Glucanase Activity Research Articles

Antifungal protein determination for submerged cultures of the medicinal mushroom <i>Ganoderma lucidum</i> (Ganodermataceae) with activity over the phytopathogen fungus Mycosphaerella fijiensis (Mycosphaerellaceae)

Banana is one of the most important edible crops in the world, however, it’s attacked by different pathogens, one of the most prominent of these is the fungus Mycosphaerella fijiensis, causal agent of Black Sigatoka. The environmental and economic issues related to the pesticides used for its control have encouraged the search for cleaner alternative biomolecules. Previous studies were made by the Biotechnology group from the Universidad de Antioquia searching for a biological alternative for the control of M. fijiensis; in these the antifungal capacity of the fungus Ganoderma lucidum was determined as an antagonist and then as a source of protein extracts with inhibitory activity in vitro and in greenhouse plants; these findings were the foundation of this work, which focuses in the study of the enzymatic capacity of the proteins present in the protein extracts, due to their potential ability to degrade different compounds, including polysaccharides, lipids, peptides and nucleic acids, constituents of essential parts of a living cell; therefore these extracts can act as possible antifungal agents. In this study, protein extracts of G. lucidum obtained from bioreactor cultures (BIOFLO 110 ®) were characterized in terms of their deoxyribonuclease, ribonuclease, protease, glucanase and chitinase enzymatic activities. The extracts were also fractionated and each fraction obtained was evaluated for its inhibitory capacity against the phytopathogen fungus M. fijiensis, and through mass spectrometry analysis the presence of different enzymes with antifungal potential was confirmed.

The construction of CRISPR-Cas9 system for endophytic Phomopsis liquidambaris and its PmkkA-deficient mutant revealing the effect on rice

The endophytic fungus Phomopsis liquidambaris efficiently promotes the nitrogen metabolism and growth of host plants such as rice and peanut. However, a lack of genetic tools limits further research regarding the mechanisms of interaction between P. liquidambaris and its host plants. Herein, a CRISPR/Cas9 system for targeted gene disruption in this strain was first constructed and optimized. The knock-out efficiency increased to over 60% when the ku70 or ku80 gene (involved in nonhomologous end-joining, NHEJ) was disrupted. Furthermore, the CRISPR/Cas9 system was applied to disrupt the PmkkA gene, encoding a mitogen-activated protein kinase kinase (MAPKK) in the cell-wall integrity (CWI) MAPK pathway of the strain. The ΔPmkkA mutant strain induced higher reactive oxygen species (ROS) production, chitinase activity and glucanase activity in rice seedlings than wild-type P. liquidambaris (WT), resulting in growth inhibition and strong resistance on rice. These results suggested that the PmkkA gene is crucial during the interaction with rice and may play a role in inhibiting the immune system of host plants. The CRISPR-Cas9 system will be of great use for the study of the interaction between P. liquidambaris and its host plants.

Some Physiological Responses of Clarias gariepinus Fed Graded Levels of Cirina forda Larvae Based Diets

The study examined the growth performance, hematological and digestive enzymes of Clarias gariepinus juveniles fed Cirina forda meal (CFM) based diets in the laboratory for a period of 10weeks. Five iso-nitrogenous (30%) experimental diets were formulated at various levels of CFM inclusion levels of 0% (control), 10%, 20%, 30%, 40% and 50%, designated as diets Q, A10, B20, C30, D40 and E50 respectively. Fish fed the CFM based diets showed mean weight gain (MWG), specific growth rate (SGR) and protein efficiency ratio (PER) comparable to the control diet. There was significant differences in the digestive enzyme activities of the fish as the CFM level in the experimental diets increased. Protease and maltase activities significantly increased, with diet C30 recording the highest maltase activity (4.37) while the cellulase and glucanase activities of the fish significantly (P<0.05) reduced. There was no significant difference (P>0.05) between the PCV and RBC of the blood of the fish fed the various diets. Highest RBC (2.75 x106/µL) was obtained in fish fed the control diet while the lowest (2.55 x106/µL) was recorded in the fish fed diet E50. The White Blood Cell count and the Neutrophils of the fish fed the trial diets were not significantly higher (P>0.05) than those of the fish fed the control diets. From the results of this experiment, it is concluded that up to 50% inclusion level of Cirina forda meal in the diet of Clarias gariepinus was tolerable for good growth and physiological well-being of the fish.

