At the excellent BSPP conference on 'Plant-Pathogen Interactions' at Wye College in December 2000, some formerly familiar members of the phytopathological world were prominent by their near-absence. These were the phytoalexins; I recall them being mentioned only twice by speakers - by John Mansfield in his Presidential Address and by Michelle Heath in the Garrett Memorial Lecture. A pathologist of a slightly older generation assured me (in the bar!) that, 20 years ago, a large part of a conference on a similar theme would have been devoted to phytoalexins. They haven't quite disappeared from British universities and institutes altogether, but there are now few labs doing active research on phytoalexins.
Why this change in emphasis over the years? Is it because phytoalexins are no longer relevant? Surely not: the induction of defence genes by pathogen infection has been a major topic of research over the last decade; why should the induction of small anti-pathogen molecules not be interesting and potentially important? Moreover, research on pre-formed anti-fungal molecules, phytoanticipins, has flourished in the Sainsbury Laboratory.
Perhaps the eclipse of the phytoalexins has been caused, at least in part, by the vagaries of fashion in research in Britain. Phytoalexins are amazingly diverse in their chemical structure, their biosynthesis and their effects on pathogens. They have complex roles in plant defence, acting as part of a network of host responses rather than the sole determinants of resistance or susceptibility. But in the last few years, there has been a drive towards research on model systems in plant biology, to investigate a small number of features common to a broad spectrum of plants, emphasising just a few key species. This has benefitted research on aspects of pathology that are indeed widely distributed among plants, notably the gene-for-gene relationship and the hypersensitive response, but has dealt a poor hand to research on systems which are inherently diverse.
However, some of the key questions about phytoalexins concern their diversity. To take just a few: how did the biochemical pathways that produce such diverse molecules evolve? What determines the range of pathogens against which they are effective? And can our greatly improved knowledge of other aspects of plant defence help us to understand how phytoalexins are integrated into the network of host responses to disease? These questions are inherently complex and the first two, at least, can only be studied by comparing many plants and many pathogens. Maybe phytoalexins are due for a revival, not least because modern, high-throughput techniques of analysing transcripts, proteins and metabolites ('transcriptomics', 'proteomics', 'metabolomics' - horrid words!) may allow some of these questions to be answered in an unprecedented level of detail.
The post-graduate studentship scheme operated by the Ministry of Agriculture, Fisheries & Food (MAFF) is apparently being resurrected. By promoting a holistic approach to solving problems in the rural environment, this Scheme served well for many years. It was simple in concept and hence cost efficient in operation producing high calibre students of which a high proportion established their careers in agricultural research and related disciplines. It seems that MAFF has been persuaded to reconsider what many felt was an ill - judged decision to abandon the Scheme; perhaps the outcry from organisations such as BSPP helped encourage this rethinking. Possibly the Scottish Executive Rural Affairs Department might like to revisit its equally misguided decision to abandon their Studentship Scheme?
Professor G R Dixon