Pershore College CP 137 - Cucumber: Development and testing of a lateral flow device for both gummy stem blight and powdery mildew in bio-aerosols during cucurbit production
(September 2017 – June 2018) – project extension to August 2020
Cucumber Powdery Mildew: Numerous vegetable crops are susceptible to powdery mildew, but cucurbits are one group that are severely affected. It is probably the most common, conspicuous, widespread and easily recognizable disease of cucurbits. Like other powdery mildew diseases, its symptoms are characterized by the talcum-like, powdery fungal growth that develops on both leaf surfaces, petioles and stems but rarely on fruits. Podosphaera fusca (also known as Podosphaera xanthii or Sphaerotheca fuliginea) and Golovinomyces (Erysiphe) cichoracearum are identified as the main agents of cucurbit powdery mildew. The disease provides one of the most important limiting factors for cucurbit production worldwide. In the absence of chemical, biological control or the use of tolerant/resistant varieties the disease can cause yield reduction (as much as 40%) and impair fruit quality.
Gummy stem blight (Black stem rot) of cucumber is caused by Mycosphaerella melonis syn. Phoma cucurbitacearum (syn. Didymella bryoniae) and is of worldwide importance, causing significant economic damage of glasshouse cucumber & other cucurbits, including outdoor crops. It causes extensive stem & leaf infections which when severe can debilitate or even kill plants. Like the powdery mildew pathogen, airborne spores are produced and involved in spread of the disease. The infection of flowers & developing fruit leads to fruit rot. Often disease symptoms are not visible until the fruit is marketed. This leads to rejection and reduced retailer & consumer confidence in the product. Fungicides are used routinely in an attempt to suppress the disease and prevent plant and fruit losses. The fungicides that are available in the UK for use in cucumber production (primarily for powdery mildew control) provide only a partial suppression or reduction of the disease.
Under an AHDB Horticulture funded project (PE001) a range of alternative fungicides have been assessed for their efficacy in control of the disease. Monoclonal antisera and a laboratory based ELISA test has been developed to monitor glasshouse aerosols for M. melonis spore disease transmission events. The timed application of control measures was made during periods of peak spore production (>2000 spores m3) to provide improved fungicide efficacy. However as a result of postal delays the time period between spore monitoring, data capture, interpretation, communication and fungicide spray application was too long . To provide this information in a more timely way the laboratory based immunoassay test (ELISA) could be transferred to a lateral flow ‘on-site’ format for direct grower or consultant use.
Lateral flow immunoassays are used for qualitative and semi-quantitative detection of target analytes. Lateral flows consist of a carrier material containing dry reagents that are activated by applying a liquid sample. Movement of this liquid allows passage across various zones where molecules have been attached that exert specific interactions with target analytes. Results are generated with 5 – 10 minutes with the formation of a control and test line as appropriate to the sample and the test type. They are designed for single use, can provide a multiplex test platform and, are available commercially for a wide range of applications. The most well known test of this type is the Unilever Clear Blue Pregnancy Test Kit. More recently they have become increasingly important in the diagnosis of plant pathogens. A range of lateral flows have been developed through AHDB Horticulture funding to measure bio-aerosols for a range of plant pathogens. These include Powdery mildew (Erysiphe cruciferarum) and ringspot (Mycosphaerella brassicicola) in field brassica cropping systems.
Aim
The aim of the project is to produce on-site tests which can be used singly or in a multiplex format to monitor glasshouse bio-aerosols for gummy stem blight and powdery mildew in glasshouse cucumbers. Intervention/control measures would be applied in response to disease risk from the on-site tests. The tests would be validated for use within commercial cropping systems. Commercial ‘do it yourself’ test kits would be made available at the end of the project to the UK horticulture industry. To encourage industry uptake of the technology ‘hands on’ workshops would be run in both East Yorkshire and the Lee Valley in the final year of the project
Objectives
Develop a monoclonal antibody probe to selectively measure bio-aerosols for cucumber powdery mildew.
Provide the UK cucumber industry with on-site tests for the early detection of pathogen threshold levels of both Mycosphaerella and powdery mildew in glasshouse bio-aerosols.
Provide sufficient on-site tests (which have confirmed shelf-life for use) for commercial supply to the UK cucumber industry for start of 2018.
For further information please contact Professor Roy Kennedy: rkennedy@warwickshire.ac.uk
