Suppression of Rice Blast by Bacterial Strains Isolated from Cultivated Soda Saline-Sodic Soils

Rice blast caused by Magnaporthe oryzae is one of the most serious rice diseases worldwide. Biological control is gaining popularity as a promising method for the control of this disease; however, more effective microbial strains with strong adaptability in rice fields need to be identified. Here, we report for the first time the successful identification of biocontrol bacterial strains from frozen soils of the soda saline-sodic land. We isolated 82 bacterial strains from rice fields in the western Songnen Plain of China, one of the three major soda saline soils in the world. Five of the isolated strains exhibited strong inhibition to M. oryzae growth. The potential strains were identified as Bacillus safensis JLS5, Pseudomonas koreensis JLS8, Pseudomonas saponiphila JLS10, Stenotrophomonas rhizophila JLS11 and Bacillus tequilensis JLS12, respectively, by 16s RNA gene sequence analysis. The antagonistic assay and the artificial inoculation tests showed that JLS5 and JLS12 could effectively inhibit conidial germination and pathogenicity of the rice blast fungus, both preventively and curatively. The suppression of pathogenicity was further confirmed by greenhouse experiments, showing the effectiveness of JLS5 and JLS12 as a potential biological control agents of M. oryzae. The potential application of these cold-tolerant strains for rice blast control in cold regions is discussed. Our data suggest that soda saline-sodic soils are a rich source for biocontrol strain isolation.

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Pyrrolnitrin Biosynthesis From Rhizospheric Serratia Spp. With Antifungal Activity and Binding Interactions of PrnF With Ligands

10.21203/rs.3.rs-56362/v1 ◽

2020 ◽

Author(s):

Shraddha P. Pawar ◽

Ambalal B. Chaudhari

Keyword(s):

Antifungal Activity ◽

Phytopathogenic Fungi ◽

Bacterial Strains ◽

Rrna Sequence ◽

16S Rrna Sequence ◽

Protein Model ◽

Stenotrophomonas Rhizophila ◽

K 12 ◽

Layer Chromatography

Abstract Pyrrolnitrin (PRN) from rhizobacteria displays a key role in biocontrol of phytopathogenic fungi in rhizospheric soil. Therefore, different rhizospheric soils were investigated for the prevalence of PRN producer in minimal salt (MS) medium containing tryptophan (0.2 M NaCl; pH 8) using three successive enrichments. Of 12% isolates, only five bacterial strains had shown PRN secretion, screened with Thin Layer Chromatography (Rf 0.8) and antifungal activity (27 mm) against phytopathogen. The phenetic and 16S rRNA sequence revealed the close affiliation of isolates (KMB, M-2, M-11, TW3, and TO2) to Stenotrophomonas rhizophila (KY800458), Enterobacter spp. (KY800455), Brevibacillus parabrevis (KY800454), Serratia marcescens (KY800456) and Serratia nemtodiphila (KY800457). Purified compound from isolates was characterised using UV, IR, HPLC, LCMS and GCMS as PRN. However, BLASTn hit of prn gene sequences from both Serratia species showed 99% similarity with NADPH dependent FMN reductase component (prnF). The homology protein model of prnF was developed from translated sequence of S. marcescens TW3 with chromate reductase of Escherichia coli K-12. Docking with FMN and NADPH was performed. The study demonstrated the possible role of prnF NADPH dependent FMN reductases in prnD for supply of reduced flavin in rhizobacterial strain of Serratia spp. which may pave a way to understand PRN production.

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Xylanolytic Psychotrophs From Andosolic Sedge Fens and Moss Heaths in Iceland

Fine Focus ◽

10.33043/ff.4.2.171-186 ◽

2018 ◽

Vol 4 (2) ◽

pp. 171-186

Author(s):

Olivia J. Rickman ◽

M. Auður Sigurbjörnsdóttir ◽

Oddur Vilhemsson

Keyword(s):

