cerasiforme accessions showed an interesting performance under salt stress, one of which showing also good adaptation to water stress. In general, both stresses showed a negative impact on leaf size and fruit fresh weight, especially in the big-sized fruits. However, flowering, fruit setting and earliness remained unaltered or even improved when compared to control conditions. Stressed plants yielded fruits with higher ° Brix. Response to stresses seemed to be linked to origin environmental conditions, notwithstanding, variability was observed among accessions of the same region.