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The conference was organised by the International Maize and Wheat Improvement Centre (CIMMYT) and focused on two of the most destructive diseases on wheat Septoria tritici blotch caused by Mycosphaerella graminicola and glume blotch caused by Stagnospora nodorum. It is held every 3-4 years with the aim of updating the knowledge on both diseases and other related diseases for a better understanding and minimizing losses occurring.
The participants were focused on a few interesting points such as estimation of losses from the diseases in time of increasing global wheat consumption (consumption has risen by 27% in the last ten years in India), new employment of resistant genes and how to introduce them, change of sowing date and its relation with disease spread, fungicide resistance with greater focus on azole resistance and its association with CYP51 gene alterations. . .
From me the most interesting points were the existence of yield penalty when the focus is on pathogen resistance genes. Septoria data obtained from disease trials in England in 2006 and 2008 with yield data had been obtained from an earlier series of trials in the UK, France, and Germany have supported the hypothesis that there is a yield penalty of having septoria resistance when wheat is grown in modern, intensive farming conditions. Therefore, one recommendation was that breeders must select for more yield and less for resistance to septoria. A moderate resistant of level 5 would be good for resistance rather than to have level 9 (the highest) which has low yield.
The erosion of the efficacy of azole fungicides was another major point raised in the conference. A few talks and posters emphasised the rapid increase in the mutations in the CYP51 gene which found to be related to low azole performance in M. graminicola. Emphasis has been shown the greater effect of combination of mutations in the CYP51 gene rather than single mutations. For instance, the S524T mutation alone has no effect but when combine with D134G will increase the insensitivity to azoles.
With this progressive and continuous increase of resistance to DMIs, the mechanism of multidrug resistance (MDR) is also emerging. Several mutations in the target encoding the CYP51 gene have been recorded to be highly resistant to DMIs, cross-resistance with QoIs and SDHIs (two fungicide classes of respiratory inhibitors), suggesting a combination of alterations in the CYP51 gene and overexpression of drug efflux transporters to be involved in the multidrug resistant phenotypes. With the rapid evolution of resistance recently in many fungicides groups, researchers in ARVALIS, France, plan to reduce fungicides to 50% by 2018. Alternative farming practices was suggested with the existence of the decline in fungicide efficiency and breakdown of resistance genes. Mixtures of wheat cultivars with different resistances to pathogens, as a within-field genetic diversity, were discussed. This can gain performance compared to pure stands. On-farm trials have shown that cultivar mixtures with single fungicide application can slightly reduce septoria leaf blotch epidemics while stabilizing productivity and crop quality. The aim of these trials was to assess the effect of plant architecture on the delivery of pycnidiospores with the aid of rain splashes.
Another interesting point related to control of septoria tritici blotch was change of sowing date and collection of stubble in the right time. Both methods are to avoid the fungal maturity and produce of teleomorph stage of the pathogen which causes genetic recombination and emerge of new virulent strains. These sexual airborne ascospores also found to be more efficient in pathogen dissemination.
University of Nottingham
The 8th International Symposium on Mycosphaerella and Stagonospora Diseases of Cereals comprised of individual sessions addressing the many diverse areas of study of these pathogens, all with the aim of stimulating multidisciplinary approaches to control these globally important diseases. The symposium attracted a global audience with participants from Europe, Africa, Asia, North, Central and South Americas, and Australia which lead to some interesting discussions, both during and after the conference sessions. The conference began with a trip to the Aztec ‘pyramids’ at Teotihuacan. This provided the perfect start to the conference and the chance to meet colleagues both old and new in an informal setting. It also served as a fascinating introduction to the history of Mexico.
Day two was down to business, with the keynote address from Jacques Mathieu, the General Director of Arvalis, France. He summed up the multidisciplinary approach of sustainable management that the French wheat growing industry is taking towards septoria tritici blotch (STB). This was followed by a session on pathogen biology and evolution, starting with a talk by Prof. Gero Steinberg, University of Exeter, who is attempting to transfer his work on how fungi actively invade plant tissues, using the tractable fungus Ustilago maydis, to M. graminicola. Although he is finding that the latter is a much less tractable and much more morphogenically variable pathogen.
The session on pathogen, genetics and genomics highlighted how the sequencing of the genome of M. graminicola has enabled many new discoveries that will hopefully lead to better control of STB in the future.
Of particular interest to me was the session on host-pathogen interactions. I presented a talk during this session entitled; A blotch on the landscape: M. graminicola and its interaction with wheat and mildew. This was my first talk to a large audience and the talk was well received. I had lots of interesting comments about how to develop the study further. During this session there were also talks on Stagonospora nodurum from Dr Tim Friesen and Dr Christine Cowger, who have investigated necrotrophic effectors present in this pathogen. Tim Friesen has shown that SnTox1 induces a defence response when it interacts with the product of the wheat gene Snn1 and that the interaction requires the light. Christine Cowger has shown that the S. nodurum population in South Eastern U. S. has a novel set of necrotrophic effectors that have probably been selected for by the presence of regionally specific host genes. Work on transcriptomics of the wheat interaction with M. graminicola at INRA, France was presented by Dr Marc-Henri Lebrun. Their work mirrored the work I have done during my PhD and it was interesting to see that their results were similar and just as variable as the results I have obtained, indicating once again that this pathogen is complex and variable in its mode of infection.
The session on cultural measures and disease management served to highlight the challenges ahead for controlling STB in light of increasing insensitivities to fungicides and, in Europe at least, a reduction in the numbers of chemicals that will be available to control it. Dr Lise Nistrup Jørgensen, Aarhus University, introduced the concept of the Intergrated Pest Management model that is beginning to be used in Denmark. By far the largest session covered host genetics and resistance breeding which emphasised the wide range of germplasm available to breeders on an international scale and how identifying quantitative trait loci for resistance to STB can assist in breeding programs.
The conference was extremely well organised by CIMMYT, and the scientific committee put together a programme of extremely interesting talks which covered all aspects of research into Mycosphaerella and Stagonospora diseases of cereals. I thank the BSPP for the funding that allowed me to attend this conference.
John Innes Centre