The endophytic bacteria isolated from elephant grass (Pennisetum purpureum Schumach) promote plant growth and enhance salt tolerance of Hybrid Pennisetum

Abstract

Background: Elephant grass (Pennisetum purpureum Schumach) and Hybrid Pennisetum (Pennisetum americanum × P. purpureum Schumach) are tall, fast-growing perennial C4 bunchgrasses that have been in recent developed as the most appropriate biomass feedstock in many countries for exploring various biofuel products. However, the challenges of increasing plant biomass yield and enhancing their stress tolerance, especially on marginal lands, have been existed for a long while. In the past several years, bacterial endophytes used as bio-fertilizers for improving crop production have offered an opportunity to facilitate high biomass yield of energy crops in a more sustainable manner.Results: A total of 16 endophytic bacteria strains were isolated and purified from the roots of elephant grass, which were classified into four bacterial genera: Sphingomonas, Pantoea, Bacillus, and Enterobacter. Four strains, pp01, pp02, pp04, and pp06, represented four different genera, were then selected and tested in vitro for their plant growth promoting properties, effects on plant growth and salt stress tolerance of Hybrid Pennisetum. The inoculation with these four bacterial mixture demonstrated a significant plant growth promotion for Hybrid Pennisetum from the normal to salt stress conditions at 0, 50, 100, and 200 mM NaCl, respectively. The highest promotion rate for biomass yield was 116.01 and 81.72 % for shoot fresh weight and dry weight, respectively. The bacterial strains tested were shown to solubilize insoluble phosphate, fix nitrogen, produce indole acetic acid and ammonia, but only strains from Sphingomonas, Bacillus, and Enterobacter can produce siderophore. In addition, the endophyte strains tested were all able to successfully colonize the roots of Hybrid Pennisetum, reaching upto 12.12 ± 0.98 CFU g −1 fresh roots at the 3rd day of inoculation. Conclusion:The four endophytic bacteria from elephant grass significantly promoted plant growth and biomass yield, alleviated the harmful effects of salt stress on Hybrid Pennisetum. These bacteria have indicated some unique properties that are very valuable for exploiting bio-inoculants aiding in the efforts to establish a sustainable and largescale feedstock production system for Hybrid Pennisetum, particularly, on the saline marginal lands.

Pseudomonas knackmussiiMLR6, a rhizospheric strain isolated from halophyte, enhances salt tolerance inArabidopsis thaliana

“…Additionally, the MLR6 isolate displayed also indirect plant promotion traits such as NH 3 + and chitinase production. The above-mentioned traits were reported for their role in alleviating salt stress (Goswami et al 2014;Patel et al 2015;Li et al 2016;Sapre et al 2018) and their implication in the plant growth. In our study, plant height and shoot fresh weight decreased in control plants under NaCl stress but A. thaliana inoculation with MLR6 increased significantly the plant growth parameters under normal as well as under saline stress conditions.…”

Improvement Salt Tolerance of Safflower Plants by Endophytic Bacteria

“…In recent years, endophytes have been used as one of the practical measurements to alleviate salt stress and improve plant and yield under saline conditions [52,51,53]. In addition, in our study, the used bacterial isolates have the ability to achieve systemic tolerance via production of ACC (1-amino cyclopropane-1-carboxylase) deaminase which has the ability to reduce the production of stress hormone ethylene.…”

A newly discovered ageing-repair bacterium,Pseudomonas geniculata, isolated from rescuegrass (Bromus cartharticusVahl) promotes the germination and seedling growth of aged seeds

“…When the total number of seedlings was fewer than 10, all seedlings were measured. The germination index (Gi) was estimated as follows (Li et al 2016):…”

“…The most widely studied genera of PGPR are Pseudomonas, Azospirillum, Azotobacter and Bacillus, among others. Due to their highly beneficial effects on the growth and health of host plants, to date, PGPR have been actively applied worldwide as bio-inoculants to facilitate plant growth and alleviate various stresses, such as salinity, drought, and heavy-metal contamination (Li et al 2016). Various PGPR can promote plant growth through a wide variety of mechanisms, such as the production of phytohormones, the use of 1-Aminocyclopropane-1-carboxylate deaminase (ACCD) to lower ethylene levels, the enhancement of antioxidative activities, biological nitrogen fixation, or the up-or down-regulation of stress responsive genes (Carrozzi et al 2012;Liu et al 2012).…”