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Phosphorus constitutes a crucial macronutrient for crop growth, yet its availability often limits food production. Efficient phosphorus management is crucial for enhancing crop yields and ensuring food security. This study aimed to enhance the efficiency of a short-chain polyphosphate (PolyP) fertilizer by integrating it with plant growth-promoting bacteria (PGPB) to improve nutrient solubilization and wheat growth. Specifically, the study investigated the effects of various bacterial strains on wheat germination and growth when used in conjunction with PolyP. To achieve this, a greenhouse experiment was conducted in which the wheat rhizosphere was amended with a short-chain PolyP fertilizer. Based on the morphological aspect, eight bacteria, designated P1 to P8, were isolated and further characterized. Plant growth-promoting traits were observed in all bacterial strains, as they presented the ability to produce Indole Acetic Acid (IAA) in significant amounts ranging from 7.5 ± 0.3 µg/mL to 44.1 ± 2 µg/mL, expressed by B. tropicus P4 and P. soyae P1, respectively. They also produced ammonia, hydrogen cyanide (HCN), and siderophores. Their effect against the plant pathogen Fusarium culmorum was also assessed, with P. reinekei P2 demonstrating the highest biocontrol activity as it presented a total inhibitory effect. Additionally, some strains exhibited the ability to solubilize/hydrolyze phosphorus, potassium, and zinc. In vivo, the initial growth potential of wheat seeds indicated that those inoculated with the isolated strains exhibited elevated germination rates and enhanced root growth. Based on their plant growth-promoting traits and performance in the germination assay, three strains were selected for producing the best results, specifically phosphorus hydrolyzation/solubilization, zinc solubilization, IAA production, HCN, and siderophores production. Wheat seeds were inoculated by drenching in a bacterial suspension containing 1010 CFU/mL of log phase culture, and an in planta bioassay was conducted in a growth chamber using three selected strains (Pseudomonas soyae P1, Pseudomonas reinekei P2, and Bacillus tropicus P4), applied either individually or with PolyP on a P-deficient soil (28 mg/kg of P Olsen). Our findings demonstrated that the combination of Pseudomonas soyae P1 and PolyP achieved the highest shoot biomass, averaging 41.99 ± 0.87 g. Notably, applying P. soyae P1 or Bacillus tropicus P4 alone yielded similar results to the use of PolyP alone. At the heading growth stage, the combination of Bacillus tropicus P4 and PolyP significantly increased the Chlorophyll Content Index (CCI) to 37.02 µmol/m2, outperforming both PolyP alone (24.07 µmol/m2) and the control (23.06 µmol/m2). This study presents an innovative approach combining short-chain PolyP with bacterial biostimulants to enhance nutrient availability and plant growth. By identifying and characterizing effective bacterial strains, it offers a sustainable alternative to conventional fertilizers. [ABSTRACT FROM AUTHOR]

The gram‐positive bacterium Bacillus velezensis strain DMW1 produces a high level of antimicrobial metabolites that can suppress the growth of phytopathogens. We investigated the mechanism used by degQ and the degS/degU two‐component system to regulate the biocontrol characteristics of DMW1. When degQ and degU were deleted, the biofilm formation, cell motility, colonization activities, and antifungal abilities of ΔdegQ and ΔdegU were significantly reduced compared to wild‐type DMW1. The expression levels of biofilm‐related genes (epsA, epsB, epsC, and tasA) and swarming‐related genes (swrA and swrB) were all down‐regulated. We also evaluated the impact on secondary metabolites of these two genes. The degQ and degU genes reduced surfactin and macrolactin production and up‐regulated the production of fengycin, iturin, bacillaene, and difficidin metabolites. The reverse transcription‐quantitative PCR results were consistent with these observations. Electrophoretic mobility shift assay and microscale thermophoresis revealed that DegU can bind to the promoter regions of these six antimicrobial metabolite genes and regulate their synthesis. In conclusion, we provided systematic evidence to demonstrate that the degQ and degU genes are important regulators of multicellular behaviour and antimicrobial metabolic processes in B. velezensis DMW1 and suggested novel amenable strains to be used for the industrial production of antimicrobial metabolites. [ABSTRACT FROM AUTHOR]

