Breeding poplars with durable resistance to Melampsora larici-populina leaf rust : a multidisciplinary approach to understand and delay pathogen adaptation

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Breeding poplars with durable resistance to Melampsora larici-populina leaf rust : a multidisciplinary approach to

understand and delay pathogen adaptation

Arnaud Dowkiw, Catherine Bastien, Véronique Jorge, Marc Villar, Elodie Voisin, Vanina Guérin, Patricia Faivre-Rampant, Alois Bresson, Frederique

Bitton, Sébastien Duplessis, et al.

To cite this version:

Arnaud Dowkiw, Catherine Bastien, Véronique Jorge, Marc Villar, Elodie Voisin, et al.. Breeding

poplars with durable resistance to Melampsora larici-populina leaf rust : a multidisciplinary approach

to understand and delay pathogen adaptation. 4. International Workshop on the Genetics of Host-

Parasite Interactions in Forestry : ”Disease and Insect Resistance in Forest Trees”, United States

Department of Agriculture - USDA (USA) (USDA). Forest service, Ville service, USA., Jul 2011,

Eugene, Oregon, United States. 112 p. �hal-02748005�

United States Department of Agriculture Forest Service Pacific Southwest Research Station

Fourth International Workshop on the Genetics of Host-Parasite

Interactions in Forestry

Meeting Abstracts

July 31 – August 5, 2011, Eugene, Oregon, USA

DEPA R TMENT OF AGRICULTURE

13

ABSTRACTS FROM THE FOURTH INTERNATIONAL WORKSHOP ON HOST-PARASITE INTERACTIONS IN FORESTRY

Breeding Poplars with Durable Resistance to Melampsora larici-populina Leaf Rust: A Multidisciplinary Approach to Understand and Delay Pathogen Adaptation

Arnaud Dowkiw, Catherine Bastien, Véronique Jorge, Marc Villar, Elodie Voisin, and Vanina Guérin, INRA, UAGPF, 2163 avenue de la Pomme de Pin, BP20619 ARDON, 45166 Olivet Cedex, France; arnaud.dowkiw@orleans.inra.fr; Patricia Faivre-Rampant, Aloïs Bresson, and Frédérique Bitton, INRA-URGV, 2 rue Gaston Crémieux, CP5708, 91057 Evry Cedex, France; Sébastien Duplessis, Pascal Frey , Annegret Kohler, Cécile Rinaldi, and Bénédicte Fabre, INRA UMR IAM, 54280 Champenoux, France; and Christophe Plomion and Céline Lalanne, INRA UMR BIOGECO, 69 route d’Arcachon, 33612 CESTAS Cedex, France

During the last decades, European poplar breeders learned the hard way that Melampsora larici-populina has an impressive adaptive potential. This pathogen defeats qualitative (i.e. complete) resistances in less time than needed to grow a poplar tree. After several resistances inherited from Populus deltoides had been overcome, breeding for quantitative resistance (QR) was considered a more durable strategy.

At least three recent results raise doubts on this optimistic point of view. First, elucidat- ing the genetic determinism of quantitative resistance in P. detloides x P. trichocarpa hybrid progenies did not reveal as complex a genetic determinism as expected. Loci with major effects on one or several QR components were identified, such as R US inherited from P. trichocarpa. Second, quantitative and qualitative resistances did not appear to be completely independent. Most identified defeated qualitative resistances inherited from P. deltoides (e.g. R 1 ), had statistical effects on QR. Third, strains of the pathogen able to defeat the R US -mediated QR have been identified, possibly due to pre-adaptation in the pathogen’s populations.

Being both “easy” to map and defeated, R US is used as a model locus to understand host- pathogen quantitative interactions. Fine mapping of R US is being conducted using a 1,410 genotype F 1 progeny, and a BAC library was constructed to generate a physical map of 2,000 kb around R US . The first results support the idea that qualitative and quantitative resistances share not only functional but also structural similarities.

Urged by poplar growers to deliver new cultivars, breeders explore multiple (possibly combinable) very pragmatic strategies to delay pathogen adaptation. Sources of resistance are being diversified. In particular, the genetic variability available in the co-evolved European species P. nigra is being explored more attentively. A collection of 1,100 P.

nigra genotypes collected in different European populations has recently been screened

for rust resistance. The available variability for additional traits like avoidance and toler-

ance is also being tested in fungicide-treated vs. untreated experiments while new deploy-

ment strategies, such as using clonal mixtures, are also evaluated.