Successful Biocontrol Agent Research Articles

Potential distribution of Acerophagus papayae, a parasitoid of the papaya mealybug (Paracoccus marginatus), across Africa

The papaya mealybug, Paracoccus marginatus, is a highly polyphagous invasive pest that affects at least 133 economically important crops, and causes economic losses worldwide. Acerophagus papayae (Noyes and Schauff), a parasitic wasp, has proven to be a successful biocontrol agent, but its use in Africa is limited. Here, we use a predictive correlative model to explore the potential distribution of A. papayae and relate it to data showing the potential distribution of P. marginatus, to highlight potentially suitable areas for biological control of P. marginatus, for its current distribution, as well as its potential future distribution.The resulting model performed well with a test AUC of 0.89. Areas that were highly suitable for P. marginatus and were also suitable for A. papayae were highest across West Africa. Whilst there were areas which were suitable for both species in both East Africa and Central Africa, there were large areas of cropping land which were highly suitable for P. marginatus although not suitable for A. papayae. Across Northern and Southern Africa, there were limited cropping areas which were suitable for P. marginatus and where there was suitability, it was only moderate. Across these areas, there was limited suitability for A. papayae.Our results offer refined information on the potential suitability for A. papayae across Africa with the aim to help guide decisions on the areas where use of A. papayae could be used effectively as a part of an integrated pest management programme against P. marginatus.

Mechanistic insights to Paenibacillus lentimorbus mediated biocontrol of Alternaria solani in Solanum lycopersicum L. through carbohydrate reallocation and sweet immunity suppression

Researchers envisaged that PGPR (plant growth promoting rhizobacteria) has vast possibilities as a bioinoculant that will lead to revolution. However, it's still very far from becoming commercially successful. Here, the information regarding the root colonization of PGPR in host plants and plant response towards PGPR is inadequate. It can provide valuable information for developing successful biofertilizers and biocontrol agents. PGPR (Paenibacillus lentimorbus NRRL B-30488 or CHM12) has been previously reported as a successful commercial biofertilizer and biocontrol agent. However, the exact mechanism of plant growth promotion and biocontrol is poorly studied. So, CHM12 was appraised for biotic stress amelioration of pathogen Alternaria solani in Tomato (Solanum lycopersicum L.) var. S-22 plants. PGPR CHM12 was assessed for various plant growth parameters such as proline, sugar content, etc. in pathogen A. solani (AS) challenged plants and compared with the CHM12 treated plants in a greenhouse study. Then, the metabolomics tool (GC-MS) was used to identify metabolites and their respective genes playing pivotal roles in colonization tactics availed by PGPR. Further, gene expression analysis was done to affirm the involvement of various genes related to metabolites providing biotic stress tolerance in Tomato plants. The current research discerned that PGPR CHM12 revealed significant differences in different plant growth parameters studied. There were 33 distinct metabolites identified, which stipulated the involvement of carbohydrate metabolism mainly in combating biotic stress in this study. Thus, our study reconfirmed very few reported previous results through gene expression analysis, suggesting the downregulation of carbohydrate metabolism genes in PGPR-treated plants. This downregulation of carbohydrate genes might be the critical factor for suppressing the plant's immune response to gaining entry inside the host plant. This also helps in retaining and reallocating carbohydrates in plant cells to reduce pathogen proliferation.

Behavioral and histopathological changes of Clarias gariepinus as a predatory fish against Culex pipiens larvae following exposure to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide

Summary Clarias gariepinus is one of the widespread culturable freshwater fish species in Africa, which is prevalent in various natural and human-made aquatic habitats including rice-fish system. This fish species displays predation potential on the aquatic stages of mosquitoes. Bensulfuron-methyl and quinclorac are herbicide active substances that have been extensively applied in rice culture in Egypt and other countries worldwide. This study assessed the adverse effects of sublethal concentration of a commercial herbicide formulation containing quinclorac and bensulfuron-methyl on the predation potential of C. gariepinus female and male predatory fish on Culex pipiens mosquito larvae. Also, stomach and intestine histopathology of the treated fish was investigated. The exposure of C. gariepinus to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide produced detrimental effects on prey consumption and histopathological changes in the stomach and intestine of the fish. The mosquito consumption by the treated female and male fish decreased significantly compared to the untreated fish of both sexes. The histological changes in the intestines were hyperplasia of the intestinal epithelium and goblet cells; edema of lamina propria and broad intestinal villi, and distortion in intestinal villi in comparison to control. The stomach histopathology changes were necrosis and sloughing of mucosal epithelium with severe damage of sub-mucosa. Thus, the tested herbicide at sublethal concentration on C. gariepinus decreased the prey consumption on mosquito larvae and caused histopathological alterations in the fish that may impair its digestive physiology. These findings suggest a threat of the tested herbicide to C. gariepinus survival and potential as a native successful biocontrol agent against Cx. pipiens larvae.

