Antagonistic activity and application of Bacillus velezensis strain Bv-303 against rice bacterial-blight disease caused by Xanthomonas oryzae pv. oryzae / 生物工程学报

In this study, a new Bacillus velezensis strain Bv-303 was identified and its biocontrol effect against rice bacterial-blight (BB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) was investigated. Cell-free supernatant (CFS) of strain Bv-303 under different growth conditions were prepared to test the antagonistic activity and stability against Xoo by the Oxford-cup method in vitro. The antibacterial effect of strain Bv-303 to BB disease in rice were further analyzed in vivo by spraying the cell-culture broth (CCB), CFS and cell-suspension water (CSW), respectively, on the rice leaves inoculated with Xoo. Additionally, rice seeds germination rate and seedling growth under the strain Bv-303 CCB treatment were tested. The results showed that the strain Bv-303 CFS significantly inhibited Xoo growth by 85.7%‒88.0% in vitro, which was also stable under extreme environment conditions such as heat, acid, alkali and ultraviolet light. As tested in vivo, spraying the CCB, CFS or CSW of strain Bv-303 on the Xoo-infected leaves enhanced rice plant resistance to BB disease, with CCB showing the highest increase (62.7%) in disease-resistance. Notably, CCB does not have negative effects on rice seed germination and seedling growth. Therefore, strain Bv-303 has great potential for biocontrol of the rice BB disease.

Influence of microbial consortia on the incidence of grey mold (Botrytis cinerea) in strawberry (Monterey variety)

Botrytis cinerea, the causal agent of grey mold disease, is one of the most destructive pathogens of strawberry crops, both in vegetative development and postharvest. The control of this pathogen is complex due to its aggressiveness and ability to attack and infect various plant tissues and is mainly based on chemical control; however, the incorrect use of pesticides, mainly due to overdosing, causes the presence of traces of these agrochemicals in the fruits, as well as the selection of pathogen resistance to fungicides, making it a risk to human health and the environment. The objective of the study was to use biological regulation strategies, with the application of microbial consortia made up of mycorrhizal fungi, antagonistic bacteria and Trichoderma harzianum, as an alternative for the management of grey mold in strawberry crops (Monterey variety) under field conditions. Treatments T4 (mycorrhizal fungi), T8 (mycorrhizal fungi, antagonistic bacteria and T. harzianum) and T2 (T. harzianum) presented the lowest incidence of the pathogen with 2.6, 3.1 and 3.6 %, respectively, compared to control plants with 16.6%. The influence of all biological treatments on the regulation of B. cinerea was greater than the control.

Botrytis cinerea, el agente causal de la enfermedad del moho gris, es uno de los patógenos más destructivos del cultivo de fresa, tanto en el desarrollo vegetativo como en poscosecha. El control de este patógeno es complejo, debido a su agresividad y capacidad de atacar e infectar diversos tejidos de la planta y se basa, principalmente, en el control químico; sin embargo, el uso incorrecto de plaguicidas, principalmente por sobredosificación, provoca la presencia de trazas de estos agroquímicos en los frutos, así como la selección de resistencia del patógeno a los fungicidas, convirtiéndolo en un riesgo para la salud humana y el ambiente. El objetivo del estudio fue utilizar estrategias de regulación biológica, con la aplicación de consorcios microbianos, conformados por hongos micorrícicos, bacterias antagonistas y Trichoderma harzianum, como alternativa para el manejo del moho gris, en cultivos de fresa (variedad Monterey), en condiciones de campo. Los tratamientos T4 (hongos micorrízicos), T8 (hongos micorrízicos, bacterias antagonistas y T. harzianum) y T2 (T. harzianum) presentaron la menor incidencia del patógeno, con 2,6, 3,1 y 3,6 %, respectivamente, en comparación con las plantas control, con 16,6 %. La influencia de todos los tratamientos biológicos en la regulación de B. cinerea fue mayor respecto al control.

Study on colonization of endophytic antagonistic strain JYg07 of Schisandra chinensis / 中草药

Objective: The colonization of endophytic antagonistic bacteria in different parts of Schisandra chinensis was tested in the meantime. Methods: Using antibiotic notation method, mutant strains of JYg07 resistant to streptomycin and rifampin at the same time were obtained. To test the colonization the labeled strains of JYg07 with different vaccination methods of root irrigation, spray, injection, and stabbing leaves. Results: Through the natural orifice and the wound, the strain JYg07 could enter the plant of S. chinensis and long live in soil. Bacterial liquid concentration influenced the time of colonization peak. Using four vaccination methods, the labeled strains of JYg07 could colonize and engraft rapidly in S. chinensis, and the colonization ability in the roots was higher than that in the stems and leaves. High concentration of nutrient solution method and root irrigation method could make JYg07 in the best colonization state in S. chinensis. Conclusion: Strain JYg07 could colonize and engraft rapidly in S. chinensis, which could be developedt and utilized as new resources of biocontrol bacteria.

