Wheat sharp eyespot is a serious disease caused by the phytopathogens Rhizoctonia cerealis and R. solani. Some species in the genus Streptomyces have been identified as potential biocontrol agents against phytopathogens. In this investigation, the physiological, biochemical, phylogenetic, and genomic characteristics of strain HU2014 indicate that it is a novel Streptomyces sp. most closely related to Streptomyces albireticuli. Strain HU2014 exhibited strong antifungal activity against R. cerealis G11 and R. solani YL-3. Ultraperformance liquid chromatography–mass spectrometry on the four extracts from the extracellular filtrate of strain HU2014 identified 10 chemical constituents in the Natural Products Atlas with high match levels (more than 90%). In an antifungal efficiency test on wheat sharp eyespot, two extracts significantly reduced the lesion areas on bean leaves infected by R. solani YL-3. The drenching of wheat in pots with spore suspension of strain HU2014 demonstrated a control efficiency of 65.1% against R. cerealis G11 (compared with 66.9% when treated by a 30% hymexazol aqueous solution). Additionally, in vitro and pot experiments demonstrated that strain HU2014 can produce indoleacetic acid, siderophores, extracellular enzymes, and solubilized phosphate, and it can promote plant growth. We conclude that strain HU2014 could be a valuable microbial resource for growth promotion of wheat and biological control of wheat sharp eyespot.

Salt stress affects the growth and global production of wheat (Triticum aestivum L.). Plant growth-promoting microbes can enhance plant resistance to abiotic stresses. In this study, we aimed to assess the inoculation of soil with Streptomyces sp. HU2014 to improve wheat tolerance to salt stress from multiple perspectives, including the interaction of the strain, the addition of NaCl, the condition of the wheat, and rhizosphere microbial communities. The results showed that the strain promoted wheat growth under NaCl stress by increasing biomass by 19.8%, total chlorophyll content by 72.1%, proline content by 152.0%, and malondialdehyde content by 106.9%, and by decreasing catalase by 39.0%, peroxidase by 1.4%, and soluble sugar by 61.6% when compared to the control. With HU2014 soil inoculation, total nitrogen, nitrate nitrogen, total phosphorus, and Olsen phosphorus increased, whereas ammonium nitrogen and pH decreased. HU2014 inoculation and/or the addition of NaCl affected the diversity of rhizosphere bacteria, but not fungi. The structure of the microbial community differed after HU2014 inoculation, with Proteobacteria, Acidobacteriota, Bacteroidota, and unclassified fungi being the dominant phyla, and these taxa correlated with the above-mentioned soil parameters. Thus, this study provided a promising way to enhance wheat tolerance to salt stress and improve the agricultural ecological environment by using plant growth-promoting microbes.

Ризобактерії, які стимулюють ріст рослин, широко поширені в ризосфері рослин. Вони забезпечують живлення та продукують деякі антибіотичні речовини для пригнічення фітопатогенів і сприяння росту рослин. Тому вивчення алелопатії є дуже важливою частиною взаємодії між ризобактеріями та рослиною. Streptomyces, рід актиноміцетів, добре відомий своїми біоактивними метаболітами, головним чином – антибіотиками, гормонами та гідролазою, які можуть впливати на ріст рослин. У цьому дослідженні було оцінено алелопатію метаболітів штаму Streptomyces sp. HU2014 на пшеницю та мишій зелений з використанням індексу відповіді RI. Негативні значення RI вказували на пригнічення росту рослин; позитивні показники свідчили про стимуляцію їх росту. Чотири фракції (F2, F4, F6 та F8) з безклітинних фільтратів культурального бульйону HU2014 мали певний вплив на довжину проростків та коренів рослин. Для пшениці результати показали, що фракція F2 при 10 мг/мл мала найбільш виразний ефект пригнічення довжини проростків (RI=-0,53) і кореня (RI=-0,22). Однак фракція F2 при 1 мг/мл сприяла збільшенню довжини проростка (RI=0,01). Фракції F4 і F6 при 10 мг/мл мали найбільше пригнічення довжини проростків та коренів. Для фракції F8 зафіксовано найбільше зменшення довжини проростків (RI = -0,66) при 5 мг/мл і довжини кореня (RI = -0,66) при 10 мг/мл. Для мишію зеленого фракція F2 при 10 мг/мл пригнічувала як довжини проростків (RI = -0,73), так і кореня (RI =-1,00). Фракція F4 показала найвище пригнічення проростку (RI = -0,69) при 5 мг/мл і кореня (RI = -0,85) при 10 мг/мл. Фракція F6 мала найвище пригнічення довжини проростка (RI = -0,59) при 10 мг/мл і кореня (RI = -0,80) при 5 мг/мл. Фракція F8 показала найвищий рівень інгібування довжини проростка (RI = -0,47) при 5 мг/мл і кореня (RI = -0,93) при 10 мг/мл. З наведених вище результатів ми можемо зробити висновок, що чотири фракції мали алелопатичний вплив на довжину проростків і коренів двох досліджуваних видів рослин, за винятком фракції F2 при 1 мг/мл, яка сприяла збільшенню довжини пагонів пшениці. Таким чином, на ранній стадії росту рослин низька концентрація алелопатичних речовин, які продукує HU2014, може сприяти росту пшениці, тоді як ці речовини пригнічують ріст мишію зеленого. Тому цей штам може бути перспективним як у якості біофунгіциду, так і – біогербіциду.

