Using soybean starting material in breeding process

. The paper evaluates new promising soybean varieties and their parental forms with high yield, seed quality, and resistance to diseases and the stress conditions of Primorsky kray for a number of traits. The soybean accessions were used in a breeding program for constructing genotypes. Based on the research results, we selected promising soybean varieties characterized by a high yield and a high content of protein and oil in seeds. The yield of varieties Primorskaya 1670 and Primorskaya 1672 exceeded the standard by more than 32.2%. Varieties Primorskaya 1551 and Primorskaya 1674 had a high oil content in seeds – 23.8% and 24.1%, respectively. Variety Primorskaya 1659 was characterized by a high content of protein (41.2%). The parental forms used in the breeding of the new varieties were evaluated for a number of economically important traits. The yield of the starting forms ranged from 0.149 to 0.405 kg/m2. It was determined that 69.5% of the soybean accessions belonged to the group with mid-season maturity. A high content of protein in seeds (> 40.0 %) was detected in varieties of various origin – Primorskaya 13, Hefeng 25, NIISKH 2, XN 4, Arisa, and Kioto; variety NIISKH had a high oil content (24.2%). Varieties NIISKH 6, D 402-HH51, Arisa, NIISKH 5, XN 8, and XN 4 demonstrated a high potential adaptability to stress conditions.


Introduction
Soybean is a strategic crop, whose production and consumption increase every year.The crop has to meet certain requirements as well, e.g.high yield, adaptability to weather and soil conditions, and resistance to diseases and stress factors [1][2][3].Breeding is a mechanism for combining a number of desirable traits in one genotype [4,5].Soybean breeding aimed at improving varietal properties is based on the heredity of genetic information (hybridization).For this reason, it is necessary to select correct parental (starting) forms for crossbreeding when creating new soybean varieties [6][7][8].Usually parental forms are the collection material that was tested in certain growing conditions for many years [9][10][11].Due to a low yield and adaptability, incompatibility between biological and genetic characteristics, not all soybean accessions should be used in breeding [12,13].
The soybean collection of FSBSI "FSC of Agricultural Biotechnology of the Far East named after A.K. Chaiki" is regularly replenished with new specimens of various geographical and environmental origin and studied for a number of economically important traits.Annually the best specimens are used in breeding programs for the creation of new soybean varieties with a high yield, an increased content of protein and oil in seeds, and resistance to environmental factors of Primorsky kray.
This defined our research objectives: -evaluating created promising soybean varieties and their parental forms for economically important traits and adaptability to the conditions of Primorsky kray; -assessing the resistance of soybean varieties from the collection to fungal pathogens in natural infectious conditions; -determining the potential adaptability and resistance of the parental soybean forms to stress under the conditions of Primorsky kray.

Materials and methods of research
New promising soybean varieties were studied in 2021-2022, varieties from the collection (parental forms) -in 2002-2007 and 2009-2016 by the Laboratory of Soybean Breeding at FSBSI "FSC of Agricultural Biotechnology of the Far East named after A.K. Chaiki" near Ussuriysk.

Soil and climatic conditions
Over the years of our research, weather conditions were contrasting allowing a more objective evaluation of the promising soybean varieties.According to the data of the meteorological station "Timiryazevsky" (FSBI "Department of Hydrometeorology and Environmental Monitoring of Primorsky kray"), the weather conditions of 2021 differed significantly from the long-term annual average -high temperatures in combination with a long drought period negatively affected the yield of the crop.A comparison to the long-term annual average precipitation revealed that monthly rainfall from June to September was lower by 2.3-54.7 mm.The lowest precipitation occurred in the second ten-day period of August (3.8mm compared to a long-term annual average of 43.0 mm) and in the first ten-day period of September (2.4 mm compared to 41.0 mm).The conditions of 2022 were characterized by excessive rainfall.Monthly rainfall from June to September exceeded the long-term annual average by 24.7-101.0mm.The highest precipitation was noted in the third ten-day period of June (78.8mm compared to a long term annual average of 25.0 mm), in the second tenday period of July (163.4mm compared to 38.0), and in the third ten-day period of August (81.7 mm compared to 45.0 mm).The favorable combination of the high moisture level and warmth positively affected soybean yield.The weather conditions over the years of our research were diverse but they generally facilitated the growth and development of soybean plants.

Field experiment
The research was conducted on soybean varieties from the collection and promising varieties of FSBSI "FSC of Agricultural Biotechnology of the Far East named after A.K. Chaiki".Mid-season variety Primorskaya 4, which was admitted to use in the Far Eastern region, was E3S Web of Conferences 462, 02009 (2023) AFE-2023 https://doi.org/10.1051/e3sconf/202346202009used as the standard.The research was set up according to the methodology of field experiment [15].Soybean was grown using the agricultural technology commonly accepted in Primorsky kray [16].The seeding rate was 500 thousand seeds per hectare.The area of one field plot was 22.0 m 2 for the promising varieties and 1.8 m 2 for the soybean varieties from the collection.Soybean was sown and harvested with agricultural machinery in the bigger plots and manually in the smaller plots.Economically important traits were evaluated and recorded in compliance with the methodology [17].The content of protein and oil in seeds was determined by the Laboratory of Agrochemical Analyses employing Inframatic 9200 (Perten Instruments AB, Sweden).
The resistance of the studied soybean varieties to fungal pathogens was assessed in natural infectious conditions.The damage caused by fungal pathogens (Septoria blight, Cercospora blight, and downy mildew) was visually evaluated and recorded at the developmental stages V5 and R6 based on the guidelines [18].

