biocontrol strain
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2023 ◽  
Vol 83 ◽  
Author(s):  
A. Abrar ◽  
S. Sarwar ◽  
M. Abbas ◽  
H. Chaudhry ◽  
N. Ghani ◽  
...  

Abstract Dengue fever vectored by the mosquito Aedes aegypti is one of the most rapidly spreading insect-borne diseases. Current reliance of dengue vector control is mostly on chemical insecticides. Growing insecticide resistance in the primary mosquito vector, Aedes aegypti, limits the effectiveness of vector control through chemical insecticides. These chemical insecticides also have negative environmental impacts on animals, plants and human health. Myco-biocontrol agents are naturally occurring organisms and are found to be less damaging to the environment as compared to chemical insecticides. In the present study, entomopathogenic potential of local strains of fungi isolated from soil was assessed for the control of dengue vector. Local fungal isolates presents better alternative to introducing a foreign biocontrol strain, as they may be better adapted to environmental conditions of the area to survive and may have more entomopathogenic efficacy against target organism. Larvicidal efficacy of Fusarium equiseti and Fusarium proliferatum was evaluated against Aedes aegypti. Local strains of F. equiseti (MK371718) and F. proliferatum (MK371715) were isolated from the soil of Changa Manga Forest, Pakistan by using insect bait method. Larvicidal activity of two Fusarium spp. was tested against forth instar larvae of A. aegypti in the laboratory, using concentrations 105, 106, 107 and 108 conidia /ml. LC50 values for F. equiseti after 24h, 48h, 72h and 96h of exposure were recorded as 3.8x 108, 2.9x107, 2.0x107, and 7.1x106 conidia /ml respectively while LC50 values for F. proliferatum were recorded as 1.21x108, 9.6x107, 4.2x107, 2.6x107 conidia /ml respectively after 24h, 48h, 72h and 96h of exposure. The results indicate that among two fungal strains F. equiseti was found to be more effective in terms of its larvicidal activity than F. proliferatum against larvae of A. aegypti.


Author(s):  
Connel Ching'anda ◽  
Joseph Atehnkeng ◽  
Ranajit Bandyopadhyay ◽  
Kenneth Callicott ◽  
Marc J Orbach ◽  
...  

Aspergillus flavus infects a wide range of crops, including pistachios, and subsequent aflatoxin contamination results in significant economic losses. Application of biocontrol products based on non-aflatoxigenic (atoxigenic) strains of A. flavus is one of the most effective tactics for controlling aflatoxins in crops. Both risk of aflatoxin contamination and effectiveness of biocontrol are influenced by the extent to which A. flavus spores move into pistachio tree canopies during periods of nut development. Thus, the purpose of this study was to evaluate spatial and temporal population dynamics of A. flavus, including the applied biocontrol strain AF36, in canopies of pistachio orchards in Arizona. Propagule densities of A. flavus were quantified on leaf samples collected from lower, middle, and upper canopies from spring through harvest in 2018 and 2019. Aspergillus flavus propagule densities peaked during periods of high temperature and rainfall in 2018 (up to 600 CFU/g) and 2019 (up to 23 CFU/g), which coincided with nut development and maturation. The applied biocontrol strain AF36 was detected at all canopy heights, but overall propagule densities were greater in the upper and middle canopy (mean = 70 CFU/g) compared to the lower canopy (mean = 47 CFU/g). Results suggest June to August is the period during which A. flavus inoculum increases in Arizona pistachio orchards, and to most effectively displace aflatoxin-producing fungi in tree canopies, biocontrol applications should precede this period. In addition, this study demonstrates that soil-applied biocontrol strains can successfully disperse throughout the canopies of commercial tree nut orchards.


2022 ◽  
Vol 12 ◽  
Author(s):  
Constantine Uwaremwe ◽  
Liang Yue ◽  
Yun Wang ◽  
Yuan Tian ◽  
Xia Zhao ◽  
...  

