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RESISTANCE TO LEPTOSPHAERIA MACULANS IN THE PETIOLE OF BRASSICA NAPUS

E.J. PIRIE1, B.D.L. FITT1, O. LATUNDE-DADA1

1ROTHAMSTED RESEARCH, HARPENDEN, HERTS. AL5 2JQ

Leptosphaeria maculans is the main causal agent of phoma stem canker, the most important disease of oilseed rape in the UK and worldwide. Leaves are infected by air-borne ascospores in the autumn, causing pale lesions full of pycnidia. The fungus grows from these lesions down the petiole to the stem where it causes a canker and subsequent yield loss. Major gene resistance occurring in the leaf has been identified but there is evidence for the breakdown of this resistance in the field. Resistance to L. maculans may also occur in the petiole, stopping, or slowing growth. If the mechanisms of this resistance could be elucidated then they may provide a more durable form of resistance for field crops.

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Identification of candidate genes involved in vertical rust resistance in poplar

Inge Maertens*, Peter Breyne°, Marijke Steenackers° & Godelieve Gheysen*

* Department of Molecular Biotechnology, Faculty of Agriculture and Applied Biological Sciences, UGent, Ghent, Belgium, ° Institute for Forestry and Game Management, Geraardsbergen, Belgium

The genus Populus is one of the most widespread and economically important wood resources in the world. Leaf rust fungi are the major class of pathogens that affect poplar. They can cause premature defoliation, shoot and root growth reduction, and even plant death. In Europe, Melampsora larici-populina is the most damaging species. In this study, we investigate the poplar transcriptome after infection with M. larici-populina race E1. The aim of the cDNA-AFLP study is to identify key regulatory genes induced early upon infection which might be the initial triggers leading to vertical resistance. Expressed genes can be detected by cDNA-AFLP and no sequence information is required. The analysed full sib family, an interspecific cross between Populus deltoides ‘S9-2’ and P. nigra ‘Ghoy’, segregates for rust resistance/sensitivity against races E1, E2 and E3. To minimize the detection of genetic polymorphisms, pools were made of 10 resistant and of 10 sensitive offsprings. 66 leaf disks were collected of each offspring and incubated upside down in multiwell plates. Half of the leaf disks were sprayed with a spore suspension (race E1) and the other half with water as a negative controle. The multiwell plates were stored in a climate chamber. As a verification of the race/plant interaction, two samples were left in the climate chamber for ten days. The infection level was then scored by means of the digital image processing system. In total, 4 conditions are being analysed: resistant-rust infected (R+), resistant-not infected (R-), sensitive-rust infected (S+) and sensitive-not infected (S-). All the conditions were sampled at 31 timepoints (0h, 0.5h, every hour from 1h until 24h, 36h, 48h, 72h, 96h and 120h). Total RNA was extracted from each sample and converted into double-stranded cDNA. In the cDNA-AFLP analyses, 20 random primer combinations (BstYI+1/MseI+2) were investigated. A comparison will be made between the expression profiles of the different conditions. Differentially expressed transcript tags will be further analysed.

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resistance of winter wheat cultivars to tan spot in the czech republic.

Šárová J.*, Hanzalová A.

Research Institute of Crop Production, Prague 6 - RuzynÄ›, Drnovská 507, 161 06, Czech Republic. e-mail: sarova@vurv.cz

Tan spot, caused by homothallic ascomycete Pyrenophora tritici-repentis (Died.) Drechs., is one of the most important wheat leaf spot diseases in the Czech Republic. The reaction of 45 winter wheat cultivars (predominantly Czech registered cultivars) and new breeding lines to artificial infection with P. tritici-repentis was tested in greenhouse conditions. In total three different monosporic isolates of P. tritici-repentis originated from the Czech Republic were used for inoculation. The conidial suspensions of the isolates were applied on seedlings at the two-leaf stage. Reaction of the cultivars was rated about 7 days after inoculation, using the 1 to 5 rating scale (1 = resistant, 5 = susceptible). The study proved differences in the reaction of individual cultivars. The majority of the tested cultivars showed moderately resistant to moderately susceptible reaction. Cultivars/lines LP500U96, Clarus, Genova, Šárka, Rapsodia, and SG-U-7029 were moderately resistant to P. tritici-repentis in our greenhouse experiments. Only cultivar Biscay was susceptible to this pathogen. Differences in aggressiveness of P. tritici-repentis isolates were found out. This study was supported by the National Agency for Agricultural Research (project No. QD 1311), by the Ministry of Agriculture (project No. M 01-01-03).

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Stem canker of oilseed rape: molecular tools and mathematical modelling to deploy durable resistance

Neal Evans1, Bruce Fitt1, Frank van den Bosch1, Maria Eckert1, Yong-Ju Huang1, Stephane Pietravalle1, Zbigniew Karolewski1,10, Thierry Rouxel2. Marie-Helene Balesdent2, Simon Ross2,  Lilian Gout2, Hortense Brun3, Didier Andrivon3, Lydia Bousset3, Peter Gladders4, Xavier Pinochet5, Annette Penaud5, Malgorzata Jedryczka6, Piotr Kachlicki6, Anna Stachowiak6, Julia Olechnowicz6, Anna Podlesna8, Ingrid Happstadius7, Jan Meyer7 and Michel Renard9

1 Rothamsted Research, Harpenden, Herts., AL5 2JQ, U.K. E-mail:neal.evans@bbsrc.ac.uk 2 INRA, Unité PMDV, Route de St Cyr, Versailles 78026, France. E-mail: rouxel@versailles.inra.fr 3 INRA UMR BiO3P and

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