Agriculture 2022, 12, 183. https://doi.org/10.3390/agriculture12020183 www.mdpi.com/journal/agriculture Article Salt Tolerant Eggplant Rootstocks Modulate Sodium Partitioning in Tomato Scion and Improve Performance under Saline Conditions Satish Kumar Sanwal 1, *, Anita Mann 1 , Arvind Kumar 1 , Hari Kesh 1 , Gurpreet Kaur 1 , Arvind Kumar Rai 1 , Raj Kumar 1 , Parbodh C. Sharma 1 , Ashwani Kumar 1 , Anant Bahadur 2 , Bijendra Singh 2 and Pradeep Kumar 3, * 1 ICAR-Central Soil Salinity Research Institute, Karnal 132001, Haryana, India; anita.mann@icar.gov.in (A.M.); arvind.kumar2@icar.gov.in (A.K.); harikeshkaul55@gmail.com (H.K.); gurpreetkaurcssri@gmail.com (G.K.); ak.rai@icar.gov.in (A.K.R.); rajkumar2@icar.gov.in (R.K.); Parbodh.Chander@icar.gov.in (P.C.S.); Ashwani.Kumar1@icar.gov.in (A.K.) 2 ICAR-Indian Institute of Vegetable Research, Varanasi 221305, Uttar Pradesh, India; anant.bahadur@icar.gov.in (A.B.); bsinghiivr@gmail.com (B.S.) 3 ICAR-Central Arid Zone Research Institute, Jodhpur 342003, Rajasthan, India * Correspondence: satish.sanwal@icar.gov.in (S.K.S.); pradeep.kumar4@icar.gov.in (P.K.) Abstract: Grafting on salt tolerant eggplant rootstocks can be a promising approach for enhancing the salinity tolerance of tomato. In this study, the performance of tomato cv. Kashi Aman grafted on two salt tolerant eggplant rootstocks (IC-111056 and IC-354557) was evaluated against non-grafted control under saline (ECiw 6 and 9 dS m −1 ) and non-saline (ECiw ~1 dS m −1 ) irrigation for 2 years. Grafting improved tomato plant performance under salt stress. Moreover, rootstock IC-111056 outperformed IC-354557. An increase in the average fruit yield of grafted plants com- pared with non-grafted control at 6 and 9 dS m −1 was 24.41% and 55.84%, respectively with root- stock IC-111056 and 20.25% and 49.08%, respectively with IC-354557. Grafted plants maintained a superior water status under saline irrigation, evidenced with the relative water content and chlo- rophyll SPAD index, along with higher proline and antioxidant enzyme activities (superoxide dismutase, catalase, and ascorbate peroxidase). Rootstocks mediated the partitioning of toxic saline ions in the scions by promoting higher Na + accumulation (14% of mean accumulation) in the older leaves and lower (24%) in the younger leaves of grafted plants. This resulted in higher K + /Na + ratios within the younger (active) leaves of the grafted plants. Our study demonstrates that grafting to- mato seedlings on selected salt tolerant eggplant rootstocks is a viable alternative for improving plant physiological status and fruit yield under salt stress, through favorable modulation of salt ion partitioning in the scions. Keywords: tomato grafting; Na + partitioning; salinity tolerance; antioxidant enzymes; fruit yield 1. Introduction Among abiotic stresses, salinity is one of the critical stresses inhibiting plant growth and crop yields. Globally, salt-affected soils represent 7% of the total area, where saline and alkaline soils constitute about more than 1100 million hectares of land [1]. Salinity has affected approximately 20–33% of agricultural land across the world [2]. Soil salinity often occurs concomitantly with saline ground water in arid and semi-arid regions, exacerbating the effect on crop growth. Higher levels of salt in soil reduce the productivity of most of the agricultural crops, including vegetables, with the latter as more salt sensitive. The salinity-induced stress can be triggered by the excessive use of poor-quality ground water for irrigation, along with climate change and excessive Citation: Sanwal, S.K.; Mann, A.; Kumar, A.; Kesh, H.; Kaur, G.; Rai, A.K.; Kumar, R.; Sharma, P.C.; Kumar, A.; Bahadur, A.; Singh, B.; Kumar, P. Salt Tolerant Eggplant Rootstocks Modulate Sodium Partitioning in Tomato Scion and Improve Performance under Saline Conditions. Agriculture 2022, 12, 183. https://doi.org/10.3390/ agriculture12020183 Academic Editor: Yuan Huang Received: 19 December 2021 Accepted: 24 January 2022 Published: 27 January 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and insti- tutional affiliations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/license s/by/4.0/).