Field Performance of Xanthosoma sagittifolium L. Schott Minitubers Grown Under the Influence of Poultry Manure and NPK Fertilizers: Changes in Content of Some Secondary Metabolites

The response of white and red cultivar (cv) cocoyam (Xanthosoma sagittifolium (L.) Schott) minituber seeds to different rates of poultry manure (PM) and NPK (20:10:10) fertilizer was studied under field conditions in the 2017 cropping season on an experimental farm at Ngog Bibega, Mbankomo Sub-division, (outskirsts of Yaounde) Centre region, Cameroon. Treatment combinations comprising of three rates each of poultry manure (0, 20 and 30t ha -1 ) and NPK fertilizer (0, 120 and 150 kg ha -1 ) were factorized and fitted into a randomized complete block design with three replicates. Physico-chemical analysis of all treatment plots revealed clay loam textures and poultry manure treatment plots significantly (P<0.05) increased soil pH, organic content, total carbon and cation exchange capacity while NPK treatments significantly (p<0.05) increased available phosphorus compared to the control treatments. Poultry manure(30t ha -1 ) treatments significantly (P<0.05) enhanced plant height, leaf number and leaf area in both cultivars after 6 months of growth as compared to all other treatments. Under the same treatments of poultry manure (30t ha -1 ) the white cultivar plants recorded the most significant mean yield parameters after 9 months of growth. The average tuber number per plant (8), tuber weight (250g), tuber length (14cm) and tuber girth (18.5cm) compared to the red cultivar average yield parameters: tuber number per plant (5.7), tuber weight (124.7g), tuber length (8cm) and tuber girth (14.5cm). Biochemically the application of various treatments of poultry manure and NPK fertilizers significantly (P<0.05) influenced the changes observed in the secondary metabolites studied. Two months after planting, NPK (150kg ha -1 ) treatments showed the most significant phenolic content (1.22±0.13mg eq catechin.g -1 FW) and flavonoid content (1.08±0.16mg g -1 FW) in white cv cocoyam plants. After 6 months of growth, the poultry manure (30t ha -1 ) treatments recorded the most significant protein content (5.04±0.38mg eq BSA.g -1 FW) and peroxidase activity (4.89±1.36 UE min -1 ) in white cv cocoyam plants while red cv cocoyam plants had the most significant glucanase activity (9.33±1.17 mg eq glucose g -1 FW). NPK (150kg ha -1 ) treatments in white cv cocoyam plants recorded the most significant polyphenol oxidase activity (4.99±0.10 in D330 nm -1 min -1 UE -1 g -1 FW) 6 months after planting. Keywords: Xanthosoma sagittifolium L. Schott; Minitubers; cation exchange capacity; Poultry manure; NPK fertilizers; yield parameters and secondary metabolites. DOI : 10.7176/JBAH/9-20-05 Publication date :October 31 st 2019

Characterisation of three novel β-1,3 glucanases from the medically important house dust mite Dermatophagoides pteronyssinus (airmid)

The European house dust mite, Dermatophagoides pteronyssinus is a major source of airborne allergens worldwide and is found in half of European homes. Interactions between microbes and house dust mites (HDM) are considered important factors that allow them to persist in the home. Laboratory studies indicate the European HDM, D. pteronyssinus is a mycophagous mite, capable of utilising a variety of fungi for nutrients, however specific mycolytic digestive enzymes are unknown. Our previous work identified a number of putative glycosyl hydrolases present in the predicted proteome of D. pteronyssinus airmid and validated the expression of 42 of these. Of note, three GH16 proteins with predicted β-1,3 glucanase activity were found to be consistently present in the mite body and excretome. Here, we performed an extensive bioinformatic, proteomic and biochemical study to characterize three-novel β-1,3 glucanases from this medically important house dust mite. The genes encoding novel β-1,3 glucanases designated Glu1, Glu2 and Glu3 were identified in D. pteronyssinus airmid, each exhibited more than 59% amino acid identity to one another. These enzymes are encoded by Glu genes present in a tri-gene cluster and protein homologs are found in other acari. The patchy phyletic distribution of Glu proteins means their evolutionary history remains elusive, however horizontal gene transfer cannot be completely excluded. Recombinant Glu1 and Glu2 exhibit hydrolytic activity toward laminarin, pachyman and barley glucan. Excreted β-1,3 glucanase activity was increased in response to D. pteronyssinus airmid feeding on baker's yeast. Active β-1,3 glucanases are expressed and excreted in the faeces of D. pteronyssinus airmid indicating they are digestive enzymes capable of breaking down β-1,3 glucans of fungi present in house dust.