The rhizosphere microbiome and phytohormone signaling are critical determinants of plant growth and stress resilience. This study evaluated the combined effects of Streptomyces sp. HU2014 and coronatine (COR) on maize (Zea mays L.) seedlings. Four treatments were established: control (CK), COR seed soaking (Cor), HU2014 soil inoculation (S), and combined S + Cor (SCor). Growth parameters, chlorophyll content, and antioxidant/oxidative stress markers were measured, and root and leaf transcriptomes, together with root metabolomes, were compared between SCor and CK, followed by qRT-PCR validation. Compared with CK, SCor treatment significantly increased stem diameter (~60%), plant height (~20%), and relative chlorophyll content (SPAD, ~50%). Soluble sugar levels were elevated by over 40% in both leaves and roots, accompanied by tissue-specific modulation of antioxidant enzymes. Transcriptomic analysis of SCor vs. CK revealed 2459 differentially expressed genes (DEGs) in leaves and 3444 DEGs in roots; leaves exhibited upregulation of photosynthetic pigment metabolism (porphyrin and carotenoid pathways) and volatile defense compounds (alkaloids and monoterpenoids), whereas roots showed enrichment in phenylpropanoid/flavonoid biosynthesis, benzoxazinoid synthesis, and starch/sucrose metabolism. Metabolomics of SCor vs. CK identified 526 differentially accumulated metabolites (DAMs) in roots, with significant enrichment in aminoacyl-tRNA biosynthesis, phenylalanine metabolism, and linoleic acid metabolism. Integrative multi-omics analysis further revealed that the JA precursor 13-epi-12-oxo-phytodienoic acid co-clustered with stress-responsive transcription factors (e.g., DREB1C), while tricarboxylic acid (TCA) intermediates and phenylpropanoid metabolites were linked to energy and lignin biosynthesis genes. qRT-PCR confirmed the expression trends of 14 out of 15 tested genes. Collectively, combined HU2014 and COR application triggers tissue-specific transcriptional and metabolic reprogramming in maize, coupling JA-mediated stress signaling with enhanced carbon metabolism and secondary defense compound synthesis to promote rhizosphere adaptation and seedling vigor.

Goal. To determine changes in the activity of enzymes (POD, PAL and GLU) of Triticum aestivum when Streptomyces sp. HU2014, Rhizoctonia cerealis G11 are introduced into the soil and their simultaneous application. Methods. Laboratory: cultivation of microorganisms and wheat plants, introduction of actinomycetes and fungus into the soil. Physico-chemical: POD, PAL and GLU colorimetry. Analytical and mathematical: analysis of the obtained results and their statistical comparison. Results. Changes in the activity of enzymes (POD, PAL and GLU) were noted in the leaves of wheat plants at different time intervals, compared to the control variant. The change manifested mostly in the increase of their activity. The maximum amount of enzyme activity was noted on one variety ZM22: on the third day of POD when inoculated according to the CKP scheme (15762.69 U/g) and GLU when introducing the microorganism into the soil according to the PF3 scheme (28.45 U/g); on the fourth day of the PAL study according to the treatment scheme PF3 (29.37 U/g). The induction of resistance was also determined by the wheat variety. Conclusions. The activity of POD, PAL and GLU was determined by the plant treatment scheme, time period and genotype of the crop. In most cases, during soil treatment with microorganisms, the activity of all three studied enzymes from the leaves of three varieties of wheat increased in different periods of time, compared to the control. The activity of PAL enzyme increased to the greatest extent. It was established that the activity of the POD enzyme was mostly determined by R. cerealis and the dual use of microorganisms, the PAL enzyme by a strain of Streptomyces sp. HU2014, and the GLU enzyme — by inoculation with a phytopathogen and introduction of actinomycetes. That is, changes in the activity of all three enzymes were mostly determined by the strain of Streptomyces sp. HU2014. At the same time, it was shown that R. cerealis G11 mainly induced the defense system of AK58 and ZM22 varieties, and HU2014 induced the defense of BN307.

Biocontrol microorganism have a diverse range of activities and they have been focused on potential biocontrol agents in agriculture. They can induce plant defensed response and enhance plant disease resistance. Streptomyces sp. produce active metabolites that can inhibit the growth of phytopathogens. Induced resistance is usually indicated by the activity of Peroxidase (POD), Polyphenoloxidase (PPO), and Phenylalanine ammonia-lyase (PAL) or other defense enzymes. The related reports mainly focused on disease control or promoting growth of cash crops or vegetables, but less on wheat presently. Moreover, the information about the concentration of fermentation broth and mycelia of Streptomyces affected the quantitative changes of defensed enzyme activities is limited. In this study, we started from isolating a Streptomyces strain, named S. sp. strain HU2014, and demonstrated (POD), (PPO), (PAL) enzymes in different concentration of the mycelia (M) and extracellular filtrate (EF) of the strain with the application of soil drench treatment. The enzyme activities were determined by visible spectrophotometry. The results showed that the activities of POD and PAL at the concentration of 10³-fold dilution of the EF increased significantly to some extent in comparison with untreated control, by 173.86 % (P < 0.05) and 71.92 % (P < 0.05), respectively. In the range of different concentration of the M, POD and PPO activities were enhanced with the increasing of dilution ratio, but the difference was not significant. It is expected to be an excellent resource for the development of new biological preparations.