New Beauveria bassiana Strains from Kyrgyzstan with Endophytic and Insecticidal Activities

Beauveria bassiana (Ascomycota: Cordycipitaceae) is an entomopathogenic fungus used as an ecofriendly insecticide to infect arthropods. B. bassiana also possesses endophytic activity to contribute to plant growth. This study aimed to evaluate the potential insecticidal and endophytic activity of native B. bassiana isolates. The nymphal and adult stages of the apple tree aphid (Aphis pomi) and whitefly (Trialeurodes vaporariorum) were used as targets in bioinsecticidal experiments, and vegetables (beans, tomatoes and cucumbers) were used as targets in biostimulant experiments. The endophytic activity of the B. bassiana strains was assessed after inoculation them to the crop seeds and plants via soil drenching, foliar spraying and seed immersion. In bean plants, seed immersion was the most effective application method. Soil drenching was more effective in the cucumber and tomato plants. The results of in vitro bioassay tests against pests have revealed the LC50 and LT50 values of B. bassiana isolate Col-2. The LC50 of this isolate for A. pomi adults and nymphs was 2.5 × 106 conidia/mL−1;for T. vaporariorum, it was lower 1.8 × 106 conidia/mL−1. Such mortality occurred after 55.49 h. in A. pomi adults and nymphs (LT50), after 62.3 h. in T. vaporariorum (LT50).

Fire Blight Disease Caused by Erwinia amylovora on Rosaceae Plants in Kyrgyzstan and Biological Agents to Control This Disease

Erwinia amylovora species were isolated from the blossoms, exudates, infected fruits, leaves and bent branches of diseased apple, pear and hawthorn trees, selected in the Chy, Osh and Jalal Abad regions. Biochemical and pathogenicity tests, alongside PCR analyses, were conducted to identify the local isolates of Erwinia amylovora. The alternative antagonistic microorganisms which combat bacterium E. amylovora were tested within in vitro and in vivo conditions. The results revealed the ability of Streptomyces antagonistic bacteria to decrease fire blight severity on pear and apple trees during the first stage of the fire blight disease in leaf tissues. Streptomyces strain C1-4 suppressed E. amylovora disease symptoms in the leaf tissues and excised apple and pear shoots. The incidence of fire blight on leaves was reduced by about 70% with two applications of bacterial antagonists. Further studies at different locations in Kyrgyzstan, using large scale application, would allow for stronger recommendations to be made, including studies and recommendations on their ability to prevent disease and to use them as main components in an integrated pest management program.

Biological Control of Erwinia carotovora ssp. carotovora by Streptomyces Species

Ten isolates of Erwinia carotovora ssp. carotovora (Ecc) were isolated from infected potato tubers of Picasso, Sante, and Nevskiy varieties collected from different regions in Kyrgyzstan. Isolates were identified as Erwinia carotovora ssp. carotovora (Ecc) by standard bacteriological techniques and pathogenicity tests on tubers and also by PCR analyses. Tests on the pathogenicity of E. carotovora ssp. carotovora (Ecc) strains to host plants by artificial inoculation have shown a high sensibility of the Picasso variety. As a result, five isolates were chosen, three isolates (EcPo1, EcPo2, and Eco3) were highly pathogenic, while two isolates (Eco4 and Eco5) were weakly pathogenic. The antagonistic bacteria, Streptomyces diastatochromogenes strain sk-6, and Streptomyces graminearuss strain sk-2, have a highly significant effect on soft rot bacteria isolates (Ecc), more than the other tested antagonistic organisms in vitro screening biotests. The Streptomyces diastatochromogenes sk-6 was selected for the control assay of storage potatoes against the most common soft rot bacterial strain in Kyrgyzstan, Erwinia carotovora sp. carotovora EcPo2. The pretreatment of potato tubers with antagonistic bacteria successfully prevented the initial infection multiplication of soft rot bacteria and reduced soft rot disease of potatoes in storage. These results justify selection of the dose 106 cells/ml of bacteria Streptomyces diastatochromogenes sk-6 for use in powdering the infected or non-infected potato tubers to suppress the development soft rot during storage. Streptomyces diastatochromogenes sk-6 as a biological disinfectant could destroy surface and internal infections, protect the tubers from the growth of phytopathogenic bacteria in the early period of their reproduction, and improve the overwintering of winter crops.

