Biocontrol Efficacy (biocontrol + efficacy)

Distribution by Scientific Domains

Selected Abstracts

Use of a breeding approach for improving biocontrol efficacy of Phlebiopsis gigantea strains against Heterobasidion infection of Norway spruce stumps

Hui Sun
Abstract Sixty-four wild heterokaryotic isolates of Phlebiopsis gigantea were analysed for asexual spore production, growth rate and competitive ability against Heterobasidion in vitro, as well as growth rate in Norway spruce wood. These P. gigantea traits were considered important for controlling infection of Norway spruce stumps by spores of Heterobasidion spp. Ten most promising P. gigantea isolates were crossed with each other and 172 F1 progeny heterokaryons were analysed for the above-mentioned traits. Thirteen most promising progeny heterokaryons were selected and their biocontrol ability against infection by Heterobasidion was compared with the parental isolates in stem pieces of Norway spruce. The results indicated that the progeny strains had generally better traits and control efficacy than the parental strains. The genetic effects accounted for a part of the variations between progeny and parental strains. This further suggests that there is a potential to improve the biocontrol properties of P. gigantea through breeding. [source]

Response surface methodology study of the combined effects of temperature, pH, and aw on the growth rate of Trichoderma asperellum

B.A.D. Begoude
Abstract Aims:, To evaluate the influence of environmental parameters (water activity aw, temperature, and pH) on the radial growth rate of Trichoderma asperellum (strains PR10, PR11, PR12, and 659-7), an antagonist of Phytophthora megakarya, the causal agent of cocoa black pod disease. Methods and Results:, The radial growth of four strains of T. asperellum was monitored for 30 days on modified PDA medium. Six levels of aw (0·995, 0·980, 0·960, 0·930, 0·910, and 0·880) were combined with three values of pH (4·5, 6·5, and 8·5) and three incubation temperatures (20, 25, and 30°C). Whatever the strain, mycelial growth rate was optimal at aw between 0·995 and 0·980, independently of the temperature and pH. Each strain appeared to be very sensitive to aw reduction. In addition, all four strains were able to grow at all temperatures and pH values (4·5,8·5) tested, highest growth rate being observed at 30°C and at pH 4·5,6·5. The use of response surface methodology to model the combined effects of aw, temperature, and pH on the radial growth rate of the T. asperellum strains confirmed the observed results. In our model, growth of the T. asperellum strains showed a greater dependence on aw than on temperature or pH under in vitro conditions. Conclusion:,aw is a crucial environmental factor. Low aw can prevent growth of T. asperellum strains under some conditions. The observed and predicted radial growth rate of strain PR11 showed its greater capacity to support low aw (0·93) as compared with other tested strains at 20°C. This is in agreement with its better protective level when applied in medium-scale trials on cocoa plantations. Significance and Impact of the Study:, This study should contribute towards improving the biocontrol efficacy of T. asperellum strains used against P. megakarya. Integrated into a broader study of the impact of environmental factors on the biocontrol agent,pathogen system, this work should help to build a more rational control strategy, possibly involving the use of a compatible adjuvant protecting T. asperellum against desiccation. [source]

Improving low water activity and desiccation tolerance of the biocontrol agent Pantoea agglomerans CPA-2 by osmotic treatments

N. Teixidó
Abstract Aims:, To study the improvement of tolerance to low water activity (aw) and desiccation during spray drying in Pantoea agglomerans cells subjected to mild osmotic stress during growth. Methods and Results:, The micro-organism was cultured in an unmodified liquid (control) or in aw -modified media, and viability of these cells was evaluated on unstressed (0·995) and 0·96 aw stressed solid media, in order to check total viability and aw stress tolerance respectively. Significant improvements in viability on unmodified medium were observed with cells grown for 24 h in NaCl 0·98 aw, glycerol 0·98 aw and 0·97 aw and for 48 h in NaCl 0·98 aw and 0·97 aw modified media. Both yield improvements and water stress tolerance were achieved with low aw media. Cells grown for 24 h in NaCl 0·98 aw or for 48 h in NaCl 0·98 aw, 0·97 aw and 0·96 aw, glucose 0·97 aw and glycerol 0·97 aw showed improved aw stress tolerance in comparison with control cells. The best results were obtained with NaCl treatments (0·98 aw and 0·97 aw) which also exhibited better survival rates than control cells during spray-drying process and maintained their efficacy against postharvest fungal pathogens in apples and oranges. Conclusions:, NaCl treatments are very appropriate for improving P. agglomerans low aw tolerance obtaining high production levels and maintaining biocontrol efficacy. Significance and Impact of the Study:, Improving stress tolerance of biocontrol agents could be an efficient way to obtain consistency and maintain efficacy of biological control under practical conditions. [source]