A total of 18 Streptomyces species were isolated from the rhizospheric soil of maize. Among 18 isolates, SDSRO-13 showed strong inhibition against Colletotrichum spp. of chilli. SDSRO-13 was identified as Streptomyces sp. based on morphological, biochemical and 16S rRNA partial gene sequence analysis. In this study, two strains of Colletotrichum sp. were used for pathogenicity test. For in vivo antifungal activity, spore suspension of the test pathogens were used on the fresh chilli fruit by making a small puncture on the fruit, in completely sterile conditions and incubated for up to 21 days. The chilli fruits treated with SDSRO-13 and test pathogens showed no disease symptoms. The infected fruits were subjected for Koch's postulate test and they showed the similar morphological features compared to the pure cultures of the pathogens. We conclude that actinomycetes, especially members of the genus Streptomyces are potential biocontrol agents which offer safer alternative management strategy to control the chilli fungal pathogens. [ABSTRACT FROM AUTHOR]

Apple ring rot, one of the most common apple postharvest diseases during storage, is caused by Botryosphaeria dothidea. Fungicide application is the most widely used method to control this disease, but the increasing environmental and food safety concerns greatly limit their use. The present study aimed to examine the biocontrol activity and underlying action mechanism of Bacillus halotolerans strain Pl7 against B. dothidea. The results revealed that B. halotolerans strain Pl7 exhibited strong inhibitory activity against B. dothidea by 69% in vitro. The culture filtrate of strain Pl7 possessed cellulase, β-1, 3-glucanase, protease activity and mediated the antifungal activity against B. dothidea. Further analysis demonstrated that culture filtrate of strain Pl7 could cause cell membrane permeabilization of B. dothidea. Apple fruit suffering from ring rot induced by a carbendazim (CBZ)-sensitive or -resistant B. dothidea isolate was much suppressed after being treated with strain Pl7, maintaining postharvest quality. The ability of strain Pl7 to swiftly colonize and thrive in apple fruit wounds was demonstrated by a re-isolation assay. Additional transcriptome studies of untreated and treated apple fruit with strain Pl7 revealed that strain Pl7 mostly changed the expression of genes functioning in plant secondary metabolite biosynthesis and plant-pathogen interaction. In light of these outcomes, the underlying antagonistic mechanism was investigated, and B. halotolerans strain Pl7 was identified as a promsing microbial biocontrol agent against apple postharvest decay. [ABSTRACT FROM AUTHOR]

Introduction: Several microorganisms in the plant root system, especially in the rhizosphere, have their own compositions and functions. Corm rot is the most severe disease of Crocus sativus, leading to more than 50% mortality in field production. Methods: In this study, metagenomic sequencing was used to analyze microbial composition and function in the rhizosphere of C. sativus for possible microbial antagonists against pathogenic Fusarium oxysporum. Results: The microbial diversity and composition were different in the C. sativus rhizosphere from different habitats. The diversity index (Simpson index) was significantly lower in the C. sativus rhizospheric soil from Chongming (Rs_CM) and degenerative C. sativus rhizospheric soil from Chongming (RsD_CM) than in others. Linear discriminant analysis effect size results showed that differences among habitats were mainly at the order (Burkholderiales, Micrococcales, and Hypocreales) and genus (Oidiodendron and Marssonina) levels. Correlation analysis of the relative lesion area of corm rot showed that Asanoa was the most negatively correlated bacterial genus (ρ = −0.7934, p < 0.001), whereas Moniliophthora was the most negatively correlated fungal genus (ρ = −0.7047, p < 0.001). The relative lesion area result showed that C. sativus from Qiaocheng had the highest resistance, followed by Xiuzhou and Jiande. C. sativus groups with high disease resistance had abundant pathogen resistance genes, such as chitinase and β-1,3-glucanase genes, from rhizosphere microorganisms. Further, 13 bacteria and 19 fungi were isolated from C. sativus rhizosphere soils, and antagonistic activity against pathogenic F. oxysporum was observed on potato dextrose agar medium. In vivo corm experiments confirmed that Trichoderma yunnanense SR38, Talaromyces sp. SR55, Burkholderia gladioli SR379, and Enterobacter sp. SR343 displayed biocontrol activity against corm rot disease, with biocontrol efficiency of 20.26%, 31.37%, 39.22%, and 14.38%, respectively. Discussion: This study uncovers the differences in the microbial community of rhizosphere soil of C. sativus with different corm rot disease resistance and reveals the role of four rhizospheric microorganisms in providing the host C. sativus with resistance against corm rot. The obtained biocontrol microorganisms can also be used for application research and field management. [ABSTRACT FROM AUTHOR]

