Microbial Antagonists Research Articles

APPLICATION OF Trichoderma spp. AND LIGNOHUMATE TO SUPPRESS A PATHOGEN OF CLUBROOT (Plasmodiophora brassicae WOR.) AND PROMOTE PLANT GROWTH OF CABBAGE

The high economic value of cabbage crop leads farmers to make various efforts to suppress the pathogen of club root which is detrimental to plants. Efforts that need to be put forward must be environmentally safe. One way that is environmentally friendly is to control a pathogen biologically using antagonistic microbes. Therefore, the use of microbes such as Trichoderma which has been widely studied is important because it was able to suppress clubroot incidence and stimulate plant growth as well. Meanwhile, the need for plant nutrients to maximize plant growth requires an input of organic materials such as lignohumate which preserve soil nutrients, improve soil structure and increase plant resistance to biotic and abiotic stresses. The previous study on this scheme found an effective indigenous Trichoderma to suppress clubroot, therefore it is used in the current study. The objective of this study was to find out a combination treatment of Trichoderma and lignohumate which can suppress clubroot and increase plant growth. This experiment used a Randomized Block Design with 2 factors and 3 replications. Trichoderma concentration consisted of 3 levels, namely 0 spores (control), 1x106 spores. 2x106 spores, and 3x106 spores per plant which were suspended in 150 ml of water. The lignohumate treatments were 0.01, 0.02, 0.05, 0.1, 0.5, 1.0, and 2%. The results showed that lignohumate treatment was interact with Trichoderma population number on disease incidence, total clubroot, root dry weight, but not to canopy dry weight. The most suitable combination of treatments was the Trichoderma population of 3x106 spores (15 g) in combination to lignohumate of 0.5%. This combination resulted in the lowest disease incidence, the lowest total clubroot, root dry weight, and the highest canopy dry weight. The higher the lignohumate concentration up to 0.5%, the higher the number of microbes (fungi and bacteria) growth, howeverit decreased above the concentration of 0.5%.

Azteca ants maintain unique microbiomes across functionally distinct nest chambers.

The microbiome of built structures has considerable influence over an inhabitant's well-being, yet the vast majority of research has focused on human-built structures. Ants are well-known architects, capable of constructing elaborate dwellings, the microbiome of which is underexplored. Here, we explore the bacterial and fungal microbiomes in functionally distinct chambers within and outside the nests of Azteca alfari ants in Cecropia peltata trees. We predicted that A. alfari colonies (1) maintain distinct microbiomes within their nests compared to the surrounding environment, (2) maintain distinct microbiomes among nest chambers used for different functions, and (3) limit both ant and plant pathogens inside their nests. In support of these predictions, we found that internal and external nest sampling locations had distinct microbial communities, and A. alfari maintained lower bacterial richness in their 'nurseries'. While putative animal pathogens were suppressed in chambers that ants actively inhabited, putative plant pathogens were not, which does not support our hypothesis that A. alfari defends its host trees against microbial antagonists. Our results show that ants influence microbial communities inside their nests similar to studies of human homes. Unlike humans, ants limit the bacteria in their nurseries and potentially prevent the build-up of insect-infecting pathogens. These results highlight the importance of documenting how indoor microbiomes differ among species, which might improve our understanding of how to promote indoor health in human dwellings.

Biological Control of Citrus Postharvest Phytopathogens.

Citrus are vulnerable to the postharvest decay caused by Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii, which are responsible for the green mold, blue mold, and sour rot post-harvest disease, respectively. The widespread economic losses in citriculture caused by these phytopathogens are minimized with the use of synthetic fungicides such as imazalil, thiabendazole, pyrimethanil, and fludioxonil, which are mainly employed as control agents and may have harmful effects on human health and environment. To date, numerous non-chemical postharvest treatments have been investigated for the control of these pathogens. Several studies demonstrated that biological control using microbial antagonists and natural products can be effective in controlling postharvest diseases in citrus, as well as the most used commercial fungicides. Therefore, microbial agents represent a considerably safer and low toxicity alternative to synthetic fungicides. In the present review, these biological control strategies as alternative to the chemical fungicides are summarized here and new challenges regarding the development of shelf-stable formulated biocontrol products are also discussed.

