Biocontrol and plant growth promoting activities of a Streptomyces corchorusii strain UCR3-16 and preparation of powder formulation for application as biofertilizer agents for rice plant

Feather degrading, phytostimulating, and biocontrol potential of native actinobacteria from North Eastern Indian Himalayan Region

Twelve actinobacterial strains were isolated from tomato rhizospheric soil from Manipur, a state in North East Indian Himalayan Region and screened for keratinolytic and plant growth promoting traits. Nine promising isolates were identified as Streptomyces species using partial 16S rRNA gene sequencing. Among the seven isolates showing chicken feather degradation activity, three keratinolytic strains RCM-SSR-2, -6, and -12 were found to be the most efficient feather degrading strains achieving 90% feather weight loss within 48 h of incubation. They also showed maximum keratinase and soluble peptide production. Strain RCM-SSR-2, -5, -6, -8, and -11 showed positive results for all plant growth promoting traits tested. Maximum indole-3-acetic acid production was exhibited by RCM-SSR-6. Strain RCM-SSR-1, -2, -5, -6, -9, and -11 showed antagonistic activity against three important plant pathogens. Feather hydrolysate of RCM-SSR-6 was also evaluated for in vitro seed germination test using garden pea seeds. Higher concentration of feather protein hydrolysate (3 mg ml^-1 ) inhibited shoot and root length of the germinating embryo. However, lower concentration (0.01 mg ml^-1 ) of feather protein hydrolysate promoted seed germination. Among the 12 strains, four isolates namely RCM-SSR-1, -2, -5, and -6 were found to be promising as multi-traits plant growth promoting rhizobacteria for development of organic fertilizer, phytostimulator, and biocontrol agents.

Induction of defense responses against Magnaporthe oryzae in rice seedling by a new potential biocontrol agent Streptomyces JD211

The induced resistance against plant pathogens via biocontrol agents is considered as an eco-friendly and promising strategy. In this study, the induced resistance against Magnaporthe oryzae (M. oryzae) in rice seedling by a new potential biocontrol agent Streptomyces JD211 (JD211) was evaluated. The effects of JD211 on defense-related enzymes activities and defense genes expression were investigated. The biocontrol efficacy of different JD211 concentrations was different, and the treatment of 10 g kg^-1 JD211 achieved the highest biocontrol efficacy. Activities of catalase, phenylalanine ammonia-lyase (PAL) and β-1,3-glucanase significantly increased in the presence of JD211. The gene expression level of both PAL and pathogenesis related protein 1 increased when rice seedlings were inoculated with JD211 alone or co-inoculated with M. oryzae, and the expression level of chitinase gene was enhanced by JD211 in the later stage. All results suggested that JD211 could increase the rice resistance by stimulating a series of defense responses, which was the result of induced systemic resistance by JD211. This work will provide a new biocontrol agent against Magnaporthe oryzae in rice seedling.

Potential for plant biocontrol activity of isolated Pseudomonas aeruginosa and Bacillus stratosphericus strains against bacterial pathogens acting through both induced plant resistance and direct antagonism

Phytopathogenic bacteria have caused significant damage to agricultural crops in both controlled and open cultivation practices, imposing heavy losses to farmers. Thereby, the goal of this study was to evaluate Pseudomonas aeruginosa and Bacillus stratosphericus isolated from soil has antagonistic activity against bacterial phytopathogens with the potential to control plant diseases. Isolated novel strains of P. aeruginosa and B. stratosphericus showed broad spectrum of antagonistic activity against five bacterial phytopathogens. Antagonistic activity was examined under optimized pH (8 and 7), carbon sources (lactose and starch), nitrogen sources (ammonium chloride, peptone and ammonium nitrate) for P. aeruginosa and B. stratosphericus, respectively, and biocatalyst production (chitinase, protease and amylase) was studied. Additionally, up-regulation of defense-related genes (PR-1a and PAL) was studied in tomato plants treated with P. aeruginosa and B. stratosphericus. The induction of defense-related genes in tomato plant was triggered after 12 h treatment with a cell concentration of 0.20 O.D. for P. aeruginosa and 0.21 O.D. for B. stratosphericus during treatment period. Broad spectrum antagonistic activity was observed due to antibiotic and siderophore production by P. aeruginosa and B. stratosphericus.

Characterization and assessment of two biocontrol bacteria against Pseudomonas syringae wilt in Solanum lycopersicum and its genetic responses

Pseudomonas and Bacillus species are attractive due to their potential bio-control application against plant bacterial pathogens. Pseudomonas aeruginosa strain D4 and Bacillus stratosphericus strain FW3 were isolated from mine tailings in South Korea. In these potent bacterial strains, we observed improved antagonistic activity against Pseudomonas syringae DC3000. These strains produced biocatalysts for plant growth promotion, and in vivo examination of Solanum lycopersicum included analysis of disease severity, ion leakage, chlorophyll content, and H₂O₂ detection. In addition, regulation of the defense genes pathogen-related protein 1a (PR1a) and phenylalanine ammonia lyase (PAL) was compared with treated plants and untreated control plants. The results suggest that these two bacterial strains provide protection against plant pathogens via direct and indirect modes of action and could be used as a bio-control agent.

