Biopolymers as Seed-Coating Agent to Enhance Microbially Induced Tolerance of Barley to Phytopathogens.

Infections of agricultural crops caused by pathogen ic fungi are among the most widespread and harmful, as they not only reduce the quantity of the harvest but also significantly deteriorate its quality. This study aims to develop unique seed-coating formulations incorporating biopolymers (polyhydroxyalkanoate and pullulan) and beneficial microorganisms for plant protection against phytopathogens. A microbial association of biocompatible endophytic bacteria has been created, including Pseudomonas flavescens D5, Bacillus aerophilus A2, Serratia proteamaculans B5, and Pseudomonas putida D7. These strains exhibited agronomically valuable properties: synthesis of the phytohormone IAA (from 45.2 to 69.2 µg mL-1), antagonistic activity against Fusarium oxysporum and Fusarium solani (growth inhibition zones from 1.8 to 3.0 cm), halotolerance (5-15% NaCl), and PHA production (2.77-4.54 g L-1). A pullulan synthesized by Aureobasidium pullulans C7 showed a low viscosity rate (from 395 Pa·s to 598 Pa·s) depending on the concentration of polysaccharide solutions. Therefore, at 8.0%, w/v concentration, viscosity virtually remained unchanged with increasing shear rate, indicating that it exhibits Newtonian flow behavior. The effectiveness of various antifungal seed coating formulations has been demonstrated to enhance the tolerance of barley plants to phytopathogens.

Polyhydroxyalkanoates (PHAs) from Endophytic Bacterial Strains as Potential Biocontrol Agents against Postharvest Diseases of Apples.

Due to the increasing use and accumulation of petrochemical plastics in the environment and the rapid depletion of natural resources, microbial polyhydroxyalkanoates have great potential to replace them. This study provides new insights in the field of obtaining of polyhydroxyalkanoates (PHAs) from endophytic bacterial strains and applying them as potential biocontrol agents against postharvest diseases of apples. Two strains-Pseudomonas flavescens D5 and Bacillus aerophilus A2-accumulated PHAs in amounts ranging from 2.77 to 5.9 g L-1. The potential to use low-cost substrates such as beet molasses and soapstock for PHA accumulation was shown. The PHAs produced by the Ps. flavescens D5 strain had pronounced antagonistic activity against Penicillium expansum (antifungal property = 62.98-73.08%). The use of PHAs as biocontrol agents significantly reduced the severity of apple blue mold, especially in the preventive treatment option.

Phosphate Mobilization by Culturable Fungi and Their Capacity to Increase Soil P Availability and Promote Barley Growth.

Large-scale screening of 848 culturable soil and endophytic filamentous fungi and yeasts for the ability to mobilize inorganic and organic P compounds was performed. Five strains of filamentous fungi having the highest level of phosphate-mobilizing ability were selected: Penicillium bilaiae Pb14, P. bilaiae C11, P. rubens EF5, Talaromyces pinophilus T14, and Aspergillus sp. D1. These strains in vitro actively solubilized Ca, Al, and Fe phosphates and Ca phytate. The amount of mobilized P negatively correlated with pH of the medium and positively correlated with fungal biomass. The proposed mechanisms for P mobilization were acidification of the medium, organic acid release, and phosphatase activity. The fungi decreased pH of the medium from 7.0 to 2.3-5.0. Ten different organic acids were produced by fungi with pyruvic acid being a major component. Acid phosphatase activity varied from 0.12 EU to 0.84 EU, and alkaline phosphatase activity varied from 0.08 EU to 0.61 EU depending on the strain. Available P concentration in soil was increased by 13-28% after introduction of the fungi. The fungi also produced phytohormones auxins, salicylic acid, and abscisic acid. All the strains, except Aspergillus sp. D1, promoted elongation and increased biomass of barley seedlings grown in soil. Shoot P concentration increased by 17-26% after inoculation with P. bilaiae Pb14, T. pinophilus T14, and Aspergillus sp. D1. It was concluded that the selected fungal strains promoted plant growth due to P mobilization and phytohormone production.

Characterization of cadmium-tolerant endophytic fungi isolated from soybean (Glycine max) and barley (Hordeum vulgare).

