Browsing by Author "Tut, Gurkan"
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Item Open Access Critical evaluation of two commercial biocontrol agents for their efficacy against B. cinerea under in vitro and in vivo conditions in relation to different abiotic factors(MDPI, 2021-09-17) Tut, Gurkan; Magan, Naresh; Brain, Philp; Xu, XiangmingThe study evaluated the dose–response relationship of two commercial microbial biocontrol agents, Bacillus subtilis and Gliocladium catenulatum, against Botrytis cinerea both in vitro and in vivo. Inoculum doses, formulation, temperature and foliar leaf part all affected the control achieved by the two BCAs. In vitro competition assays on modified PDA plates tested a range of BCA doses (log10 3–10 CFUs or spores/droplet) at 4, 10 and 20 °C on the development of B. cinerea colonies. The dose–response relationship was influenced by both the BCA formulation and temperature. In vivo studies on lettuce plants in semi-commercial greenhouses examined the BCA dose (log10 5–9 CFUs or spores/mL) for controlling B. cinerea with a high inoculum (log10 6 spores/mL). Leaf disc assays showed that the dose–response relationship was influenced by the leaf parts sampled. These results suggest that the dose–response relationship between a BCA and specific pathogen will be significantly influenced by environmental conditions, formulation and plant phyllosplane tissue.Item Open Access Influence of abiotic factors on kinetics of viable populations of biocontrol agents in the phyllosphere of lettuce and strawberry leaves(Wiley, 2023-02-28) Tut, Gurkan; Magan, Naresh; Xu, XiangmingThere is little information on the effect of temperature, relative humidity (RH) and vapour pressure deficit (VPD) on the viable populations of two commercial biocontrol strains, Bacillus subtilis QST 713 (recently classified as B. velezensis) and Gliocladium catenulatum J1446 (syn. Clonostachys rosea). The PMAxx-qPCR molecular assay was used to quantify the viable biocontrol agent (BCA) populations on fully extended lettuce and strawberry leaves under a range of temperature and RH combinations. Overall, there was a small decline in the population size of viable cells for the two biocontrol organisms on strawberry and lettuce leaves within 10 days of application. However, for most experimental runs, which contained general UK agronomy climates, such a decline was not statistically significant. Moreover, for a few runs, the viable populations increased significantly in optimal BCA growth temperatures with high RH. Only temperature (ambient) and dew point significantly affected the rate of temporal changes in the viable biocontrol population size. Thus, an increasing temperature led to decreased daily mortality. It should be noted that much of the variability in the estimated daily mortality rates remains unaccounted for, thus unless under extreme conditions, the biocontrol efficacy in practice is less likely to be affected by the survival of biocontrol microbes but more likely by other factors that influence the density of biocontrol cells in the phyllosphere, especially dilution due to rapid host leaf expansion, spray coverage and rain wash-off.Item Open Access Molecular assay development to monitor the kinetics of viable populations of two biocontrol agents, Bacillus subtilis QST 713 and Gliocladium catenulatum J1446, in the phyllosphere of lettuce leaves(MDPI, 2021-03-15) Tut, Gurkan; Magan, Naresh; Brain, Philip; Xu, XiangmingOptimising the use of biocontrol agents (BCAs) requires the temporal tracking of viable populations in the crop phyllosphere to ensure that effective control can be achieved. No sensitive systems for quantifying viable populations of commercially available BCAs, such as Bacillus subtilis and Gliocladium catenulatum, in the phyllosphere of crop plants are available. The objective of this study was to develop a method to quantify viable populations of these two BCAs in the crop phyllosphere. A molecular tool based on propidium monoazide (PMA) (PMAxx™-qPCR) capable of quantifying viable populations of these two BCAs was developed. Samples were treated with PMAxx™ (12.5–100 μM), followed by 15 min incubation, exposure to a 800 W halogen light for 30 min, DNA extraction, and quantification using qPCR. This provided a platform for using the PMAxx™-qPCR technique for both BCAs to differentiate viable from dead cells. The maximum number of dead cells blocked, based on the DNA, was 3.44 log10 for B. subtilis and 5.75 log10 for G. catenulatum. Validation studies showed that this allowed accurate quantification of viable cells. This method provided effective quantification of the temporal changes in viable populations of the BCAs in commercial formulations on lettuce leaves in polytunnel and glasshouse production systems.Item Open Access Optimising the use of biocontrol agents to improve the control of botrytis cinerea in key vegetable and fruit crops.(Cranfield University, 2019-07) Tut, Gurkan; Magan, Naresh; Xu, Xiangming; Medina-Vayá, ÁngelFor sustainable agriculture, efficient usage of biocontrol agents (BCAs) is crucial. As BCAs are living organisms effective biocontrol ability is governed by complex ecological processes. Because of this, biocontrol of plant diseases can become constrained. Research on the ecology, mechanisms of action and population ecology in the phyllopshere environment is critical for modelling the efficacy of BCAs for control of foliar plant pathogens, especially Botrytis cinerea. The aim of the research was to obtain ecological knowledge on Bacillus subtilis QST 713 and Gliocladium catenulatum J1446, and if feasible use this ecological information to apply these two BCAs against B. cinerea. Thus the objective initially was to (i) develop a molecular based assay to quantify viable population changes of the two BCAs, and use this novel assay for investigating: (ii) the dose response relationship of B. cinerea to the bacterial and fungal BCA, (iii) impact of relative humidity (RH) and temperature used in UK agronomic production systems on BCA populations, (iv) produce a simple model to predict BCA fate, (v) identify the colonisation and dispersion kinetics of the two BCAs on expanding foliage, and finally from the collected ecological knowledge (vi) suggest optimisations strategies for the two BCAs. This study successfully developed a PMAxxᵀᴹ-qPCR method for quantifying the kinetics of viable population changes for both the BCAs. The dose response relationship of B. cinerea to the BCAs’ was deciphered and G. catenulatum median effective dose was 1 × 10⁸ spores/ml, while for B. subtilis this was 3 × 10⁸ CFUs/ml⁻¹ . However, this changed with temperature, formulation, and leaf tissue type. Both temperature and humidity impacted on viable population dynamics of the two BCAs, and showed that viable populations were sustained, increased or reduced depending on abiotic factors (temperature, R.H.), with efficacy best at conditions close to the BCAs optimum growth conditions. From the collected data, models were produced and tested for their ability to predict the fate of each BCA in commercial growing sites. The dispersion and colonisation kinetics of the two BCAs were analysed on growing lettuce and strawberry leaves. The two BCAs behaved in different ways, while their ability to disperse and colonise virgin leaf tissue was effective, the rate depended on the season (temperature and RH) and host. This study has developed significant new ecological knowledge on these two BCAs and their behaviour when applied to strawberry and lettuce leaf surfaces, and their establishment to control B. cinerea in these agronomic crop systems.