Plant growth and resistance promoted by Streptomyces spp. in tomato

Plant Growth Promoting Rhizobacteria (PGPR) represent an alternative to improve plant growth and yield as well as to act as agents of biocontrol. This study characterized isolates of Streptomyces spp. (Stm) as PGPR, determined the antagonism of these isolates against Pectobacterium carotovorum subsp. brasiliensis (Pcb), evaluated the ability of Stm on promoting growth and modulating the defense-related metabolism of tomato plants, and the potential of Stm isolates on reducing soft rot disease in this species. The VOC profile of Stm was also verified. Promotion of plant growth was assessed indirectly through VOC emission and by direct interaction with Stm isolates in the roots. Evaluation of soft rot disease was performed in vitro on plants treated with Stm and challenged with Pcb. Enzymes related to plant defense were then analyzed in plants treated with three selected isolates of Stm, and PM1 was chosen for further Pcb-challenging experiment. Streptomyces spp. isolates displayed characteristics of PGPR. PM3 was the isolate with efficient antagonism against Pcb by dual-culture. Most of the isolates promoted growth of root and shoot of tomato plants by VOC, and PM5 was the isolate that most promoted growth by direct interaction with Stm. Soft rot disease and mortality of plants were significantly reduced when plants were treated with StmPM1. Modulation of secondary metabolism was observed with Stm treatment, and fast response of polyphenoloxidases was detected in plants pretreated with StmPM1 and challenged with Pcb. Peroxidase was significantly activated three days after infection with Pcb in plants pretreated with StmPM1. Results suggest that Streptomyces sp. PM1 and PM5 have the potential to act as PGPR.

Isolation and characterization of bioactive metabolites producing marine Streptomyces parvulus strain sankarensis-A10

The significance and frequency of marine microorganisms as producers of bioactive metabolites-a natural source of drug discovery had varied significantly during the last decades, making marine ecosystem a huge treasure trove of novel isolates and novel compounds. Among the twelve actinomycetes isolated from marine sediment sample (Lat. 17°41'962″N, Long. 83°19'633″E), amylase, protease, lipase and cellulase activities were exhibited by 8,7,4,3 isolates respectively. Five isolates exhibited l-asparaginase activity, while 5, 6, 2 isolates exhibited antibacterial, antifungal and antimicrobial activities respectively. One isolate VMS-A10 efficiently producing alpha-amylase (25.53 ± 0.50 U/mL), protease (19.26 ± 0.25 U/mL), lipase (36.25 ± 0.10 U/mL), cellulase (14.43 ± 0.513 U/mL), l-asparaginase (0.125 ± 0.004 U/mL), antimicrobial metabolites against B. subtilis (503.33 ± 5.77 U/mL), S. aureus (536.66 ± 5.77 U/mL), E. coli (533.33 ± 5.77 U/mL), P. aeruginosa (500.00 ± 10.0 U/mL), MRSA (538.33 ± 5.77 U/mL), C. albicans (353.33 ± 11.54 U/mL) and A. niger (443.33 ± 15.27 U/mL) was selected, identified on the basis of morphological, cultural, physiological, and biochemical properties together with 16S rDNA sequence, designated as Streptomyces parvulus strain sankarensis-A10 and sequencing product (1490 bp) was deposited in the GenBank database under accession number KT906299, Culture Deposit No: NCIM-5601. Isolation and characterization of each potential actinobacteria having immense industrial and therapeutic value on an unprecedented scale from marine sediments of Visakhapatnam coast will have a burgeoning effect.

Biochar and flyash inoculated with plant growth promoting rhizobacteria act as potential biofertilizer for luxuriant growth and yield of tomato plant

Overuse of agrochemical fertilizers alarmingly causes deterioration in soil health and soil-flora. Persistence of these agrochemicals exerts detrimental effects on environment, potentially inducing toxic effects on human health, thus pronouncing an urgent need for a safer substitute. The present study investigates the potential use of agricultural and industrial wastes as carrier materials, viz. biochar and flyash, respectively, for preparation of bioformulations (or biofertilizers) using two plant growth promoting rhizobacteria, Bacillus sp. strain A30 and Burkholderia sp. strain L2, and its effect on growth of Lycopersicon esculentum Mill. (tomato). The viability of strains was determined based on colony forming units (cfu) count of each bioformulation at an interval of 60 days for a period of 240 days. Seeds were coated with different carrier based bioformulations and pot experiment(s) were carried out to access its effects on plant growth parameters. Biochar based bioformulations showed higher cfu count and maximum viability for strain L2 (10⁷ cfu g^-1) at 240 days of storage. Maximum percentage of seed germination was also observed in biochar inoculated with strain L2. Significant (p < 0.05) increase in plant growth parameters (dry and fresh biomass, length, number of flowers) were ascertained from the pot experiment and amongst all bioformulations, biochar inoculated with strain L2 performed consistently thriving results for tomato yield. Furthermore, post-harvest study of this bioformulation treated soil improved physico-chemical properties and dehydrogenase activity as compared to pre-plantation soil status. Overall, we show that prepared biochar based bioformulation using Burkholderia sp. L2 as inoculum can tremendously enhance the productivity of tomato, soil fertility, and can also act as a sustainable substitute for chemical fertilizers. In addition, mixture of biochar and flyash inoculated with strain L2 also showed noteworthy results for the growth parameters and yield, and future studies are required to strengthen flyash utilization as carrier materials to resolve its disposal problem and waste management.