A new partititvirus isolated from a Trichoderma harzianum strain (T673), collected in China, was characterized and annotated as Trichoderma harzianum partitivirus 2 (ThPV2). The genome of ThPV2 consists of a 1693 bp dsRNA1 encoding a putative RNA-dependent RNA polymerase (RdRp) and a 1458 bp dsRNA2 encoding a hypothetical protein. In comparative studies employing the ThPV2-infected strain (T673) and a strain cured by ribavirin treatment (virus-free strain T673-F), we investigated biological effects of ThPV2 infection. While the growth rate of the virus-infected fungus differed little from that of the cured variant, higher mycelial density, conidiospore, and chlamydospore production were observed in the virus-infected strain T673. Furthermore, both the ThPV2-infected and the cured strain showed growth- and development-promoting activities in cucumber plants. In vitro confrontation tests showed that strains T673 and T673-F inhibited several important fungal pathogens and an oomycete pathogen in a comparable manner. Interestingly, in experiments with cucumber seeds inoculated with Fusarium oxysporum f. sp. cucumerinum, the ThPV2-infected strain T673 showed moderately but statistically significantly improved biocontrol activity when compared with strain T673-F. Our data broaden the spectrum of known mycoviruses and provide relevant information for the development of mycoviruses for agronomic applications. [ABSTRACT FROM AUTHOR]

Aims: To study the effects of mixed culture fermentation (MCF) of Bacillus amyloliquefaciens and Trichoderma longibrachiatum on its constituent strains and the application values for agricultural production, with the intention of developing efficient and environmentally friendly biocontrol agents. Methods and results: In this study, an in vitro antifungal growth experiment showed that the inhibitory rate of the MCF broth on pathogenic fungi (Fusarium oxysporum f. sp. lycopersici, Botrytis cinerea, Trichothecium roseum and Colletotrichum gloeosporioides) was less than that of B. amyloliquefaciens culture fermentation (BCF). Moreover, the content and gene expression of lipopeptide antibiotics were also lower than that in the BCF group. However, the pot experiments based on irrigation with appropriately diluted fermentation broth showed that the biocontrol effect of MCF on tomato Fusarium wilt was significantly higher than that of TCF (T. longibrachiatum culture fermentation) and BCF, and was approximately 15.79% higher than that of the BTF group which made by mixing equivalent amounts of BCF and TCF. In MCF broth, two micro‐organisms antagonized and coexisted, and the growth of T. longibrachiatum was inhibited. Using transcriptomic analysis, we speculated that MCF can upregulate the expression of genes related to carbon and nitrogen metabolism, oxidation–reduction activity, sporulation, environmental information response and chemotaxis, and biosynthesis of secondary metabolites of B. amyloliquefaciens, which might enhance the nutrient substances metabolism and competitiveness, survival ability, colonization and adaptability to the environment to increase its biocontrol potential. Conclusions: Mixed culture fermentation could promote the more reasonable and effective utilization of biocontrol micro‐organisms though improving biocontrol effect, enhancing strains survival and competitiveness, increasing beneficial metabolites, combined with resistance induction or synergistic control. Significance and Impact of the Study: Using MCF agronomically utilizes biocontrol agents in an efficient way, which has a good potential for commercial implementation and could reduce production costs. [ABSTRACT FROM AUTHOR]

The phosphate solubility and biocontrol activity of fungi isolated from rhizosphere soil of Marathwada were studied in the present study. Fungi were isolated from rhizosphere soil and all the 11 fungal isolates showed good phosphate solubilizing ability. The potent phosphate solubilising isolates Aspergillus niger (PQ9), Trichodermaspp (PQ36) and Penicillium spp (PQ19) showed significant zone of solubilization with 34, 31 to 30 mm respectively after 48 hours of incubation. All potent phosphate solubilising fungal isolates were tested for in vitro antagonistic activity against bacterial plant pathogen Fusarium oxysporum, Fusarium solani, Rhizoctonia solani, Rhizopus oryzae and Macrophomina phaseolina. The study therefore proposed that these fungal species have strong phosphate solubilizing properties and the isolated fungal strains in present investigation indicates broad spectrum activity against tested fungal phytopathogen. Therefore, the fungal species can be used for excellent crop productivity as a biofertilizer and as biocontrol agent. [ABSTRACT FROM AUTHOR]

