Source material for breeding soft winter wheat in the forest-steppe of the Middle Volga region

The source material is the initial link of the selection process of any crop. A careful study of it in specific environmental conditions largely determines the effectiveness of breeding activities. The paper presents the results of a study of 102 cultivars of soft winter wheat of various ecological and geographical origin in terms of the yield, winter hardiness, the plant height, the duration of the growing season, the resistance to the frit fly. The sources of individual and a complex of economically valuable indicators were identified and recommended as the source material for breeding use in the forest-steppe conditions of the Middle Volga region. In the winter wheat selection for high winter hardiness, the varieties Omskaya 6, Bagrationovskaya, Novosibirskaya 32, Novosibirskaya 51, Biyskaya Ozimaya, Filatovka, Kulundinka, Poema (Russia), Banga (Latvia), Emoile (Bulgaria), Myropol, Mykolayvka, Dashenka, Kalyanova, Lytavinka, Vinnychanka, Manzheliya, Khersonska bezostaya (Ukraine), Xiao Yan 107, Zhong Pin 1535 (China) are of great interest. Highly productive varieties are Victoria 95, Poema, Biyskaya Ozimaya (Russia), Zamozhnist, Kalyanova, Yasnogorka (Ukraine). Varieties Vdachna, Shestopalivka, Myropol (Ukraine), Svilena, Emoile (Bulgaria), KS 96 WGRC 37, KS 96 WGRC 40, Pacer (USA), Kitami 46 (Japan) XiaoYan 6, Ji Mai 30, Ji Mai 36 (China) are characterized by early ripeness. Short-stalked wheat varieties are Cameo (Russia), Ninka (Ukraine), Ji Mai 18 (China), Kitami 35 (Japan). Highly resistant varieties to the frit fly are Donskaya 50, Dominanta, Poema (Russia), Yasnogorka (Ukraine), Orienta, KS 96 WGRC34, KS 96 WGRC40 (USA), Xiao Yan 7, Zhong Pin 1507, Zhong Pin 1535 (China), Kitami 35 (Japan). Reliable correlations between winter hardiness and productivity, winter hardiness and plant height, plant height and productivity of soft winter wheat were established, which is of practical importance both for crop breeding and for its production use.


Introduction
Soft winter wheat is one of the leading crops in agriculture in the Ulyanovsk region, which is located in the forest-steppe zone of the Middle Volga region. In some years (2009,2011,2015,2019,2020), its sown area exceeded 250 thousand hectares, which is more than 25.0% of the total sown area of agricultural crops [1]. The varietal composition of soft winter wheat cultivated in the region does not completely provide the desired level of grain yield of this crop and its stability, which is primarily associated with insufficient resistance to unfavorable environmental factors.
In this regard, the demand for new varieties with a complex of valuable indicators and capable of producing high yields in variable environmental conditions is constantly increasing [2]. Well-studied initial material is required to create new varieties.
At the same time, special attention should be paid to the expansion of the genetic diversity of crossed forms, which will make it possible to increase the productivity of breeding achievements significantly, to overcome the vulnerability of agricultural crops to biotic stresses and expand their adaptation to changing environmental conditions [3][4][5].
The purpose of the conducted studies was to investigate the range of soft winter wheat of various ecological and geographical origin by a set of indicators and to highlight the sources of economically valuable traits and properties as the source material for breeding soft winter wheat in the forest-steppe conditions of the Middle Volga region.

Materials and methods
Two sets of soft winter wheat cultivars (51 pcs. each) of various ecological and geographical origin from the collection of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources served as the material for the study. The plot area is 0.9 m 2 without replication. The predecessor is bare fallow. Sowing was carried out at the time recommended for the studied crop -from August 25 to September 5. The winter hardiness assessment, plant height, phenological phases of growth and development of soft winter wheat and yield registration were carried out according to the techniques recommended for variety trials [6,7]. The variety Volzhskaya K was adopted as the standard one in the variety testing of soft winter wheat in the Ulyanovsk region during the years of studies.