Gene Sequencing ◽

16S Rrna Gene Sequencing ◽

Rrna Gene ◽

Bacterial Strains ◽

Cold Environments ◽

Specific Pcr ◽

Xylanolytic Activity ◽

Cold Active ◽

Rrna Gene Sequencing ◽

Stenotrophomonas Rhizophila

Nine xylanolytic bacterial strains were isolated from fen and heath soils in northern Iceland. They were found by 16S rRNA gene sequencing to belong to the genera Paenibacillus, Bacillus, Pseudomonas, and Stenotrophomonas. Using a simple, plate-based semiquantitative assay with azo-crosslinked xylan as the substrate, it was determined that although isolated from cold environments, most of the strains displayed greater xylanolytic activity under mesophilic conditions, with only the paenibacilli displaying markedly cold-active xylanolytic activity. Indeed, for one isolate, Paenibacillus castaneae OV2122, xylanolytic activity was only detected at 15°C and below under the conditions tested. Of the nine strains, Paenibacillus amylolyticus OV2121 displayed the greatest activity at 5°C. Glycohydrolase family-specific PCR indicated that the paenibacilli produced multiple xylanases of families 10 and 11, whereas a family 8 xylanase was detected in Pseudomonas kilonensis AL1515, and a family 11 xylanase in Stenotrophomonas rhizophila AL1610.

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Fengycins, Cyclic Lipopeptides from MarineBacillus subtilisStrains, Kill the Plant-Pathogenic FungusMagnaporthe griseaby Inducing Reactive Oxygen Species Production and Chromatin Condensation

Applied and Environmental Microbiology ◽

10.1128/aem.00445-18 ◽

2018 ◽

Vol 84 (18) ◽

Cited By ~ 31

Author(s):

Linlin Zhang ◽

Chaomin Sun

Keyword(s):

Mass Spectrometry ◽

Reactive Oxygen Species ◽

Biological Control ◽

Bacillus Subtilis ◽

Rice Blast ◽

Marine Bacterium ◽

Magnaporthe Grisea ◽

Chromatin Condensation ◽

Oxygen Species ◽

Content Type

ABSTRACTRice blast caused by the phytopathogenMagnaporthe griseaposes a serious threat to global food security and is difficult to control.Bacillusspecies have been extensively explored for the biological control of many fungal diseases. In the present study, the marine bacteriumBacillus subtilisBS155 showed a strong antifungal activity againstM. grisea. The active metabolites were isolated and identified as cyclic lipopeptides (CLPs) of the fengycin family, named fengycin BS155, by the combination of high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Analyses using scanning and transmission electron microscopy revealed that fengycin BS155 caused morphological changes in the plasma membrane and cell wall ofM. griseahyphae. Using comparative proteomic and biochemical assays, fengycin BS155 was demonstrated to reduce the mitochondrial membrane potential (MMP), induce bursts of reactive oxygen species (ROS), and downregulate the expression level of ROS-scavenging enzymes. Simultaneously, fengycin BS155 caused chromatin condensation in fungal hyphal cells, which led to the upregulation of DNA repair-related protein expression and the cleavage of poly(ADP-ribose) polymerase (PARP). Altogether, our results indicate that fengycin BS155 acts by inducing membrane damage and dysfunction of organelles, disrupting MMP, oxidative stress, and chromatin condensation, resulting inM. griseahyphal cell death. Therefore, fengycin BS155 and its parent bacterium are very promising candidates for the biological control ofM. griseaand the associated rice blast and should be further investigated as such.IMPORTANCERice (Oryza sativaL.) is the most important crop and a primary food source for more than half of the world's population. Notably, scientists in China have developed several types of rice that can be grown in seawater, avoiding the use of precious freshwater resources and potentially creating enough food for 200 million people. The plant-affecting fungusMagnaporthe griseais the causal agent of rice blast disease, and biological rather than chemical control of this threatening disease is highly desirable. In this work, we discovered fengycin BS155, a cyclic lipopeptide material produced by the marine bacteriumBacillus subtilisBS155, which showed strong activity againstM. grisea. Our results elucidate the mechanism of fengycin BS155-mediatedM. griseagrowth inhibition and highlight the potential ofB. subtilisBS155 as a biocontrol agent againstM. griseain rice cultivation under both fresh- and saltwater conditions.

