The teleomorph stage, Mycosphaerella graminicola, in epidemics of septoria tritici blotch on winter wheat in the UK

Abstract

Earlier studies have shown that primary infections of winter wheat crops by septoria tritici blotch are initiated in autumn by air‐borne ascospores of the teleomorph stage, Mycosphaerella graminicola, which originate from sources outside the crop. Subsequent disease development within the crop, and damage to the upper leaves in summer, were commonly ascribed to the anamorph stage, Septoria tritici, which first arises from primary, ascosporic lesions and develops to give rise to splash‐borne pycnidiospores produced in pycnidia. Trapping studies, using a Burkard volumetric trap sited adjacent to field trials of winter wheat, showed that ascospores are released from pseudothecia throughout the year; peak release is not restricted to the autumn and early winter when the primary infections occur. As M. graminicola ascospores can be confused with those of other species, their authenticity was established by incubating ascospores on trap tapes for 24–48 h before counting. Examination of wheat plants cv. Riband, removed from unsprayed crops just prior to harvest and exposed to external weather conditions over the winter in 1995 and 1996, showed that pseudothecia mature on residues of the upper leaf layers between August and March. However, peak development occurred in December/January, when there was a corresponding decline in pycnidial formation. On regenerated wheat in set‐aside (left uncultivated) fields, sources of pseudothecia of M. graminicola were exhausted by February of the following year. Natural development of the teleomorph stage was monitored in an unsprayed crop of winter wheat cv. Riband during the 1996–97 season, and was present on leaf 8 at growth stage 32 (24 April) and on leaf 3 at growth stage 85 (8 July), then a week later, on both leaf 2 and the flag leaf. The temporal development of M. graminicola asexual and sexual phases was also studied in inoculation experiments under external weather conditions on pot‐grown seedlings of winter wheat cv. Longbow, using inoculum from two single‐ascospore cultures.

Weather Conditions Associated with the Release and Dispersal of Zymoseptoria tritici Spores in the Argentine Pampas Region

“…Only 30 min of moistening stubble is necessary for ascospore release and dispersal [7]. Hunter et al [8] suggested that airborne ascospore plays the major role in epidemiology during the growing season and, together with splash dispersal spores, both have implications for the forecasting of the disease.…”

“…Hunter et al [8] suggested that ascospores are dispersed in air currents rather than by rain splash, having important implications for risk-based decisions on disease control.…”

A New Method To Monitor Airborne Inoculum of the Fungal Plant Pathogens Mycosphaerella brassicicola and Botrytis cinerea

“…Airborne spores of fungal plant pathogens have commonly been detected and enumerated by microscopic examination of surfaces on which spores have been impacted (2,13). Sampling procedures may involve passive collection of spores by gravitational deposition (14) and/or sampling specific volumes of air with "active" spore-trapping devices (1,9,18).…”

“…B 7-day traps have been used routinely to monitor fungal air spora (12,13,24,26) and in a wide variety of air-sampling studies (3,10). Ascospores on the Melinex spore tape were detected and quantified by immunofluorescence, as described by Kennedy et al (17).…”

Spring air temperature accounts for the bimodal temporal distribution of Septoria tritici epidemics in the winter wheat stands of Luxembourg

“…Yield losses caused by S. tritici in humid regions range from 30 to 50% if left uncontrolled (Ziv and Eyal, 1978;Burke and Dunne, 2006;Royle et al, 1986). The sexual ascospores represent the primary source of inoculum infecting young winter wheat plants in autumn (Gladders et al, 2001;Hunter et al, 1999). The asexual conidiospores are formed in fruiting bodies (pycnidia) and these spores represent the secondary inoculum for the epidemic spread and vertical transfer to the upper leaves in spring and summer (Gladders et al, 2001;Palmer and Skinner, 2002;Royle et al, 1986).…”