Growth enhancement and alleviation of deleterious effects induced by salt stress in Faba Bean (Vicia Faba) by PGPB
The present investigation was led to evaluate the impact of various levels of sodium chloride (NaCl) on Faba Bean plant in the presence or absence of Bacillus megaterium bacteria. Pot experiments were conducted on two varieties of Faba Bean plant under different salinity levels (0, 2,4,6,8 ds/m) with and without B. megaterium. The pots were irrigated with different concentrations of NaCl, each salinity level had both inoculated and non-inoculated B. megaterium. Salt stress in pots without B. megaterium caused reduction in growth parameters (shoot height, number of leaves, fresh and dry weight, root mass…), reduction in yield parameters, increased sodium and chloride percentage in leaves and reduced the absorption of other important chemical elements which indicates the deleterious effects of salinity. Plant-growth-promoting bacteria (PGPB) can improve plant growth, development, and stress adaptation even that the mechanism is still largely un clear. Application of B. megaterium mitigates the effect of sodium chloride stress and improved the growth and yield in the present study. The inoculation with remarkably B. megaterium increased plant height, number of leaves, number of flowers, plant biomass, early flowering, improved chlorophyll content, root system and in contrast, alleviated sodium chloride accumulation in leaves, increased the absorption of K, Ca, P . Inoculated plants with B. megaterium displayed stronger ability to tolerate salt stress than non-inoculated plants. Result revealed that incubation led to higher induction of plant height 39 % at 8ds/m of salinity, the noticed increase in the height of the stem could be due to the positive changes in enzyme activity and growth hormones. The maximum fresh weight was 159.27 g at 8 ds/m in plants with B. megaterium compared to plant without B. megaterium the fresh weight 85.77 at 8 ds/m. The effect of B. megaterium increase Faba Bean root fresh weight 35.99%. In relation to flowering periods, results revealed that salinity slightly reduced the days to flowering in non-inoculated plants, in contrast Vicia Faba inoculated with B. megaterium revealed early flowering by 19 % at 6 ds/m which combined with highest nodule formation 5, pod weight 38.7 g, seed number 27.8, pod number 11.66, seed fresh weight 11.06g and dry weight 1.85g. . Potassium and Calcium content increased by 5% in plants treated with B. megaterium compared to non-inoculated plants. Many studies claimed that salinity negatively affects soil bacterial activity by high osmotic strength and toxic effects by salts, but that salt-tolerant bacteria (B. megaterium) can survive and proliferate in the soil and in the rhizosphere in a harsh environment. The study revealed that the soil salinity could be reduced by using B. megaterium with plants, this led to reduction in about 10% of soil salinity compared to soil without B. megaterium.