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Insecticidal Activity of Bacteria from Larvae Breeding Site with Natural Larvae Mortality: Screening of Separated Supernatant and Pellet Fractions

Pathogens ◽

10.3390/pathogens9060486 ◽

2020 ◽

Vol 9 (6) ◽

pp. 486 ◽

Cited By ~ 1

Author(s):

Handi Dahmana ◽

Didier Raoult ◽

Florence Fenollar ◽

Oleg Mediannikov

Keyword(s):

Biological Control ◽

Insecticidal Activity ◽

Breeding Site ◽

Bacterial Strains ◽

Activity Prediction ◽

Pcr Screening ◽

Breeding Sites ◽

Insecticide Activity ◽

New Compounds

Mosquitoes can transmit to humans devastating and deadly pathogens. As many chemical insecticides are banned due to environmental side effects or are of reduced efficacy due to resistance, biological control, including the use of bacterial strains with insecticidal activity, is of increasing interest and importance. The urgent actual need relies on the discovery of new compounds, preferably of a biological nature. Here, we explored the phenomenon of natural larvae mortality in larval breeding sites to identify potential novel compounds that may be used in biological control. From there, we isolated 14 bacterial strains of the phylum Firmicutes, most of the order Bacillales. Cultures were carried out under controlled conditions and were separated on supernatant and pellet fractions. The two fractions and a 1:1 mixture of the two fractions were tested on L3 and early L4 Aedes albopictus. Two concentrations were tested (2 and 6 mg/L). Larvae mortality was recorded at 24, 48 and 72 h and compared to that induced by the commercialized B. thuringiensis subsp. israelensis. Of the 14 strains isolated, 11 were active against the A. albopictus larvae: 10 of the supernatant fractions and one pellet fraction, and mortality increased with the concentration. For the insecticide activity prediction in three strains of the Bacillus cereus complex, PCR screening of the crystal (Cry) and cytolytic (Cyt) protein families characteristic to B. thuringiensis subsp. israelensis was performed. Most of the genes coding for these proteins’ synthesis were not detected. We identified bacterial strains that exhibit higher insecticidal activity compared with a commercial product. Further studies are needed for the characterization of active compounds.

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Evaluation of bacteria isolated from rice for plant growth promotion and biological control of seedling disease of rice

Canadian Journal of Microbiology ◽

10.1139/w01-097 ◽

2001 ◽

Vol 47 (10) ◽

pp. 916-924 ◽

Cited By ~ 71

Author(s):

Tika B Adhikari ◽

C M Joseph ◽

Guoping Yang ◽

Donald A Phillips ◽

Louise M Nelson

Keyword(s):

Biological Control ◽

Plant Growth ◽

Plant Growth Promotion ◽

Growth Promotion ◽

Disease Incidence ◽

Control Plant ◽

16S Rrna Genes ◽

Rrna Genes ◽

Bacterial Strains ◽

Seedling Disease

Of 102 rhizoplane and endophytic bacteria isolated from rice roots and stems in California, 37% significantly (P [Formula: see text] 0.05) inhibited the growth in vitro of two pathogens, Achlya klebsiana and Pythium spinosum, causing seedling disease of rice. Four endophytic strains were highly effective against seedling disease in growth pouch assays, and these were identified as Pseudomonas fluorescens (S3), Pseudomonas tolaasii (S20), Pseudomonas veronii (S21), and Sphingomonas trueperi (S12) by sequencing of amplified 16S rRNA genes. Strains S12, S20, and S21 contained the nitrogen fixation gene, nifD, but only S12 was able to reduce acetylene in pure culture. The four strains significantly enhanced plant growth in the absence of pathogens, as evidenced by increases in plant height and dry weight of inoculated rice seedlings relative to noninoculated rice. Three bacterial strains (S3, S20, and S21) were evaluated in pot bioassays and reduced disease incidence by 50%73%. Strain S3 was as effective at suppressing disease at the lowest inoculum density (106 CFU/mL) as at higher density (108 CFU/mL or undiluted suspension). This study indicates that selected endophytic bacterial strains have potential for control of seedling disease of rice and for plant growth promotion.Key words: biological control, plant growth promotion, endophytes, rice, seedling disease.