Extracts from cultures of Pseudomonas fluorescens induce defensive patterns of gene expression and enzyme activity while depressing visible injury and reactive oxygen species in Arabidopsis thaliana challenged with pathogenic Pseudomonas syringae.

We evaluated the ability of metabolic elicitors extracted from Pseudomonas fluorescens N21.4 to induce systemic resistance (ISR) in Arabidopsis thaliana against the pathogen Pseudomonas syringae DC3000. Metabolic elicitors were obtained from bacteria-free culture medium with n-hexane, ethyl acetate and n-butanol in three consecutive extractions. Each extract showed plant protection activity. The n-hexane fraction was the most effective and was used to study the signal transduction pathways involved by evaluating expression of marker genes of the salicylic acid (SA) signalling pathway (NPR1, PR1, ICS and PR2) and the jasmonic acid/ethylene (JA/ET) signalling pathway (PDF1, MYC2, LOX2 and PR3). In addition, the level of oxidative stress was tested by determining the activity of enzymes related to the ascorbate-glutathione cycle. N-hexane extracts stimulated both pathways based on overexpression of ICS, PR1, PR2, PDF1 and LOX2 genes. In addition, activity of the pathogenesis-related proteins glucanase (PR2) and chitinase (PR3), lipoxygenase and polyphenol oxidase was enhanced together with an increased capacity to remove reactive oxygen species (ROS). This was associated with less oxidative stress as indicated by a decrease in malondialdehyde (MDA), suggesting a causative link between defensive metabolism against P. syringae and ROS scavenging.

HPAEC-PAD and Q-TOF-MS/MS analysis reveal a novel mode of action of endo-β-1,3(4)-d-glucanase Eng16A from coprinopsis cinerea on barley β-glucan

We previously reported that an endo-β-1,3(4)-d-glucanase, Eng16A, from C. cinerea shows a higher degradation activity toward barley β-glucan than laminarin. HPAEC-PAD and Q-TOF-MS/MS analyses show that Eng16A-digestion products of barley β-glucan not only contain some oligosaccharides with (1 → 3)-β-linkage adjacent to the reducing end, which is consistent with β-1,3(4)-glucanase-digestion products, but also include some oligosaccharides containing (1 → 4)-β-linkage adjacent to the reducing end which is consistent with cellulase-digestion products. Thus, Eng16A possesses both cellulase and β-1,3(4)-glucanase activities. Because Eng16A does not degrade cellulose, we propose that the insertion of a (1 → 3)-β-linkage among the groups of (1 → 4)-β-linkages may make these (1 → 4)-β-linkages prone to cleavage by Eng16A. Furthermore, Eng16A also possesses transglycosylation activity which leads to some products containing one or a few consecutive (1 → 3)-β-linkages adjacent to the non-reducing end. Therefore, HPAEC-PAD and Q-TOF-MS/MS analyses provide an efficient approach to reveal complicated modes of action of some endo-β-1,3(4)-d-glucanases on barley β-glucan.

Monitoring the Activity of Feed Enzymes in Vitro and Their Activity in the System that Modulates the GIT

