The Effect of Inoculation of Growth-Promoting Bacteria Enterobacter sp. S16-3 on the Morpho-Physiological Traits of Rapeseed under Drought Stress

Rapeseed is the third source of edible oil production, however, its yield is strongly affected by drought. As an approach to mitigate the effects of stress, growth promoting bacteria (PGPBs) have been considered, which have the ability to increase tolerance to abiotic stresses, to provide nutrients, and to synthesize growth regulators. Giving the positive impact of PGPBs in improving plant growth during drought, this study was conducted with the aim of investigating the effect of Enterobacter sp. S16-3, a growth-promoting bacterium, on rapeseed traits under drought stress.

The effect of the growth-stimulating bacteria Enterobacter sp. S16-3 on the morpho-physiological traits of rapeseed cultivar Okapi (tolerant to drought) under drought stress was investigated as a factorial experiment based on a randomized complete block design in 3 replications in greenhouse conditions. The treatment combinations included irrigation treatment (normal irrigation and water shortage stress-60% of field capacity) and bacteria treatment (Enterobacter sp. S16-3 and control). Drought treatment was started four weeks after germination and applied for two weeks, and then morphological, physiological and biochemical traits were measured.

Drought stress causes of decrease in root length (35%), stem weight (27%), relative water content (32%), protein content (28%), SOD enzyme activity (69%), CAT enzyme activity (51%), chlorophyll (28%) and carotenoid (25%), as well as an increase in electrolyte leakage (42%) and proline concentration (30%). Bacterial treatment, in turn, significantly improved the morphological, physiological and biochemical traits of rapeseed when compared to drought stress. It led to an increase of 24% in root length, 25% in stem weight, 28% in relative water content, 21% in protein content, 22% in SOD enzyme activity, 29% in CAT enzyme activity, 26% chlorophyll, and 23% carotenoids as well as a decrease of 23% in electrolyte leakage and 18% in proline concentration.

Although drought stress had significant negative effects on morphological, biochemical, and physiological traits of rapeseed; however, the bacterial treatment was able to significantly reduce these negative effects. Therefore, it seems that the bacterial treatment of Enterobacter sp. S16-3 is an efficient approach in mitigating the impact of drought through the positive adjustment of rapeseed morpho-physiological traits.