Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

with double-distilled water and
scraping the agar surface with a
rubber spatula. This suspension of
pycnidia was blended for 30 s in a
blender to release pycnidiospores
and then filtered through four
layers of cheesecloth. Tween-20
(polyoxyethylene-20-sorbitan
monolaurate) was added to the
pycnidiospore suspension at a rate
of 100 µl/l to facilitate the uniform
distribution and adsorption of
inoculum onto the leaf surfaces.
Barley seedlings were
inoculated with the pycnidiospore
suspension (5 x 10 5
pycnidiospores/ml) at the two-leaf
stage (10-12 days old). Inoculated
seedlings were incubated at 21ºC/
dark and 25ºC/light for 72 h in
mist chambers, where the relative
humidity was maintained near
100%. The first 40 h of incubation
was in darkness, followed by a
photoperiod of 5 h for next two
days. Plants were allowed to dry
off slowly before being transferred
to the greenhouse under the same
conditions previously described.
The reaction of the entries to S.
passerinii was assessed on the
second leaves of seedlings 17 days
after inoculation using a 0-5 rating
scale where 0, 1, and 2 are
indicative of resistance and 3, 4,
and 5 of susceptibility. Resistant
(cv. Atlas) and susceptible (cv.
Betzes) checks were included in the
experiment.
Results and Discussion
Hordeum vulgare and H. vulgare
subsp. spontaneum accessions were
classified as susceptible or resistant
based on their reaction to S.
passerinii at the seedling stage.
Sources of Resistance to Septoria passerinii in Hordeum vulgare and H. vulgare subsp. spontaneum 157
Marked differences were observed
in the reaction of barley accessions
to S. passerinii infection. In total, 79
lines were found resistant to S.
passerinii. Of the 24 H. vulgare
subsp. spontaneum accessions
tested, 17 were resistant. These
accessions all originated from the
Middle East, except one, which was
from Tibet. Similar results were
obtained by Metcalfe et al. (1977)
who found that all H. vulgare
subsp. spontaneum accessions
collected in the Middle East were
resistant to S. passerinii.
All of the major 6-rowed
malting (Foster, Stander, and
Robust), and 2-rowed feed
(Bowman, Conlon, and Logan)
cultivars grown in the Upper
Midwest region were susceptible.
Of 120 advanced midwestern 6and
2-rowed breeding lines, 41
were resistant. Most of these
breeding lines have Gloria”S”/
Copal”S” (an ICARDA/CIMMYT
barley line) in their pedigree. This
line exhibited S. passerinii resistance
under field conditions in North
Dakota and is presumed to be the
source of resistance to S. passerinii
in these breeding lines (J.
Franckowiak, personal
communication).
Nine accessions (AC Hamilton,
Atlas, Bolron, CIho 4439, CIho
4780, CIho 10644, Feebar, Nomini,
and Starling) previously reported
to have resistance to S. passerinii
were also resistant to the North
Dakota isolate (ND97-15) used in
this study. Other barley accessions
resistant to this isolate were: Atlas
54, Baronesse, Belford, CIho 4428,
CIho 4940, Flynn 1, Glacier, and
Vaughn. Only a few studies have
been advanced on the genetics of
resistance in barley to S. passerinii.
Peterson (1956) indicated that the
variety Atlas possesses dominant
resistance genes to S. passerinii.
Buchannon (1961) found two
recessive genes conferring
resistance to S. passerinii in the
cultivar Feebar, and Rasmusson
and Rogers (1963) reported two
different dominant resistant genes,
Sep2 and Sep3, in the accessions
CIho 4780 and CIho 10644,
respectively. Metcalfe et al. (1970)
found that a single dominant gene
governs resistance to S. passerinii in
CIho 4439. It is evident that many
barley accessions possess resistance
to this pathogen; however, none
has been exploited in midwest
barley breeding programs, as all of
the major malting and feed
cultivars are susceptible to S.
passerinii.
Segregating populations
derived from some of the described
sources of resistance and
susceptible commercial cultivars
are under evaluation in our
laboratory to study the genetics of
resistance in barley to S. passerinii
and to identify molecular markers
linked to S. passerinii resistance
gene(s). All accessions found
resistant to S. passerinii in this study
will also be evaluated to S. avenae f.
sp. triticea. This test will enable us
to identify sources of resistance to
both S. passerinii and S. avenae f. sp.
triticea and to determine whether
resistance to both pathogens is
governed by the same or by
different gene(s). The development
of barley cultivars with resistance
to both S. passerinii and S. avenae f.
sp. triticea is necessary, as both
pathogens are common in the
Upper Midwest production area.