Halophytic Plant Halostachys belangeriana (Moq.) Botsch as a Source of Plant Growth-Promoting Endophytic Bacteria

Abstract

Halostachys belangeriana (Moq.) Botsch also known as Halostachys caspica C. A. Mey belongs to the Chenopodiaceae family and is distributed in deserts of Asian countries. The plant grows in severe salinity and drought conditions and its survival and growth can be associated with the activity of endophytic bacteria. The objective of our research was to isolate and screen endophytic bacteria from Halostachys belangeriana for plant growth promotion and reveal their plant-beneficial traits. Methods. Halostachys belangeriana (Moq.) Botsch plants were collected from the saline soil of the Kyzylkum desert in Uzbekistan in spring. The endophytic bacteria were isolated from the tissues of plants by cutting the outer sterilized shoots and roots and putting them into the water to let bacteria come from the tissues into the water. The suspension was transferred onto Tryptic Soy Agar to let bacteria grow and form separate colonies. The colonies different in shape and color were used to get pure cultures of bacteria. The bacteria were screened using plant growth-promoting activity in Petri plates by inoculating wheat seeds with the suspension of isolated bacteria. The best plant growth promoters were identified by analyzing their 16S rRNA gene and comparing it with sequences registered in GenBank of NCBI. The strains were tested for wheat growth promotion in a pot experiment and then examined for their plant-benefi cial traits: N2-fixation, phosphates solubilization, production of indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate deaminase (ACC-deaminase), and siderophores. Results. A total of 25 isolates of endophytic bacteria were obtained from the tissues of Halostachys belangeriana (Moq.) Botsch. Due to the high efficiency of isolates SSU-4, SSU-7, SSU-16, SSU-18, and SSU-21 in the stimulation of wheat shoot and root growth, they were chosen for identification and (OK559720), Bacillus endophyticus SSU-7 (OK559721), Bacillus subtilis SSU-16 (OK559722), Isoptericola halotolerans SSU-18 (OK559723) and Pseudomonas kilonensis SSU-21 (OK559724), respectively. The single inoculation of seeds with tested strains increased the root and shoot length and plant fresh weight. The coinoculation of seeds with a mixture of five strains resulted in an even more increase in plant growth parameters. It was revealed that the tested strains had at least two plant-beneficial properties. The strains B. pumilus SSU-4 and P. kilonensis SSU-21 had the ability for nitrogen fixation. All strains produced IAA; however, the most active IAA producer was P. kilonensis SSU-21. Three of five strains had phosphates solubilization ability and produced ACC-deaminase and siderophores. The strains B. pumilus SSU-4 and P. kilonensis SSU-21 possessed four of five tested plant-beneficial properties. The strains B. endophyticus SSU-7 and I. halotolerans SSU-18 had three of five tested plant-beneficial traits, and B. subtilis SSU-16 could just produce IAA and ACC-deaminase. Conclusions. This is the first report about the isolation of plant growth-promoting endophytic bacteria from the desert halophytic plant Halostachys belangeriana (Moq.) Botsch. The most efficient plant growth-promoting strains were: B. pumilus SSU-4, B. endophyticus SSU-7, B. subtilis SSU-16, I. halotolerans SSU-18, and P. kilonensis SSU-21. After field experiments, these strains can be suggested for use as bioinoculants improving plants growth.