Plants are considered to be the richest source of highly renewable natural insecticides. Specifically, botanical extracts provide an interesting alternative to synthetic pesticides and are safe and compatible. In the current study, isopropyl alcohol extracts of Nerium oleander and Datura stramonium leaves were tested for its efficacy in inducing mortality of rice weevil Sitophilus oryzae. The mortality percentage was tested at concentrations of 2%, 4%, 6%, 8% and 10%.The results were subjected to statistical analysis (Mean ± SD). Further, phytochemical analysis of the leaf extracts were carried out using standard protocols. Results of the biocontrol activity revealed that mortality rate increased with increasing concentration. Among the two leaf extracts, Datura stramonium leaf extracts exhibited maximum biocontrol activity. Datura stramonium leaf extracts when tested for the phytochemical revealed the presence of Alkaloids, Tannins, Steroids, Saponnins and Cardiac glycosides. It may be concluded on the basis of the result of present study that isopropyl alcohol extracts of plants have toxic effects with significant insecticidal effects. [ABSTRACT FROM AUTHOR]

A new partititvirus isolated from a Trichoderma harzianum strain (T673), collected in China, was characterized and annotated as Trichoderma harzianum partitivirus 2 (ThPV2). The genome of ThPV2 consists of a 1693 bp dsRNA1 encoding a putative RNA-dependent RNA polymerase (RdRp) and a 1458 bp dsRNA2 encoding a hypothetical protein. In comparative studies employing the ThPV2-infected strain (T673) and a strain cured by ribavirin treatment (virus-free strain T673-F), we investigated biological effects of ThPV2 infection. While the growth rate of the virus-infected fungus differed little from that of the cured variant, higher mycelial density, conidiospore, and chlamydospore production were observed in the virus-infected strain T673. Furthermore, both the ThPV2-infected and the cured strain showed growth- and development-promoting activities in cucumber plants. In vitro confrontation tests showed that strains T673 and T673-F inhibited several important fungal pathogens and an oomycete pathogen in a comparable manner. Interestingly, in experiments with cucumber seeds inoculated with Fusarium oxysporum f. sp. cucumerinum, the ThPV2-infected strain T673 showed moderately but statistically significantly improved biocontrol activity when compared with strain T673-F. Our data broaden the spectrum of known mycoviruses and provide relevant information for the development of mycoviruses for agronomic applications.

Alternaria solani responsible for early blight of eggplant is a worldwide spread notably in Iraq. The use of biological control agents represents the best alternative and eco-friendly approach. Two soil-borne fungal (Paecilomyces lilacinus and Trichoderma harzianum) were tested in laboratory conditions using the dual confrontation technique at different concentrations of conidia filtrate (10, 20 and 30% conidia/mL) and in vivo as potential bio-agents against A. solani. T. harzianum possessed the highest antifungal potency against A. solani with an inhibition rate above 50% at a concentration of 30% conidia/mL. In greenhouse experiments, both P. lilacinus and T. harzianum treated preventively on eggplant leaves inoculated with A. solani lowered significantly the disease severity index (31.61% and 28.08%, respectively). Obtained results revealed an augmentation of the peroxidase activity (4.84 units/g/mL/min for P. lilacinus; 3.88 units/g/mL/min for T. harzianum) in comparison with positive and negative controls. The effect of these two antagonists is limited not only to the protection of eggplant plants but also to the improvement of their growth by increasing the fresh (27.01% for P. lilacinus and 34.45% for T. harzianum) and dry weights (3.31% for P. lilacinus and 5.90% for T. harzianum) of the above-ground portion. Based on our results, we can conclude that T. harzianum could be recommended for biological control use. [ABSTRACT FROM AUTHOR]

