Friesia X, 4-5

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Perithecia of L. nodorum have not previously been reported on
barley. However, the development of pycnidia on the barley leaves
inoculated with cultures obtained from ascospores clearly furnishes
the evidence that we were dealing with the pycnidial and perithecial
stages of the same species.
It is finally concluded that the pathogen under investigation was
L eptosph aer i a nodorum and t hat it was present in both t he pycnidial
a nd perithecial st age. F urthermore that t he pathogen was responsible
for the disease symptoms deseribed on barley.
PHYSIOLOGIC SPECIALIZATION
In the literature there are several in dications that physiologic
specialization occur within L eptosphaer ia nodorum. WEBER (1922)
proved experimentally that isolates from wheat also infected rye and
Poa pratensis but not eight other genera of Gr ami nea including
several species of Hordeum. His statement in a later publication
(WEBER 1923) that Hordeum vulgare pallidum was susceptible to
L. nodorum would appear to be erroneous. JOHNSON (1947) found that
six isolates of L. nodorum strongly infected wheat , but caused only
traces of symptoms on barley.
In preliminary infection experiments with two is olates of L. no dorum
from barley and two from wheat the present author found that
barley isolates did n o t attack wheat and wheat isolates did n o t
attack barley. In order further to clarify whether L. nodorum is
separated into [or mae speciales more extensive infection experiments
were performed partly on adult plants in the field, partly on seedlings
in pots.
In field experiments a composite of two isolates from barley were
used to inoculate barley and wheat. Similarly a composite of two
isolates from wheat were used to inoculate barley and wheat. The
inoculum was prepared by macerating vigorously growing cultures
in a Waring blender with water supplemented with 0.1 % gelatine. On
June 18th the mycelial suspensions were sprayed onto plants of barley
and wheat with an atomizer. At the time of inoculation ear emergence
was complete in the wheat and had just started in the barley. About
2 X 15 plants of each species were inoculated and subsequently covered
by plastic bags containing wet cotton in order to maintain high
humidity, The plastic bags were removed after 3 da ys.
17*