Biological studies on Drechslera tritici-repentis (Died.) Shoem. (teleomorph Pyrenophora tritici-repentis (Died.) Drechsler) the causal agent of a leaf spot disease on wheat
1993
Wolf, P.F.J. (Technische Univ. Muenchen, Freising-Weihenstephan (Germany). Lehrstuhl fuer Phytopathologie) | Hoffmann, G.M.
The main aspects of the life cycle and infection process of Drechslera tritici-repentis were investigated in field and laboratory studies. Under conditions in southern Bavaria, the development of pseudothecia started at the end of the crop life (full maturity). The number of pseudothecia increased until the middle of October, followed by a long period of differentiation and ripening. First mature ascospores were found at the end of February and early March. The peak occurred in early April. Following the total release of ascospores from the single pseudothecia, it was stimulated to produce conidia between the setae of the empty sporocarp. Although ascospores were actively discharged, the distribution reached only short distances. The release depended on the presence of free water, the number of released spores was influenced by temperature. In contrast, the conidia were windspread over great distances, they were found in altitudes of 3 m over infested fields. Conidia production is linked to necrotic plant tissue and high amount of humidity (over 95% rel. humidity). Under optimal conditions, i.e., temperatures of 20-25 degrees C and humidity over 95% or leaf-wetness and incubation period of approximately 2 days was established, the latent period was 6 to 7 days, leaf blotching was under these conditions very fast. The content of conidia in the air was measured over wheat fields during three vegetation periods (1987-1989). The number of conidia slowly increased until middle of June, then the concentration accelerated and remained high until crop maturity. The main release of conidia (88-93%) occurred in July. Optimal conditions for the conidia production are given at night when leaf area moisture increased to 60-100% of the leaf surface
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