Friesia X, 4-5

FRIESIA . Bind X . Hefte 4-5 . 1974
LEPTOSPHAERIA NODORUM
(SE PTORIA NODORUM),
A NEW PATHOGE N ON BARLEY I N DENMARK,
AN D ITS PHYSIOLOGIC SPECIALIZATION
ON BARLEY AND WH EAT
By V. SMEDEGÅRD-PETERSEN
Department of Plant Pathology, t he Royal Veterinary and
Agricultural University, Copenhagen.
SUMMARY
For the first time in Denmark Leptosphaeria nodorum MULLER
(stat. conid. Septo ria nodoruan (BERK.) BERK. & BR.), the cause of
glume blotch of wheat, is recorded as a pathogen on barley. In the
growing seasons 1970-73 disease symptoms were found widespread in
many areas and in 1972-73 the fungus was isolated from 11 localities
in Zealand and Jutland, often causing considerable damage to the
foliage.
Disease symptoms were most pronounced on leaf lamina and leaf
sheats where they appeared as 1-2 cm oval, lens-shaped, redbrown
lesions often extending in large chlorotic areas in the remaining
tissue. Irregular or triangular leisions typically developed at the junc­
tion between leaf lamina and sheat. Less pronounced brown spots
occurred on glumes and awns. Numerous pycnidia developed in the
lesions and were frequently followed by perithecia in late summer.
Comparative studies of L. nodorum isolated from barley and wheat
showed that isolates from these two host genera closely resemble each
other in both the perfect and imperfect stage with regard to all of
the morphological characters examined.
Physiologic specialization within L. nodorum was studied in cross
inoculation experiments on adult plants in the field and on seed-
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