Résumés
Abstract
The invasive fungal pathogens Ophiostoma ulmi and O. novo-ulmi have caused two successive pandemics of Dutch elm disease since the beginning of the 20th century. In nature, the highly aggressive O. novo-ulmi may hybridize with the less aggressive O. ulmi. Growth rate and molecular analyses were conducted on an unusual, moderately aggressive O. novo-ulmi isolate, AST27, carrying an introgressed pathogenicity gene, Pat1-m; on highly aggressive O. novo-ulmi isolate H327; on O. ulmi isolates Q412T and W9; and on progeny from laboratory crosses between H327 and AST27. Genetic analysis indicated that the Pat1 and Mat1 (mating type) loci were in different linkage groups corresponding to O. novo-ulmi H327 chromosomes 1 and 2, respectively. Most of the molecular differences between the nuclear genomes of H327 and AST27 occurred in the vicinity of Pat1 and Mat1. In addition, two putative quanti-tative trait loci, Mgr1 and Mgr2, which influence mycelial growth rate at 21°C and 28°C, the optima for O. novo-ulmi and O. ulmi, were linked to Mat1 and Pat1, respectively.
Keywords:
- Ophiostoma ulmi,
- Ophiostoma novo-ulmi,
- Dutch elm disease,
- introgression
Résumé
Les champignons pathogènes envahissants Ophiostoma ulmi et O. novo-ulmi ont causé deux pandémies successives de maladie hollandaise de l’orme depuis le début du 20e siècle. On a mesuré la croissance et procédé à des analyses moléculaires chez l’isolat O. novo-ulmi AST27, modérément agressif et chez lequel le gène de pathogénie Pat1-m est introgressé; chez l’isolat O. novo-ulmi H327; chez les isolats O. ulmi Q412T et W9; ainsi que chez les descendants de croisements dirigés entre les isolats H327 et AST27. Les analyses génétiques indiquent que les loci Pat1 et Mat1 (type sexuel) sont situés sur des groupes de liaison différents qui correspondent respectivement aux chromosomes 1 et 2. Les différences moléculaires entre les génomes nucléaires des souches H327 et AST27 se retrouvent majoritairement dans le voisinage de Pat1 et de Mat1. De plus, deux loci présumés de caractères quantitatifs, Mgr1 et Mgr2, qui influencent la croissance mycélienne à 21 °C et à 28 °C (températures optimales pour O. novo-ulmi et O. ulmi) sont liés respectivement à Mat1 et à Pat1.
Mots-clés :
- Ophiostoma ulmi,
- Ophiostoma novo-ulmi,
- maladie hollandaise de l’orme,
- introgression
Parties annexes
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