Eficiencia de los antagonistas microbanos para suprimir el daño ocasionado por Colletotrichum gloeosporioides en el cultivo de papaya: Perspectivas y desafíos

Papaya (Carica papaya L.) is one of the most valued tropical fruits worldwide due to its nutritional content. Its production is drastically affected by Colletotrichum gloeosporioides, one of the main pathogens responsible for anthracnose disease. Several techniques as an alternative of conventional chemical treatments for disease control have been studied. Among these techniques, the use of antagonist microorganism has emerged as a promising, eco-friendly alternative for postharvest disease control. This review is focused on the inhibition of Colletotrichum gloeosporioides in papaya applying microbial antagonists. Furthermore, the main purpose of this study is to provide the results of in vivo and in vitro assays, that addressed the use of microorganisms and their activity as biocontrol agents in papaya, considering its application to diminish crop losses and suggesting possible future researches addressed to their attractive usage. We believe that a specific compilation is helpful for groups that are in research of pre- and postharvest fruits management, providing useful information to create new perspectives and/or alternative in emerging technologies.

Sanitary Assurance at Biosolids Composting Facilities: Assessing the Efficiency of Temperature-Contact Time Criterion

Pathogen inactivation due to temperature exposure was studied in full-scale covered aerated static piles (CASP) treating municipal biosolids. The objectives of the study were to assess the impact of the temperature contact time on pathogen inactivation and to analyze whether the gradual increase in temperature, as occurs in compost piles, trigger a viable-but-non-culturable (VBNC) state. Twenty-two temperature probes imitating random particle behavior were seeded with Escherichia coli and Salmonella and introduced into the CASP. It was found that 92% of the compost pile experienced temperatures ≥55 °C for at least three consecutive days during the first stage of composting (36 days). This number rose to 93% after the pile was turned and composted for a further 20 days. At the end of active composting, the fecal coliforms level in the compost matrix, determined by culturing methods, was <103 MPN·g−1 total solids, while Salmonella was below its detection limit of <3 MPN·4 g−1 total solids. The molecular method indicated that there were live cells which had apparently entered a VBNC state. Nonetheless, it was concluded further study is needed to assess overall risk, since other factors such as pH, toxic compounds, and microbial competition and antagonism were excluded from this particular study. In future, as the techniques presented herein are refined, they may be useful for validating different types of composting technologies for sanitation effectiveness.

The antifungal action mode of the rice endophyte Streptomyces hygroscopicus OsiSh-2 as a potential biocontrol agent against the rice blast pathogen

Microbial antagonists and their bioactive metabolites provide one of the best alternatives to chemical pesticides to control crop disease for sustainable agriculture and global food security.The rice endophyte Streptomyces hygroscopicus OsiSh-2, with remarkable antagonistic activity towards the rice blast fungus Magnaporthe oryzae, was reported in our previous study. The present study deciphered the possible direct interaction mode of OsiSh-2 against M. oryzae. An in vitro antibiotic assay for OsiSh-2 culture filtrate revealed strong suppression of mycelial growth, conidial germination and appressorial formation of M. oryzae. Meanwhile, severe morphological and internal abnormalities in M. oryzae hyphae were observed under a scanning electron microscope and transmission electron microscope. Foliar treatment of rice seedlings by OsiSh-2 culture filtrate in the greenhouse and in the field showed 23.5% and 28.3% disease reduction, respectively. Correspondingly, OsiSh-2 culture filtrate could induce disorganized chitin deposition in the cell wall and lowered ergosterol content in the cell membrane of M. oryzae. Additionally, cell wall integrity pathway activation, large cell electrolytes release, reactive oxygen species accumulation and tricarboxylic acid cycle-related enzyme activity changes were found in M. oryzae. All these results suggested that the direct antagonistic activity of OsiSh-2 against M. oryzae may be attributed to damaging the integrity of the cell wall and membrane and disrupting mitochondrial function in the pathogen.

Foraging Macrotermes natalensis Fungus-Growing Termites Avoid a Mycopathogen but Not an Entomopathogen.