Inhibitory activity of tea polyphenol and Hanseniaspora uvarum against Botrytis cinerea infections

H.M. Liu
Abstract Aims:, To investigate the effect of tea polyphenol (TP) and Hanseniaspora uvarum alone or in combination against Botrytis cinerea in grapes and to evaluate the possible mechanisms involved. Methods and Results:, TP alone was effective in controlling grey mould in grape at all concentrations. TP at 0·5 and 1·0% in combination with H. uvarum (1 × 106 CFU ml,1) showed a lower infection rate of grey mould. TP at 0·01% or above significantly inhibited the spore germination of B. cinerea. TP at 0·1% showed inhibition ability on mycelium growth of B. cinerea. The addition of TP did not affect the growth of H. uvarum in vitro and significantly increased the population of H. uvarum in vivo. Conclusions:, TP exhibited an inhibitory effect against B. cinerea and improved the biocontrol efficacy of H. uvarum. The inhibitory effects of spore germination and mycelial growth of B. cinerea and the increased populations of H. uvarum in vivo may be some of the important mechanisms of TP. Significance and Impact of the Study:, The results suggested that TP alone or in combination with biocontrol agents has great potential in the commercial management of postharvest diseases of fruits. [source]

Relative importance of amino acids, glycine,betaine and ectoine synthesis in the biocontrol agent Pantoea agglomerans CPA-2 in response to osmotic, acidic and heat stress

T.P. Cañamás
Abstract Aims:, The objective of this work was to determine the role of different compatible solutes in adaptation of Pantoea agglomerans CPA-2 at different stages of growth to solute (0·98, 0·97, 0·96 aw), heat (35 and 40°C) and acidic (pH 4·0, 5·0, 6·0) stress. Methods and Results:, Solute stress was imposed by using NaCl, glucose or glycerol, and pH was imposed with malic and citric acids. The accumulation of glycine,betaine, ectoine and amino acids in bacterial cells was quantified using high performance liquid chromathography (HPLC). There was a significant (P < 0·05) accumulation of glycine,betaine (NaCl modified, 100,150 ,mol g,1 dry weight of cells) and ectoine (glucose modified media, >340 ,mol g,1 dry weight of cells) in the cells over a 48 h incubation period when compared with controls (<10 ,mol g,1 dry weight of cells). Chromatographic profile of amino acids was different with respect to control when NaCl or glucose was used as osmolyte. Conclusions:,Pantoea agglomerans CPA-2 cells synthesised significant amounts of glycine,betaine and ectoine in response to imposed solute stress. However, these compounds and tested amino acids were not involved in cellular adaptation to either heat or pH stress. Significance and Impact of the Study:, This type of information can be effectively applied to improve ecophysiological quality of cells of bacterial biocontrol agents for better survival and biocontrol efficacy in the phyllosphere of plants. [source]

Enhancement of biocontrol activity of yeasts by adding sodium bicarbonate or ammonium molybdate to control postharvest disease of jujube fruits

Y.K. Wan
Abstract Aims: To assess the potential of sodium bicarbonate and ammonium molybdate as additives in enhancing the biocontrol efficacy of Rhodotorula glutinis and Cryptococcus laurentii against blue mould in jujube fruits. Methods and Results: Two yeasts at a concentration of 107 CFU ml,1, in combination with 238 mmol l,1 sodium bicarbonate or 15 mmol l,1 ammonium molybdate, showed a significant inhibition effect on blue mould of jujube fruits stored at 20°C for 5 days. The colonizing ability of the yeasts in wounded sites was significantly decreased in the presence of ammonium molybdate. Conclusions: Combining R. glutinis or C. laurentii with sodium bicarbonate or ammonium molybdate provided a more effective control of postharvest disease than using the antagonistic yeasts or the chemicals alone. Significance and Impact of the Study: The addition of sodium bicarbonate or ammonium molybdate reduced the number of antagonists required to efficiently control disease of postharvest fruits, which could result in the reduction of costs. [source]

A review of fungal antagonists of powdery mildews and their potential as biocontrol agents,

Levente Kiss
Abstract There are approximately 40 fungal species that have so far been reported as natural antagonists of powdery mildews or have been tested as their potential biocontrol agents. This review summarizes the published data on their identification, taxonomy, ecology, modes of action and biocontrol efficacy. The results obtained with the two products already registered, AQ10 Biofungicide® and Sporodex®, are also discussed. © 2003 Society of Chemical Industry [source]