Endophytic Bacillus spp. as a Prospective Biological Tool for Control of Viral Diseases and Non-vector Leptinotarsa decemlineata Say. in Solanum tuberosum L.

Abstract

Viral diseases and their damage causing significant loss to economically important crops have increased by several folds during the last decade. All the conventional approaches are not able to eradicate the viral infection. Therefore, there is a need to look for efficient and eco-friendly viral disease-preventive measures. The genomic material of the majority of deleterious viruses of higher plants is RNA. One of the possible measures to control viruses is the use of ribonucleases (RNases), which can cleave RNA in the viral genome. Based on this, we investigated the RNase activity of endophytic Bacillus spp., which can enrich in 10 3 –10 5 colony-forming units per gram of wet mass of aboveground part of potato plants. A high level of RNase activity was observed in the culture medium of Bacillus thuringiensis B-6066, Bacillus sp. STL-7, Bacillus sp. TS2, and Bacillus subtilis 26D. B. thuringiensis B-5351 had low RNase activity but high ability to colonize internal plant tissues, Bacillus sp. STL-7 with high RNase activity have relatively low number of cells in internal tissues of plants. B. thuringiensis B-6066, B. subtilis 26D, and Bacillus sp. TS stimulate RNase activity in potato plants for a long time after application. Strains with high ability to colonize internal plant tissues combined with high RNase activity reduced severity of viral diseases symptoms on plants and reduced the incidence of potato viruses M, S, and Y. It is worth noting that Bacillus spp. under investigation reduced the number of Leptinotarsa decemlineata Say. egg clusters and larvae on treated plants and showed antifeedant activity. This results in increase of potato productivity mainly in the fraction of major tubers. B. subtilis 26D and Bacillus sp. TS2 combining endophytic lifestyle, RNase, and antifeedant activity may become the basis for the development of biocontrol agents for plant protection.

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

“…The study showed that treatment of potato plants with cells of the endophytic strain B. subtilis 26D promoted the restoration of plant growth after damage caused by CPBs. Previously, data on the alterations of plant growth by bacteria of the genus Bacillus under the influence of biotic and abiotic factors were summarized in the reviews [ 15 , 17 ]. However, investigations of the effect of PGPM on productivity of plants that were damaged by insect pests emphasize the direct insecticidal effect of strains under study [ 18 ] or their ability to induce plant resistance [ 16 ], but not their effect on the growth of damaged plants.…”

“…Enrichment of plants with endophytes can be more advantageous than the cultivation of transgenic plants resistant to pathogens [ 14 ]. Implementing artificial plant microbiomes with PGPM that are capable of releasing their metabolites immediately in plant tissues can become a challenging alternative to conventional methods of plant protection and growth regulation [ 15 ].…”

“…In our previous work we showed that the quantity of B. subtilis 26D in shoots of potato plants was about 10 5 cells/mg of fresh weight [ 15 ]. Thus, consuming plants containing B. subtilis 26D by CPBs resulted in 38.1% larvae death.…”

“…Thus, consuming plants containing B. subtilis 26D by CPBs resulted in 38.1% larvae death. The presence of endophytic B. subtilis 26D strain cells in potato plants enhanced the level of transcripts of jasmonate-biosynthesis genes in plant leaves damaged by L. decemlineata [ 16 ] and decreased the population density of CPBs under the field conditions [ 15 ]. In this context, the question about the influence of B. subtilis 26D on growth parameters of potato plants is very important.…”

By Modulating the Hormonal Balance and Ribonuclease Activity of Tomato Plants Bacillus subtilis Induces Defense Response against Potato Virus X and Potato Virus Y

“…Bacteria: The gram-positive aerobic B. subtilis 26D (designated as 26D) strain from the collection of the Laboratory of Biochemistry of Plant Immunity of the Institute of Biochemistry and Genetics Ufa Federal Research Center Russian Academy of Sciences (UFRC RAS) (http://ibg.anrb.ru/wp-content/uploads/2019/04/Katalog-endofit.doc, accessed on 30 January 2022) was used. The B. subtilis 26D strain synthesizes the lipopeptide surfactin, exhibits proteolytic, antifungal, insecticidal and antiviral activities and also induces systemic resistance against pathogens and pests [24]. The isolate Bacillus sp.…”