Results and Discussion
The creation of a variety with the highest possible yield level is the ultimate goal of every breeder's work. This indicator serves as the main criterion for the effectiveness of any breeding program. At the same time, selection for the yield increase is one of the most difficult tasks, which is associated with the extraordinary complexity and complication of this indicator [8,9].
In all the years of studies, the level of productivity of soft winter wheat was influenced by stress factors of the winter period. In 2012 and 2013 arid conditions in the spring-summer growing season of the crop also played a negative role in the yield formation. Severe damage to winter wheat crops by the frit fly (Oscinella frit L.) was observed in 2012, which also negatively affected its yield. In various environmental conditions, the intervarietal yield differentiation was noticed among wheats from different countries of the world (Table 1).
Winter hardiness is one of the most important indicators for winter crops [10]. In case of favorable overwintering, they give a higher yield compared to spring crops. In connection with the tendency of climate warming, more and more often the factors causing damage and death of winter crops during winter in the Middle Volga region are the so-called "effects of mild winters"damping-off (probability is 40%), thaws, sudden temperature changes, ice crust (probability is 13%) [11]. In 2011, the ice crust had a damaging effect on winter wheat plants, and in 2012 and 2013 -damping off occurred.
Among the studied range of wheat of the world collection in the forest-steppe conditions of the Middle Volga region, Hungarian wheats were characterized by low winter hardiness (1.0-2.0 points) in both years of studies, medium and increased winter hardiness (3.0-4.0 points) showed varieties of Bulgaria, increased and high (4.0-5.0 points) -Russian wheats bred in Siberia (Table  1).
Winter hardiness differentiation was observed among wheat cultivars from Ukraine, Germany, Serbia, China, USA, Japan, Estonia, Latvia, and the North Caucasian region of Russia.  In the second set of wheat cultivars, the average value of overwintering according to the experiment of 2012 was 4.2 points (Table 1), which is higher than the value of the first set (3.5 points). The reason for this was the presence of Russian wheat varieties of Siberian selection in the second set with a high level of winter hardiness. The winter hardiness grading of cultivars in 2013 was low due to strong damping off (the average value in the experiment was 2.8 points). In almost 50% of winter wheat cultivars, winter hardiness was assessed  According to the classification proposed by V.F. Dorofeyev (1986), using the height of plants, the following groups of wheat are distinguished when growing in optimal agroclimatic conditions: tall (over 120 cm), medium-sized (120-106 cm), short-stalked (105-86 cm), semi-dwarf (85-61 cm), dwarf (60-41 cm) and super dwarf (up to 40 cm) [12].
In 2011, the height of the standard variety Volzhskaya K was 104 cm. At the same time, the height of wheat varieties from Germany, Hungary, Bulgaria, Serbia, Ukraine and China varied from 34 to 94 cm with an average value of 72 cm in the experiment ( Table 2  The height of plants of a variety of soft winter wheat is not only a criterion for its morphotype, but also have influence on many important economic and biological indicators. Correlation-regression analysis established a positive relationship between the winter hardiness of soft winter wheat cultivars and the height of their plants. Correlation coefficients in 2011, 2012 and 2013 were 0.57+0.12 (reliable at the significance level of 0.1%), 0.35+0.13, 0.38+0.13 (1, 2 sets, reliable at the significance level of 5%) and 0.72+0.11 (reliable at the significance level of 0.1%), respectively (Fig. 2).
Increased and high winter hardiness (4.0-5.0 points) was combined with the short stalk rate (height up to 85 cm) among wheat cultivars of the 1 st set -Myropol, Mykolayivka, Lytavinka, Vinnychanka, KhersonskaBezostaya, Manzhelija (Ukraine), Banga (Latvia), Emoile (Bulgaria), Xiao Yan 7, Zhong Pin 1535 (China), as well as the 2 nd set -Victoria 95, Cameo, Novosibirskaya 9, Lutescens 4, Poem (Russia), Krasen (Ukraine). In contrasting humidity conditions of the environment in the absence of lodging, change in the increase in the yield of winter wheat varieties with an increase in plant height was marked (Fig. 3). The correlation coefficients between the height of plants of soft winter wheat varieties and their yield were: in 2011 -0.58+0.12 (direct relationship, average strength, reliable at the significance level of 0.1%); in 2012 -0.53+0.12 (1 st set, direct relationship, medium strength, reliable at the significance level of 0.1%) and 0.31+0.14 (2 nd set, direct relationship, medium strength, reliable at the significance level of 5%); in 2013 -0.34+0.14 (direct relationship, medium strength, reliable at the significance level of 5%) (Fig. 3).
The established positive correlations are not absolute. This means that among short-stalked wheat varieties there can be varieties with high yields, and among tall ones, on the contrary, with low yields [13]. A high yield of short-stalked wheat varieties can be achieved, for example, due to good foliage, a long-lasting photosynthetic apparatus of plants, and a strong attracting ability during the period of grain filling. And vice versa, tall genotypes, having a good assimilating surface, can be characterized by weak attraction in the last growing season and, as a consequence, a low yield.
Dwarf wheat varieties Donskaya Lira (Russia) with a plant height of 45-46 cm and Yasnogorka (Ukraine), with a plant height of 53-58 cm, gave a yield of 256 g/m 2 and 316 g/m 2 , respectively, with a yield of the standard variety Volzhskaya K of 265 g/m 2 and the average yield value in the experiment of 183 g/m 2 ( Table  2). They are of interest both for production use, and as the source material for breeding soft winter wheat for a combination of short stalk and high productivity.  The duration of the growing season is an important biological, adaptive and economically valuable property of a plant variety of any crop [14,15]. In wheat breeding, the ear formation date is usually used to assess the ripeness group of a variety or a selection sample. The interphase period of sprouting -the ear formation in comparison with the period of sprouting-maturation is less variable, which makes it possible to consider the ear formation phase as a reliable criterion to determine the growing season of winter wheat varieties.
According to the scale of the International Classifier (1984), different groups of wheat ripeness are distinguished: medium early, early, very early, medium late, late, very late, with the ear formation of 2-3, 4-5, 6 and more days earlier or later than the mid-ripening standard variety. Wheats that form the ear simultaneously with the standard variety or 1 day earlier or later belong to the mid-ripening group [16].
Among the studied range of wheats of the world collection in the forest-steppe conditions of the Middle Volga region, German varieties were characterized by late maturity, with the ear formation of 6-8 days later than the standard one. Ukrainian varieties were represented by wheats of different ripeness groups. The late-ripening group of wheats included Akter and Compliment (Germany), in which the ear formation occurred 5-8 days later than the standard variety Volzhskaya K.
The varieties Dashenka, Kalyanova, Lytavinka (Ukraine), Victoria 95, Donskaya Lira (Russia) were characterized by early maturity (the ear formation 2-8 days earlier than the standard variety) and yield at the standard level (630, 367 g/m 2 and 162 g/m 2 in 2011, 2012 and 2013, respectively) or higher. In the group of mid-ripening wheats, the Manzhelija variety (Ukraine)in the studies of 2011, 2012 formed the yield at the level of the standard variety Volzhskaya K with 635 g/m 2 and 333 g/m 2 , respectively. Wheats of the middle-late and late-ripening groups were inferior to the standard wheat in yield.