Fungus-growing termites have to defend both themselves and their monoculture fungal cultivars from antagonistic microbes. One of the ways that pathogens can enter the termite colony is on the plant substrate that is collected by termite foragers. In order to understand whether foragers avoid substrate infected with antagonists, we offered sub-colonies of Macrotermes natalensis a choice between food exposed to either a mycopathogenic or an entomopathogenic fungus, and control food. Workers did not show any preference between entomopathogen-exposed and control substrate, but significantly avoided the mycopathogen-exposed substrate. This suggests that the behaviour of foraging workers is more strongly influenced by pathogens affecting their crop than those posing risks to the termite workers themselves.

Loci identification of a N-acyl homoserine lactone type quorum sensing system and a new LysR-type transcriptional regulator associated with antimicrobial activity and swarming in Burkholderia gladioli UAPS07070

A random transposition mutant library of B. gladioli UAPS07070 was analyzed for searching mutants with impaired microbial antagonism. Three derivates showed diminished antimicrobial activity against a sensitive strain. The mutated loci showed high similarity to the quorum sensing genes of the AHL-synthase and its regulator. Another mutant was affected in a gene coding for a LysrR-type transcriptional regulator. The production of toxoflavin, the most well known antimicrobial-molecule and a major virulence factor of plant-pathogenic B. glumae and B. gladioli was explored. The absence of a yellowish pigment related to toxoflavin and the undetectable transcription of toxA in the mutants indicated the participation of the QS system and of the LysR-type transcriptional regulator in the regulation of toxoflavin. Additionally, those genes were found to be related to the swarming phenotype. Lettuce inoculated with the AHL synthase and the lysR mutants showed less severe symptoms. We present evidence of the participation of both, the quorum sensing and for the first time, of a LysR-type transcriptional regulator in antibiosis and swarming phenotype in a strain of B. gladioli

Identification of the Fungal Pathogens of Postharvest Disease on Peach Fruits and the Control Mechanisms of Bacillus subtilis JK-14.

Postharvest fungal disease is one of the significant factors that limits the storage period and marketing life of peaches, and even result in serious economic losses worldwide. Biological control using microbial antagonists has been explored as an alternative approach for the management of postharvest disease of fruits. However, there is little information available regarding to the identification the fungal pathogen species that cause the postharvest peach diseases and the potential and mechanisms of using the Bacillus subtilis JK-14 to control postharvest peach diseases. In the present study, a total of six fungal isolates were isolated from peach fruits, and the isolates of Alternaria tenuis and Botrytis cinerea exhibited the highest pathogenicity and virulence on the host of mature peaches. In the culture plates, the strain of B. subtilis JK-14 showed the significant antagonistic activity against the growth of A. tenuis and B. cinerea with the inhibitory rates of 81.32% and 83.45% at 5 days after incubation, respectively. Peach fruits treated with different formulations of B. subtilis JK-14 significantly reduced the mean disease incidences and lesion diameters of A. tenuis and B. cinerea. The greatest mean percent reduction of the disease incidences (81.99% and 71.34%) and lesion diameters (82.80% and 73.57%) of A. tenuis and B. cinerea were obtained at the concentration of 1 × 107 CFU mL−1 (colony forming unit, CFU). Treatment with the strain of B. subtilis JK-14 effectively enhanced the activity of the antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in A. tenuis and B. cinerea inoculated peach fruits. As such, the average activities of SOD, POD and CAT were increased by 36.56%, 17.63% and 20.35%, respectively, compared to the sterile water treatment. Our results indicate that the isolates of A. tenuis and B. cinerea are the main pathogens that cause the postharvest peach diseases, and the strain of B. subtilis JK-14 can be considered as an environmentally-safe biological control agent for the management of postharvest fruits diseases. We propose the possible mechanisms of the strain of B. subtilis JK-14 in controlling of postharvest peach diseases.

Probiotics Modulate a Novel Amphibian Skin Defense Peptide That Is Antifungal and Facilitates Growth of Antifungal Bacteria.

