Endophytic Strain Bacillus subtilis 26D Increases Levels of Phytohormones and Repairs Growth of Potato Plants after Colorado Potato Beetle Damage

Abstract

Plant damage caused by defoliating insects has a long-term negative effect on plant growth and productivity. Consequently, the restoration of plant growth after exposure to pathogens or pests is the main indicator of the effectiveness of the implemented defense reactions. A short-term Leptinotarsa decemlineata Say attack on potato tube-grown plantlets (Solanum tuberosum L.) led to a reduction of both the length and mass of the shoots in 9 days. The decrease of the content of phytohormones—indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin and zeatin–riboside—in shoots of damaged potato plants was found. Endophytic strain Bacillus subtilis 26D (Cohn) is capable of secreting up to 83.6 ng/mL IAA and up to 150 ng/mL cytokinins into the culture medium. Inoculation of potato plants with cells of the B. subtilis 26D increases zeatin–riboside content in shoots and the mass of roots of undamaged plants, but does not influence content of IAA and ABA and growth of shoots. The presence of B. subtilis 26D in plant tissues promoted a rapid recovery of the growth rates of shoots, as well as the wet and dry mass of roots of plants after the pest attack, which we associate with the maintenance of a high level of IAA, ABA and cytokinins in their tissues.

Effects of Abiotic Stress on Soil Microbiome

“…Microbial inoculants particularly plant growth promoting microorganism (PGPM) is one of the most efficient soil bacteria for promoting plant growth and development [215,263]. PGPM can benefits plants in three mechanisms: (i) Biofertilizer (i.e., N 2 -fixing bacteria and phosphate-solubilizing bacteria) to aid in plant nutrient absorption by delivering fixed nitrogen or other nutrients [264]; (ii) Phytostimulators that can stimulate plant growth by creating plant hormones [264][265][266]; and (iii) Biological control agents to protect from phythopathogenic organisms and abiotic stress [264]. However, positive microbial inoculants may transiently affect microbial biomass [267], and the rise in activity or biomass may be triggered by native inhabitants preying on the freshly introduced microbes [268].…”

Evaluation of Plant Growth-Promoting and Salinity Ameliorating Potential of Halophilic Bacteria Isolated From Saline Soil

“…Bacillus aryabhattai, Achromobacter denitrificans, and Ochrobactrum intermedium were isolated, which grew at 2.60 mol/L salt concentration and showed higher nitrogen fixation potential, phosphate solubilization, and IAA production at 200 mM salt stress (Sultana et al, 2021). Similarly, Bacillus amyloliquefaciens and B. subtilis were found to produce phytohormones such as gibberellins and indole acetic acid (Shao et al, 2015;Sorokan et al, 2021).…”

Bacillus for Plant Growth Promotion and Stress Resilience: What Have We Learned?

“…Cytokinins such as zeatin produced by Bacillus play a pivotal role in maintaining cellular proliferation and differentiation [ 83 ]. A study by Hussain and Hasnain [ 84 ] showed that the extracts obtained from cell cultures of B. licheniformis and B. subtilis are capable of increasing the weight and size of cucumber cotyledons separated from the seedlings, by inducing plant cell division due to the presence of cytokinins zeatin and zeatin ribose thus enhancing tolerance to salt stress.…”