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The 12th International Cereal Rusts and Powdery Mildews Conference Antalya, Turkey 13th – 16th October 2009
Every four years, the International Cereal Rusts and Powdery Mildews Conference brings together the band of researchers across the world who are crazy enough to devote their working lives to the biotrophic fungal diseases.
Usually, the pleasure of meeting likeminded colleagues is enough to compensate for whichever gloomy hall of residence we find ourselves in. Our most recent conference, however, was held in the magnificent surroundings of a purpose-built resort hotel on the Mediterranean coast of Turkey.
Apparently unlimited buffet meals, a trip to two of the many Roman sites around Antalya and an evening dinnercum- disco with a band that kept playing well into the night all helped to stimulate the informal discussions which are so important a feature of a specialist conference. Professor Mahinur Akkaya and her colleagues from the Middle East Technical University in Ankara deserve many thanks for their enthusiastic and imaginative organisation of this conference. The conference covered recent developments in the rust and mildew diseases of small-grain diseases across the whole range from the cutting-edge of molecular biology to disease control in the field. I will focus on a personal selection of a few of the most significant advances. One of the most striking recent issues is the renewed threat posed by rust diseases to wheat production world-wide. Indeed, yellow rust (Puccinia striiformis) has become possibly the most economically damaging disease of any crop. Mogens Hovmøller (Denmark) presented the results of a survey of an international sample of genotypes of P. striiformis, showing that intercontinental spread of two pathogen clones has been associated with severe outbreaks of yellow rust in areas where the disease was formerly unimportant or even unknown. Gene Milus (USA) showed that these genotypes are more aggressive than older strains and are adapted to a higher range of temperatures. Until earlier this year (Jin et al. 2010, Phytopathology 100:432- 435), the sexual stage of the yellow rust fungus was unknown and it was thought that genetic variation only accumulated by mutation. Jerôme Enjalbert (France), however, presented population genetic data showing that, in a “hot spot” for the disease in northwest China, P. striiformis almost certainly undergoes some kind of recombination. Together, these three lines of research indicate that wheat yellow rust is capable of adapting very rapidly to new climatic conditions and to new varieties and is likely to continue to be a major threat to food production for the foreseeable future.
An outbreak of another rust has received greater publicity owing to epidemics in East Africa and South- West Asia. Efforts by CIMMYT (the International Maize and Wheat Improvement Centre), national governments and other organisations to combat the Ug99 group of races of the wheat stem rust fungus (Puccinia graminis) are a model for the effective coordination of international expertise in plant disease control. The conference opened with a series of talks about Ug99, led by Ravi Singh (CIMMYT, Mexico), who described the importance of international collaboration in breeding for durable resistance to rust diseases of wheat. This was exemplified by the inter-continental array of speakers from Europe, Asia, Africa, North America and Australia who described their own contributions to breeding for rust resistance.
As in many other organisms, the extraordinary acceleration of genomics is providing exciting insights into aspects of biotrophic fungal diseases which, owing to nature of the pathogens, have hitherto been intractable. One of the most significant recent breakthroughs has been the cloning of the Lr34 gene which provides field resistance to all three rusts and to powdery mildew (Beat Keller, Switzerland). This will not only open up new opportunities to understand the biology of durable disease resistance but will also provide new tools for controlling these diseases. One opportunity opened up by genomic technology is the capacity to study many genes simultaneously. Roger Wise (USA) described how a combination of quantitative trait locus (QTL) analysis with transcriptomics has identified candidate genes for master regulators of disease resistance.
A hardy perennial among questions in plant pathology is why all plants are resistant to most parasites. In a series of talks, Rients Niks (The Netherlands) and his colleagues Thierry Marcel, Hossein Jafary and Reza Aghnoum described how their work has advanced in understanding non-host resistance of barley to biotrophic pathogens. By developing plant lines which are highly susceptible to fungi which are not normally pathogens of barley, they shown that resistance to non-adapted species of rust and mildew fungi is polygenic, different genes are effective against different non-adapted pathogen species and forms, different barley cultivars have different genes for resistance to the same non-adapted pathogen, and different genes for resistance to non-adapted mildews are specific to particular fungal growth stages. Hopefully, we are moving away from having to think about non-host resistance as an impenetrable black box and are moving towards a mechanistic understanding of this phenomenon.
The next International Cereal Rusts and Powdery Mildew Conference will be held in Beijing in August 2012, the first of this series of conferences to be held outside the European and Mediterranean area. China is an especially appropriate venue for this meeting in view of the importance of rusts and mildew to cereal production there and the large number of Chinese scientists who study them. Details will be announced shortly by the organisers at the CAAS Institute of Plant Protection.
James Brown, John Innes Centre, Norwich
