Induction of Salt Tolerant Mutants in Rhizobia Infected Pisum Sativum 1.

Six Rhizobium strains were used in this study. These strains were treated with different concentrations of sea water to be induce salt tolerant mutants. Five isolates were isolated from each concentration and then they were evaluated for IAA production. Six Rhizobium strains appeared high level of resistance against erythromycin-ethlsuccinate (Eryth) than the other antibiotics. Whereas, RL-2074 and RL-3841 showed resistance to all antibiotics used in this study. On the other hand, the growth of RL-4406 strain was inhibited by all the antibiotics, except for, erythromycin-ethlsuccinate (Eryth). Rhizobium strains; RL- 2070, RL4406, RL-207 (except for Eryth resistance) and RL-3841 (except for Cm resistance) were eliminated all antibiotic resistance genes at 37°C. On the other hand, When grown in saline medium all cured strains lost their ability to grow on saline stress, except for, the cured strains RL-4406 and RL-207 which lost their resistance to Erth , as well as, RL-3841 which didnʹt lost the resistance to Cm. However, RL-4044 strain harboring resistance genes to antibiotics appeared high stable at elevated temperature and salt stress. All Rhizobium mutants of RL-2074, RL-3841, RL-4406, RL-4404 and RL-2070 (except for SWT12, SWT17) showed significant increase in IAA produced in complete medium above the parental strains. On the other hand, all isolates resulted from RL-2070 appeared significant increase in IAA produced in complete and minimal media above the parental strains. All biofertilizer inoculants appeared significant increase in nodulation parameters above uninoculated plants. All Rhizobium inoculants induced significant increase in nodule dry weight and nodule number above uninoculated plants grown in normal and salinity soil. All biofertilizer inoculants induced significant increase in root dry weight, shoot dry weight at 45 and 90 days plant-old over uninoculated plants. Soil type was significantly affected on shoot dry weight at 45 and 90 days plant-old. Furthermore, biofertilization appeared the same effect on all growth parameters (shoot dry weight at 45 and 90 days plant-old and root dry weight). Although, the interaction between soil type and biofertilization revealed significant effect on root and shoot dry weight at 45 and 90 days plant-old. Significant increase was obtained in seeds dry weight / pod in salinity soil above that in normal soil. This indicated that salt tolerant mutants reduced the effect of salinity on yield components. Some of Rhizobium inoculants (RL-2074, SWTb RL-3841, SWT6, RL-4404, SWT11, RL-2070 and SWT21) induced significant increase in seeds number, number of pods /plant and seeds dry weight per plant above uninoculated ones among two soil types. All biofertilizers induced significant increase in Chl.a, Chl b and total Chl above uninoculated plants in both soil types above uninoculated plants. The interaction between the type of soil and biofertilization, as well as, biofertilizers was significantly affected on pigment concentrations (chlorophyll a,chlorophyll b and total chlorophyll). The results indicated that biofertilization reduced the severe effects of salinity .