Genetics of physiological and agronomical traits linked to salinity tolerance in tomato

Improvement of tomato (Lycopersicon esculentum L.) for growth in saline soils is a major goal of tomato breeders. The aim of this study was to identify the genetic combining ability and genetics of salinity tolerance in tomato. Plant materials were grown under normal (NG) and salinity stress (SSG) conditions. Results showed that the genetic controlling mechanism of salinity-related traits and fruit weight is complex and that all genetic components of additive, non-additive and maternal are involved. The nature of gene action for fruit weight and salinity-related traits was significantly affected by salinity stress. Dominance and additive gene action were predominant under NG and SSG, respectively. Under NG, the best general combiner parent for fruit weight was P3 (salt-tolerant with moderate fruit yield). Under SSG, P1 (highly salt-tolerant with low fruit yield) was the best general combiner parent for fruit weight and exhibited high genetic combining ability for K+/Na+, lipoxygenase activity, proline, relative water content, total carbohydrate and cell membrane stability. With the high frequency of genes effective in salt tolerance, the P1 parent appeared as the best specific mating partner with other parents under SSG. Simultaneous selection for fruit weight and surrogate traits (cell membrane stability, proline and relative water content) in a population derived from the P1 x P5 (susceptible with high fruit yield) cross could result in a salt-tolerant tomato genotype.