Cladobotryum mycophilum as Potential Biocontrol Agent

A study was conducted to explore the efficacy of potential biocontrol agent Cladobotryum mycophilum against different phytopathogenic fungi. The growth rates of 24 isolates of C. mycophilum were determined, and their antagonistic activity was analysed in vitro and in vivo against Botrytis cinerea, Fusarium oxysporum f. sp. radicis-lycopersici, Fusarium oxysporum f.sp. cucumerinum, Fusarium solani, Phytophthora parasitica, Phytophthora capsici, Pythium aphanidermatum and Mycosphaerella melonis. Most isolates grow rapidly, reaching the opposite end of the Petri dish within 72–96 h. Under dual-culture assays, C. mycophilum showed antagonistic activity in vitro against all phytopathogenic fungi tested, with mycelial growth inhibition ranging from 30 to 90% against all the different phytopathogens tested. Similarly, of all the selected isolates, CL60A, CL17A and CL18A significantly (p < 0.05) reduced the disease incidence and severity in the plant assays compared to the controls for the different pathosystems studied. Based on these results, we conclude that C. mycophilum can be considered as a potential biological control agent in agriculture. This is the first study of Cladobotryum mycophilum as a biological control agent for different diseases caused by highly relevant phytopathogens in horticultur

Using Modelling to Optimise the Use of Biological Control Agents Against Soil-Borne Plant Pathogens

There is considerable interest in the use of biological control agents as a control strategy against plant pathogens. However, significant variability in their success at pathogen suppression across field trials has resulted in them often not being seen as commercially viable. This thesis uses mathematical modelling to explore the interactions between a soil- borne biocontrol agent, a soil-borne pathogen, and the roots of a host plant. Understanding the dynamics of these organisms in more detail can allow us to optimise the use of biological control agents. We construct a model that focuses on the roots of a plant and whether they are infected by a pathogen or colonised by a biocontrol agent, as well as including any free-living pathogen and biocontrol agent in the surrounding soil. Although this model can be used across multiple systems, this thesis focuses on modelling the infection of winter wheat by Gaeumannomyces graminis var. tritici and suppression by the biocontrol agent 2,4-DAPG fluorescent Pseudomonas spp. Parameter values are obtained for the model through fitting it to data from this system. Application timing and amount of application were both found to affect the ability for a biocontrol agent to suppress a pathogen. Including a break crop into a simulation had a negative impact on both the pathogen and biocontrol agent, suggesting that combining multiple strategies for epidemic suppression may not always be effective. Planting a crop with even spaces between plants, or in rows with 12cm between each row, was found to reduce epidemic severity more than if rows were spaced further apart for the first year of an epidemic. However, large-scale dispersal of free-living material between growing seasons from agricultural machinery reduced any benefit of specific spatial arrangements of a crop in the second year of an epidemic. Aggregation of the pathogen and biocontrol agent were found to affect epidemic severity, with the greatest reduction from a highly aggregated pathogen and a uniformly distributed biocontrol agent. We suggest that a greater focus on optimising application, as well as a detailed understanding of how the spatial dynamics of a biocontrol agent and pathogen can affect this application, may enhance the success of biocontrol agents and allow them to be seen as a viable control strategy.BBSR

Evaluation of bee-vectored Aureobasidium pullulans for biocontrol of grey mould in strawberry

The fungal pathogen Botrytis cinerea causes grey mould in strawberry (Fragaria x ananassa) inflicting great yield loss and significant economic loss. To date, spraying with chemical fungicides is the primary management practice to control this disease. Concerns regarding resistance development of the pathogen, high treatment cost and environmental issues have led to the search for alternative methods. This study investigates if the biocontrol fungus Aureobasidium pullulans (isolate AP-SLU6) could be used as a biocontrol agent vectored by buff-tailed bumblebee, to suppress grey mould in strawberry under greenhouse conditions. To examine if A. pullulans affect bumblebees negatively, trials measuring the flight activity and the hive weight was performed. To test if the bees can carry and deposit the biocontrol agent to strawberry flowers, samples of flowers and bumblebees were collected and examined. Finally, the scoring of grey mould infection on fruits was performed pre-and postharvest. Bee activity and hive weight was not significantly affected by the carried fungal biocontrol agent. The results further showed that bumblebees successfully vectored the biocontrol agent to flowers and significantly reduced the severity of grey mould infected fruits during postharvest storage, thus leading to improved shelf life. This study concludes that A. pullulans used as a biocontrol agent vectored by bumblebees, can be an efficient method for controlling postharvest grey mould in strawberry, leading to improved plant health and reduced dependence on synthetic fungicides

Plant pathogens as biocontrol agents of Cirsium arvense : an overestimated approach?