Effects of Streptomyces <i>Biofertilizer</i>to Soil Fertility and Rhizosphere’s Functional Biodiversity of Agricultural Plants

In the present study, a biofertilizer on the basis of Streptomyces fumanus gn-2 was used for the treatment of wheat and soybean seeds (dose 104 spore/ml) before planting them in soil with low fertility in order to determine the effect of this biological agent on germination rate;the growth of seedlings, shoots, and the maturation phase of plants;the rhizosphere’s functional biodiversity;and the resistance of these plants to pathogens. Seeds were soaked in the suspension for a period of two or three hours. During the growing season of the crop, no additional fertilizing and spraying of a biopesticide against diseases or pests occurred. Despite the soil having low fertility, low quantities of organic matter, and not having been before used for the cultivation of agricultural plants, this biofertilizer showed a strong stimulatory effect on the growth of seeds and seedlings of wheat and soybeans. The average germination and seed vigor increased by 1.5 - 2.0 times, and the phenophases were accelerated to three to five days. In all phases of vegetation, the ammonifying bacteria in the presence of an antagonist (a biological agent) developed rapidly and were constantly present in significant numbers in the rhizosphere. Streptomyces fumanus introduced into non-sterile soil entered into competition with the local soil microflora and had the ability to colonize the rhizosphere system of plants. The use of a formulation of Streptomyces gn-2 has improved the composition of rhizosphere microflora, attracting saprophytic microorganisms: ammonificators and oligotrophs. The presence of the biocontrol microorganism Streptomyces fumanus in the rhizosphere plays an important role in enhancing the growth and development of useful groups, such as nitrogen-fixing bacteria.

Biodiversity of <i>Bacillus thuringiensis</i>Strains and Their <i>Cry</i>Genes in Ecosystems of Kyrgyzstan

The present study aims to isolate the unknown and known serotypes of Bacilllus thuringiensis (Bt) from natural objects in Kyrgyzstan. A total of 83 Bt strains were isolated from natural substrates, of which 30% were taken from the soil and litter samples, 69.7% from dead insects and about 0.3% from slugs. Serological examination revealed that such subspecies as var. thuringiensis (H-1), var. alesti (H-3), var. sotto (H-4a4b) and var. entomocidus (H-6) predominated in the upper horizon of soils in all climatic zones. In the dead insects such species as subsp. thuringiensis, subsp. galleria, subsp. sotto, subsp. kurstaki, subsp. Aizawai and subsp. Entomocidus dominated. A set of Bt strains isolated from insects and soil samples, selected from different ecosystems in Kyrgyzstan was molecular taxonomically characterized using the pycA gene as marker for phylogenetic reconstruction. Within the Bacillus cereus sensu lato species complex, all Kyrgyz isolates were shown to belong to the B. cereus subspecies thuringiensis. Most isolates were assigned to the lineage Bt tolworthi, with two isolates each belonging to the lineages Bt kurstaki and Bt sotto. A high degree of cry gene diversity was demonstrated in the set of Bt isolates, with several gene copies simultaneously present in a single strain;a particularly conspicuous trait was the frequent combination of Lepidopteran-specific cryI with Dipteran-specific cryIV genes in the same Bt isolate.

Scab Disease Caused by <i>Venturia inaequalis</i>on Apple Trees in Kyrgyzstan and Biological Agents to Control This Disease

Among the most economically important fruit crops in South and North Kyrgyzstan affected by scab disease are apples (Malus domestica). Natural isolates of Venturia inaequalis were isolated from diseased parts of apple trees, selected from different regions, through sedimentation of air microflora on the crowns of fruit trees. Two biocontrol agents as Trichoderma viride and Streptomyces sр. were tested for apple scab control in vitro and field conditions. Two applications of Trichoderma viride within 35 days completely stopped the scab disease in seedling leaves. Within 40 days, the seedlings were recovered;the new leaves have blossomed on branches. The Streptomyces sp. antagonists were inferior in effectiveness compared to Trichoderma viride;nevertheless, they prevented progression of the disease in the leaves. Seedlings grew new shoots and leaves around 50 days after the second treatment. Orchard experiment results provide great hope that a biological product based on Trichoderma viride could work as an effective agent to suppress the development of the pathogen in the early spring, when leaves start to show scab disease symptoms.