Probiotics can ameliorate diseases of humans and wildlife, but the mechanisms remain unclear. Host responses to interventions that change their microbiota are largely uncharacterized. We applied a consortium of four natural antifungal bacteria to the skin of endangered Sierra Nevada yellow-legged frogs, Rana sierrae, before experimental exposure to the pathogenic fungus Batrachochytrium dendrobatidis (Bd). The probiotic microbes did not persist, nor did they protect hosts, and skin peptide sampling indicated immune modulation. We characterized a novel skin defense peptide brevinin-1Ma (FLPILAGLAANLVPKLICSITKKC) that was downregulated by the probiotic treatment. Brevinin-1Ma was tested against a range of amphibian skin cultures and found to inhibit growth of fungal pathogens Bd and B. salamandrivorans, but enhanced the growth of probiotic bacteria including Janthinobacterium lividum, Chryseobacterium ureilyticum, Serratia grimesii, and Pseudomonas sp. While commonly thought of as antimicrobial peptides, here brevinin-1Ma showed promicrobial function, facilitating microbial growth. Thus, skin exposure to probiotic bacterial cultures induced a shift in skin defense peptide profiles that appeared to act as an immune response functioning to regulate the microbiome. In addition to direct microbial antagonism, probiotic-host interactions may be a critical mechanism affecting disease resistance.

Pengaruh Penggunaan Beberapa Varietas dan Aplikasi Pseudomonas fluorescens untuk Mengendalikan Penyakit Bulai (Peronosclerospora maydis) pada Tanaman Jagung (Zea mays L.)

Corn is one of the commodities that have high economic value and important role in meeting food needs in Indonesia. Unfavorable conditions on the rate of the higher demand for corn. Pests to be one limiting factor that causes a decrease in the production of corn. Peronosclerospora maydis is a pathogen that causes downy mildew on corn. P. maydis infects corn plants at the age of 2-3 weeks, with the level of damage reaches 80-100%. Control efforts against this disease one of them using antagonistic microbes such as bacteria Pseudomonas fluorescens. P. fluorescens has the potential to control downy mildew because it produces compounds that are antibiosis as chitinase enzymes that can hydrolyze the cell walls of fungi. The purpose of this study to determine the effect of the interaction of P. fluorescens isolates applications and the use of some varieties to suppress downy mildew attack P. maydis on corn. The method used is to use a random test design of a factorial group with 2 factors. The first factor is the type of varieties with three levels namely V1: Pioneer 27, V2: Pioneer 21 and V3: Bonanza. The second factor is a type of isolates P. fluorescens with three levels namely P1: without the application of P. fluorescens, P2: Isolates P. fluorescens (A) and P3: Isolate of P. fluorescens (B). The result is the application of P. fluorescens and use of some varieties can suppress downy mildew P. maydis.

The efficacy of compost, vermicompost and their combination with antagonistic microbes to reduce potato cyst nematode (Globodera rostochiensis)

The efficacy of compost, vermicompost and their combination with antagonistic microbes to reduce potato cyst nematode (Globodera rostochiensis)

Microbial Antagonism Toward Botrytis Bunch Rot of Grapes in Multiple Field Tests Using One Bacillus ginsengihumi Strain and Formulated Biological Control Products.

Botrytis bunch rot (BBR), caused by the necrotrophic fungus Botrytis cinerea, is a major disease of wine and table grapes worldwide. Due to negative effects of pesticides on the environment and human health, alternative control strategies against BBR, such as biological control agents (BCAs), are required to produce high-quality grapes and wines with high standards of food safety. However, few biological control products against BBR are available, and their efficacy is sometimes variable. This study aimed to evaluate and compare (1) the efficacy of new bacterial BCA strains developed at INRA Bordeaux and (2) the BBR reductions achieved by commercial biocontrol products that are already registered or close to being registered. During three consecutive seasons, 10 field experiments were established in six different experimental vineyards in southwestern France. Spray applications were performed at key phenological stages (five or six during the season), or at high BBR-risk periods late in the season according to a Disease Risk Index model. At harvest, BBR incidence and severity (% of symptomatic berries per bunch) were visually determined. The experiments included four bacterial strains at an early experimental stage, particularly Bacillus ginsengihumi (S38). Nine commercial BCA products were also tested, including Bacillus subtilis, Bacillus amyloliquefaciens, Aureobasidium pullulans, Ulocladium oudemansii, and Candida sake. Among the four experimental bacterial strains, only B. ginsengihumi S38 significantly controlled the BBR, presenting reductions in the average severity ranging from 35 to 60%, compared to untreated control, throughout the three seasons. Several commercial BCAs achieved significant reductions in BBR severity ranging from 21 to 58%, although not in every trial. The treatments that achieved higher reductions in severity rates were based on C. sake (45%), B. subtilis (54%), and B. amyloliquefaciens (58%). The efficacy of those BCAs was consistent throughout the studied seasons. The results confirmed the suitability of several biological control products under the conditions in vineyards in southwestern France, while also highlighting the good performance of the novel experimental BCA B. ginsengihumi S38 strain, which achieved similar control rates to the products registered for commercial use. The major factors involved in the variability in the results are also discussed.