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Genetic Differentiation of Magnaporthe oryzae Populations from Scouting Plots and Commercial Rice Fields in Korea

Phytopathology ◽

10.1094/phyto-98-4-0436 ◽

2008 ◽

Vol 98 (4) ◽

pp. 436-442 ◽

Cited By ~ 10

Author(s):

S.-Y. Park ◽

M. G. Milgroom ◽

S. S. Han ◽

S. Kang ◽

Y.-H. Lee

Keyword(s):

Genetic Differentiation ◽

Mating Type ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Disease Incidence ◽

Rice Fields ◽

Dna Fingerprint ◽

Group I ◽

Group Ii ◽

Set Up

A previous study of the diversity and population structure of the rice blast fungus, Magnaporthe oryzae, over a 20-year period in Korea, found novel fingerprint haplotypes each year, and the authors hypothesized that populations might experience annual bottlenecks. Based on this model, we predicted that M. oryzae populations would have little or no genetic differentiation among geographic regions because rice blast is commonly found throughout Korea each year and M. oryzae would have to disperse from small populations surviving annually between rice crops. To test this hypothesis, we sampled M. oryzae from rice fields in eight provinces in Korea in a single year (1999). In four provinces, we sampled from a set of rice cultivars commonly grown in commercial fields (group I); because of low disease incidence in four other provinces, we could not sample from commercial fields and instead sampled from scouting plots of different cultivars set up for detecting new pathotypes of M. oryzae (group II). All isolates were genotyped with DNA fingerprint probes MGR586 and MAGGY, a telomere-linked gene family member TLH1, the PWL2 host specificity gene and mating type. Fingerprint haplotypes clustered into two distinct lineages corresponding to the two sets of cultivars (groups I and II), with haplotype similarities of 71% between lineages and >76% within lineages. Isolates from the same cultivar within group I were genetically differentiated among locations, and isolates within the same location were differentiated among cultivars. Differentiation for TLH1 and PWL2 was significant (P < 0.03), but not as strong as for fingerprint markers. Similar analyses were not possible among group II isolates because too few isolates were available from any one cultivar. All isolates were in the same mating type, Mat1-1, ruling out sexual reproduction as a source of novel haplotypes. When the 1999 samples were compared with the historical samples from the previous study, haplotypes of group I formed a separate cluster, while those of group II clustered with haplotypes from the historical sample. Altogether, geographic subdivision, monomorphism of mating type, and correlation of haplotypes to sets of cultivars are not consistent with the hypothesis of repeated turnover of haplotypes. Instead, the previous correlations of haplotypes to year might have been caused by inadequate sampling of haplotypes each year, highlighting the need for studies of population genetics to be conducted with systematic samples collected to address specific questions.

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Occurrence, Distribution, Epidemiology, Cultivar Reaction, and Management of Rice Blast Disease in California

Plant Disease ◽

10.1094/pdis.2001.85.10.1096 ◽

2001 ◽

Vol 85 (10) ◽

pp. 1096-1102 ◽

Cited By ~ 35

Author(s):

C. A. Greer ◽

R. K. Webster

Keyword(s):

Rice Blast ◽

Large Scale ◽

Rice Fields ◽

Blast Disease ◽

Weather Data ◽

Disease Surveys ◽

Spore Trapping ◽

Small Plot ◽

Epidemic Development ◽

Major Resistance Genes

Rice blast, caused by Pyricularia grisea, was first found in California in 1996. Disease surveys have shown the blast disease is spreading at a moderate rate in California rice fields. Although no effective major resistance genes are known to occur in widely grown commercial California cultivars, there appear to be differences among the cultivars with respect to field susceptibility to the pathogen. P. grisea was recovered from rice crop residue and commercial seedlots which are suggested as possible sources of initial P. grisea inoculum in California rice fields. Examination of weather data indicates that environmental conditions in California rice-producing areas are permissive for rice blast but generally not optimal for epidemic development. Spore trapping determined that the majority of P. grisea conidia are generally not released until approximately 6:00 A.M. and would not have sufficient time for infection before leaf wetness periods end. Azoxystrobin showed positive results with respect to reduction of neck blast incidence and yield increases in small-plot and large-scale fungicide trials.

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