Negative phototaxis of jumping cocooned parasitoid wasp larvae against short wavelengths and physicochemical properties of the cocoon shell

The parasitoid wasp Bathyplectes anurus (Hymenoptera: Ichneumonidae: Campopleginae) is a successful biocontrol agent against the alfalfa weevil, Hypera postica. This weevil is a serious pest of beneficial fabaceous plants such as alfalfa and Chinese milk vetch. One of the possible reasons for the success of this wasp in hot climates may be the ability of its cocooned larvae to repeatedly jump and roll until they relocate themselves away from detrimental sunlight and heat. It is not yet known which wavelengths of light trigger this avoidance behavior or the microstructure of the cocoon shell that might allow light transmission. Here, the response of the cocooned larvae to different wavelengths, and the microstructure, hardness, and elemental components of the cocoon shell were studied. A population of cocooned larvae were introduced on the boundary line between illuminated and shaded areas with blue, green, red, or near-infrared light-emitting diodes. The cocoons moved away from the blue and green light. The distance from the boundary to the cocoons in the shaded area was longer under these long wavelengths, followed by the red light and shortest under the near-infrared light and nil under darkness. No difference was found in mortality between different wavelengths after three days of illumination. Scanning electron microscope observations of the surface of the cocoon shell revealed that the belt-like central ridge was porous, which likely allows ventilation and light transmission. The surface of the cocoon shell showed a uniform distribution of sulfur, potentially aiding in the capture of green wavelengths. The ridge had twice the thickness of the main body and was 1.9 times harder than the main body. These results may be applied to better understand the individual responses of this biological control agent to modifications to their environment, including light pollution.

Biological Disease Control by Beneficial (Micro)Organisms: Selected Breakthroughs in the Past 50 Years.

Biological control of plant disease by beneficial (micro)organisms is one of the main tools available to preserve plant health within the wider context of One Health and in line with the goals of the Agenda 2030 for Sustainable Development. The commercial development of biocontrol agents, together with a new perspective on the resident microbial community, all supported by innovative "omics" technologies, continues to gain in prominence in plant pathology, addressing the need to feed the increasing world population and to assure safe and secure access to food. The present review considers selected advances within the last 50 years, highlighting those that can be considered as breakthroughs for the biological control research field. Selected examples of successful biocontrol agents and strategies are reported, including the history of the progress in researching Trichoderma isolates as commercial biocontrol agents, the exploitation of mycoviruses to confer hypovirulence to plant pathogenic fungi, the role of microbial communities in the suppressiveness of soils, and evolving approaches including the establishment of synthetic microbial communities.

Comparative toxicity of spinetoram to Trialeurodes vaporariorum Westwood and its parasitoid Eencarsia formosa Gahan

The role of selective new generation bioisecticides, beside their effectiveness against key pests, relies on their safety to beneficial arthropods. Spinetoram, a semi-synthetic analogue of the microbial-derived bioinsecticide spinosad is registered worldwide for application in numerous crops, but assessment of its ecotoxicological risk to beneficial arthropods has scarcely been documented. Moreover, this is the first report on toxic effects of spinetoram on a pest, the greenhouse whitefly Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), and/or its successful biocontrol agent, the parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). Under laboratory conditions, we assessed the acute toxicity of spinetoram insecticide (25% a.i.) to adults, nymphs and eggs of the greenhouse whitefly, as well as to parasitoid adults and pupae. In all concentration-response bioassays, the spinetoram insecticide was applied to tobacco leaves settled onto 1% agar layer in ventilated Petri dishes using a Potter spray tower. The parameters of spinetoram acute toxicity to adults of both the pest and the parasitoid were evaluated in residual contact bioassays, while whitefly eggs and nymphs, and parasitoid pupae were topically treated with a series of spinetoram concentrations, covering a range of 10-90% mortality. Lethal spinetoram effects on the parasitoid E. formosa were assessed through selectivity ratio (SR) estimations, showing the ratios beetween median lethal concentrations (LC50s) estimated for the parasitoid, and LC50s estimated for the pest. The following LC50 values were obtained: 4.593, 15.027 and 11.73 mg a.i./l for whitefly adults, nymphs and eggs, respectively, and 0.686 and 1.715 mg a.i./l for parasitoid adults and pupae, respectively. The calculated SR estimations were below 1, indicating that spinetoram insecticide is non-selective to both tested stages of the parasitoid E. formosa. A more detailed understanding of spinetoram impact on E. formosa in whitefly integrated management requires further evaluation of sublethal effects and greenhouse trials, with an emphasis on population-level responses.

