Late Blight Team
Phytophthora infestans research at SCRI
SCRI has established itself as a leader in the study of late blight by integrating research, facilities, resources and skills into a coherent team. Our internationally recognised expertise focuses on a broad spectrum of research. This underpins both the long-term strategic objective of sustainable late blight control via host resistance and detailed applied research providing the industry with answers to current questions (for example, population change and sources of primary inoculum).
Our research on Phytophthora infestans can be grouped under six linked themes:
- P. infestans genomics
- bioinformatics
- pathogen biology
- potato-P. infestans interactions
- population biology and epidemiology
- host resistance: genetics, genomics and pre-breeding.
P. infestans genomics
Staff: Paul Birch, Stephen Whisson, Leighton Pritchard
SCRI has been active in genomics studies of P. infestans since 1998. We have prepared the highest quality bacterial artificial chromosome library and applied this resource in studies to understand the genome organisation of P. infestans. Involvement in a consortium of laboratories resulted in sequencing of over 90,000 expressed sequence tags (EST) and ensuing microarray analysis of 15,000 unigenes from P. infestans. The SCRI team has also led the application of real-time RT-PCR to quantify relative gene expression in P. infestans during infection of host plants. In recent years, the SCRI team has been actively involved in a collaborative effort with the Broad Institute to sequence the genome of P. infestans, a project that is now nearing completion.
Bioinformatics of potato-P. infestans interactions
Staff: Leighton Pritchard
Computational analyses of the large quantities of data generated through EST and genome sequencing and microarray analyses are being carried out at SCRI. Recent bioinformatics studies have involved data mining for non-protein-coding RNAs, prediction of specific peptide motifs, rational protein engineering and comparative genomics. There is more information on the Pathogen Bioinformatics page.
Pathogen biology
Staff: Stephen Whisson, Anna Avrova, Petra Boevink, Paul Birch
The lifecycle of P. infestans is complex and involves several morphogenic transitions. We are specifically interested in identifying genes involved in transitions from lifecycle stages outside the plant (for example, germinating cysts, appressoria), to infection specific stages (for example, biotrophic structures called haustoria). We use data derived from transcriptional profiling and bioinformatics analyses to prioritise candidate genes for functional analysis by gene silencing and protein localisation through tagging with fluorescent proteins.
Potato-P. infestans interactions
Staff: Paul Birch, Eleanor Gilroy, Ingo Hein, Anna Avrova, Petra Boevink, Miles Armstrong, Stephen Whisson
To overcome host innate immunity, P. infestans secretes numerous proteins to establish disease on potato (effectors). Some of these effectors are secreted into intercellular spaces while others are translocated inside host cells. P. infestans research at SCRI aims to determine which effector proteins are essential for pathogenicity, identify peptide motifs responsible for translocation inside host cells, understand the mechanisms of effector translocation, determine effector localisation and function inside host cells and identify triggers (avirulence proteins) of host resistance through genetics, genomics and high-throughput plant assays. Recent discoveries include the determination of over 20 secreted effectors required for full pathogenicity, demonstration that a dual peptide motif RxLR-EER is required for effector protein translocation inside host cells, localisation of RxLR-EER effector secretion to haustoria and identification of a candidate avirulence protein triggering resistance derived from Solanum bulbocastanum.
Population biology and epidemiology
Staff: Alison Lees, David Cooke
Our two main objectives are to examine the factors that drive change in P. infestans populations and the impact of change on the epidemiology and sustainability of blight management. SCRI has one of the largest and most diverse collections of P. infestans isolates in Europe and new isolates from late blight surveys are continually being added to this collection. We have optimised a set of multiplex microsatellite markers that have proved to be important tools for monitoring population change. Collaboration with the Plant-Pathogen Interactions team means we can examine the frequency of different alleles of effector genes in populations. Our co-ordination of the European EUCABLIGHT project has given such studies an international dimension. Primary inoculum is the source of all new blight outbreaks and we are using the latest research tools to assess the significance of different inoculum sources such as oospores and tubers. Read more on the Blight Epidemiology and Population Biology page.
Host resistance: genetics, genomics and pre-breeding
Staff: Glenn Bryan, Ingo Hein
In the Genetics programme at SCRI, we work on multiple mapping populations segregating for resistance to major potato diseases including late blight. We utilise genetic mapping and genomic resources (for example, bacterial artificial chromosome (BAC) libraries) to positionally clone genes underlying the resistance phenotype. Cloning gene(s) responsible for durable resistance, such as field resistance, is one of our main priorities. In addition to traditional map-based gene cloning approaches we utilise allele/paralogue mining strategies, with the aim of identifying orthologues from known R genes that co-localise with the resistant QTL. The function of candidate genes is initially validated by transient, Agrobacterium tumefaciens based, overexpression in Nicotiana benthamiana and subsequent challenge with P. infestans and/or single pathogen effectors.
Furthermore, we utilise the Commonwealth Potato Collection (CPC) to identify new sources of resistance. Two different approaches are used: screening of CPC accessions with P. infestans isolates having a broad range of virulence, to identify accessions with durable resistance or with highly conserved or invariant P. infestans effectors to identify accessions that specifically recognise such effectors.
Techniques and resources
SCRI has the collective expertise, facilities and techniques to enable high quality research on most aspects of late blight to be conducted. Examples of these are described below.
- Characterised genetic resources such as the P. infestans culture collection and the Commonwealth Potato Collection are housed at SCRI and provide a valuable resource for identifying triggers of disease resistance and novel sources of resistance for breeding and R gene discovery.
- Ability to manipulate P. infestans and potato to determine gene function, using techniques such as gene silencing, transformation and protein localisation with fluorescent proteins.
- In planta assays for the effects of P. infestans genes such as Agrobacterium infiltration, expression from potato virus X and yeast 2 hybrid library screening.
- Light, confocal and electron microscopy for studies into the cell biology of P. infestans-potato interactions.
- Diagnostic tools and microsatellite markers allow us to track P. infestans inoculum and monitor population changes: the population data is combined with EU partner data stored in a large database EUCABLIGHT.
- Fungicide efficacy and mode-of-action studies (for example, baseline sensitivity monitoring).
- PSD Official Recognition of Efficacy Testing Facilities (Certificate Number ORETO 203).
