1. The biology of Melampsora larici-populina Pascal Frey INRA Nancy Joint Research Unit « Tree – Microbe Interactions » Champenoux, France Melampsora Genome Consortium - 2008 Summer Workshop

2. Poplar rust is caused by several Melampsora spp. Main disease in commercial poplar cultivation worldwide Symptoms : perturbation of photosynthesis early defoliation reduction of biomass  High yield losses perturbation of automnal translocation susceptibility to secondary parasites  Death of young trees Why sequencing poplar rust ? © Jean Pinon, INRA Nancy

3. low number of cultivars planted (less than 5 per region) monoclonal and even-aged plantations large spacing plantations: peeling (veneer, packaging), sawing, particle boards Short Rotation Coppice (SRC): biomass and bioenergy France is the first poplar wood producer in the EU (ca. 2.5 millions m 3 /yr) P. nigraP. trichocarpaP. deltoides euramerican hybrids interamerican hybrids Poplar cultivation in Europe

4. A few botanical facts about the genus Populus Genus Populus : Class : Eudicotylédones Clade : Eurosidae I Order : Malpighiales Family : Salicaceae (genus Salix and Populus) Between 29 and >100 species according to different authors. Eckenwalder’s (1996) classification is widely accepted. Eckenwalder JE (1996) Systematics and evolution of Populus. In Stettler RF, Bradshaw HD Jr, Heilman PE, Hinckley TM (Eds), Biology of Populus and its implications for management and conservation, Chap. 1. pp. 7-32. NRC Research Press, Ottawa, Canada. The genus Populus comprises 6 sections, clustering intercrossing species (also a few cases of inter-sectionnal intercrosses)

5. The 6 sections among the genus Populus according to Eckenwalder (1996) NB: P. maximowiczii = P. suaveolens s.l.

6. P. nigra (N)P. trichocarpa (T)P. deltoides (D) P. x euramericana (syn. P. x canadensis) (DxN) e.g. 'Robusta', 'I214' P. x interamericana (syn. P. x generosa) (DxT or TxD) e.g. 'Beaupré' The euramerican and interamerican hybrids

7. Rust fungi are excellent botanists ! AigeirosTacamahacaPopulus Melampsora spp.P. nigraP. deltoidesP. trichocarpaP. albaP. tremulaP. tremuloides M. larici-populina+++--- M. allii-populina+++--- M. medusae f. sp. deltoidae++---- M. occidentalis?-+--- M. pinitorqua---++? M. rostrupii---++? M. larici-tremulae---++? M. magnusiana---++? M. pulcherrima---+?? M. medusae f. sp. tremuloidae---??+

8. The taxonomic position of Melampsora larici-populina Wingfield et al 2004 Austral. Plant Pathol. Basidiomycota Pucciniomycotina Pucciniomycetes Pucciniales (= Uredinales) Melampsoraceae Melampsora

9. larch poplar telia and teliospores (n+n) aecidia (n+n) plasmogamy aecidiospores (n+n) basidiospores (n) spermogonia and spermatia (n) uredinia and urediniospores (n+n) The life cycle of Melampsora larici-populina: a heteroecious macrocyclic rust meiosis caryogamy basidia (2n) + + - - X

10. + + - - X sexual reproduction poplar-larch sympatry monocyclic 3 weeks asexual reproduction epidemic phase polycyclic 5 months The life cycle of Melampsora larici-populina: a heteroecious macrocyclic rust

11. teliaspermogonia aeciauredinia basidia PoplarLarch © P. Frey, INRA The life cycle of Melampsora larici-populina:

12. The life style of Melampsora larici-populina: a strict biotrophic fungus M. larici-populina needs fresh plant tissue (poplar leaves) to grow on Numerous attempts to find artificial culture media for rust fungi, but with limited success (limited mycelial growth, but no infectious spores produced) likely due to a very specific interface between the pathogen and the host tissues: the haustorium © Stéphane Hacquard, INRA

13. Matthias Hahn, 2000 The infection process of Mlp: a « lazy » fungus

14. Laurans & Pilate, 1999, Phytopathology 89: 233-238 2 hrs post inoculation Rinaldi et al., 2007 Plant Physiol. 144: 347-366 7 days post inoculation

15. The Populus-Mlp interaction: a gene-for-gene model H.H. Flor 1942: « Each dominant resistance gene in the host plant matches a dominant avirulence gene in the pathogen » GFG relationship is very likely in the Populus-Mlp interaction, but not demonstrated yet At least 8 qualitative (major) rust resistance genes described in poplar, and 8 avirulence loci in Mlp: 8 virulence loci  2 8 = 256 possibles pathotypes Strain 98AG31: Vir3-Vir4-Vir7 (Avr1, Avr2, Avr5, Avr6, Avr8)

16. Mlp has overcome almost all the R genes released Examples: 1986: breakdown of R3 ('Luisa-Avanzo') 1994: breakdown of R7 ('Beaupré') 1997: breakdown of R8 ('Hoogvorst') In 2008, of the 130 cultivars available in the UE, only one recently released cv. is completely resistant to Mlp Dispersal of Vir7 after the breakdown of R7 199419951996199719981999 (Pinon et al. 1998)

17. Mlp has great dispersal capacities regional scale: the Durance River valley national scale: dispersal of Vir7 in France intercontinental scale: Iceland 1999 Canada 2002 Wild poplar riparian stands Poplar-larch sympatry area annual epidemic Prelles St Clément Rochebrune Monêtier Valernes Les Mées La Brillanne Mirabeau Châteauroux Embrun BPR Pont du Fossé BPR Manse BPR Manosque BPR Valernes BPR Mirabeau Cultivated poplar stands (R7) Durance 15 km

18. Mlp is among pathogens with highest evolutionnary risk Linde & McDonald, 2002, Annu. Rev. Phytopathol.

20. A nomenclatural issue about Mlp: Klebahn, 1902. Kulturversuche mit Rostpilzen Z. PflKrankh. PflPath. PflSchutz 12: 43 First description of the heteroecious rust fungus M. larici-populina (M. populina = Caeoma laricis) Saccardo P.A. (1905) Sylloge Fungorum 17: 463 M. laricis-populina

21. A nomenclatural issue about Mlp: All the literature of the 20th century concerning Mlp used the spelling M. larici-populina In 1997, first ITS sequences deposited in GenBank: they use the spelling M. laricis-populina, according to the Index Fungorum Taxonomy browser of GenBank : M. larici-populina : MycoBank (www.mycobank.org) M. laricis-populina : Index Fungorum (www.indexfungorum.org) and USDA-ARS Systematic Mycology and Microbiology Laboratory, Fungal Databases (http://nt.ars-grin.gov/fungaldatabases) DoE JGI portal for Mlp : M. laricis-populina ! according to some latinists, both can be correct, depending if one considers that larici is an hyphenation of laricis, or that the genetive laricis should apply