Influence of the genus

The authors studied the effect of treatment with bacteria Bacillus subtilis Cohn (strains 26D) and B. thuringiensis Berliner (strain B-6066) on the hydrogen peroxide (H2O2) content, the activity of hydrolytic enzymes and their protein inhibitors in potato plants (Solanum tuberosum L.) in connection with development of resistance to the late blight pathogen - oomycete Phytophthora infestans Mont. de Bary. Studies were carried out on potato plants of the susceptible Early Rose potato cultivar that were treated with a suspension of B. subtilis and B. thuringiensis bacteria (108 cells/ml) and infected with P. infestans (107 spores/ml). A decrease in the degree of leaf damage by oomycete was revealed under the influence of the genus Bacillus bacteria, depending on the strain. The increase in potato resistance to P. infestans infection was mediated by the stimulating effect of the B. subtilis 26D and the B. thuringiensis B-6066 bacteria on the concentration of H2O2, the modulating effect on the activity of hydrolytic enzymes and the enhancement of the transcriptional activity of protease and amylase inhibitor genes in plant tissues. Differences in the degree of activation of the transcriptional activity of hydrolase inhibitor genes by the B. subtilis 26D and the B. thuringiensis B-6066 bacteria were revealed, which suggests differential ways of forming the potato resistance to P. infestans under their influence

Additive Effect of the Composition of Endophytic Bacteria <i>Bacillus subtilis</i> on Systemic Resistance of Wheat against Greenbug Aphid <i>Schizaphis graminum</i> Due to Lipopeptides

The use of biocontrol agents based on endophytic bacteria against phloem-feeding insects is limited by a lack of knowledge and understanding of the mechanism of action of the endophyte community that makes up the plant microbiome. In this work, the mechanisms of the additive action of endophytic strains B. subtilis 26D and B. subtilis 11VM on the resistance of bread spring wheat against greenbug aphid Schizaphis graminum, was studied. It was shown that B. subtilis 26D secreted lipopeptide surfactin and phytohormones cytokinins, and B. subtilis 11VM produced iturin and auxins into the cultivation medium. Both strains and their lipopeptide-rich fractions showed direct aphicidal activity against greenbug aphid. For the first time, it was shown that B. subtilis 26D and B. subtilis 11VM in the same manner, as well as their lipopeptide-rich fractions, activated the expression of salicylate- and ethylene-dependent PR genes, and influenced plant redox metabolism, which led to an increase in plant endurance against aphids. The composition of endophytic strains B. subtilis 26D + B. subtilis 11VM had an additive effect on plant resistance to aphids due to an increase in the number of endophytic bacterial cells, and, as well as due to the synergistic effect of their mixture of lipopeptides − surfactin + iturin, both on the aphid mortality and on the expression of PR1 and PR3 genes. All these factors can be the reason for the observed increase in the growth of plants affected by aphids under the influence of B. subtilis 26D and B. subtilis 11VM, individually and in composition. The study demonstrates the possibility of creating in the future an artificial composition to enhance plant microbiome with endophytic bacteria, which combines growth-promoting and plant immunity stimulating properties against phloem-feeding insects. This direction is one of the most promising approaches to green pesticide discovery in the future

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

Endophytic plant-growth-promoting microorganisms can protect plants against pathogens, but they have rarely been investigated as potential biocontrol agents and triggers of induced systemic resistance (ISR), regulated by phytohormones, against viruses. We studied the role of endophytic strains Bacillus subtilis 26D and B. subtilis Ttl2, which secrete ribonucleases and phytohormones, in the induction of tomato plant resistance against potato virus X and potato virus Y in a greenhouse condition. The endophytes reduced the accumulation of viruses in plants, increased the activity of plant ribonucleases and recovered the fruit yield of infected tomato plants. Both the 26D and Ttl2 strains induced ISR by activating the transcription of genes related to salicylate- and jasmonate-dependent responses. The 26D and Ttl2 strains increased the content of cytokinins and decreased the level of indolacetic acid in plants infected with PVX or PVY. PVY led to an increase of the abscisic acid (ABA) content in tomato plants, and PVX had the opposite effect. Both strains reduced the ABA content in plants infected with PVY and induced ABA accumulation in plants infected with PVX, which led to an increase in the resistance of plants. This is the first report of the protection of tomato plants against viral diseases by foliar application of endophytes