Biocontrol potential of endosymbiotic bacteria of entomopathogenic nematodes against the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

BackgroundThe tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a major pest of tomato plants threatening global tomato production. The control of the pest is becoming increasingly difficult due to the rapid development of resistance to insecticides. Entomopathogenic nematodes (EPNs) of families Steinernematidae and Heterorhabditidae are successful biocontrol agents for many insect pests. Recently, their bacteria, Xenorhabdus spp. and Photorhabdus spp. have attracted great attention due to their major role in the pathogenicity of EPNs. In the present study, the pathogenicity of eleven EPNs isolates belonging to Steinernema feltiae and Heterorhabditis bacteriophora species was screened against the 1st/2nd and 3rd/4th instar larvae of T. absoluta. The cell-free supernatants and cell suspensions of the symbiotic bacteria from the most efficient isolates were further evaluated for their biocontrol potential in the oral and contact treatments on the larvae of T. absoluta.ResultsKBC-4 and MCB-8 isolates of S. feltiae showed superior virulence relative to other EPNs species/isolates and induced 90% larval mortality against the 3rd/4th instar of T. absoluta larvae, whereas there were no clear differences in the efficacy of EPNs species/isolates against the 1st/2nd instar of T. absoluta. The 1st/2nd instar of T. absoluta larvae was more susceptible to cell-free supernatants and cell suspension of selected EPNs. The highest mortality (80%) was obtained from X. bovienii MCB-8 strain in the contact treatment of supernatants. In contact treatment of cell suspension, higher mortalities were obtained compared to oral treatments. Mortality rates ranged between 30 and 57.5% in the contact treatments of cell suspensions while the highest mortality did not exceed 20% in oral treatments. The antifeedant activity was observed in oral treatments of cell suspension and most of the larvae avoided feeding on treated leaves.ConclusionThe results indicated that symbiotic bacteria of EPNs had a great potential against T. absoluta larvae and contact treatment of cell-free supernatants against early instars of T. absoluta can be an ideal application. However, further studies are needed to investigate the field effectiveness of symbiotic bacteria.

Biological Control of Oomycete Soilborne Diseases Caused by Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae in Solanaceous Crops

Oomycete pathogens that belong to the genus Phytophthora cause devastating diseases in solanaceous crops such as pepper, potato, and tobacco, resulting in crop production losses worldwide. Although the application of fungicides efficiently controls these diseases, it has been shown to trigger negative side effects such as environmental pollution, phytotoxicity, and fungicide resistance in plant pathogens. Therefore, biological control of Phytophthora-induced diseases was proposed as an environmentally sound alternative to conventional chemical control. In this review, progress on biological control of the soilborne oomycete plant pathogens, Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae, infecting pepper, potato, and tobacco is described. Bacterial (e.g., Acinetobacter, Bacillus, Chryseobacterium, Paenibacillus, Pseudomonas, and Streptomyces) and fungal (e.g., Trichoderma and arbuscular mycorrhizal fungi) agents, and yeasts (e.g., Aureobasidium, Curvibasidium, and Metschnikowia) have been reported as successful biocontrol agents of Phytophthora pathogens. These microorganisms antagonize Phytophthora spp. via antimicrobial compounds with inhibitory activities against mycelial growth, sporulation, and zoospore germination. They also trigger plant immunity-inducing systemic resistance via several pathways, resulting in enhanced defense responses in their hosts. Along with plant protection, some of the microorganisms promote plant growth, thereby enhancing their beneficial relations with host plants. Although the beneficial effects of the biocontrol microorganisms are acceptable, single applications of antagonistic microorganisms tend to lack consistent efficacy compared with chemical analogues. Therefore, strategies to improve the biocontrol performance of these prominent antagonists are also discussed in this review.

