Response of some tomato cultivars , beeding lines and their hybrid combinations to salinity tolerance

Four commercial tomato cultivars (Imberial, Pakmore VF, Queen and Strain-B), two salinity tolerant breeding lines (BL 1076 and BL 1239, from Asian Vegetables Research and Development Center) and all their fifteen possible hybrid combinations in one direction were used in this study to evaluate their salinity tolerance and select starting materials for a salinity tolerance breeding program in tomato. Four weeks old seedlings were transplanted into the soil under greenhouse conditions. Six water salinity levels (1.2, 2.4, 4.8, 7.2, 9.6 and 12.0 dS m -1 ) were imposed through a drip irrigation system. Plant height, stem thickness, leaf dry matter content, average fruit weight, average fruit number, total yield, and leaf concentrations of Na + , Cl , Ca ++ and K + were measured. All vegetative and fruit traits decreased significantly with increasing salinity levels, starting at 4.8 dS m -1 . Reduction in yield and average fruit weight were more than 50% for most genotypes at 12.0 dS m -1 level. Increasing salinity levels led to raising Na + and Cl , and diminishing Ca ++ and K + . Significant differences among genetic populations were detected in all traits suggesting that these traits could be taken into account when selecting for salt tolerant tomato genotypes. Based on the general performances of the parental and their F1 hybrid genotypes under salinity levels, the additive gene effects contributed to the genetic variability more than the nonadditive gene effects, since traits values of most F1 hybrids were reported to be around their respective mid-parental values. The two cultivars Pakmore VF and Strain-B J.Agric.&Env.Sci.Alex.Univ.,Egypt Vol.6 (2)2007 2 reflected good performances for most studied traits under different salinity levels and could be selected as recurrent parents (female) in back-cross breeding programs. The breeding line BL 1076 exhibited the highest salinity tolerance by most traits and could be considered as a donor (male) parent in such breeding programs. The best hybrid combinations under salt stress conditions of this study appeared to be the two crosses Pakmore VF × BL 1076 and Strain-B × BL 1076. The mentioned parents and hybrid combination will be utilized as suitable genetic materials in a tomato breeding program for salinity tolerance.