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This major international conference, the sixth in an ongoing series, reviewed the latest research on the origins, nature, development and prevention of resistance to insecticides, fungicides and herbicides. It provided a forum for researchers, consultants, regulators and industrialists to present and discuss approaches to overcoming this increasingly important constraint to effective crop protection. Themes included the current status of resistance to pesticides, resistance mechanisms, population biology and modelling, applications of genomics, risk assessment and regulation, and transgenic crops. Nearly 200 people attended this conference from 25 countries including Australia, Brazil, China, Japan, UK and other European countries.
A surprising talk was the possible origin of resistance to medical triazole fungicides in the human pathogen Aspergillus fumigatus . I t was hypothesized that resistance may have emerged through exposure to agricultural DMI fungicides as resistance was observed in patients without previous azole exposure (PE Verweij, the Netherlands). In azole-resistant isolates of Mycosphaerella graminicola, the target site changes were characterized functionally. The results provided direct evidence of the effect of CYP51 encoding changes on azole sensitivity. Alterations in regulatory regions of this gene also confer reduced sensitivity (HJ Cools, UK). We heard that fungicide applications are 60 times annually in banana plantations. It was thus understandable why azole resistant strains appeared in M.
fijiensis, the pathogen of the most important black Sigatoka disease (GHJ Kema, the Netherlands). Current situation of fungicide resistance in Japan was briefly introduced. Due to the rapid occurrence of QoI and SDHI fungicide resistance, strict guidelines indicating how to save the applications of these fungicides will be announced to farmers soon. A novel SDHI fungicide fluopyram exhibited high control efficacy against highly boscalid-resistant isolates of two cucumber pathogens, Corynespora cassiicola and Podosphaera xanthii (H Ishii, Japan). Results of monitoring for SDHI fungicide sensitivity were reported. Furthermore, molecular mechanism of SDHI resistance was elucidated in Alternaria alternata and Botrytis cinerea and resistance has been found to be mainly governed by mutations leading to H272Y/R in SDH B subunit in various pathogens. These mutations affect only specific compounds occasional ly although the SDHI fungicides belong to the same cross-resistance group (H Sierotzki , Switzerland). I t was emphasized in apple scab disease control that the approaches used to implement Integrated Pest Management have contributed to the development of fungicide resistance (J Beckerman, USA). It might be true if apple growers rely more on recently developed fungicides such as QoI or SDHI fungicides. However, integrating host resistance and fungicide treatment reduces selection for a fungicide resistant strain (N Paveley, UK). It is well known that the biggest fungicide market is against Asian soybean rust (caused by Phakopsora pachyrhizi) at present in Brazil. Sensitivity of the pathogen to tebuconazole has decreased and the use of solo product stopped. In contrast, prothioconazole can still be used as sensitivity to this DMI fungicide maintained. In the case of QoIs, no sensitivity change was detectable (A Mehl, Germany).
Fungicide performance and antiresistance strategies to P. pachyrhizi were further introduced. Soybean receives 58. 7% of overall fungicides applied in Brazil. In 2009, only premixes of triazole-QoI have been recommended. Efficacy of triazoles alone in 2010/11 remained lower than 30% (C Godoy, Brazil). Resistance management strategies to delay the selection for fungicide insensitivity were discussed. When two high-risk fungicides are employed, the ranking of the strategies is mixture use > alteration > concurrent use, with respect to the length of effective lifetime (P Hobbelen, UK). Isolates of Cercospora beticola, the cause of Cercospora leaf spot of sugar beet, were served for the comparative studies on resistance to DMI and QoI fungicides between the USA and Europe. Isolates from Europe generally had higher levels of resistance to these fungicides as compared with USA isolates. When considering differential application strategies, alterations of fungicides at full rates may better manage resistance than combinations of fungicides at reduced rates, especially for the DMI fungicides (G Secor, USA).
In poster presentations, the sequence analysis was conducted for s-tubulin and CYP51 genes which relate benzimidazole and DMI fungicide resistance, respectively, in oilseed rape pathogen Pyrenopeziza brassicae (H Car ter , UK) . The function of CYP51genes was also studied using heterologous expression system of Saccharomyces cerevisiae after addition of doxycyline to suppress the native expression (J Fan, UK). Protein modeling and inhibitor docking studies were performed to establish if SDHI fungicides have different binding properties against the target enzyme SDH in M. graminicola (Fraaije, UK and the Netherlands).
I have attended this conference three times and it might be the most successful one this time. I really enjoyed the technical sessions. But one thing which I felt sorry about was the decrease of real experts on fungicide resistance, as some representative researchers in this field have left after retirement. It is difficult but essential to transmit important knowledge and experiences to the next generation otherwise the same experimental trials and technical discussion could be repeated.
Finally, I’d like to thank the BSPP for supporting my attendance to this conference. We are also grateful to your generous help from all around the world after the disaster occurred on 11th March 2011 in Japan.
Hideo Ishii
National Institute for Agro-Environmental Sciences, Japan
