Genetic analysis of salt tolerance during vegetative growth in tomato, Lycopersicon esculentum Mill

Breeding for salt tolerance in tomato has been impeded by insufficient knowledge of the genetic control of tolerance. The genetic basis of salt tolerance during vegetative growth was investigated by growing a salt-tolerant (PI174263) and a salt-sensitive tomato cultivar (UCT5) and their F-1, F-2 and backcross progeny in saline solutions with electrical conductivity of 0.5 (control) and 20 dS/m (salt-stress). The relative salt-tolerance of each generation was determined as the percentage of growth (i.e. dry matter production) under salt-stress relative to growth under control conditions. In all generations, shoot growth was significantly reduced by salt stress. The reduction was largest in UCT5 (56.1%) and smallest in the F-1 (27.4%), followed by PI174263 (32.3%). Analysis of the absolute and relative growth under salt-stress indicated that genes contributing to vigour might be different from genes conferring tolerance. Generation means analyses of the absolute and relative growth indicated that the majority of the genetic variation among generations were due to simple (additive and dominance) genetic effects; nonallelic interactions, although significant, were far less important. Partitioning of the total genetic variance by weighted least-square regression analysis and variance component analysis indicated that 88% or more of the variation was due to additive genetic effects. A moderate estimate of narrow sense heritability (0.49 +/- 0.09) was obtained for shoot DW under salt-stress treatment. The results indicate that tomato salt-tolerance during vegetative growth can be improved by breeding and selection.