Monosporascus cannonballus responsible for cucurbits Monosporascus root rot and vine decline, is worldwide spread notably in Tunisia. The most appropriate strategies to suppress disease development are those able to reduce the ascospores population using eco-friendly approach treatments. Seven soilborne fungal isolates were tested in vitro (by dual confrontation technique) and in vivo in the greenhouse as potential bioagents against three virulent M. cannonballus isolates. In vivo experiments were divided into two assays, preventive and curative treatments. Trichoderma viride and T. harzianum exhibited high inhibitory activities against M. cannonballus mycelial growth with values more than 90%, followed by Aspergillus niger (87.89%) and Paecilomyces victoriae (80.44%). Furthermore, these two Trichoderma spp. when applied preventively and curatively in in vivo trials, reduced significantly disease incidence (8.33% and 16.67-20.83%), root disease index (0.79-0.8 and 1.25-1.17), and reduced also ascospores index (1.5-1.54 asc/g of peat) and (2.54-2.42 asc/g of peat), respectively, in comparison with control treatments. Moreover, T. viride and T. harzianum enhanced the growth development of watermelon plants treated preventively and curatively in the greenhouse. They significantly improved different horticultural measurements with mean values of plant height (76.75-79.83 cm, and 81.83-80.92 cm), root volume (2.39-2.22 cm3, and 1.84-1.88 cm3), above grounds fresh weight (16.07-16.57 g, and 12.84-14.93 g) and dry wt. (2.49-2.6 g, and 2.66-2.70 g), underground fresh wt. (0.725-0.654 g, and 0.717-0.690 g) and dry wt. (0.147-0.214 g, and 0.156-0.152 g). Based on current results, it appears that Trichoderma spp. could be employed in soil treatments to promote watermelon plant growth and development.

Many studies on plant biostimulants and organic fertilizers have been focused on the ability of these products to increase crop productivity and ameliorate crop tolerance to abiotic stresses. However, little information is available on their effect on plant microbiota, whereas it is well known that microorganisms associated with plant play crucial roles on the health and productivity of their host. The aim of this study was to evaluate the effect of a vegetal-derived protein hydrolysate (PH), a vegetal-derived PH enriched with copper (Cu-PH), and a tropical plant extract enriched with micronutrients (PE) on shoot growth and the epiphytic bacterial population of lettuce plants and the ability of these products to enhance the growth of beneficial or harmful bacteria. The three plant-derived products enhanced shoot biomass of lettuce plants indicating a biostimulant effect of the products. Data obtained using culture-independent (Terminal Restriction Fragment Length Polymorphism and Next Generation Sequencing) and culture-dependent approaches indicated that foliar application of commercial products altered the composition of the microbial population and stimulated the growth of specific bacteria belonging to Pantoea , Pseudomonas , Acinetobacter , and Bacillus genus. Data presented in this work demonstrated that some of these strains exhibited potential plant growth-promoting properties and/or biocontrol activity against fungi and bacteria phytopathogens including Fusarium , Trichoderma , and Erwinia species. No indication of potential health risks associated to the enrichment of human or plant bacterial pathogens emerged by the analysis of the microbiota of treated and no-treated plants. Overall, the findings presented in this study indicate that the commercial organic-based products can enhance the growth of beneficial bacteria occurring in the plant microbiota and signals produced by these bacteria can act synergistically with the organic compounds to enhance plant growth and productivity. [ABSTRACT FROM AUTHOR]

Viable biomass production is a key determinant of suitability of antagonistic yeasts as potential biocontrol agents. This study investigated the effects of three metal ions (magnesium, ferrous, and zinc) on biomass production and viability of the antagonistic yeast, Candida diversa. Using response surface methodology to optimize medium components, a maximum biomass was obtained, when the collective Mg2+, Fe2+, and Zn2+ concentrations were adjusted in a minimal mineral (MM) medium. Compared with the unmodified MM, and three ion-deficient MM media, yeast cells cultured in the three ion-modified MM medium exhibited a lower level of cellular oxidative damage, and a higher level of antioxidant enzyme activity. A biocontrol assay indicated that C. diversa grown in the ion-modified MM exhibited the greatest level of control of gray mold on apple fruit. These results provide new information on culture medium optimization to grow yeast antagonists in order to improve biomass production and biocontrol efficacy.

Rhoeo discolor has been known to have a good adaptation to various environmental conditions. This character might be due to mutualistic association with endophytic bacteria. The objective of this study was to isolate endophytic bacteria from roots of R. discolor and to evaluate their potency as biocontrol agents and plant growth promoters. The methods to isolate endophytic bacteria involved the following methods, sterilization of root surface, grinding of root tissues, dilution, and plating in the medium tryptone soya agar (TSA). A total of 21 isolates of endophytic bacteria were isolated from the roots of R. discolor. Based on hypersensitivity test on tobacco leaves, 19 isolates showed negative reaction (no necrosis symptom) and only 2 isolates showed positive reaction (necrosis was developed). The results on biocontrol and growth promoters assay showed that 7 isolates were able to inhibit the growth of Fusarium oxysporum under in vitro test and 12 isolates were able to increase the growth of rice seedlings.