Statistical analysis
The statistical processing of the obtained data was performed by ANOVA using Microsoft Excel [15].
The assessment of the compensatory ability, stress-resistance, yield, and plasticity of the soybean varieties was conducted according to the methodology of A.A. Rossielle and J. Hemblin as presented by А.А.Goncharenko [19,20].The resistance of soybean varieties to stressful growing conditions (stress-resistance) was determined as a difference between the the minimum and maximum values of the parameter (Хmin-Хmax), the results were negative numbers.Additional parameters of stress-resistance -genetic plasticity and compensatory ability under contrasting (stressful and favorable) conditions -were calculated by the formula (Хmin+Хmax)/2.Genetic variability was characterized by the range between the minimum (Хmin) and maximum (Хmax) yield.The coefficient of adaptability (CA) was based on the comparison between the yield of each studied soybean variety and the average yield in a certain year of the research and calculated by the method of L.A. Zhivotkov et al. [21].

Created promising soybean varieties
Based on the results of our research on soybean breeding material, promising varieties were selected and studied for a number of economically important traits to be submitted for the state variety testing at FSBI "The State Commission of the Russian Federation for the Testing and Protection of Breeding Achievements" and to be introduced into agricultural production (Table 1).
A significant part of the promising soybean varieties in the experiment (71.4 %) belonged to the group with mid-season maturity (a growing period of 111-119 days).The studied varieties were characterized by a moderate plant height.Almost all the varieties exceeded the yield of the standard (Primorskaya 4) by 0.02-0.82t/ha.On average over two years, Primorskaya 1670 and Primorskaya 1672 had the highest yield and in 2022 it was 3.57 and 3.68 t/ha, respectively.The soybean varieties with a lower yield (compared to the standard) generated interest as the sources of certain traits needed in breeding programs.For example, Primorskaya 1659 had a relatively high content of protein and oil in seeds (41.2 %), Primorskaya 1674 was characterized by early maturity (by seven days earlier than the standard) and a high oil content (24.1 %).Variety Primorskaya 1673 should be noted for a small seed size (TKW -135 g), which is a desirable traits for seeds used in the production of sprouts.
Three varieties (Primorskaya 1659, Primorskaya 1666, and Primorskaya 1670) had a high TKW (above 200 g) and could be of value in the breeding programs aimed at creating soybean accessions with large seeds (Table 1).All the studied varieties exceeded the standard in terms of the protein content by 0.1-3.6 % but only Primorskaya 1551 and Primorskaya 1674 had a higher oil content.The tested varieties were characterized by moderate resistance to Septoria blight and high resistance to downy mildew and Cercospora blight.
This set of promising soybean varieties was obtained through the hybridization of the best accessions from the collection.The hybridization of and study on starting (parental) forms were conducted in different years (Table 2).Some soybean varieties were represented by sixteen hybrid combinations and had genotypes created in a more recent (2017) and earlier period (2005).

