Genetic basis of physiological traits related to salt tolerance in tomato, Lycopersicon esculentum Mill

Genetic relationships between salt tolerance and expression of various physiological traits during vegetative growth in tomato, Lycopersicon esculentum Mill., were investigated. Parental, F-1, F-2 and backcross progeny of a cross between a salt tolerant (PI174263) and a salt sensitive tomato cultivar ('UCT5') were evaluated in saline solutions with electrical conductivity of 0.5 (non-stress) and 20 dS/m (salt stress). Absolute growth. relative growth, tissue ion content, leaf solute potential and the rate of ethylene evolution were measured. Growth of both parents nas reduced under salt stress; however, the reduction was significantly less in PI174263 than 'UCT5', suggesting greater salt tolerance of the former. Under salt stress, leaves of PI174263 accumulated significantly less Na+ and Cl- and more Ca2+ than leaves of 'UCT5'. Across parental and progeny generations, growth under salt stress was positively correlated with leaf Ca2+ content and negatively correlated with leaf Na+ content. In contrast, no correlation was observed between growth and either leaf solute potential or the rate of ethylene evolution under salt stress. Generation means analysis indicated that under salt stress both absolute and relative growth and the Na+ and Ca2+ accumulations in the leaf were genetically controlled with additivity being the major genetic component. The results indicated that the inherent genetic capabilities of PI174263 to maintain high tissue Ca2+ levels and to exclude Na+ from the shoot were essential features underlying its adaptation to salt stress and that these features were highly heritable. Thus, tissue ion concentration may be a useful selection criterion when breeding for improved salt tolerance of tomato using progeny derived from PI174263.