Natural parasitization of Cotesia spp. and Bracon spp. on Spodoptera litura Fab. in castor crop

The larval stage of Spodoptera litura Fab. is more prone to parasitism. Larval parasitoids such as braconids belongs to family Braconidae of order Hymenoptera acts as Ecto parasitoids. Braconids have wide host range and successful biocontrol agent recommended for the control of lepidopteran larvae in many crops and stored grains. The present study on parasitization of braconids on S. litura was conducted under laboratory conditions. The larva of S. litura collected from castor crop from various locations near by Nagpur, Maharashtra, India and reared on castor leaves under laboratory conditions. The larvae were parasitized by two parasitoids namely, Cotesia spp. and Bracon spp. The study revealed that the field collected larva of S. litura when reared on castor leaves showed an average parasitization of 11% and 4.3% by Cotesia spp. and Bracon spp. respectively.

Proteomics of Two Thermotolerant Isolates of Trichoderma under High-Temperature Stress.

Several species of the soil borne fungus of the genus Trichoderma are known to be versatile, opportunistic plant symbionts and are the most successful biocontrol agents used in today’s agriculture. To be successful in field conditions, the fungus must endure varying climatic conditions. Studies have indicated that a high atmospheric temperature coupled with low humidity is a major factor in the inconsistent performance of Trichoderma under field conditions. Understanding the molecular modulations associated with Trichoderma that persist and deliver under abiotic stress conditions will aid in exploiting the value of these organisms for such uses. In this study, a comparative proteomic analysis, using two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/time-of-flight (MALDI-TOF-TOF) mass spectrometry, was used to identify proteins associated with thermotolerance in two thermotolerant isolates of Trichoderma: T. longibrachiatum 673, TaDOR673 and T. asperellum 7316, TaDOR7316; with 32 differentially expressed proteins being identified. Sequence homology and conserved domains were used to identify these proteins and to assign a probable function to them. The thermotolerant isolate, TaDOR673, seemed to employ the stress signaling MAPK pathways and heat shock response pathways to combat the stress condition, whereas the moderately tolerant isolate, TaDOR7316, seemed to adapt to high-temperature conditions by reducing the accumulation of misfolded proteins through an unfolded protein response pathway and autophagy. In addition, there were unique, as well as common, proteins that were differentially expressed in the two isolates studied.

Kairomone gel formulations enhance biocontrol efficacy of Trichogramma japonicum Ashmead on rice yellow stem borer, Scirpophaga incertulas Walker

The egg parasitoid, Trichogramma japonicum (Hymenoptera:Trichogrammatidae) is a documented successful biocontrol agent to reduce rice yellow stem borer (YSB), Scirpophaga incertulas (Lepidoptera: Crambidae). In the present study, three kairomone gel formulations: T1: n-hexadecanoic acid (200 ppm); T2: n-octadecanoic acid (500 ppm) and; T3: octadecane (500 ppm); were applied 24 h after each release of adult T. japonicum in low land rice field plots during the rainy season (2018) and summer season (2019). The study evaluated whether the combination of the kairomone gel treatments with parasitoid could improve suppression of YSB. The best results were from T3: application of octadecane gel, 24 h after each T. japonicum release (@ 50,000 wasps/ha × 4 releases) on the 32nd, 39th, 46th, 53rd days after transplanting (DAT) at weekly intervals during the rainy season (2018). This regime reduced incidence of YSB induced damage called: ‘dead heart’ and ‘white ear’ by 30.01%–37.06% compared to T5: control. During the summer season (2019) again the best results were observed in T3: octadecane augmented wasps releases, the reduction in damages by YSB ranged from 17.86% to 24.47% below control. The grain yields in T3, increased from 14.61% to 15.73% across both seasons measured. These results support augmenting T. japonicum releases with the kairomone gel containing octadecane provide an affordable treatment to increase parasitic activity and to reduce damage in rice crops caused by YSB.