Root rot disease is a serious infection leading to production loss of Chinese wolfberry (Lycium barbarum). This study tested the potential for two bacterial biological control agents, Bacillus amyloliquefaciens HSB1 and FZB42, against five fungal pathogens that frequently cause root rot in Chinese wolfberry. Both HSB1 and FZB42 were found to inhibit fungal mycelial growth, in vitro and in planta, as well as to promote the growth of wolfberry seedlings. In fact, a biocontrol experiment showed efficiency of 100% with at least one treatment involving each biocontrol strain against Fusarium oxysporum. Metagenomic sequencing was used to assess bacterial community shifts in the wolfberry rhizosphere upon introduction of each biocontrol strain. Results showed that HSB1 and FZB42 differentially altered the abundances of different taxa present and positively influenced various functions of inherent wolfberry rhizosphere bacteria. This study highlights the application of biocontrol method in the suppression of fungal pathogens that cause root rot disease in wolfberry, which is useful for agricultural extension agents and commercial growers.


Author(s):  
Alexandra Schamann ◽  
Markus Schmidt-Heydt ◽  
Rolf Geisen

AbstractNon-aflatoxigenic Aspergillus flavus strains are used as a biocontrol system on maize fields to decrease the aflatoxin biosynthesis of aflatoxigenic A. flavus strains. A. flavus strain AF36 was the first commercially available biocontrol strain and is authorized for use on maize fields by the US Environmental Protection Agency, e.g., in Texas and Arizona. A droplet digital PCR (ddPCR) assay was developed to analyze the mechanisms of competition and interaction of aflatoxigenic and non-aflatoxigenic A. flavus strains. This assay enables the parallel identification and quantification of the biocontrol strain A. flavus AF36 and the aflatoxigenic A. flavus strain MRI19. To test the assay, spores of both strains were mixed in varying ratios and were incubated on maize-based agar or maize kernels for up to 20 days. Genomic equivalent ratios (genome copy numbers) of both strains were determined by ddPCR at certain times after incubation and were compared to the spore ratios used for inoculation. The aflatoxin biosynthesis was also measured. In general, A. flavus MRI19 had higher competitiveness in the tested habitats compared to the non-aflatoxigenic strain, as indicated by higher final genomic equivalent ratios of this strain compared to the spore ratios used for inoculation. Nevertheless, A. flavus AF36 effectively controlled aflatoxin biosynthesis of A. flavus MRI19, as a clear aflatoxin inhibition was already seen by the inoculation of 10% spores of the biocontrol strain mixed with 90% spores of the aflatoxigenic strain compared to samples inoculated with only spores of the aflatoxigenic A. flavus MRI19.


2021 ◽  
Vol 164 ◽  
pp. 104766
Author(s):  
Lining Zheng ◽  
Jinpeng Zhang ◽  
Xian Wu ◽  
Xuehu Gu ◽  
Shuanglong Wang ◽  
...  

2021 ◽  
Author(s):  
Yixin Luo ◽  
Min Liao ◽  
Yuhao Zhang ◽  
Na Xu ◽  
Xiaomei Xie ◽  
...  

