Interspecific grafting to enhance physiological resilience to flooding stress in tomato (Solanum lycopersicum L.)

• Grafting onto eggplant rootstock enhanced flooding tolerance of tomato plants.
• Plants grafted onto rootstocks had higher PN, gs and chlorophyll fluorescence than the ungrafted/self-grafted plants under flooding.
• The rootstock grafting improved sugar and starch contents and fruit yield of tomato plants under flooding.
• The graft combination of AR/AN displayed best response.

Tomato (Solanum lycopersicum L.) is highly susceptible to flooding stress. In order to improve its flooding tolerance, the study was conducted to determine the effect of grafting tomato plants (cv. Arka Rakshak, AR) onto different eggplant (Solanum melongena L.) rootstocks [BPLH-1, Arka Neelkanth (AN), Mattu Gulla (MG) and Arka Keshav (AK)] against flooding during rainy season (July-September). The tomato plants were subjected to flooding stress at flowering stage for 6 days by submerging in a tank with the water level at 2.0 cm above the soil surface in the pots. The gas exchange parameters, photosynthesis rate (PN), stomatal conductance (gs) and internal CO2 concentration (Ci), chlorophyll fluorescence, leaf water potential (ψL) and chlorophyll content showed a lesser decline in eggplant rootstock grafted plants as compared with self-grafted and ungrafted plants. In general, eggplant rootstock grafted plants exhibited better survival, enhanced physiological adaptation and improved fruit yield over the self-grafted and ungrafted plants under flooding. Between the rootstock grafted plants, the graft combinations AR/AN and AR/BPLH-1 were more efficient in sustaining the above attributes. Flooding conditions favoured accumulation of total sugar, reducing sugar, sucrose and individual sugar like sucrose and glucose in the leaves of grafted and ungrafted plants and the eggplant rootstocks grafted plants under flooding conditions accumulated higher sugars and starch as compared with self-grafted and ungrafted plants. Among the grafts, AR/AN showed in high sugar and starch accumulation under flooding. The recovery was better in eggplant rootstock grafted plants as reflected by recovery of PN, gs and ψL, and decline in sugar and starch levels. The study indicated that the eggplant rootstock grafting is of great relevance in improving physiological tolerance in tomato under flooding. Among the eggplant rootstock grafted tomato plants, AR/AN showed better survival and plant yield after experiencing flooding.