Impact of grafting, salinity and irrigation water composition on eggplant fruit yield and ion relations

Authors: SEMIZ, GULUZAR - University Of Ankara; Suarez, Donald

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 12/18/2019
Citation: Semiz, G.D., Suarez, D.L. 2019. Impact of grafting, salinity and irrigation water composition on eggplant fruit yield and ion relations. Scientific Reports. 9. https://doi.org/10.1038/s41598-019-55841-0.
DOI: https://doi.org/10.1038/s41598-019-55841-0

Interpretive Summary: High value vegetable crops are relatively salt sensitive, thus salinity is often a significant factor impacting yield when these crops are grown in semiarid regions. Grafting has been shown to increase crop yield and improve production under saline conditions but it is not always clear if salt tolerance has been improved. We evaluated fruit production, salt tolerance and ion composition of eggplant cv Angela, both nongrafted and when grafted on tomato cv Maxifort rootstock, at 5 salinity levels and two water composition types. We salinized the irrigation water with either a Na+-Ca2+- Cl- composition typical of coastal Mediterranean ground waters as well as a mixed Na+-Ca2+-SO42- Cl- type water, a composition more typical of interior continental basin ground waters such as those of the Central Valley California, U.S.A. There were no statistically significant differences in the fruit yield relative to the water type, indicating that Cl- ion toxicity is not a major factor in eggplant yield associated with salinity. Grafted eggplant exhibited a large increase in yield both under control and elevated salinity levels relative to nongrafted plants. In addition the salt tolerance (relative yield) of the grafted plants was much greater than that of the nongrafted plants. The electrical conductivity of the saturation extract at which yield is predicted to be reduced by 50% was 4.6 dS m-1 for the grafted plants vs. 1.33 dS m-1 for the nongrafted plants. Eggplant grafted on Maxifort tomato rootstock had significantly lower leaf and fruit Na concentrations as compared to nongrafted eggplant under saline treatments. Relative yield was very well correlated to leaf Na concentrations regardless of grafting status, indicating that Na is the toxic ion responsible for eggplant yield loss under saline conditions. In contrast leaf Cl was not well correlated with relative yield consistent with the fact that there were no significant differences in yield related to water type, both indicating that Cl is not a major factor in eggplant yield loss. Maxifort rootstock imparted cv Angela eggplant with increased salt tolerance, attributed to reduced Na uptake and increased Ca and K uptake. This information is of use to extension specialists evaluating water for crop irrigation as well as plant breeders developing salt tolerant vegetable varieties.

Technical Abstract: Scarcity of fresh water in arid and semi-arid regions means that we must use more saline waters for irrigation and develop tools to improve crop salt tolerance. The objectives of our study were to (1) Evaluate fruit production, salt tolerance and ion composition of eggplant cv Angela, both nongrafted and when grafted on tomato cv Maxifort rootstock and (2) Evaluate eggplant specific toxicity effect of Cl- and Na+ ions under saline conditions. We salinized the irrigation water with either a Na+-Ca2+- Cl- composition typical of coastal Mediterranean ground waters as well as a mixed Na+-Ca2+-SO42- Cl- type water, a composition more typical of interior continental basin ground. For each water type we evaluated 5 different salinity (osmotic) levels of –0.003 (control), –0.15, –0.30, –0.45 and –0.60'MPa. There were no statistically significant differences in the fruit yield relative to the water type, indicating that Cl- ion toxicity is not a major factor in eggplant yield associated with salinity. This conclusion was confirmed by the determination that leaf Cl content was not correlated with relative yield. The electrical conductivity of the saturation extract (ECe) at which yield is predicted to be reduced by 50% was 4.6 dS m-1 for the grafted plants vs. 1.33 dS m-1 for the nongrafted plants. The relative yield was very well correlated to leaf Na concentrations regardless of grafting status, indicating that Na is the toxic ion responsible for eggplant yield loss under saline conditions. The increased salt tolerance of cv Angela eggplant when grafted onto tomato Maxifort rootstock is attributed to a reduced Na uptake and increased Ca and K uptake with Maxifort rootstock.