Abstract In order to explore whether the newly discovered biocontrol strain Paenibacillus sp., LYX-1 having antagonistic effect on peach brown rot was resistant to Cd2+, a series of growth of strain LYX-1 under different Cd concentration and biosorption experiments were conducted to living and dead strain LYX-1. Meanwhile, the Cd2+ resistance and biosorption mechanisms were further identified by Cd-resistant genes, TEM, SEM-EDS, FTIR and XPS analysis. The results showed that strain LYX-1 could resist 50 mg/L Cd2+ and the adsorption process of both living and dead strain LYX-1 all satisfied the pseudo-second kinetic equation. Under pH 8.0 and at a dose of 1.0 g/L strain, the removal capacities of living and dead cells were as high as 90.39% and 75.67% at 20 mg/L Cd2+, respectively. For the adsorption isotherm test, results revealed that both Langmuir (R2=0.9704) and Freundlich (R2=0.9915) model could describe the Cd2+ biosorption well for living strain LYX-1. The maximum equilibrium biosorption capacities of living and dead biomass were 30.6790 and 24.3752 mg/g, respectively. The adsorption mechanism was controlled by chemisorption with -OH, -NH, -C=O, O=C-O, C-N, S2− and phosphate functional groups on the cell surface of strain LYX-1, which were further identified by XPS. The insignificant biosorption difference of living and dead biomass was caused by CzcD gene in strain LYX-1 detoxifying cadmium through the heavy metal efflux system. The above results indicated that strain LYX-1 had higher tolerance and fixed capacity to Cd2+.


Plant Disease ◽  
2021 ◽  
Author(s):  
Juan Moral Moral ◽  
MARÍA TERESA GARCÍA LOPEZ ◽  
Ana Gordon ◽  
Alejandro Ortega-Beltran ◽  
Ryan D Puckett ◽  
...  

Aflatoxin contamination of almond kernels, caused by Aspergillus flavus and A. parasiticus, is a severe concern for growers due to its high toxicity. In California, the global leader of almond production, aflatoxin can be managed by applying the biological control strain AF36 of A. flavus and selecting resistant cultivars. Here, we classified the almond genotypes by K-Means cluster analysis into three groups [Susceptible (S), Moderately Susceptible (MS), or Resistant (R)] based on aflatoxin content of inoculated kernels. The protective effects of the shell and seedcoat in preventing aflatoxin contamination were also examined. The presence of intact shells reduced aflatoxin contamination over 100-fold. The seedcoat provided a layer of protection, but not complete. In kernel inoculation assays, none of the studied almond genotypes showed a total resistance to the pathogen. However, nine traditional cultivars and four advanced selections were classified as R. Because these advanced selections contained germplasm derived from peach, we compared the kernel resistance of three peach cultivars to that shown by kernels of a R (‘Sonora’) and a S (‘Carmel’) almond cultivar and five pistachio cultivars. Overall, peach kernels were significantly more resistant to the pathogen than almond kernels, which were more resistant than pistachio kernels. Finally, we studied the combined effect of the cultivar resistance and the biocontrol strain AF36 in limiting aflatoxin contamination. For this, we co-inoculated almond kernels of R ‘Sonora’ and S ‘Carmel’ with AF36 72 h before or 48 h after inoculating with an aflatoxin-producing strain of A. flavus. The percentage of aflatoxin reduction by AF36 strain was greater in kernels of ‘Carmel’ kernels (98%) than in those of ‘Sonora’ (83%). Cultivar resistance also affected the kernel colonization by the biological control strain. AF36 strain limited aflatoxin contamination in almond kernels even when applied 48 h after the aflatoxin-producing strain. Our results show that biocontrol combined with the use of cultivars with resistance to aflatoxin contamination can result in a more robust protection strategy than the use of either practices in isolation.


Author(s):  
Marjolein Hooykaas ◽  
Paul Hooykaas

We report here the complete genome sequence of the Rhizobium rhizogenes (formerly Agrobacterium rhizogenes) strain LBA9402 (NCPPB1855rifR), a pathogenic strain causing hairy root disease. In order to assemble a complete genome we obtained short-reads from Illumina sequencing as well as long-reads from Oxford Nanopore Technology sequencing. The genome consists of a 3,958,212 bp chromosome, a 2,005,144 bp chromid (secondary chromosome) and a 252,168 bp Ri plasmid (pRi1855), respectively. The primary chromosome was very similar to that of the avirulent biocontrol strain K84, but the chromid showed a 724 kbp deletion accompanied by a large 1.8 Mbp inversion revealing the dynamic nature of these secondary chromosomes. The sequence of the agropine Ri plasmid was compared to other types of Ri and Ti plasmids. Thus we identified the genes responsible for agropine catabolism, but also a unique segment adjacent to the TL-region that has the signature of a new opine catabolic gene cluster including the three genes that together encode an opine dehydrogenase. Our sequence analysis also revealed a novel gene at the very right end of the TL-DNA, which is unique for the agropine Ri plasmid. The protein encoded by this gene was most related to the succinamopine synthases of chrysopine and agropine Ti plasmids and thus may be involved in synthesis of the unknown opine that can be degraded by the adjacent catabolic cluster. The available sequence will facilitate the use of R. rhizogenes and especially LBA9402 in both the laboratory and for biotechnological purposes.


