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Frequency of Avirulence Alleles in Field Populations of Leptosphaeria maculans in Europe |
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| Authors: | Anna Stachowiak Julia Olechnowicz Malgorzata Jedryczka Thierry Rouxel Marie-Hélène Balesdent Ingrid Happstadius Peter Gladders Akinwunmi Latunde-Dada Neal Evans |
| Institution: | 1. Institute of Plant Genetics, Polish Academy of Sciences, Strzeszynska 34, PL-60479, Poznań, Poland 2. Unité PMDV, Institut National de la Recherche Agronomique, Route de Saint Cyr, F-78026, Versailles, France 3. Sval?f Weibull AB, SE-268 81, Sval?v, Sweden 4. ADAS Boxworth, Cambridge, CB3 8NN, UK 5. Rothamsted Research, Harpenden, AL5 2JQ, Hertfordshire, UK |
| Abstract: | This paper describes the first large-scale Europe-wide survey of avirulence alleles and races of Leptosphaeria maculans. Isolates were collected from the spring rape cultivar Drakkar, with no known genes for resistance against L. maculans, at six experimental sites across the main oilseed rape growing regions of Europe, including the UK, Germany, Sweden and Poland. Additionally in Poland isolates were collected from cv. Darmor, which has resistance gene, Rlm9. In total, 603 isolates were collected during autumn in 2002 (287 isolates from Germany and the UK) and 2003 (316 isolates from Poland and Sweden). The identity of alleles at eight avirulence loci was determined for these isolates. No isolates had the virulence allele avrLm6 and three virulence alleles (avrLm2, avrLm3 and avrLm9) were present in all isolates. The isolates were polymorphic for AvrLm1, AvrLm4, AvrLm5 and AvrLm7 alleles, with virulence alleles at AvrLm1 and AvrLm4 loci and avirulence alleles at AvrLm7 and AvrLm5 loci predominant in populations. Virulent avrLm7 isolates were found at only one site in Sweden. Approximately 90% of all isolates belonged to one of two races (combinations of avirulence alleles), Av5-6-7 (77% of isolates) or Av6-7 (12%). Eight races were identified, with four races at frequencies less than 1%. The study suggested that Rlm6 and Rlm7 are still effective sources of resistance against L. maculans in oilseed rape in Europe. The results are comparable to those of a similar survey done in France in autumn 2000 and 2001. |
| Keywords: | blackleg Phoma lingam race structure resistance genes stem canker winter oilseed rape |
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