Isolation and screening of endophytic bacteria with antagonistic activity from Schisandra chinensis / 中草药

Objective: To isolate the endophytic bacteria from the plants in Schisandra chinensis. collected from different regions, and to study the flora density, antagonistic bacteria screening, and antibacterial activity. Methods: The endophytic bacteria were isolated by plate isolation method, and to purify their typical strains. Their antagonistic activity in vitro and antibacterial activity were tested by plate confrontation method and growth rate method, respectively. Results: The difference in the flora density of endophytic bacteria in the wild cultivars of S. chinensis was significantly higher than that in the cultured cultivars. Among the parts of S. chinensis, the density of endophytic bacteria was the highest in the roots, followed by the stems, and the lowest in the leaves. Endophytic bacteria (302 strains) were obtained from the isolated bacteria by purification, and the ratio of antagonistic bacteria was 24.19%. Twelve strains were selected with antagonistic action against the pathogens of Fusarium oxysporum, Fusarium Solani, Fusarium oxysporum, Botrytis cirerea, and Alternaria panax, and the fermention of them had inhibitory effect on inhibiting mycelial growth of the tested pathogens. The inhibitory rate of JYg-2 to A. panax was the highest with 80.02%. Conclusion: Plenty of endophytic bacteria are found in healthy plant of S. chinensis and some of them have stable antagonistic activity. Endophytic bacteria of S. chinensis have the great potential on developing biocontrol bacteria.

Studies on Novel bacteriocin like inhibitory substance (BLIS) from microalgal symbiotic Vibrio spp MMB2 and its activity against aquatic bacterial pathogens.

The present study was aimed to isolate the antagonistic bacteria from marine microalgal sample(Chlorella salina), the isolated bacterial strains were identified , screened for their bioactivity against the aquatic pathogens, to extract and characterize the compounds produced by antagonistic bacteria. Among the isolates Vibrio sp.MMB2 strain and Pseudomonas sp. had good antagonistic property against all tested pathogens. The maximum biogenic activity was occurred at the stationary phase culture. The metabolites extracted from Vibrio sp. MMB2 was showed highest zone of inhibition against A.hydrophylla .One active fraction was isolated by TLC. The functional group was identified through FTIR analysis ,the bacterial metabolites contains Nitrogenous compound as a functional groups. The Partially purified CFNS (bacteriocin) of Vibrio sp. MMB2 was showed two distinct bands on SDS-PAGE, its high molecular weight of antimicrobial peptides. The bacterial metabolites effectively controlled the pathogens at broad range, to compare commercial antibiotics.

Isolation of Rhizobacteria in Jeju Island Showing Anti-Fungal Effect against Fungal Plant Pathogens

To select active bacterial strains to control plant diseases, 57 bacterial strains were isolated from the rhizosphere of the plants growing in various areas such as coast, middle and top of Halla Mountain in Jeju Island. Anti-fungal effect of isolated bactrial strains was tested in vitro by incubating in potato dextrose agar with isolates of four fungal plant pathogens Rhizoctonia solani, Fusarium oxysporum, Colletotrichum gloeosporioides and C. orbiculare, respectively. Thirty-four bacterial strains inhibited the hyphal growth of the plant pathogens, from which 17 strains inhibited one of the tested fungi, 10 strains two fungi, six strains three and a strain TRL2-3 inhibited all of the tested fungi. Some bacterial strains could inhibit weakly the hyphal growth of the plant pathogens, whereas some did very strongly with apparent inhibition zone between the plant pathogens and bacterial strains indicating the unfavorable condition for hyphal growth. Although there was no apparent inhibition zone, some bacterial strains showed a strong suppression of hyphal growth of plant pathogens. Especially, the inhibition by TRL2-3 was remarkably strong in all cases of the tested plant pathogens in this study that could be a possible candidate for biological control of various plant diseases.

Isolation of Endophytic Bacteria from Glycyrrhiza and Identifying of Antagonistic Bacteria / 微生物学通报

98 endophytic bacteria strains were isolated from different internal tissues of Glycyrrhiza uralensis plants collected from Innermongolia region. Results indicated that the population densities of endophytic bacteria ranged from 5.0?104cfu/g～2.9?107cfu/g fresh weight although it varied depending on tissue of the plant. Among these strains, Bacillus sp. was the most prevalent endophytic bacterium, which was amount to 30%.Of the 98 isolates, 6 strains exhibited extensive antagonistic activities against pathogenic bacteria. Characterization showed that these bacteria were Bacillus atrophaeus、Paenibacillus polymyxa、Bacillus subtilis、Paenibacillus ehimensis. This study indicated that selected 6 endophytic bacteria strains have potential for biological control of plant disease.