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.
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,
. Using response surface methodology to optimize medium components, a maximum biomass was obtained, when the collective Mg
, Fe
, and Zn
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
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.
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.
Phosphate (P)-solubilizing microorganisms as a group form an important part of the microorganisms, which benefit plant growth and development. Growth promotion and increased uptake of phosphate are ...not the only mechanisms by which these microorganisms exert a positive effect on plants. Microbially mediated solubilization of insoluble phosphates through release of organic acids is often combined with production of other metabolites, which take part in biological control against soilborne phytopathogens. In vitro studies show the potential of P-solubilizing microorganisms for the simultaneous synthesis and release of pathogen-suppressing metabolites, mainly siderophores, phytohormones, and lytic enzymes. Further trends in this field are discussed, suggesting a number of biotechnological approaches through physiological and biochemical studies using various microorganisms.
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.
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.
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.
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.
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