Cirsium arvense is one of the worst weeds in agriculture. As herbicides are not very effective and not accepted by organic farming and special habitats, possible biocontrol agents have been investigated since many decades. In particular plant pathogens of C. arvense have received considerable interest and have been promoted as “mycoherbicides” or “bioherbicides”. A total of 10 fungi and one bacterium have been proposed and tested as biocontrol agents against C. arvense. A variety of experiments analysed the noxious influence of spores or other parts of living fungi or bacteria on plants while others used fungal or bacterial products, usually toxins. Also combinations of spores with herbicides and combinations of several pathogens were tested. All approaches turned out to be inappropriate with regard to target plant specificity, effectiveness and application possibilities. As yet, none of the tested species or substances has achieved marketability, despite two patents on the use of Septoria cirsii and Phomopsis cirsii. We conclude that the potential of pathogens for biocontrol of C. arvense has largely been overestimated

In vitro biocontrol activity of Trichoderma harzianum on Alternaria alternata in the presence of growth regulators

http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582001000200006&lng=es&nrm=isoThe in vitro biocontrol ability of Trichoderma harzianum on the phytopathogen Alternaria alternata improved in the presence of the growth regulators gibberellic acid (GA3), or indolacetic acid (IAA) or benzylaminopurine (BAP) or foliar nutrient at concentrations similar or higher than those used at the field level. These plant hormones decreased the secretion of endopolygalacturonase (endo-PG) of A. alternata by approximately 20%, did not modify endochitinase (endo-CH) secretion of T. harzianum and did not alter germination of conidia or mycelia growth of any of these fungi. The presence of T. harzianum decreased endo-PGase secretion of A. alternata by about 50%. This inhibitory effect was independent of the presence of growth regulators. The level of secreted endo-PG of T. harzianum was not modified by the presence of A. alternata, but the presence of this phytopathogen in cultures of T. harzianum, increased both the growth of the biocontroller and its secretion of endo-CH

Reliability of the entomovector technology using Prestop-Mix and Bombus terrestris L. as a fungal disease biocontrol method in open field

Botrytis cinerea Pers.: Fr. is a major plant pathogen, and a new approach is needed for its control in strawberry to minimise the increasing use of synthetic fungicides. The biofungicide Prestop-Mix, which contains Gliocladium catenulatum, is effective against Botrytis infections; however, the need for frequent applications increases the costs for farmers. Here, we demonstrate that bumble bees, Bombus terrestris L., effectively disseminate the preparation onto flowers in open field conditions. Over the course of three years, we found a highly significant decrease in the rate of Botrytis infection. Pathogen control was achieved with relatively low numbers of G. catenulatum spores per flower, even using flowers that are not highly attractive to bumble bees. An even distribution of spores was detected up to 100 m from the hives, either due to primary inoculation by bumble bees or secondary distribution by other flower visitors such as honey bees and solitary bees. We showed that the application of a biocontrol agent by bumble bees is reliable for the use of environmentally friendly pest control strategies in northern climatic conditions. This low cost technology is especially relevant for organic farming. This study provides valuable information for introducing this method into practice in open strawberry fields

Biocontrol of leucoagaricus gongylophorus of leaf-cutting ants with the mycoparasitic agent trichoderma koningiopsis