24 feed enzyme endo-1,4-glucanase (glucanase) and endo-1,4-xylanase (xylanase) have been described. Their activity was studied under in vitro conditions simulating the gastrointestinal tract of the poultry. A decrease in the temperature of the medium from 50°C to 38°C reduced the activity of all enzymes. Fekord 2004-S, Agrocell Plus, Agrocell, Rovabio max AP, Xibeten-Gel, Axtra XAP 101 TPT, Endofeed DC at pH 3, 38°C retained the highest initial xylanase activity: 81, 80, 70, 70, 67, 67, 65% respectively. The minimum stability at pH 3 was established for Sunzyme, Hostazym С-100, Ronozyme VP, Natugrain TS and Ronozyme WX: 46, 44, 42, 40, and 38%, respectively. At pH 7, 38°C it was better activity than the average for all preparations showed С Axtra XAP 101 TPT, Fekord-2004-C, Econase XT-25, Agrocell: 52, 47, 47, 45%; minimal activity was shown by Rovabio Exel AR, Cellulase, Cellolux F, Sunzaim: 4, 5, 7, and 8%, respectively. An outstanding high activity of cellulаse at pH 3, 38°C was found in Fekord 2004-C - 90%, above the average value it was in Econase XT 25, Acra XB 201 TPT, Agroxil Plus and Vilzim: 63, 62, 60 and 58%. The minimum activity at pH 3, 38°С was found in Rovabio Exel, Rovabio Max AR, Cellolux F and Xybeten-Cel: 20, 23, 23 and 25%. At pH 7, 38°С, the maximum activity of most enzymes remained within 30%, excluding Hostazym S-100 - 52%. The minimum glucanase activity at pH 7 was shown by Rovabio Max AP - 4%, Xybeten-Cel - 5%, Endofeed DC - 6%, and Rovabio Exel AP -6%. The average activity of cellulase for all studied enzymes was 19.1% of that determined at pH 5, and 50C. Under all experimental conditions, the activity of xylanases of the studied enzymes was mainly better than glucanases. This indicates greater cellulases stability. It has been substantiated that the activity indicated by the manufacturer serves only for labeling the product and does not reflect its action in the body. Used matrix values of enzymes are intended for commercial purposes and weakly reflect the real effect of enzyme.

Biological Control of Postharvest Spoilage in Fresh Mandarins (Citrus Reticulata Blanco) Fruits Using Bacteria During Storage

Citrus fruit can be infected by many fungal pathogens, and these pathogens cause considerable losses during storage and transportation. Recently, biological control methods of postharvest diseases are getting more prevalent due to the effects of chemical residues on fruits. The present study was carried out to determine the antifungal activities of a total of four candidate biocontrol bacterial strains (Bacillus subtilis TV-6F, B. subtilis TV-17C, Pseudomonas flourescens RK-1105 and Agrobacterium rubi RK-33) against some pathogenic fungi (Alternaria alternata, Sclerotinia sclerotiorum, Pythium ultimum, Penicillium digitatum and P. italicum) on Petri plate assays. They were also tested to evaluate the potential application of the bacteria to bio-control postharvest decay on mandarin fruits during storage. In addition, they were tested to investigate the enzyme activities of the bacteria. The results of the present study showed that all non-pathogenic bacterial strains showed less or more antifungal activity against the tested pathogens on Petri plate assays. They were also significantly reduced disease severity on mandarin fruits during storage. Chitinase, glucanase and protease enzyme activities of the bacteria were positive except A. rubi RK-33. B. subtilis TV-17C and A. rubi RK-33 strains were the most effective bacteria. In controlling postharvest decay of mandarin fruit, these bacterial strains can be used as new bio-control agents. Hence, further study is necessary to develop a long-term carrier material, to complete cytotoxicity using human cell, ecotoxicity and toxicity tests of these bacterial strains on target organisms.

A Novel Thermostable GH3β-Glucosidase fromTalaromyce leycettanuswith Broad Substrate Specificity and Significant Soybean Isoflavone Glycosides-Hydrolyzing Capability

A novel β-glucosidase gene (Bgl3B) of glycoside hydrolase (GH) family 3 was cloned from the thermophilic fungus Talaromyce leycettanus JM12802 and successfully expressed in Pichia pastoris. The deduced Bgl3B contains 860 amino acid residues with a calculated molecular mass of 91.2 kDa. The purified recombinant Bgl3B exhibited maximum activities at pH 4.5 and 65°C and remained stable at temperatures up to 60°C and pH 3.0−9.0, respectively. The enzyme exhibited broad substrate specificities, showing β-glucosidase, glucanase, cellobiase, xylanase, and isoflavone glycoside hydrolase activities, and its activities were stimulated by short-chain alcohols. The catalytic efficiencies of Bgl3B were 693 and 104/mM/s towards pNPG and cellobiose, respectively. Moreover, Bgl3B was highly effective in converting isoflavone glycosides to aglycones at 37°C within 10 min, with the hydrolysis rates of 95.1%, 76.0%, and 75.3% for daidzin, genistin, and glycitin, respectively. These superior properties make Bgl3B potential for applications in the food, animal feed, and biofuel industries.

