PROBLEMS OF CARYOPSIS AND STABILITY OF WINTER AND SPRING FORMS OF CEREALS TO PHYTOPATHOGENIC FUNGI OF GENUS FUSARIUM LINK - Ecological Consequences of Increasing Crop Productivity - page 98

11.1 INTRODUCTION
The problem of stability to diseases and creation of steady cultivars continue to remain
actual for selectionists. Laboratory methods of estimation have a considerable impor-
tance for the acceleration of plant-breeding work on the selection of steady cultivars.
Often they are express methods, because they provide the information in a very short
time period, and the estimations of stability are performed at all stages of organogen-
esis of plants.
Crop-growing conditions in different areas of the Tyumen region are formed un-
evenly. The climate is affected by cold air masses from the Arctic Ocean and from Si-
beria, as well as by dry winds blowing from Kazakhstan and Central Asia. The climate
is typically continental, and all the climatic factors vary greatly over the years, both in
strength and duration. There are elements of the climate similar to the western region
(dry summer periods), circumpolar areas (very short and cold growing season), and
the deserts of the south (dry, oppressive weather from spring to fall) [1].
Harsh cold winters, relatively short summers, short springs, and autumns, a small
frost-free period, and sharp changes in temperature during the year and even during
the day characterize agricultural areas of the Tyumen region. One of the causes of the
yield decrease in agricultural crops, including cereals, is the growth of infection of the
most dangerous diseases. Plants suffer from both pathogens belonging to soil patho-
logical complex (root rot, Fusarium wilt, etc.) and air-spread infections (rust, Septoria ,
smut disease, powdery mildew, etc.) [2].
Phytopathogenic fungi of the genus Fusarium belong to the most dangerous among
more than 350 species of toxigenic fungi known in agriculture [3]. It is shown that the
contamination of seeds of spring wheat can occur both in the hidden and explicit form,
and to a large extent it is determined by the varietal characteristics [4].
11.2 MATERIAL AND METHODOLOGY
Fungi were singled out from seven genera of pathogenic microflora of grains of spring
wheat, barley, and rye cultivars of different eco-geographical origin and different years
of harvest. Of these genera, Alternaria , Helminthosporium , Trichothecium , Tilletia ,
and Fusarium are representatives of field microflora; Mucor and Penicillium belong to
mold species. The fungal spores of the genus Alternaria dominated on most grains of
all cultivars. Pathogens from the genera Helminthosporium and Fusarium of the most
harmful type, causing root rot and spot, were detected.
An index characterizing the development of disease was calculated as follows:
, where i and ai are degree of damage and the corre-
sponding number of ill seedlings, respectively; N is the amount of plants in a test; and
k is the maximum degree of damage [5-7]. Degree of damage was set according to
the scale of Rusakov and Strachov as follows: 0—no damage; 1—below 10 percent of
seedling surface is damaged; 2—11-25 percent; 3—26-50 percent; 4—more than 50
percent of plant surface is damaged.