F. Thurwachter et al., Ascospore discharge, leaf infestation and variations in pathogenicity as criteria to predict impact of Leptosphaeria maculans on oilseed rape, J PHYTOPATH, 147(4), 1999, pp. 215-222
Citations number
39
Categorie Soggetti
Plant Sciences
Journal title
JOURNAL OF PHYTOPATHOLOGY-PHYTOPATHOLOGISCHE ZEITSCHRIFT
The aim of this investigation was to evaluate criteria for the forecast and
targeted control of basal stem canker (blackleg) caused by Leprosphaeria m
aculans on oilseed rape. Ascospore discharge, ratio of aggressive and nonag
gressive isolates and leaf and stem infestations were determined during 199
1/92-1993/94 at 6-10 sites in Northern Germany. On a 1-9 scale, blackleg in
tensity varied from 2.3 to 6.3 at BBCH 81 between different sites and years
. Ascospore discharge started in September or October, and reached maxima 1
or 2 months later, without an apparent relationship to blackleg or leaf in
festation. There was a positive relationship between leaf infestation and b
lackleg, However, correlation coefficients were too low to be used as a bas
is for forecasting. On plant residues from the stem base, aggressive isolat
es were dominant (> 80%) on all sites. From higher parts of the stem and fr
om leaves also, non-aggressive isolates were isolated with higher frequenci
es on some locations, but the proportion of aggressive isolates was not rel
ated to the blackleg intensity. Taken all together, the three criteria alon
e seem to be insufficient for the development of a system of blackleg forec
asting and targeted control. Further factors (e.g. climatic factors, seed-
and soilborne inoculum, cultural practices) have to be included in models f
or forecasting the impact of blackleg on oilseed rape.