Cadmium stress disrupts plant-microbial interactions and reduces plant growth and development. In plants, the tolerance to stress can be increased by inoculation with endophytic microorganisms. The aim of this study was to investigate the distribution of endophytic fungi in various plant organs of barley and soybean and evaluate their Cd removal ability. Two hundred fifty-three fungal strains were isolated from various organs of barley (Hordeum vulgare cv Arna) and soybean (Glycine max cv Almaty). The colonization rate ranged from 13.6% to 57.3% and was significantly higher in the roots. Ten genera were identified: Fusarium, Penicillium, Aspergillus, Metarhizium, Beauveria, Trichoderma, Rhodotorula, Cryptococcus, Aureobasidium and Metschnikowia. Twenty-three fungal strains have a Cd tolerance index from 0.24 to 1.12. Five strains (Beauveria bassiana T7, Beauveria bassiana T15, Rhodotorula mucilaginosa MK1, Rhodotorula mucilaginosa RH2, Metschnikowia pulcherrima MP2) with the highest level of Cd tolerance have minimum inhibitory concentrations from 290 to 2400 µg/ml. These fungi were able to remove Cd up to 59%. The bioaccumulation capacity ranged from 2.3 to 11.9 mg/g. Selected fungal strains could be considered as biological agents for their potential application in the bioremediation of contaminated sites.

Bacterial endophytes of Trans-Ili Alatau region's plants as promising components of a microbial preparation for agricultural use.

In this study, 382 isolates of bacterial endophytes from tissues of plants grown in the foothills and piedmont plains of the Trans-Ili Alatau were isolated. It was found that certain strains actively produce indole-3-acetic acid (IAA) in a medium containing l-tryptophan. Among the strains studied, 26 strains (66%) showed a positive response to production of IAA. Bacteria synthesized IAA in the range of 18.6 ± 1.1 to 82.4 ± 2.3 µg/ml. IAA was synthesized more actively by Streptosporangium sp. KK1 (44.1 µg/ml), Rhodococcus sp. KK 2 (42.5 µg/ml), Streptomyces tendae KK3 (44.9 µg/ml) strains. The most active auxin's producer is a Jeotgalicoccus halotolerans BAK1 strain, whose total level of IAA production reached 82.4 µg/ml. Such strains as Streptomyces griseorubiginosis KK4, Streptomyces sp. KK5 and Jeotgalicoccus halotolerans BAK1 were found to have a significant stimulating effect which was reflected in the increase of the length of the roots of soybean and barley. As a result, 8 promising strains with fungicidal, growth-stimulating, phosphorus dissolving and enzymatic activities were selected for the further development of highly microbiological preparations for crop research.

The effect of application of micromycetes on plant growth, as well as soybean and barley yields.

The possibility of application of micromycetes (strains Penicillium bilaiae Pb14, Aureobasidium pullulans YA05 and Rhodotorula mucilaginosa YR07) to increase yields of soybean (Glycine max cv Almaty) and barley (Hordeum vulgare cv Arna) was estimated. It was shown that the most positive effect on germination energy and seed germination after seed treatment with liquid culture, supernatant and filtrate, is achieved at 1:5 dilution. In studying the influence of cell-associated and extracellular biologically active compounds of micromycetes (liquid culture and supernatant) on biometric parameters of seedlings, the maximum stimulating effect was observed in the variants with liquid culture. These strains of micromycetes were used as a bases for various compositions of preparations - application of each strain separately and application of micromycetes mixes. In microfield experiments, the increase of soybean yield ranged from 4.5 to 9.4 quintal/ha, barley - from 2.9 to 5.9 quintal/ha. A significant increase in various parameters of structure of the yield was shown in all experimental variants when compared to the control. It was found that an increase in soybean and barley yields and yield components was higher in the variant with a mix of micromycetes when compared to the separate application of each strain. The most efficient mixture was based on the mix of fungal strains (culture filtrate of P. bilaiae Pb14 diluted 1:5 + liquid cultures of A. pullulans YA05 and Rh. mucilaginosa YR07 in a 1:5 dilution).

Plant growth-promoting and antifungal activity of yeasts from dark chestnut soil.

538 yeast strains were isolated from dark chestnut soil collected from under the plants of the legume family (Fabaceae). The greatest number of microorganisms is found at soil depth 10-20 cm. Among the 538 strains of yeast 77 (14.3%) strains demonstrated the ability to synthesize IAA. 15 strains were attributed to high IAA-producing yeasts (above 10 µg/ml). The most active strains were YA05 with 51.7 ± 2.1 µg/ml of IAA and YR07 with 45.3 ± 1.5 µg/ml. In the study of effect of incubation time on IAA production the maximum accumulation of IAA coincided with maximum rates of biomass: at 120 h for YR07 and at 144 h for strain YA05. IAA production increased when medium was supplemented with the L-tryptophan. 400 µg/ml of L-tryptophan showed maximum IAA production. 10 strains demonstrated the ability to inhibit the growth and development of phytopathogenic fungi. YA05 and YR07 strains formed the largest zones of inhibition compared to the other strains--from 21.6 ± 0.3 to 30.6 ± 0.5 mm. Maximum zone of inhibition was observed for YA05 against Phytophtora infestans and YR07 strains against Fusarium graminearum. YA05 and YR07 strains were identified as Aureobasidium pullulans YA05 (GenBank accession No JF160955) and Rhodotorula mucilaginosa YR07 (GenBank accession No JF160956).