Seasonal development of apothecia of the cereal eyespot pathogen Tapesia yallundae on straw stubble in the UK

Five field sites growing winter wheat were inoculated with isolates of the W-and R-types of Tapesia yallundae in 1990 and 1991. After harvest, plots of uncultivated stubble were monitored for the production of apothecia during 1992 and 1993. Apothecia were found on the stem bases of straw stubble over a 9-month period from mid-October to July, but with a peak in numbers present during late January to March, 5 to 7 months after harvest. This was associated with mean monthly temperatures between 3°C and 8°C. Rainfall appeared to be less important than temperature in apothecial development. Single ascospore isolates obtained from apothecia collected from areas inoculated with W-, R-, or mixed W- and R-type isolates all produced colonies with morphologies and growth rates characteristic of the W-type. Thus there was no indication that the W- and R-types are sexually compatible.