Features of the hemicellulose structure of some species of regional raw materials and products of their enzymatic hydrolysis

Nowadays, it is recognized that a lot of polysaccharides are biologically active. It is well known that these biomolecules show the highest level of their activity if they are water-soluble preparations, their molecular weight being 15–25 kDa, and if they preserve the supramolecular structure of carbohydrates. Basing on the fact that β-glucans of mushrooms are characterized by the antitumor, anticoagulant, anti-inflammatory, and immunomodulatory activities, it is important to determine whether regional raw material contains polysaccharides of a similar structure, and to define the conditions for their fragmentation to obtain products with a given molecular weight. The purpose of the work was to characterize the features of the structure of the hemicellulose complex of the Agaricus bisporous and Pleurotus ostreatus and products of their limited enzymatic hydrolysis. To determine the primary structure of hemicellulose polysaccharides, the 1H-NMR spectra of the samples were registered. It has been shown that β-D-(1→3)/β-(1→6)-glucan dominates in the hemicellulose of Pleurotus ostreatus. Among the hemicelluloses in the Agaricus bisporis, the main polysaccharide was galactoglucan. Its main chain consisted of β-D-glucopyranose residues interconnected with (1→3)-glucosidic bonds. The positions of O-6 monosaccharide are joined by the side branches in the form of β-D-glucopyranoses and the terminal residues of β-D-galactopyranoses. The hemicelluloses of Pleurotus ostreatus also contain manogalactan. Complexes of hemicelluloses of both types of mushrooms contain linear α-(1→3)-glucan in small quantities. It has been studied how the molecular-weight distribution of products of limited hydrolysis of hemicelluloses depends on the conditions of their treatment with the enzyme with β-(1→3)-glucanase activity. The maximum accumulation of a fraction with a given molecular weight of 15–25 kDa was observed at a ratio of E:S = 1:45 and treatment time of 21 hours. A specific reaction with congo red has proved there is a triple helical conformation of the main chain of the polysaccharide for this fraction of carbohydrates, so the supramolecular structure of the molecule is preserved.

Differential Induction of β-1,3-Glucanase Gene in Expression of Partial Resistance to Rust (Uromyces fabae (Pers.) de-Bary) in Pea (Pisum sativum L.)

The present study highlights differential induction of pathogenesis related protein PR-2 (β-1,3- glucanases) in expression of rust resistance in pea using different resistant and susceptible recombinant inbred lines of pea (Pisum sativum L.). The enhanced levels of glucanase expression was noted in resistant genotypes at 24 h post inoculations that was negatively correlated (–0.54) with Area Under Disease Progress Curve (AUDPC) and positively correlated (0.67) with lignin accumulations. A significant role of structural defence mechanism in rust resistance in pea was evident from reduced colony size and lesser number of haustorium per colony in resistant lines as well as their negative correlations with lignin accumulation and AUDPC. Gene specific markers indicated constitutive nature of glucanase and peroxidase genes in test genotypes, though differential expression of the glucanase activity was observed in the resistant and susceptible genotypes. However, association of peroxidases with resistance to pea rust is yet to be established due to its non-specific role in slow rusting in pea. The result showed a significant role of β-1,3-glucanase in expression of rust resistance in pea.

Protein components of water extracts from fruiting bodies of the reishi mushroom Ganoderma lucidum contribute to the production of functional molecules

Mushrooms have been widely considered as health foods as their extracts have anti-hypertensive and anti-tumor activities. After a thorough literature survey, we hypothesized that enzymes in mushroom extracts play an important role in synthesizing functional molecules. Therefore, in this study, proteins extracted from reishi mushroom (Ganoderma lucidum), which is used in oriental medicine, were identified by the proteomic approach, and appropriate extraction methods for improving angiotensin-converting enzyme (ACE) inhibitory activities were investigated. Various glycoside hydrolases (GHs), such as β-N-acetylhexosaminidase (GH family 20), α-1,2-mannosidase (GH family 47), endo-β-1,3-glucanase (GH family 128), and β-1,3-glucanase (GH152), that degrade glycans in the fruiting body were identified. The residual glucanase activities generated β-oligosaccharides. Additionally, the glutamic acid protease of the peptidase G1 family was determined as the major protein in the extract, and the residual peptidase activity of the extracts was found to improve ACE inhibitory activities. Finally, it was observed that extraction at 50 °C is suitable for yielding functional molecules with high ACE inhibitory activities. Water extraction is generally believed to extract only functional macromolecules that exist in mushroom fruiting bodies. This study proposed a new concept that describes how functional molecules are produced by enzymes, including proteases and GHs, during extraction. © 2018 Society of Chemical Industry.