Complex evaluation of starting soybean material
The best parental forms were selected for a number of economically important traits during our research on the soybean collection in 2002-2007 and 2009-2016 to be used in our breeding program (Table 3).Table 3 presents the three-year averages for the traits of the selected parental forms.On average over three years of the research, soybean yield varied from 0.149 to 0.405 kg/m 2 , variety NIISKH 6 had the highest yield and variety Dong nong 690 showed the lowest result due to small seeds (TKW -100 g).Large seeds were characteristic of Chinese varieties mostly (TKW from 202 to 233 g).The group with mid-season maturity included 69.5 % of the studied soybean varieties, the rest were medium-late with a growing period of 120 days and longer and only Dong nong 690 was a medium-early variety.The protein content was higher than 40.0 % in seeds of the following soybean varieties Primorskaya 13 (Russia); Hefeng 25, NIISKH 2 and XN 4 (China); Arisa and Kioto (Canada).Chinese variety NIISKH 6 stood out for a high oil content (24.2 %).
When comparing the economically important traits of the parental forms to the ones of the newly created soybean genotypes (promising varieties), it could be observed that a parameter value inherited by the progeny was the average between the parameter values of its two parental forms.The absolute inheritance of the highest parameter values was not typical for this set of varieties.
A breeding program requires evaluating starting soybean material for resistance to the most dangerous fungal pathogens in the Far Eastern region (Figure).In our research, the immunological status of soybean was assessed using the methodology of N.I.Korsakov [17].According to the scale, four varieties (Primorskaya 1385, NIISKH 3, NIISKH 6, and D 433-GY22-CJY) were characterized by high resistance to Septoria blight (Septoria glycines Hemmi); the infection rate did not exceed 25.0 % in their case.One accession (XN 2) was determined to be sensitive to the pathogen, and the rest were moderately resistant.Resistance to downy mildew (Peronospora manshurica (Naum.)Syd.ex Gaum.) was noted in 69.5 % of the studied varieties; the infection rate was lower than 20.0 %.Variety XN 2 had the highest potential susceptibility to the mixed infection (Septoria blight and downy mildew).All the varieties displayed high resistance to Cercospora blight (Cercospora sojina Наrа), except for four accessions -Venera and Primorskaya 1385 (Russia), XN 2 and XN 6 (China), which were moderately resistant.
The highly resistant soybean varieties can be the sources of resistance to the local populations of the fungal pathogens in a breeding program.Considering the contrasting nature and specificity of the climatic conditions in Primorsky kray, it is necessary to evaluate the adaptability of starting soybean accessions to weather conditions and to determine the statistical parameters that influence the resistance of parental forms to biotic and abiotic stress factors.The following soybean varieties had high resistance to stress conditions: NIISKH 6, D 402-HH51, and Arisa (whose parameter value was -0.006), NIISKH 5 (-0.013),XN 8 (-0.015), and XN 4 (-0.019)(Table 4).The highest genetic variability and the lowest stress-resistance (from -0.080 to -0.175) was characteristic of XN  The highest genetic plasticity (from 0.282 to 0.405) was observed in Taifun, Primorskaya 1385, Kofu, and NIISKH 6, whose parameter values reflected their high compensatory ability under contrasting growing conditions.
The coefficient of adaptability provides objective and accurate information about the adaptive potential of a particular variety under certain growing conditions.In our research, the coefficient of adaptability varied from 74.5 to 165.3 %; it was higher than 132.0 % in nine soybean varieties and the highest in Taifun, Kofu, and NIISKH 6.

Discussion
Soybean is a popular protein and oil crop due to a wide spectrum of its use.This crop is a valuable food source , which means that consumer requirements influence the breeding of new soybean varieties [22].The main parameters of a variety are yield, the qualitative composition of seeds, adaptability to weather and soil conditions in a certain region, and  [23].For this reason, when creating new varieties, it is necessary to pay attention to the analysis of starting material and subsequent goal-oriented selection of promising forms, which will be then used for constructing a genotype [24,25].
The results of our research on the promising soybean varieties showed that the majority of them belonged to the group with mid-season maturity.The yield of varieties Primorskaya 1670 and Primorskaya 1672 was the highest in the experiment -they produced 3.57 and 3.68 t/ha, respectively, in the year with high precipitation and temperatures (2022).A study conducted in the southern forest-steppe of the West Siberia supported the hypothesis that high precipitation and temperatures were required for the formation of high soybean yield [26].
The promising soybean varieties were obtained through hybridization -an effective and widely used method for breeding various crops [27].Evaluating the parental soybean forms revealed that Chinese and Canadian varieties were mainly characterized by high parameter values.Similar results were obtained by researchers when studying the soybean collection under the conditions of Amur Oblast [28].
The most dangerous fungal diseases of soybean in the Russian Far East and the West Siberia are Septoria blight, Cercospora blight, and downy mildew [29].Based on the immunological evaluation, the studied varieties were classified as highly and moderately resistant to these pathogens.
The potential adaptability of the starting soybean forms to the conditions of Primorsky kray was high enough in varieties with high and moderate yield.The results of a research conducted in Tyumen oblast demonstrated the opposite, i.e. accessions with a lower yield had higher stress-resistance [30].

Conclusion
Based on the results of the conducted research on starting soybean material, promising soybean varieties were selected for a number of economically important traits.Compared to Primorskaya 4 used as the standard, varieties Primorskaya 1670 and Primorskaya 1672 a higher yield (> 32.0 %).Varieties Primorskaya 1674, Primorskaya 1673, and Primorskaya 1695 had a shorter growing period (105 and 109 days).Primorskaya 1673 generated interests for the production of sprouts due to a small seed size (TKW -135 g).Varieties Primorskaya 1659, Primorskaya 1666, and Primorskaya 1670 had a high TKW (higher than 200 g).Varieties Primorskaya 1551 and Primorskaya 1674 exceeded the standard in terms of the protein content by 0.1-3.6%,Primorskaya 1551 and Primorskaya 1674 -in terms of the oil content.A set of the promising soybean varieties was obtained through the hybridization of the best starting forms from our soybean collection.

Table 2 .
Origin of promising soybean varieties

Table 3 .
Characteristics of soybean parental forms, Primorsky kray

Table 4 .
Vitaz' 50, Taifun, and Kordoba.When the growing conditions were more favorable, they were able to produce high yield.Adaptability of soybean varieties