The study was performed to examine 11 isolates of Trichoderma for their bio-control potentials against Sclerotium rolfsii Sacc. causing stem rot in groundnut. The antagonists Trichoderma were subjected to sequence related amplified polymorphism (SRAP) based molecular diversity analysis and compared with their hardness to S. rolfsii with respect to secretary antifungal and antioxidant profile . T. virens NBAII Tvs 12 evident highest (87.91 %) growth inhibition of test pathogen followed by T. koningii MTCC 796 (67.03 %) at 7 days after inoculation (DAI). Microscopic study confirmed biocontrol mechanism as mycoparasitism for Tvs 12 and antibiosis for MTCC 796. The growth inhibition of test pathogen was significantly negatively correlated with sclerotia formation and lipid peroxidation during antagonism due to release of secretary bioactive antioxidants by antagonists to terminate oxidative burst generated by S. rolfsii and causing inhibition of sclerotium formation. The GC-MS profile identified antifungal and antioxidant constituents hexadecane, 1,2-benzenedicarboxylic acid, mono (2-ethylhexyl) ester, 1-hexadecanesulfonyl chloride, and octadecane in potent antagonists Tvs 12; and nonacosane and octadecane in MTCC 796 along with two novel compounds 1-pentadecene and 1-heneicosyl formate for biocontrol activity. Molecular diversity of Trichoderma isolates associated with antagonistic activity was assessed by SRAP markers. The 115 primer combinations generate total 1328 amplified products of which, 1095 are shared polymorphic and 199 are unique polymorphic. The 15 SRAP combinations produced 18 bands to diagnose best antagonist Tvs 12 and 13 SRAP combinations generated 19 unique bands for identification of MTCC 796. The mycoparasitic antagonist Tvs 12 would be the best antagonist and released unique antifungal and antioxidant constituents to combat pathogen infection. The SRAP based genetic diversity indicates Tvs12 strain clustered with T. viride NBAII Tv23 and shared only 52 % similarity with other isolates of Trichoderma. The SRAP similarities explained substantial diversity (19-68 %) across Trichoderma isolates. [ABSTRACT FROM AUTHOR]

To discover new biological control agents, the biocontrol activity of azaleas endophytic bacteria strain DJ-6 was interpreted by dual-cultural plate method. Based on the morphological, chemical and molecular taxonomy methods, the field effect test of DJ-6 biocontrol agent (BCA) were conducted. The results showed that the strain DJ-6 displayed a broad-spectrum inhibitive activity. Data of field experiments of BCA demonstrated that the field biocontrol efficacy was all superior to the chemical control (Carbendazim). According to the morphological, physiological, biochemical characteristics, 16S rDNA and gyrB gene sequence, the strain DJ-(D was identified as Bacillus subtilis. [ABSTRACT FROM AUTHOR]

Apple ring rot, one of the most common apple postharvest diseases during storage, is caused by Botryosphaeria dothidea . Fungicide application is the most widely used method to control this disease, but the increasing environmental and food safety concerns greatly limit their use. The present study aimed to examine the biocontrol activity and underlying action mechanism of Bacillus halotolerans strain Pl7 against B. dothidea . The results revealed that B. halotolerans strain Pl7 exhibited strong inhibitory activity against B. dothidea by 69% in vitro . The culture filtrate of strain Pl7 possessed cellulase, β-1, 3-glucanase, protease activity and mediated the antifungal activity against B. dothidea . Further analysis demonstrated that culture filtrate of strain Pl7 could cause cell membrane permeabilization of B. dothidea . Apple fruit suffering from ring rot induced by a carbendazim (CBZ)-sensitive or -resistant B. dothidea isolate was much suppressed after being treated with strain Pl7, maintaining postharvest quality. The ability of strain Pl7 to swiftly colonize and thrive in apple fruit wounds was demonstrated by a re-isolation assay. Additional transcriptome studies of untreated and treated apple fruit with strain Pl7 revealed that strain Pl7 mostly changed the expression of genes functioning in plant secondary metabolite biosynthesis and plant-pathogen interaction. In light of these outcomes, the underlying antagonistic mechanism was investigated, and B. halotolerans strain Pl7 was identified as a promsing microbial biocontrol agent against apple postharvest decay., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Yuan, Yuan, Shi, Wang, Huang, Zhu, Hou, Wang and Tu.)

