Genetic Basis of Physiological Traits Related to Salt Tolerance in Tomato

Abstract

Genetic relationships between salt tolerance and expression of various physiological traits during vegetative growth in tomato were investigated. Parental, F1, F2, and backcross progeny of a cross between a salt tolerant (PI174263) and a salt sensitive cultivar (UCT5) were evaluated in saline solutions with electrical conductivity of 0.5 (non-stress) and 20 dS·m–1 (salt-stress). Absolute growth, relative growth, tissue ion content, leaf solute potential and the rate of ethylene evolution by leaf petioles were measured. Growth of both parents were reduced under stress, however, the reduction was significantly less in PI174263 than UCT5 suggesting greater salt tolerance of the former. Under salt-stress, PI174263 accumulated in the leaf significantly less Na+ and Cl– and more Ca2+ than UCT5. The F1 hybrid performed intermediate relative to parents and the backcross populations approached recurrent parents in both growth response and ion accumulation. In all generations, leaf solute potential decreased and the rate of ethylene evolution increased under salt-stress, however, there were little or no differences among generations under either treatment. Across generations growth under salt-stress was positively correlated with Ca2+ and negatively correlated with Na+ accumulation in the leaf. In contrast, growth was not correlated with either leaf solute potential or the rate of ethylene evolution. Generation means analysis indicated that Na+ and Ca2+ accumulations were genetically controlled with additivity being the major genetic components. The results indicated that the inherent genetic capabilities of PI174263 to maintain high tissue Ca2+ levels and to exclude Na+ from shoot were essential features underlying its adaptation to salinity. Thus, tissue ion concentration may be a useful selection criterion when breeding for improved salt tolerance of tomato using progeny derived from PI174263.