Trichoderma based biological management of major fungal diseases in pulse crops

Pulses are an integral part of Indian agriculture due to their multiple utility in human food, animal feed and soil health. India has the distinction of being the top producer of pulses in the world. About 8–10% grain yield of pulse crops are annually lost due to various diseases. Majority of the fungal diseases are soil and seed borne in nature therefore, difficult to manage by conventional management practices consisting of growing resistant cultivars and use of fungicides. Among the various types of biological control agents, Trichoderma species have been extensively exploited. They were found to be effective against large number of soil, seed and air borne fungal plant pathogens. The ideal characteristic features like high reproductive capacity, rhizosphere modification ability, survival ability under adverse conditions, nutrients utilization efficiency, aggressiveness against plant pathogens and promoting plant growth and defense mechanism makes Trichoderma as a successful biocontrol agent. Seed and soil application bio-formulations were developed from different potential species of Trichoderma to increase shelf life and efficacy. Pusa 5SD a seed dressing formulation and Pusa Biopellet (PBP) a soil application formulation showed longer shelf life. The efficacies of newly developed bio-formulations were evaluated in pot and filed experiments against several diseases of pulse crops namely, dry (Rhizoctonia bataticola) and wet root rot (R. solani) of mungbean and ckickpea, wilt (Fusarium oxysporum f. sp. ciceris) of chickpea and root rot (Rhizoctonia solani) and damping off (Pythium ultimum) complex in French bean. T. harzianum based formulations were found superior over others against R. bataticola and Fusarium species whereas, T. virens based formulations were found superior against R. solani. A combined application of PBP 10G (T. harzianum) in soil and Pusa 5SD + carboxin as seed treatment showed superiority over any other formulations alone in reducing the dry root rot incidence and increasing grain yield of mungbean and chickpea. Soil application of PBP 4G (T. viride) and seed treatment with Pusa 5SD (T. harzianum) + carboxin provided the highest yield attributing parameters with the lowest wilt incidence in chickpea. T. virens based Pusa 5SD and PBG 6 were found effective in reducing wet root rot and increasing yield in mungbean and chickpea. Seed treatment proved superiority over soil application for all the parameters recorded. Both the formulations (soil and seed treatment) showed growth promoting ability. During validation, Pusa 5SD (T. harzianum) alone and in combination with Vitavax power (carboxin + thiram) reduced the wilt incidence and enhanced the grain yield of chickpea at 8 different locations across the country. French bean seeds treated with T. harzianum based Pusa 5 SD + P. fluorescens provided the highest seed germination, root and shoot lengths, dry plant weight, pod yield and the lowest disease incidence. Further, combined application of Pusa 5SD (T. harzianum), PGPR strain P. fluorescens, M. ciceri and Vitavax power as seed treatment gave extreme protection to germinating chickpea plants with the highest grain yield and the lowest wilt incidence.

Impacts of a biocontrol agent on invasive Ageratina adenophora in Southwest China: Friend or foe?

Classical biological control of invasive plants depends on the introduction of host-specific natural enemies. Many natural enemies have provided successful control, but the impacts of herbivorous insects on their hosts are highly variable and context dependent. Under some circumstances, overcompensation can even occur, with plant reproduction temporarily increasing rather than decreasing in response to herbivory. The stem-galling fly Procecidochares utilis has been widely introduced to help control Ageratina adenophora, a globally significant weed, but its impact has been inconsistent and in places ineffective. Its galling is known to stimulate production of side branches in plants under laboratory conditions. We examined the abundance and impact of P. utilis at four A. adenophora sites of Southwest China that were invaded at different times and support different densities of the insect. Stems with galls were more likely to be branched and produced more capitula. Furthermore, seed numbers in capitula from galled and un-galled stems were similar, and galling resulted in only slightly reduced seed weights. However, the increase in above-ground vegetative biomass associated with branching resulted in less efficient capitulum production relative to vegetative growth. Clearly Procecidochares utilis is not providing effective biocontrol of Ageratina adenophora in Southwest China so far. In the long term, galled plants may display reduced competitive ability and lower lifetime reproductive success, but the short term increases in seed production it generates suggest it may be favouring its host’s range expansion. The fly has been a successful biocontrol agent in dry area of Hawii, so understanding the factors that determine its effectiveness represent a major challenge for the future.