Introduction: Several microorganisms in the plant root system, especially in the rhizosphere, have their own compositions and functions. Corm rot is the most severe disease of Crocus sativus , leading to more than 50% mortality in field production., Methods: In this study, metagenomic sequencing was used to analyze microbial composition and function in the rhizosphere of C. sativus for possible microbial antagonists against pathogenic Fusarium oxysporum ., Results: The microbial diversity and composition were different in the C. sativus rhizosphere from different habitats. The diversity index (Simpson index) was significantly lower in the C. sativus rhizospheric soil from Chongming (Rs&#95;CM) and degenerative C. sativus rhizospheric soil from Chongming (RsD&#95;CM) than in others. Linear discriminant analysis effect size results showed that differences among habitats were mainly at the order (Burkholderiales, Micrococcales, and Hypocreales) and genus ( Oidiodendron and Marssonina ) levels. Correlation analysis of the relative lesion area of corm rot showed that Asanoa was the most negatively correlated bacterial genus (ρ = -0.7934, p < 0.001), whereas Moniliophthora was the most negatively correlated fungal genus (ρ = -0.7047, p < 0.001). The relative lesion area result showed that C. sativus from Qiaocheng had the highest resistance, followed by Xiuzhou and Jiande. C. sativus groups with high disease resistance had abundant pathogen resistance genes, such as chitinase and β-1,3-glucanase genes, from rhizosphere microorganisms. Further, 13 bacteria and 19 fungi were isolated from C. sativus rhizosphere soils, and antagonistic activity against pathogenic F . oxysporum was observed on potato dextrose agar medium. In vivo corm experiments confirmed that Trichoderma yunnanense SR38, Talaromyces sp. SR55, Burkholderia gladioli SR379, and Enterobacter sp. SR343 displayed biocontrol activity against corm rot disease, with biocontrol efficiency of 20.26%, 31.37%, 39.22%, and 14.38%, respectively., Discussion: This study uncovers the differences in the microbial community of rhizosphere soil of C. sativus with different corm rot disease resistance and reveals the role of four rhizospheric microorganisms in providing the host C. sativus with resistance against corm rot. The obtained biocontrol microorganisms can also be used for application research and field management., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Zhang, Lu, Zhu, Huang, Qin and Zhu.)

Background: Some Pseudomonas strains function as predominant plant growth-promoting rhizobacteria (PGPR). Within this group, Pseudomonas chlororaphis and Pseudomonas fluorescens are non-pathogenic biocontrol agents, and some Pseudomonas aeruginosa and Pseudomonas stutzeri strains are PGPR. P. chlororaphis GP72 is a plant growth-promoting rhizobacterium with a fully sequenced genome. We conducted a genomic analysis comparing GP72 with three other pseudomonad PGPR: P. fluorescens Pf-5, P. aeruginosa M18, and the nitrogen-fixing strain P. stutzeri A1501. Our aim was to identify the similarities and differences among these strains using a comparative genomic approach to clarify the mechanisms of plant growth-promoting activity. Results: The genome sizes of GP72, Pf-5, M18, and A1501 ranged from 4.6 to 7.1 M, and the number of protein-coding genes varied among the four species. Clusters of Orthologous Groups (COGs) analysis assigned functions to predicted proteins. The COGs distributions were similar among the four species. However, the percentage of genes encoding transposases and their inactivated derivatives (COG L) was 1.33% of the total genes with COGs classifications in A1501, 0.21% in GP72, 0.02% in Pf-5, and 0.11% in M18. A phylogenetic analysis indicated that GP72 and Pf-5 were the most closely related strains, consistent with the genome alignment results. Comparisons of predicted coding sequences (CDSs) between GP72 and Pf-5 revealed 3544 conserved genes. There were fewer conserved genes when GP72 CDSs were compared with those of A1501 and M18. Comparisons among the four Pseudomonas species revealed 603 conserved genes in GP72, illustrating common plant growth-promoting traits shared among these PGPR. Conserved genes were related to catabolism, transport of plant-derived compounds, stress resistance, and rhizosphere colonization. Some strain-specific CDSs were related to different kinds of biocontrol activities or plant growth promotion. The GP72 genome contained the cus operon (related to heavy metal resistance) and a gene cluster involved in type IV pilus biosynthesis, which confers adhesion ability. Conclusions: Comparative genomic analysis of four representative PGPR revealed some conserved regions, indicating common characteristics (metabolism of plant-derived compounds, heavy metal resistance, and rhizosphere colonization) among these pseudomonad PGPR. Genomic regions specific to each strain provide clues to its lifestyle, ecological adaptation, and physiological role in the rhizosphere. [ABSTRACT FROM AUTHOR]

