Early stages of septoria tritici blotch epidemics of winter wheat: build-up, overseasoning, and release of primary inoculum

• Published in: Plant pathology Vol. 60; no. 2; pp. 166 - 177
• Main Authors: Suffert, F, Sache, I, Lannou, C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-04-2011; Blackwell; Wiley Subscription Services, Inc; Wiley
• Subjects: Agronomy. Soil science and plant productions; alternative host; ascospore; Ascospores; Biological and medical sciences; Crops; Disease transmission; Epidemics; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Grasses; Infection; Inoculum; Leaves; Life Sciences; Mycosphaerella graminicola; Phytopathology. Animal pests. Plant and forest protection; Plant debris; pycnidiospore; Pycnidiospores; Seeds; Septoria tritici; septoria tritici blotch; Stubble; Triticum aestivum; volunteer plants; Monocotyledones; Plant pathology; Plant pathogen; Early stage; Epidemiology; Volunteer plant; Cereal crop; Spores; Fungi; Alternative host; Gramineae; Angiospermae; Primary; Fungi Imperfecti; Debris; C3-Type; Release; Ascomycota; Epidemic; Vegetals; pycnidiospore; Ascospore; plant debris; Mycosphaerella graminicola; volunteer plants; Winter crops; Spermatophyta; Septoria tritici; Triticum aestivum; Inoculum; PYCNIDIOSPORE; MYCOSPHAERELLA GRAMINICOLA; PLANT DEBRIS; SEPTORIA TRITICI; ASCOSPORE; VOLUNTEER PLANTS; ALTERNATIVE HOST
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/j.1365-3059.2010.02369.x

Septoria tritici blotch (STB), caused by Mycosphaerella graminicola, is the most prevalent disease of wheat worldwide. Primary inoculum and the early stages of STB epidemics are still not fully understood and deserve attention for improving management strategies. The inoculum build-up and overseasoning involves various fungal structures (ascospores, pycnidiospores, mycelium) and plant material (wheat seeds, stubble and debris; wheat volunteers; other grasses). Their respective importance is assessed in this review. Among the mechanisms involved in the early stages of epidemics and in the year-to-year disease transmission, infection by ascospores wind-dispersed from either distant or local infected wheat debris is the most significant. Nevertheless, infection by pycnidiospores splash-dispersed either from neighbouring wheat debris or from senescent basal leaves has also been inferred from indirect evidence. Mycosphaerella graminicola has rarely been isolated from seeds so that infected seed, although suspected as a source of primary inoculum for a long time, is considered as an epidemiologically anecdotal source. Mycosphaerella graminicola can infect a few grasses other than wheat but the function of these grasses as alternative hosts in natural conditions remains unclear. Additionally, wheat volunteers are suspected to be sources of STB inoculum for new crops. This body of evidence is summarized in a spatio-temporal representation of a STB epidemic aimed at highlighting the nature, sources and release of inoculum in the early stages of the epidemic.