title: Temperature regulates the initiation of chasmothecia in powdery mildew of strawberry.
abstract: The formation of chasmothecia by the strawberry powdery mildew pathogen (Podosphaera aphanis) is widespread but often sporadic throughout the range of strawberry cultivation. In some production regions, notably in warmer climates, chasmothecia are reportedly rare. We confirmed that the pathogen is heterothallic, and that initiation of chasmothecia is not only dependent upon the presence of isolates of both mating types but also largely suppressed at temperatures >13°C. Compared with incubation at a constant temperature of 25°C, progressively more chasmothecia were initiated when temperatures were decreased to 13°C for progressively longer times. At lower temperatures, production of chasmothecia was associated with a decline in but not total cessation of conidial formation, and pairings of compatible isolates sporulated abundantly at 25°C. We developed mating-type markers specific to P. aphanis and used these to confirm the presence of both mating types in populations that had not yet initiated chasmothecia. The geographic discontinuity of chasmothecia production and the sporadic and seemingly unpredictable appearance of chasmothecia in P. aphanis are possibly due to the combined influence of heterothallism and suppression of chasmothecia formation by high temperatures.
authors: Department of Plant and Environment Sciences, Norwegian University of Life Sciences, Norway. belachew.asalf.tadesse@umb.no
authors: Belachew
authors: B
authors: Asalf
authors: David M
authors: DM
authors: Gadoury
authors: Anne Marte
authors: AM
authors: Tronsmo
authors: Robert C
authors: RC
authors: Seem
authors: Lance
authors: L
authors: Cadle-Davidson
authors: Marin Talbot
authors: MT
authors: Brewer
authors: Arne
authors: A
authors: Stensvand
mesh_terms: D001203:Ascomycota / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure; D031985:Fragaria / Q000382:microbiology*; D049770:Genes, Mating Type, Fungal / Q000235:genetics; D005819:Genetic Markers; D005838:Genotype; D060885:Multiplex Polymerase Chain Reaction; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D013172:Spores, Fungal; D013696:Temperature
chemical_list: D005819:Genetic Markers