Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

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Populations of Septoria spp. Affecting Winter Wheat in
the Forest-Steppe Zone of the Ukraine
S. Kolomiets*
Institute of Plant Protection, Ukrainian Academy of Agrarian Sciences, Kiev, Ukraine
Abstract
Data in the literature and results of our investigations indicate that septoria leaf blotch of winter wheat has been reported
annually in the forest-steppe zone of the Ukraine. Septoria tritici is the predominant species among the causal agents of
septoria leaf blotch of winter wheat. However, the portion caused by Stagonospora nodorum increased to 23-44% in recent
years.
Septoria tritici, the pathogen that
causes leaf blotch, and Stagonospora
nodorum, the pathogen that induces
spike and leaf blotch, are the most
widespread pathogens of winter
wheat in the forest-steppe zone of
the Ukraine.
Septoria spp. induce a decrease
in assimilation surface,
developmental retardation,
premature leaf desiccation, and
1000-grain weight. In epidemic
years, yield losses may reach 30–
50%. Total yield losses caused by
these pathogens all over the world
are estimated at 9 million tons.
Developing cultivars resistant
to the pathogens and establishing
their cultivation is impossible
without investigating the
composition of pathogenic species
in a given area and systematically
recording its changes. Climatic
conditions, the composition of
biocenoses, and the substrate
where pathogens develop
significantly affect the ratio
between species. In the literature
data on the areas occupied by the
pathogens are quite limited, but
can be found in articles published by
Kovalenko (1975), Vasetskaja et al.
(1983), Dyak (1990), and Sanina and
Antsiferova (1991).
In 1995–97, we investigated the
composition of Septoria pathogens in
the forest-steppe zone of the Ukraine
(Kyiv, Cherkasy, Vinnytsya,
Khmelnytskyy, Ternopil, Zhytomyr,
and Poltava regions). Studies were
conducted on promising and
cultivated cultivars of winter wheat
using routine methodologies. The
species were identified via
evaluation of stable traits: form,
length, and width of conidia and
ends.
Our research demonstrated that
the forest-steppe zone of the Ukraine
is occupied by both Septoria
pathogens, but S. tritici
predominated in the 1970s, while S.
nodorum was found only in certain
years (Kovalenko, 1975). In the 1980s
S. nodorum was reported in Kyiv (30-
36%) and Ternopil (13-23%) regions
(Dyak, 1990). In Cherkasy region
(6.6%) the pathogen was reported
only in certain years and was not
detected at all in Vinnytsya region.
* Author prevented from attending workshop by unforeseen travel problems.
In the mid 1990s, the proportion
of S. nodorum increased among the
species. Septoria tritici dominated in
all investigated regions: the highest
percentage was reported in
Vinnytsya region (76%), while the
lowest was reported in Ternopil
region (53%). In Kyiv, Cherkasy,
Poltava, Khmelnytskyy, and
Zhytomyr regions, it reached 68,
65, 69, 72, and 72%, respectively
(Figure 1). Data from the literature
and our own research results
indicate an increase in the area
occupied by S. nodorum, as well as
in its ratio of Septoria pathogens
present.
Changes in the ratio of the
pathogens may be explained by
changes in climatic conditions, the
range of cultivars used and,
possibly, by the spread of S.
nodorum infection through seeds,
especially in recent years, when
seeds were not properly treated.
Thus the spread of S. nodorum–the
most aggressive and damaging
Septoria pathogen–increased under
the above conditions.