Do rootstock-scion combinations and irrigation water salinity affect the growth and yield of grafted tomatoes under root-restricted conditions?

The experiment evaluated the impact of several commercial rootstocks on the growth and yield of a selected tomato cultivar under restricted volume conditions. The experiment included six different rootstocks and a single tomato cultivar (<italic>Solanum lycopersicum</italic> cv. Izmir). The respective rootstock-scion combination and self-grafted tomato plants were tested in a randomized complete block design. The plants, transplanted into 5 L plastic pots, were irrigated daily with equal amounts of a nutrient solution and were subject to two different levels of salinity, 0- or 50-mM NaCl solution, respectively. The relative stem elongation rate and new leaf emergence rate were calculated from day 1 to day 42 after transplanting, and nutrient concentrations of mature leaves were analyzed by the end of this period. Fruits were harvested at full maturity, and Brix (°Bx) and fruit acidity were measured using a digital refractometer. While the Na concentration of mature leaves significantly increased, the rise of salinity in the nutrient solution significantly reduced the plants' relative growth rate, K and P concentration of mature leaves, and the yield of tomato plants. Although the grafted plants demonstrated improved shoot growth and increased new leaf emergence rate, indicating enhanced capabilities to alleviate salinity stress, most of the rootstocks did not contribute to any increase in tomato yield. Since only carefully selected rootstock-scion combinations might contribute to higher yields and better quality, the introduction of new rootstocks should be followed by continuous testing of their compatibility with specific, well-recognized tomato cultivars under diverse growing conditions.