Application of filamentous phages in environment: A tectonic shift in the science and practice of ecorestoration.

Theories in soil biology, such as plant–microbe interactions and microbial cooperation and antagonism, have guided the practice of ecological restoration (ecorestoration). Below‐ground biodiversity (bacteria, fungi, invertebrates, etc.) influences the development of above‐ground biodiversity (vegetation structure). The role of rhizosphere bacteria in plant growth has been largely investigated but the role of phages (bacterial viruses) has received a little attention. Below the ground, phages govern the ecology and evolution of microbial communities by affecting genetic diversity, host fitness, population dynamics, community composition, and nutrient cycling. However, few restoration efforts take into account the interactions between bacteria and phages. Unlike other phages, filamentous phages are highly specific, nonlethal, and influence host fitness in several ways, which make them useful as target bacterial inocula. Also, the ease with which filamentous phages can be genetically manipulated to express a desired peptide to track and control pathogens and contaminants makes them useful in biosensing. Based on ecology and biology of filamentous phages, we developed a hypothesis on the application of phages in environment to derive benefits at different levels of biological organization ranging from individual bacteria to ecosystem for ecorestoration. We examined the potential applications of filamentous phages in improving bacterial inocula to restore vegetation and to monitor changes in habitat during ecorestoration and, based on our results, recommend a reorientation of the existing framework of using microbial inocula for such restoration and monitoring. Because bacterial inocula and biomonitoring tools based on filamentous phages are likely to prove useful in developing cost‐effective methods of restoring vegetation, we propose that filamentous phages be incorporated into nature‐based restoration efforts and that the tripartite relationship between phages, bacteria, and plants be explored further. Possible impacts of filamentous phages on native microflora are discussed and future areas of research are suggested to preclude any potential risks associated with such an approach.

Valley Fever on the Rise-Searching for Microbial Antagonists to the Fungal Pathogen Coccidioides immitis.

The incidence of coccidioidomycosis, also known as Valley Fever, is increasing in the Southwestern United States and Mexico. Despite considerable efforts, a vaccine to protect humans from this disease is not forthcoming. The aim of this project was to isolate and phylogenetically compare bacterial species that could serve as biocontrol candidates to suppress the growth of Coccidioides immitis, the causative agent of coccidioidomycosis, in eroded soils or in areas close to human settlements that are being developed. Soil erosion in Coccidioides endemic areas is leading to substantial emissions of fugitive dust that can contain arthroconidia of the pathogen and thus it is becoming a health hazard. Natural microbial antagonists to C. immitis, that are adapted to arid desert soils could be used for biocontrol attempts to suppress the growth of the pathogen in situ to reduce the risk for humans and animals of contracting coccidioidomycosis. Bacteria were isolated from soil samples obtained near Bakersfield, California. Subsequently, pairwise challenge assays with bacterial pure cultures were initially performed against Uncinocarpus reesii, a non-pathogenic relative of C. immitis on media plates. Bacterial isolates that exhibited strongly antifungal properties were then re-challenged against C. immitis. Strongly anti-C. immitis bacterial isolates related to Bacillus subtilis and Streptomyces spp. were isolated, and their antifungal spectrum was investigated using a selection of environmental fungi.

