Increasing Triticum aestivum (var. Narin) yield with bacteria isolated from rhizosphere of Seidlitzea rosmarinus, Atriplex lentiformis and Halostachys belangeriana under salinity stress

Increasing world population, along with climate change and environmental stresses, has posed a serious challenge to adequate food supply. Salinity is one of the most important stresses affecting the reduction of agricultural products. In recent years, the use of new strategies for sustainable production of food products under salinity stress has been considered, including plant growth promoting rhizosphere bacteria. Due to the strategic importance of wheat in food security, this study was designed and conducted with the aim of increasing the salinity resistance of wheat (Var. Narin) using plant growth promoting rhizosphere bacteria isolated from the rhizosphere of several halophyte plants in Yazd province.

Plant growth promoting traits such as ability to produce auxin, siderophore, hydrogen cyanide, and phosphate solubility and salinity resistance of isolated bacteria from rhizosphere of halophyte plants (Atriplex lentiformis, Seidlitzea rosmarinus, Halostachys belangeriana and Tamarix ramossima) in their habitats in Chahafzal in Yazd Province were investigated. Then, wheat seeds were inoculated with the best three bacteria in terms of plant growth-promoting traits and salinity resistance, and then was irrigated with water with salinities of 4, 8 and 16 ds m-1. After the growth period, total biomass, seed weight and spike components and seed amylose and amylopectin were measured.

The studied bacteria including Bacillus safensis, B. pumilus and Zhihengliuella halotolerans had the ability to produce auxin, siderophore, hydrogen cyanide, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC deaminase) and phosphate solubility. The highest amount of auxin production was measured in B. safensis (29.72 μg ml–1) and the highest amount of hydrogen cyanide production and phosphate solubility was in Z. halotolerans. The highest amount of ACC deaminase was measured in B. pumilus (8 μmol of α-ketobutyrate h–1 mg–1 protein). The results showed that increasing salinity levels decreased spike length, spike weight, number of spikelets, number of florets, number of seed, seed weight, amylose and amylopectin content of seeds. The length and weight of spikes at salinity of 16 dS  m–1 decreased by 36% and 18%, respectively, compared to the non-salinity control. Instead, B. safensis, Z. halotolerans and B. pumilus caused an average increase of 35, 22, and 17.6% of the spike length at salinity stress levels (4, 8, and 16 dS m-1), respectively, compared to the uninoculated controls. Also, B. safensis, B. pumilus and Z. halotolerans bacteria caused an average increase of 69, 43 and 30% of spike weight in salinity stress levels compared to the uninoculated control, respectively. The number of spikelets and number of florets at salinity of 16 dS m-1 decreased by 27 and 43%, respectively, compared to the non-salinity control. In all salinity stress levels, B. safensis, Z. halotolerans and B. pumilus caused an average increase of 48, 26 and 13% of total biomass, and an average increase of 59, 23 and 7% of seed weight in all salinity stress levels compared to control. B. safensis, more than the other two bacteria, improved the total biomass and seed weight of wheat.

Plant growth promoting rhizosphere bacteria in this experiment significantly improved the resistance of wheat to salinity stress. Comparison between the studied bacteria showed that B. safensis had a greater effect on the promotion of total biomass, yield and all traits of the studied components than B. pumilus and Z. halotolerans, due to the superiority of B. safensis in auxin production and increasing the ratio of potassium to sodium. It can be concluded that the auxin and the potassium are of key importance in increasing the reproductive performance of Narin cultivar. It is also concluded that the rhizosphere of halophytic rangeland plants can be a good source for the isolation of salinity-resistant bacteria to improve the resistance of wheat plants to salinity.