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.
Highlights
Semiarid regions of the world have a scarcity of good-quality water
Assaha et al.[11] measured a 49% decrease in vegetative growth when eggplant was irrigated for 14 d with 50 mM NaCl, Heuer et al.[12] in a field experiment determined that fruit yield decreased above electrical conductivity of the saturation extract (ECe) = 1.1 dS m−1
In our experiment, the positive effect induced by grafting tomato rootstock on eggplant fruit salt tolerance increased with the level of salt stress
Summary
Semiarid regions of the world have a scarcity of good-quality water. Competitive demand for fresh water among urban, industrial, and agricultural sectors has led researchers to focus on using marginal waters for agricultural production[1]. A large percentage of salinity studies on horticultural or agronomic crops use NaCl as the sole salinizing agent The use of these single salt salinizing compositions may limit the extent to which the results can transferred to field conditions, especially if the salinity damage is caused by specific toxic ions rather than osmotic effects. Earlier studies on tomato have found no significant effects comparing self-grafted and nongrafted rootstock of tomato indicating that grafting per se had no impact on fruit yield[9,15], or qualitative fruit parameters and measured fruit ion composition[15]. The effects of salt ion composition on plant salt tolerance are important for improved prediction of crop response to salinity under field conditions and for identifying specific ion toxicity for future salt tolerance breeding
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