Management of Charcoal Rot (Macrophomina phaseolina) Infection in Geranium (Pelargonium graveolens L) Using Biocontrol Agents and Essential Oils

IN a trial to control charcoal rot disease (Macrophomina phaseolina) in geranium using ecofriendly strategies, antagonistic microbes and essential oils were used. the treatments included three bacterial isolates, Bacillus polymixa, B. circulance, B. Subtilis and one fungus Tricoderma harzianum in addition to five essential oils, (Syzygium aromaticum(cloves), Ocimum basilicum L. (basil), Mentha spicata (Spearmint), Majorana hortensis Moench (Marjoram) and Mentha piperita L. (Peppermint). The in vitro antagonistic effect of microbial isolates and essential oils against M. phaseolina isolated from infected geranium was estimated in Petri plats, The essential oils were used in three concentrations 1, 3 and 5 microliter/plate. the most promising treatments were applied in an artificially infested geranium in a greenhouse experiment along two growing seasons of 2017, 2018. The in vitro screening step indicated that among the treatments, Bacillus subtilis and Trichoderma harzianum were the most promising microbes against the fungal pathogen under study using the dual culture technique. On the other hand, Peppermint oil recorded the highest reduction in radial growth of pathogen followed by Basil oil while Marjoram oil had no effect on the growth of pathogen. The green house experiment showed that, most treatments were efficient in pathogenicity reduction but the microbial treatment exhibited an advantage over essential oil where growth and yield parameters were sharply improved. The maximum enhancement was attained at T5 treatment (infested + dipping for 30 min before planting and spraying with T. harzianum after every cutting process) at all cuts during 2017 and 2018 seasons. Also, T. harzianum increased oil %, which recorded 0.45, 0.30 and 0.38% at 2017 season and 0.47, 0.31 and 0.39% at 2018 season for 1st, 2nd and 3rd cut respectively. Therefore, microbial and essential oil treatments not only reduced the fungal infection but also enhanced vegetative growth of geranium plants.

Inactivation of viable Ascaris eggs during faecal sludge co-composting with chicken feathers and market waste

Author(s): Manga, M; Camargo-Valero, MA; Evans, BE | Abstract: Faecal Sludge (FS) contains high concentrations of pathogenic microorganisms that are 10-100 times higher than those in domestic wastewater. Proper and sustainable treatment is required to inactivate these pathogens if FS is to be recycled in agriculture, so as to minimise public health and environmental risks. Composting is one of the common low-cost technologies of sanitising FS in Urban Africa; however, it is associated with longer pathogen inactivation periods that make it commercially uneconomical. This study investigated the effect of different organic wastes types and their mixing ratios with FS on the inactivation efficiency of viable Ascaris eggs (suum and lumbricoides) during composting. Dewatered FS was mixed with market waste (MW), chicken feathers (CF) and sawdust (SD) in different ratios. Compost piles of FS:MW:SD and FS:CF:SD both in volumetric ratios of 1:2:1 and 1:3:1 were set-up in duplicate (3 m3 each), composted and monitored weekly for viable Ascaris eggs presence for a period of 15 weeks. The results suggest that the organic waste types have a significant effect on the temperature evolution and pathogen inactivation efficiency while their mixing ratios do not. Piles containing CF achieved the shortest pathogen survival period of 4 weeks compared with 6-8 weeks for those with MW. The temperature-time factor was found to be the most important variable responsible for viable Ascaris eggs inactivation. However, other mechanisms such as microbial antagonism or antibiotic action induced by indigenous microorganisms and toxic by-products such as free ammonia were found to have also played an important role in Ascaris eggs inactivation. All piles attained 100% Ascaris eggs inactivation from FS, and therefore, the compost was safe for use in agriculture. The study findings suggest that composting of FS with CF can reduce Ascaris eggs inactivation periods by 42%, which may thus reduce the operational costs of FS treatment facilities.

Disease Incidence in Sugar Beet Fields Is Correlated with Microbial Diversity and Distinct Biological Markers

Sugar beets (Beta vulgaris), which are one of the major sources for sugar, alternative energy, and fuel, are affected by several fungal pathogens at harvest time. In order to identify correlations between the microbiome of field-grown sugar beets and their health status before harvest, we studied 2,200 antifungal antagonists together with 73 amplicon datasets obtained with 16S rRNA gene fragments as well as the fungal internal transcribed spacer region in samples from 13 different field sites in Austria and Germany. Overall, a substantial loss of microbial diversity (bacteriome H’: 8 versus 6.5; mycobiome H’: 4.5 versus 3.5) as well as a substantially different taxonomic composition was observed in root rot-affected sugar beets when compared with healthy beets. The Gram-positive Lactobacillales as well as distinct fungal taxa such as Candida, Penicillium, and Fusarium were identified as indicators of root rot on the microbiome level. In contrast, higher microbial diversity as well as distinct fungal genera assigned to Vishniacozyma and Plectosphaerella were associated with the microbiome of healthy plants. The taxonomic shifts in the fungal microbiome were accompanied by trophic specialization; pathotrophic and symbiotrophic fungi were replaced by saprotrophic fungi in diseased sugar beets. Moreover, samples with high proportions of antagonistic bacteria were not vulnerable to shifts in the fungal microbiome. The overall findings show implications between microbial antagonists and plant health as well as key taxa that are indicative for the health status in beets. They provide the basis for the development of improved disease management systems and preventive counteractions.

