Potential use of endophytic and rhizosheath bacteria from the desert plant Stipagrostis pennata as biostimulant against drought in wheat cultivars

Abstract

The use of bacteria associated with desert plants seems to have a higher potential to alleviate the negative effects of drought stress on water deficit-stressed non-desert plants. The aim of this study was to investigate the potential effect of superior endophytic (E1) and rhizosheath (R11) bacterial strains (B0-control, E1, R11 and E1 + R11), selected based on their tolerance to drought stress and plant growth-promoting (PGP) traits, from the root and rhizosheath of Stipagrostis pennata, a pioneer plant species in the desert, on growth indices (morphological, biophysiological and nutritional responses) of two wheat cultivars (Sirvan, resistant to drought, and Sivand, sensitive to drought) under water-deficit stress conditions (50–55% FC, water deficit stress and 80–88% FC, non-stress). This evaluation was carried out in the form of a completely randomized design in factorial arrangement with three replications under greenhouse conditions. The results showed that with the application of water-deficit stress, wheat growth indices decreased in both cultivars, but this decrease was more in Sivand cultivar. However, with the use of superior endophytic (E1) and rhizosheath (R11) bacterial strains and a mixture of these two strains with a greater effect, the negative impact of water-deficit stress on the growth indices of two cultivars (an increase in plant height by 27%, in root length by 27%, in shoot dry weight by 56%, in root dry weight by 50%, in chlorophyll index by 30%, in superoxide dismutase activity by 8% and in the concentration of shoot N, P and K by 30%, 56% and 31%, respectively, and a decrease in proline concentration by 59%) was alleviated. Bacterial performance also was variable depending on stress level and cultivar, as the effect of these isolates on Sirvan cultivar was more than Sivand cultivar. This can be a challenge for producing biofertilizers for cultivars whose tolerance to drought is unknown. This limitation can probably be managed by developing biofertilizers composed of different bacterial strains containing a wide range of PGP traits and compatible with different plant cultivars. Based on 16S rRNA sequence analysis, E1 and R11 isolates were identified as Pseudomonas sp. and Pantoea agglomerans, respectively. In general, this study showed that the rhizosheath and endosphere of the desert plant S. pennata can be a suitable source for isolating drought-resistant bacteria with multiple PGP traits. These bacteria can also play an important role in promoting the tolerance of non-desert plants (e.g., wheat) to drought and can be used as biofertilizers to increase the growth of the plants in arid and semi-arid regions after their field assays. The results of this study also emphasize on considering the best bacterial strain-wheat cultivar-stress level combination to increase wheat yield.