Effect of humidity and temperature on the performance of three strains of Aphalara itadori, a biocontrol agent for Japanese Knotweed

Japanese knotweed (Fallopia japonica) is a highly damaging invasive species affecting UK infrastructure and biodiversity. Under laboratory conditions, the psyllid Aphalara itadori has demonstrated its potential to be a successful biocontrol agent for F. japonica. However, this potential has not materialised in the field where long-term establishment of A. itadori has been unsuccessful and faces the added challenge of climate change. Intraspecific variation (variation among individuals of a species) has been shown to support establishment in alien species and improve resilience to changing environmental conditions. Here we propose it could improve the performance of biocontrols. To test this possibility we compared the performance and impact on F. japonica of three strains of A. itadori with different genetic backgrounds, including a newly created hybrid. We hypothesize that genetic variability would be increased in hybrids resulting in greater biocontrol effectiveness (greater impact on plant growth). We also explored the potential influence of changing climate on performance, testing all strains under two humidity conditions (with the same temperature). Contrary to our expectation, the hybrid strain had the worst performance (slowest development rate and lower survival from egg to adult emergence) under both environmental conditions. Exposure to different strains of A. itadori did not result in consistent differences in plant growth, suggesting similar biocontrol effectiveness among strains. Under the drier, more stressful, conditions plants exposed to A. itadori had fewer leaves and accumulated less above-ground biomass. Overall, our results suggest that genetic variability may not be the key to improve A. itadori biocontrol effectiveness, but that predicted climate change, which anticipates drier and hotter summers in the UK, could reduce the growth potential of F. japonica when exposed to A. itadori.

Isolation of 12 polymorphic tetranucleotide microsatellite markers of the leaf beetle Ophraella communa, a promising Ambrosia biocontrol agent also in Europe

ABSTRACTFollowing its first record in Europe in 2013, the North American ragweed leaf beetle Ophraella communa, used already as a most successful biocontrol agent against common ragweed in China, is spreading rapidly, asking for a detailed analysis of the potential benefit and risk of this introduction for Europe. Here, we report twelve specific and polymorphic tetranucleotide microsatellite markers, which can be used for redrawing its global invasion history and spread across native and introduced ranges. The high level of polymorphism (i.e. from 4 to 18 alleles per locus) and the genetic variation detected within and between one native and two introduced populations provide adequate statistical power for elucidating the beetle’s invasion process.

Co-occurrence of thelytokous and bisexual Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) in a natural population

Trichogramma dendrolimi is one of the most successful biocontrol agents in China. However, an inundative condition is necessary to obtain acceptable parasitism effect. A good solution to this is the application of its thelytokous counterparts which unfortunately are scarce in field. We here report the first case of a natural T. dendrolimi population in China comprising both bisexual wasps and an extremely low proportion of thelytokous wasps. These two forms of T. dendrolimi are phylogenetically related based on the reconstructions of ITS-2 and COI genes. Also, the phylogenetic results suggested a potentially Wolbachia-drived ITS-2 variation. The expression of thelytoky was hardly affected by temperature, which might help control Asian corn borer and Dendrolimus punctatus. Wolbachia are responsible for current thelytoky according to phylogenetic analyses, antibiotic treatment and introgression experiment. We also present the third case of paternal sex ratio chromosome that restrains the expansion of Wolbachia. Moreover, the low frequency of thelytoky may be common in natural populations. Consequently if for biological control it is determined that a thelytokous strain is to be preferred, then large number of field collected females should be set up as isofemale lines, to detect the rare thelytoky.

Trichoderma and Its Prospects in Agriculture of Nepal: An Overview

In the world, the traditional agricultural practices are getting affected by various problems such as disease, pest, drought, decreased soil fertility due to use of hazardous chemical pesticides, pollution and global warming. As a result, there is a need for some eco-friendly bio-control agents that help in resolving the previous mentioned problems. The various types of biological control agents such as bacteria and fungi are involved in bio-control activity. Among them, fungal genus Trichoderma plays a major role in controlling the plant diseases. Species of Trichoderma are diverse fungal microbial community known and explored worldwide for their versatilities as biocontrol and growth promoting agents. These fungi reproduce asexually by production of conidia and chlamydospores and in wild habitats by ascospores. Trichoderma species are efficient mycoparasites and prolific producers of secondary metabolites, some of which have clinical importance. However, the ecological or biological significance of this metabolite diversity is sorely lagging behind the chemical significance. Several Trichoderma spp. positively affect plants by stimulating plant growth, and protecting plants from fungal and bacterial pathogens. They are used in biological plant protection as bio-fungicides as well as in bioremediation. A large number of research groups are working on various aspects of Trichoderma viz., diversity, ecology and their applications. The capacity of Trichoderma fungi to produce lytic enzymes is used in animal feed, and wine making and brewery industries. Trichoderma spp. are the most successful bio-control agents as more than 60% of the registered bio-fungicides used in today’s agriculture belongs to Trichoderma -based formulation. The increase in incidence and severity of diseases and emergence of new diseases causes the significant yield losses of different crops in Nepal. But the research and studies on plant diseases are limited.
 Int. J. Appl. Sci. Biotechnol. Vol 7(3): 309-316