Leaf-cutting ants are one of the main agricultural and agroforestry pests in the Neotropic region. The essential food source of these ants is Leucoagaricus gongylophorus. Therefore one of the main biocontrol agents under study are Trichoderma species, because of their biocontrol activity against a diverse range of fungi. Here, Trichoderma koningiopsis, isolated from a leaf-cutting ants nest was tested against three Leucoagaricus gongylophorus strains from leaf-cutting ants by dual culture technique under laboratory conditions. The molecular analysis of ITS sequence data showed three well-separated main clades in which the isolated Trichoderma strain was assembled as a sole subclade among T. koningiopsis strains. The tests also showed that T. koningiopsis strain inhibited the growth of all L. gongylophorus strains tested. The values of radial inhibition of L. gongylophorus ranged from 58% to 69% with an average mean value of 65%. This is the first report on a strain of T. koningiopsis isolated from a naturally parasitized nest of leaf-cutting ants with biocontrol ability over L. gongylophorus tested in dual culturing method.Fil: Castrillo, María Lorena. Universidad Nacional de Misiones. Facultad de Cs.exactas Quimicas y Naturales. Departamento de Bioquimica Clinica. Laboratorio de Biotecnologia Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bich, Gustavo Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Cs.exactas Quimicas y Naturales. Departamento de Bioquimica Clinica. Laboratorio de Biotecnologia Molecular; ArgentinaFil: Zapata, Pedro Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Cs.exactas Quimicas y Naturales. Departamento de Bioquimica Clinica. Laboratorio de Biotecnologia Molecular; ArgentinaFil: Villalba, Laura. Universidad Nacional de Misiones. Facultad de Cs.exactas Quimicas y Naturales. Departamento de Bioquimica Clinica. Laboratorio de Biotecnologia Molecular; Argentin

Improving control of storage diseases on apple by combining biological and physical post-harvest methods

Post-harvest non-chemical treatments consists of a large range of different approaches, including strengthening of the commodity’s natural defence mechanisms, thermotherapy, application of antagonistic microorganisms and natural antimicrobial substances. NEX0101 is a promising antagonistic biocontrol agent containing the yeast Candida oleophila as the active ingredient. NEX0101 was developed by Bionext, a spin-off from the laboratory of Dr. H. Jijakli, and is currently evaluated for commercial use. The product contains a yeast strain isolated from apple fruit and was originally developed for the control of post-harvest diseases on apple. The antifungal effectiveness of this antagonist can be increased by addition of calcium salts. As the mode of action of this yeast is based on the colonisation of wounds, the mean targets of NEX0101 are blue mould, caused by Penicillium expansum, and grey mould, caused by Botrytis cinerea. Facing possible latent infections, thermotherapy by using hot water treatments could provide an advanced control towards lenticelrot (Gloeosporium spp.). A combination of both physical and biological treatment techniques could broaden the spectrum to all key pathogens on apple and pear. The use of NEX0101 for the control of P. expansum was examined in combination with calcium gluconate. According to the results the combination NEX0101 with calcium gluconate provides an advanced mould control towards P. expansum The best results were achieved using NEX0101 in combination with post-harvest dipping by thermotherapy. The hot water treatment alone was clearly inefficient towards wound parasite P. expansum, on the contrary thermotherapy stimulates the decay caused by this postharvest pathogen. For the future a combination of biological and physical treatments could offer a worthy non-chemical alternative for organic and integrated fruit growers towards fruit rot decay, although more research is necessary to implement these methods in practice

Two Entomophagous Isolated From Sumatera Utara; Potential as Biocontrol Agent Againts Nematode

Two species of nematophagous fungi has been isolated from Sumatera Utara soil, with an aim of harnessing their potential in the biological control of plant parasitic nematodes or animal parasitic nematodes in Indonesia, especially in Sumatera Utara. Soil samples were collected from tobacco plantations, vegetable fields and ornamental plantings in the Berastagi area, and also from livestock in local farms and a dairy farm in Berastagi Area, Karo Regency. Soil also collected from un-cultivated area in Sibolangit National Park, Karo Regency. The pour method described by Larsen et al., (1988) and the sprinkle method described by Jafee et al., (1996) were used to isolate the nematophagous fungi from soil. In this study the Chloramphenicol Water Agar Media has been used as culture media and Ceanorhabditis elegans has been used as bait. Two nematophagous fungi known as insect pathogens (entomophagous) have been isolated and determined as Lecanicillium lecanii and Paecilomyces fumosoroseus