Effective degradation of curdlan powder by a novel endo-β-1→3-glucanase

Curdlan is a water-insoluble microbial exo-polysaccharide that is hardly degraded. The gene CcGluE encoding an endo-β-1→3-glucanase consisting of 412 amino acids (44 kDa) from Cellulosimicrobium cellulans E4-5 was cloned and expressed in Escherichia coli. The recombinant CcGluE hydrolysed curdlan powder effectively. CcGluE shows high endo-β-1→3 glucanase activity and low β-1,4 and β-1,6 glucanase activities with broad substrate specificity for glucan, including curdlan, laminarin and β-1→3/1→6-glucan, and the highest catalytic activity for curdlan. Moreover, the hydrolytic products of curdlan were glucan oligosaccharides with degrees of polymerisation of 2–13, and the main products were glucobiose and glucotriose. Degradation mode analysis indicated that CcGluE is more likely to hydrolyse glucopentaose and revealed that CcGluE was an endo-glucanase. Furthermore, upon combination with a homogenising pre-treatment method with curdlan, the degradation efficiency of CcGluE for curdlan powder was greatly improved 7.1-fold, which laid a good foundation for the utilisation of curdlan.

Chitinase and Glucanase Activities of Antagonistic Streptomyces Spp Isolated From Fired Plots under Shifting Cultivation In Northeast India

Actinobacteria are most widely distributed and distinct group of microorganisms in nature. Actinobacteria, Streptomyces species in particular, has been a broadly exploited group of microorganisms for the production of important secondary metabolites and enzymes in the field of medicine and agriculture.

Systemic inducing resistance against late blight by applying antagonist Trichoderma Viride

Biological control by Phytophthora infestans (Mont.) de Bary, a pathogen causing late blight disease on potatoes, has attracted scholars as an environmentally alternative preference to chemical pesticide. Some species of Trichoderma spp. has proven to be capable of triggering resistance mechanism of plant against fungal pathogens. The aim of this research was to analyze the effect of Trichoderma viride SP1 suspension to induced systemic resistance on potato plant as showing glucanase activity and total phenol content. The method used was Completely Randomized Design with six treatments and seven times repeated. Variables observed were total phenol content and total crop. The result showed that glucanase activity and total phenol content in plants treated with Trichoderma viride and fungicide (1587 μg/g and 1934 μg/g) significantly increased. In addition, T. viride enhanced induced systemic resistance on potato plant and increased potato yield.

Safety and efficacy of Amylofeed® (endo-1,3(4)-β-glucanase and endo-1,4-β-xylanase and α-amylase) as a feed additive for piglets and minor growing porcine species.

Amylofeed® is a feed additive that contains glucanase, xylanase and amylase activities, and it is intended to be used as a zootechnical additive for weaned piglets and minor porcine species. In previous assessments, the additive was characterised and the safety for the target species, consumers and environment was established. Considering the safety for the user, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive should be considered as a potential skin and eye irritant and a potential skin and respiratory sensitiser. Furthermore, the Panel concluded that the additive has a potential to be efficacious in the target species. However, the efficacy at the recommended enzyme activities could not be established. In order to overcome this limitation, the applicant proposed to modify the specifications of the additive whilst keeping the recommended level of addition of 500 mg additive/kg feed. The Panel evaluated the new specifications and their impact on the relevant aspects of the safety and efficacy of the additive. The newly proposed specifications of the additive were supported by analytical data. The Panel considered that the modification proposed by the applicant on the specifications would not have an impact on the safety aspects related to the consumer, user and environment. Therefore, the conclusions previously drawn would still apply. Moreover, it was considered that the tolerance trial previously evaluated would still support the safety for the target species. The addition of the additive with the new specifications would result in higher enzyme activities than those that were found in the efficacy studies that supported the efficacy of the product. Therefore, the additive has the potential to be efficacious at the newly proposed level of enzyme activities.