Prospects for biological control of cactus weeds in Namibia

ABSTRACTAustralia and South Africa have a long history of sharing successful biocontrol agents for cactus weeds but other countries, such as Namibia, could also benefit. There are four biological control agents that are widely utilised in South Africa and/or Australia for the control of 10 invasive alien Cactaceae in Namibia.

Cuticle-degrading proteases of entomopathogenic fungi: from biochemistry to biological performance

Entomopathogenic fungi are among the most successful biocontrol agents for preventing economic loss from insects. The identification of virulent species or isolates, the development of formulation technology and the improvement of efficiency are avenues being pursuing by researchers in diverse scientific disciplines. A successful entomopathogenic fungus deploys a combination of mechanical and biochemical processes to overcome the first defensive barrier in insects, the integument. A precise understanding of the mechanisms underlying fungal pathogenicity, particularly the roles of enzymes such as proteases, is essential in order to highlight the potential of entomopathogenic fungi and increase their virulence via genetic modifications. Cuticle-degrading proteases are divided into subtilisin-like (Pr1) and trypsin-like (Pr2) proteases, which are secreted in the initial stages of penetration. The biochemical structure contains the catalytic triad Asp39, His69 and Ser224 in addition to Ca2+ binding sites. Studies have shown a molecular weight of almost 19–47 kDa, an optimal pH of 7–12 and an optimal temperature of 35–45 °C. Different species or isolates of entomopathogenic fungi exhibit differences in the secretion and activity of cuticle-degrading proteases, which may indicate their virulence capacity. Genetic engineering techniques have been developed to create isolates with protease overexpression. Such isolates have significantly higher virulence against the host because they not only ensure fungal penetration but also exhibit direct toxicity to insects.

Genome sequence and comparative analyses of atoxigenic Aspergillus flavus WRRL 1519

ABSTRACTAflatoxins are toxic secondary metabolites produced by Aspergillus flavus and a few other closely related species of Aspergillus. These highly toxigenic and carcinogenic mycotoxins contaminate global food and feed supplies, posing widespread health risks to humans and domestic animals. Field application of nonaflatoxigenic strains of A. flavus to compete against aflatoxigenic strains has emerged as one of the best management practices for reducing aflatoxins contamination, yielding successful commercial products for corn, cotton seed, and peanuts. In this study, we sequenced the genome and transcriptome of atoxigenic (does not produce aflatoxin or cyclopiazonic acid) A. flavus strain WRRL 1519 isolated from a tree nut orchard to define the genetic characteristics of the strain in relation to aflatoxigenic and other nonaflatoxigenic A. flavus strains. WRRL 1519 strain was similar to other strains in size (38.0 Mb), GC content (47.2%), number of predicted secondary metabolite gene clusters (46), and number of putative proteins (12 121). About 87.4% of the predicted proteome had high shared identity with protein sequences derived from other A. flavus genomes. However, the atoxigenic A. flavus strain WRRL 1519 had deletions, or low shared identity, for many genes in the clusters required for aflatoxins and cyclopiazonic acid (CPA) synthesis. Over half of the aflatoxin synthesis gene cluster was missing, and none of the components of the CPA gene cluster were identified with high sequence similarity. Importantly, the strain appeared to maintain functional sequences of several genes thought to be required for high infectivity. Since the ability to grow on target crop is an important attribute for a successful biocontrol agent, these results indicate that the nonaflatoxigenic A. flavus strain WRRL 1519 would be a good candidate as a biocontrol agent for reducing aflatoxin and CPA accumulation in high-value nut crops.