First record of Tapesia yallundae as the teleomorph of Pseudocercosporella herpotrichoides var. acuformis, and its occurrence in the field in the Federal Republic of Germany

Abstract

Tapesia yallundae is reported for the first time in the Federal Republic of Germany. Apothecia were found on wheat and rye stubble at two sites in the north of the country and one in the centre, in April 1988. Isolates of Pseudocercosporella herpotrichoides var. acuformis were obtained from germinating single ascospores, identified on the basis of colony morphology, mode of conidial production and pathogenicity to wheat and rye.

Incidence of apothecia of Tapesia yallundae at setaside sites in England and sensitivity of the ascospore offspring to the fungicides benomyl and prochloraz

“…The first clear finding was that the sexual stage of T, yallundae was present at almost half of the set-aside sites surveyed throughout England in 1992-94, This confirms that sexual reproduction is an intrinsic part of the life cycle of the pathogen, and follows the discovery of apothecia of T, yallundae in the field in Australia, New Zealand, England, Belgium, Germany, France and South Africa (Wallwork, 1987;Sanderson & King, 1988;Hunter, 1989;Moreau et al, 1989;King, 1990King, , 1991Dyer et at., 1994a,;Robbertse et at,, 1994;Cavelier, 1994), The occurrence of II II II II II II II II II II II II II II II c the sexual cycle is significant because it leads to greater variation within the ascospore offspring owing to recombination and segregation (Nicholson et al, 1991b;Dyer et al, 1993); ejected ascospores may also provide a source of wind-dispersed inoculum of the fungus. The potential importance of ascospores in the spread of disease has been emphasized by the recent discovery that they are able to infect directly wheat seedlings in vitro (A, Daniels, M. Papaikonomou, P,S,D, & J,A,L,, unpublished results).…”

“…The results of the colony morphology and growth rate tests revealed that the ascospore offspring (from sites where discharge was successfully obtained) almost all had characteristics ofthe W-type of T, yattundae. The only exception was from one site in Lincolnshire, full details of which have been reported previously (Dyer et at., 1994b), The ascospore discharge from other field apothecia from the northern and southern hemispheres has also been mostly of the W-type, except for two reports of ascospore offspring with R-type characteristics from Germany and Belgium (King, 1990; J. M. Moreau & H. Maraite, pers, comm.). This suggests that the sexual stage ofthe W-type occurs more frequently in nature than that of the R-type and may explain why the R-type exhibits less genotypic variation than the W-type (Nicholson & Rezanoor, 1994), as the W-and R-types are sexually incompatible (Nicholson et al, 1995).…”

Development of apothecia of the eyespot pathogen Tapesia on cereal crop stubble residue in England

“…Alternatively, field isolates of T. acuformis may exhibit inherently low sexual potential, possibly arising from mutation away from sexuality, as is evident in the plant pathogen Magnaporthe grisea and some Fusarium species (Booth, 1984; Notteghem & Silué, 1992). This may explain the apparent rarity of apothecia of T. acuformis in the wild (King, 1990; Dyer et al ., 1994b; Moreau & Maraite, 1995). Less genetic variation has been detected in populations of T. acuformis than in T. yallundae , possibly as consequence of lower sexual reproduction in populations of the former species (Nicholson & Rezanoor, 1994).…”

“…acuformis ) (synonym Ramulispora acuformis ) (Robbertse et al ., 1995; Dyer et al ., 1996). However, apothecia of T. acuformis have been reported much less frequently than those of T. yallundae , with only three field observations from Germany, England and Belgium (King, 1990; Dyer et al ., 1994b; Moreau & Maraite, 1995). No investigations have been made to determine the conditions under which the sexual cycle might occur in the field.…”

Development of apothecia ofTapesia yallundae in contrasting populations selected by fungicides

“…This is further evidence that sexual repro- [Bateman et al,, 1995], but using data only from those plots that yielded single ascospore isolates. duction in the field is almost entirely restricted to the W-type (although the contribution of the inoculated isolates to the mating population is not known); there are only two reports of ascospores producing colonies characteristic of the R-type [King, 1990;Dyer et al, 1994b]. The reason for the rarity of sexual reproduction in the R-type is unclear, but there may be a lack of compatible isolates in the field or of a particular environmental trigger.…”