Alternaria-Brassica Associations: Research progress and prospects

Alternaria is a ubiquitous fungal genus that comprises saprobic, endophytic, and pathogenic species. the Alternaria blight or black spot disease(however, the disease is known by more than 40 names on the basis of symptoms formed on different parts of cruciferous crops) is the main bottleneck in the global production of cultivated oilseed brassica crops. Four Alternaria species including A. alternata, A.brassicae, A. brassicicola and A. raphani have been recorded pathogenic to cruciferous crops. An abrupt epidemic breakout of plant disease can cause huge economic losses. to manage such circumstances, understanding plant disease triangle and disease epidemic forecasting is very important. Although, the genus Alternaria is known as an imperfect fungus, it shows genetic variability within a species and this variability might be due to the existence of mutation, somatic hybridization, hetero-karyoses, uniform host selection, extensive dispersal or of a cryptic sexual stage. some useful information is available on chemical control of various Alternaria diseases, however, much more is needed in order to develop a viable disease control strategy under field conditions. Efforts should also continue to search for low cost effective chemicals, which can provide economically significant disease control. Active ingredient of plant extracts should also be identified. Control of Alternaria diseases in rapeseed-mustard by microbial antagonists should also be explored. seed treatment with Trichoderma spp., Gliocladium spp., Penicillium spp., and Mycostop-like preparations of Streptomyces spp. should be further investigated to determine their level of control and economic feasibility under field conditions. Similarly, control by foliar applications of Streptomyces rochei, S. higroscopicus, S. arabicus and Nectria inventa should also be evaluated under field conditions. No single methods or approach can be effective and economical. therefore, all means of plant disease control including chemical, biological, cultural, host resistance and biotechnology tools for early detection of disease should be integrated to manage the disease at early stage of plant growth. Considering the role of insects like aphids (virus transmission) and flea beetles (transmission of A. brassicicola to cabbage) insecticides should be one of the components in integrated disease management package and practices. disease forecasting system should be strengthened using modern information technology to warn farmers in advance for timely action by adopting proper control strategy.

Improved control on decay and postharvest quality deterioration of strawberry by microbial antagonists

Strawberry is a fruit of high commerce but it is prone to many postharvest diseases such as gray mold, Rhizopus rot, leather rot and Aspergillus rot. Although various fungicides have been recommended for the management of postharvest diseases of strawberry but due to carcinogenicity and acute residual toxicity, their use is discouraged. Therefore, the postharvest application of antagonistic microorganisms has emerged as an effective strategy to combat decay caused by fungi. Three micro-organisms viz., Debaryomyces hansenii, Bacillus subtilis DTBS-5 and Pseudomonas fluorescens DTPF-3 were used at a concentration of 107 log cfu/ml to control the postharvest diseases of ‘Winter Dawn’ strawberry fruits. Treated fruits were stored under ambient (25±2 oC and 50–55% RH) and low temperature (5±1 oC and 90% RH) storage conditions. Results revealed that among those antagonists, D. hansenii was able to effectively control the postharvest diseases of strawberry and maintain the fruit quality. Minimum decay (20.42%) was observed in Debaryomyces hansenii treated fruit whereas maximum fruit decay was observed in water washed (control) strawberry fruit (26.36%) under ambient conditions. Under ambient storage conditions, the treated fruits sustained till three days whereas at low temperature conditions, the fruit remained acceptable for 10 days. The physio-chemical parameters were well maintained in treated strawberry fruits till the end of storage both under low as well as ambient storage conditions as compared to the control fruit.