Trichoderma elicitors create a potential chemical barrier through induced systemic resistance against Colletotrichum falcatum and minimise sucrose losses in sugarcane

Red rot disease caused by Colletotrichum falcatum leads to acute sucrose losses in sugarcane. Minimising sucrose losses through Trichoderma elicitors will fetch an eco-friendly technology to sugarcane growers. An experiment was conducted for evaluating the effects of elicitors from Trichoderma strains (STr 83, STr 108 and STr 116) against Colletotrichum falcatum for minimising sucrose losses. Following Trichoderma elicitor perception, a chemical barrier against C. falcatum was activated in sugarcane through enhanced accumulation of phenols, enhanced polyphenol oxidase, peroxidase, superoxidase dismutase, phenylalanine ammonia lyase, tyrosine ammonia lyase, chitinase and β-1,3 glucanase activities arrayed in setts at 45 days after pathogen inoculation (dpi). Phenol fluxes and enhanced activities of polyphenol oxidase, peroxidase, superoxidase dismutase, phenylalanine ammonia lyase, tyrosine ammonia lyase, chitinase and β-1,3 glucanase in foliar tissues were carried forward till 330 dpi (harvest stage). STr 83 elicitors exhibited maximum increase in phenols (106%), chitinase (540%), 1, 3 β-glucanases (160%) and activities of polyphenol oxidase (125%), peroxidase (346%), superoxide dismutase (54%), phenylalanine ammonia lyase (162%) and tyrosine ammonia lyase (206%) at 210 dpi. This chemical barrier orchestrated the diverse biochemical pathways for induced systemic resistance and minimised sucrose losses by 0.19–0.26 t ha−1 at cane harvest stage.

Indigenous Pseudomonas spp. Strains from the Olive (Olea europaea L.) Rhizosphere as Effective Biocontrol Agents against Verticillium dahliae: From the Host Roots to the Bacterial Genomes.

The use of biological control agents (BCA), alone or in combination with other management measures, has gained attention over the past decades, driven by the need to seek for sustainable and eco-friendly alternatives to confront plant pathogens. The rhizosphere of olive (Olea europaea L.) plants is a source of bacteria with potential as biocontrol tools against Verticillium wilt of olive (VWO) caused by Verticillium dahliae Kleb. A collection of bacterial isolates from healthy nursery-produced olive (cultivar Picual, susceptible to VWO) plants was generated based on morphological, biochemical and metabolic characteristics, chemical sensitivities, and on their in vitro antagonistic activity against several olive pathogens. Three strains (PIC25, PIC105, and PICF141) showing high in vitro inhibition ability of pathogens' growth, particularly against V. dahliae, were eventually selected. Their effectiveness against VWO caused by the defoliating pathotype of V. dahliae was also demonstrated, strain PICF141 being the rhizobacteria showing the best performance as BCA. Genotypic and phenotypic traits traditionally associated with plant growth promotion and/or biocontrol abilities were evaluated as well (e.g., phytase, xylanase, catalase, cellulase, chitinase, glucanase activities, and siderophore and HCN production). Multi-locus sequence analyses of conserved genes enabled the identification of these strains as Pseudomonas spp. Strain PICF141 was affiliated to the “Pseudomonas mandelii subgroup,” within the “Pseudomonas fluorescens group,” Pseudomonas lini being the closest species. Strains PIC25 and PIC105 were affiliated to the “Pseudomonas aeruginosa group,” Pseudomonas indica being the closest relative. Moreover, we identified P. indica (PIC105) for the first time as a BCA. Genome sequencing and in silico analyses allowed the identification of traits commonly associated with plant-bacteria interactions. Finally, the root colonization ability of these olive rhizobacteria was assessed, providing valuable information for the future development of formulations based on these strains. A set of actions, from rhizosphere isolation to genome analysis, is proposed and discussed for selecting indigenous rhizobacteria as effective BCAs.

Mechanisms employed by Debaryomyces hansenii in biological control of anthracnose disease on papaya fruit

The mechanisms of action associated with the biocontrol capacity of Debaryomyces hansenii against Colletotrichum gloeosporioides, causal agent of anthracnose in papaya, were studied by means of in vitro and in situ assays. In vitro the yeast exhibited a variety of different antagonistic mechanisms against the phytopathogenic fungus including: volatile organic compounds (VOCs) production, β-1, 3 glucanase and protease activity, inhibition of spore germination, and the competition for saccharose, glucose, fructose and total carbohydrates. Results in situ indicated that disease incidence and lesion diameter of anthracnose on papaya var. Maradol fruit was significantly reduced with a higher concentration of D. hansenii. Our study indicates that D. hansenii is an excellent agent of control to anthracnose disease on papaya var. Maradol fruit.