Tomato seeds (Lycopersicon esculent

Tomato seeds (Lycopersicon esculentum) var. ‘Campbell’ were disinfected with 5% commercial bleach for 1 min then rinsed with sterile distilled water (SDW) and inoculated with bacterial isolates at a concentration of 108 CFU mL− 1 during 30 min. Un-inoculated control seeds were similarly treated with SDW. After inoculation, seeds were sown in trays containing the peat. Fifteen days after germination, 10 plants per replicate were transplanted into plastic bags containing 2/3 peat and 1/ 3 sand. The length of the stem and the number of leaflets were measured weekly and only data for the 5th week were reported. The germination rate was calculated on the 7th day as follow:% germination = (number of germinated seeds / total number of seeds)* 100. Vigor index was determined as germination rate multiplied by stem length measured on the 5th week. The roots were also weighed on the same date; they were carefully removed and rinsed with water to eliminate traces of soil and then weighed to obtain the root fresh weight. Leaf samples were also taken from three plants and the leaf area was determined from 30 leaves using Mesurim software at http://acces. ens-lyon.fr/acces/logiciels/mesurim (J.F. Madre ENS Lyon, France). The amount of chlorophylls a and b was determined from leaves in triplicates according to method of Lichtenthaler (1987). As biochemical parameters associated with growth nitrate reductase activity and proline content were determined in three replicates. Nitrate reductase (NR, EC 1.6.6.1) activity was assayed in leaves of 5 weeks old tomato plants as described in Smaili et al. (2018) by measuring nitrite production in 300 mg of leaves subjected to vacuum infiltration with buffered nitrate solution consisting of 20 mM KNO3, 1% isopropanol, and 100 mM K2HPO4 and adjusted to pH 7.2. Plant tissues were then incubated in the buffer for 1 h at 28 ◦C in the dark. After incubation, the reaction was stopped by the addition of 0.2% sulphanilamide solution prepared in 3 N HCl and 0.02% N-(1-naphthyl) ethylenediamine dichloride. Coloration was allowed to develop during 15 min and the absorbance was determined at 540 nm. NR activity was calculated on the basis of a calibration curve using KNO2 as a standard. The results were expressed as the amount of nitrite synthesized in mmol per gram of fresh weight per hour. Proline was determined from leaves of 5 weeks old tomato plants according to the modified method of Bates et al. (1973). Three hundred mg of leaves were extracted with 3 mL of 40% methanol by heating at 100 ◦C for 45 min. After cooling and centrifugation at 5000 x g for 15 min, 1 mL of the supernatant was added to 1 mL of acetic acid solution containing 25 mg of ninhydrin and 1 mL of a mixture of orthophosphoric acid and 6 M glacial acetic acid (3v/2v). The reaction was heated for 20 min and after cooling, the chromophore was extracted with toluene and warmed to room temperature and then the absorbance was recorded at 528 nm. Proline content was determined using l-proline as a standard.