Biological control of plant diseases has received worldwide attention in recent years mainly as a response to use of hazardous chemicals in the environment. Soil actinomycetes particularly Streptomyces spp. enhance soil fertility and have antagonistic activity against wide range of soil-borne plant pathogens. In study of antifungal activity of streptomycetes against plant fungal-pathogens Fusarium oxysporum (Schlecht.), F. culmorum (Wm. G. Sm.) Sacc. and Rhizoctonia solani (Kühn) causing damping-off of pine seedlings, in vitro and in vivo tests were carried out. Two types of in vitro tests in mixed cultures of actinomycetes and fungi were performed. In majority of the cases, an inhibitory effect of actinomycetes on fungi was noticed. Three isolates (SG9, SR2, SR4) were highly active against pathogenic fungi and were chosen for exopolysaccharides extraction and in vivo tests. The sensitivity to exopolysaccharide action was noted in fungi from the genus Fusarium. Fusarium oxysporum showed a higher sensitivity to the analyzed exopolysaccharides than F. culmorum. Biocontrol interactions both in sterile and non-sterile soil were found for the actinomycete Streptomyces cyaneus (strain SG9) isolated from root free soil of the pine. The latest experiment confirmed the strong pathogenicity of the fungus Rhizoctonia solani. Antifungal properties of Streptomyces cyaneus (strain SG9) need further comprehensive studies. [ABSTRACT FROM AUTHOR]

Biological control of soilborne plant pathogens is a possible alternative to the use of chemical pesticides, which are harmful to the environment. Under greenhouse and field conditions, several isolated strains of the fungus Trichoderma have been found to be effective biocontrol agents of various soilborne plant pathogenic fungi. The use of phosphate solubilizing microorganisms (PSMs) has a considerable synergistic effect on the growth and development of crop plants. In the present study, T. harzianum was isolated from 10 different agro-climatic zones of Karnataka and tested for the potential of antagonistic activity against the plant pathogen Xanthomonas and the ability of phosphate solubility under in vitro conditions. Variations within the 10 isolates of T. harzianum were assayed using the Rapid Amplification of Polymorphic DNA (RAPD) method. [ABSTRACT FROM AUTHOR]

A possible synergy between the biological control agent Beauveria bassiana (Bb) and potassium silicate (KSil) for the control of two spotted spider mite (TSM) was investigated. Greenhouse experiments were carried out on cucumber, eggplant, bean and maize plants. Potassium silicate was added to nutrient solutions at 0.02, 0.04, 0.08 and 0.16% (v/v) (equivalent to 20, 40, 80, 160 mg of pure Si per liter, respectively). Conidia of Bb (Isolate R444) were suspended in Break-thru® and sprayed onto plants 7 d after TSM inoculation. Plants treated with KSil at higher concentrations, 0.08 and 0.16%, suffered less damage by TSM. However, KSil alone did not kill mites. Higher mortality of adult mites, as well as juveniles, were caused by Bb and this enhanced efficiency when the fungus was combined with KSil. These results indicate that the application of KSil as a plant nutrient may provide some protection of plants against TSM infestations in both monocotyledonous and dicotyledonous plants, and enhance the biocontrol efficacy of Bb. [ABSTRACT FROM AUTHOR]

Agar-based screening assays are the method of choice when evaluating antagonistic potential of bacterial biocontrol-candidates against pathogens. We showed that when using the same medium, but different agar compositions, the activity of a bacterial antagonist against Agrobacterium was strongly affected. Consequently, results from in vitro screenings should be interpreted cautiously. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we followed the development and compared the biocontrol potential of four phylogenetically related species of Pseudozyma (P. antarctica, P. flocculosa, P. fusiformata and P. rugulosa) all known to release glycolipids with antifungal activity in vitro. To this end, we developed GFP transformants and specific primers for each species and conducted in situ observations and quantification of their population sizes over time on both healthy and powdery mildew-infected leaves. Although all species shared many similar features, only P. flocculosa antagonized powdery mildew colonies and grew specifically in their presence. Population quantification by qRT-PCR following inundative applications showed a drastic decline in population for all species, including P. flocculosa on healthy leaves, but a sharp and steady increase of the latter over 72h on infected leaves. These results suggest that production of glycolipids, and more specifically flocculosin or ustilagic acid, is not the sole factor dictating biocontrol activity among Pseudozyma spp. [Copyright &y& Elsevier]