2020 ◽  
Vol 11 ◽  
Author(s):  
Kasumi Takeuchi ◽  
Wataru Tsuchiya ◽  
Zui Fujimoto ◽  
Kosumi Yamada ◽  
Nobutaka Someya ◽  
...  

Many root-colonizing Pseudomonas spp. exhibiting biocontrol activities produce a wide range of secondary metabolites that exert antibiotic effects against other microbes, nematodes, and insects in the rhizosphere. The expression of these secondary metabolites depends on the Gac/Rsm signal transduction pathway. Based on the findings of a previous genomic study on newly isolated biocontrol pseudomonad strains, we herein investigated the novel gene cluster OS3, which consists of four genes (Os1348–Os1351) that are located upstream of putative efflux transporter genes (Os1352–Os1355). Os1348 was predicted to encode an 85-aa small precursor protein, the expression of which was under the control of GacA, and an X-ray structural analysis suggested that the Os1348 protein formed a dimer. The mutational loss of the Os1348 gene decreased the antibiotic activity of Pseudomonas sp. Os17 without changing its growth rate. The Os1349–1351 genes were predicted to be involved in post-translational modifications. Intracellular levels of the Os1348 protein in the deficient mutant of each gene differed from that in wild-type cells. These results suggest that Os1348 is involved in antibiotic activity and that the structure or expression of this protein is under the control of downstream gene products.


Plant Disease ◽  
2020 ◽  
Author(s):  
MARÍA TERESA GARCÍA LOPEZ ◽  
Yong Luo ◽  
Alejandro Ortega-Beltran ◽  
Ramon Jaime ◽  
Juan Moral Moral ◽  
...  

The species Aspergillus flavus and A. parasiticus are commonly found in the soils of nut-growing areas in California. Several isolates can produce aflatoxins that occasionally contaminate nut kernels conditioning their sale. The strain AF36 of A. flavus, which does not produce aflatoxins, is registered as a biocontrol agent for use in almond, pistachio, and fig crops in California. After application in the orchards, AF36 displaces aflatoxin-producing Aspergillus spp. and thus reduces aflatoxin contamination. Vegetative compatibility assays (VCA) have traditionally been used to track AF36 in soils and crops where it has been applied. However, VCA is labor-intensive and time-consuming. Here, we developed a quantitative real-time PCR (qPCR) protocol to quantify proportions of AF36 accurately and efficiently in different substrates. Specific primers to target AF36 and toxigenic strains of A. flavus and A. parasiticus were designed based on sequence of aflC, a gene essential for aflatoxin biosynthesis. Standard curves were generated to calculate proportions of AF36 based on threshold values (Cq). Verification assays using pure DNA and conidial suspension mixtures demonstrated a significant relationship by regression analysis between known and qPCR-measured AF36 proportions in DNA (R2 = 0.974; P < 0.001) and conidia mixtures (R2 = 0.950; P < 0.001). The tests conducted by qPCR in pistachio leaves, nuts, and soil samples demonstrated the usefulness of the qPCR method to precisely quantify proportions of AF36 in diverse substrates, ensuring important time and cost savings. The outputs of the current study will serve to design better aflatoxin management strategies for pistachio and other crops.


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