1. Introduction

Uzbek scientists have also conducted a number of scientific studies on the physiological and biochemical characteristics of soybean and other leguminous crops, as well as on the role of soybean in improving soil fertility [1,2,10]. Soybean seeds are of particular importance due to their content of 28-52% protein enriched with high-quality amino acids, making them comparable to essential food products such as meat, milk, and eggs. Additionally, they contain 18-27% environmentally friendly vegetable oil, various mineral salts, and vitamins. At present, the area under soybean cultivation is steadily increasing [3].

The main reason for the widespread cultivation of soybean in many countries is its nutritional value, as both its grain and green mass can be used in food, feed, industrial, and medical sectors. Depending on the variety and growing conditions, soybean seeds contain 30-55% protein and 17-26% oil. Additionally, soybean seeds have 20-25% carbohydrates, over 4-5% minerals (including Ca, P, K, Na, I, Mo, and others), as well as vitamins such as E, B1, B2, and B6 [4,5]. More than a thousand products are derived from soybeans. Soybean is considered one of the main crops in the production of feed protein, oil, meal, and compound feed [6,7]. It is well known that mutation breeding is an effective method for improving valuable agronomic traits in agricultural crops, including enhancing both the quality and quantity of yield. Using this effective approach, Geehan Mohsen (2023) and others conducted studies aimed at increasing the protein and oil content, as well as the yield of soybean. In their research, seeds of the soybean genotypes Giza 21, Giza 22, Giza 82, Giza 83, and 117 were treated with gamma radiation at doses of 50, 100, 200, and 300 Gray before sowing. In subsequent field experiments, these soybean genotypes were evaluated for yield-related morphological traits, as well as characteristics such as seed weight, protein content, and oil content. The results showed that in the M3 mutant lines, gamma irradiation at a dose of 100 Gray had a positive effect on yield traits compared to the parent plants. Gamma irradiation at a dose of 100 Gray was found to have a particularly positive effect on traits such as the number of fruiting branches, pods, and seeds per plant, as well as the protein content in the seeds. Gamma irradiation at a dose of 200 Gray was also reported to have a positive effect on traits such as plant height, number of pods, and oil content [8].

An analytical article on induced mutagenesis in soybean was published by Mudasir Hafiz Khan and Sunil Dutt Tyagi (2013). In this article, it is stated that mutations identified through induced mutagenesis in soybean have been extensively covered in various publications. It is emphasized that mutation breeding is more widely applied compared to other breeding methods in agricultural crops and has proven effective in developing new forms with valuable traits. The effectiveness of this method is also characterized by the induction of new mutant forms in different crops, leading to the development of new varieties. The article focuses on providing a comprehensive review of the scientific studies conducted on induced mutagenesis in soybean, based on available literature. In addition, the review article provides detailed information on different mutagens that cause mutations, their positive effects on soybean yield and seed quality, and other mutagens that enhance resistance to various diseases [9].

The aim of this study is to investigate the effects of treating seeds of certain soybean varieties from the botanical and genetic collection with gamma (Ƴ) radiation at doses of 50, 100, 200, 300, and 400 Gray before sowing, focusing on their impact on the morphological and agronomic traits of soybean.

2. Materials and Methods

The experiments were conducted at the Durmon field trial site of the Institute of Genetics and Experimental Plant Biology, Academy of Sciences of Uzbekistan. As research materials, soybean varieties Nafis, Genetik-1, Selecta-302, Sochilmas, Khotira, Gen-8, Gen-9, Gen-25, BK-6, and Kol-17, available at the "Leguminous, Oilseed, and Medicinal Plants Genetics, Breeding, and Seed Production" laboratory, were used. Before sowing, the soybean seed samples were treated with gamma (Ƴ) radiation at doses of 50, 100, 200, 300, and 400 Gray. The treatment of soybean seeds with various doses of gamma radiation before sowing was carried out by expert scientists from the Institute of Nuclear Physics, Academy of Sciences of Uzbekistan. All experiments were repeated three times, and the obtained data were analyzed using the ANOVA STATGRAPHICS statistical software.

3. Results and Discussion

In the field experiments, for each soybean variety, 20 seeds were sown for both the control and treatment variants (50, 100, 200, 300, and 400 Gray). The germination of M1 plants, whose seeds were treated with different doses of gamma (Ƴ) radiation before sowing, was comparatively studied in both control and treatment variants. In the control variant of the experiment, the germination rate of the plants ranged from 75% to 97%. The highest rate was observed in the Genetik-1 variety at 97%, while the lowest rate was recorded in the Khotira variety at 75%. In the treatment variant where seeds were exposed to a 50 Gray dose before sowing, the number of germinated plants was somewhat lower compared to the control, ranging from 55% to 72%. In the variant treated with a 100 Gray dose of gamma (Ƴ) radiation, the highest germination rate was observed in the Ehtiyoj variety at 58%, while in the Kol-17 sample, this rate was 47% (Fig. 1).

Figure 1. The effect of gamma (Ƴ) radiation on the germination of different soybean varieties and samples

As seen from the data presented in Figure 1, it can be observed that as the dose of physical mutagen treatment increases, the germination rate decreases. Under the influence of the 200 Gray dose of gamma (Ƴ) radiation, germination in various soybean varieties and samples decreased by up to 50% in some samples, while in others, a slight reduction in germination was observed. A significant decline in germination was recorded in the samples treated with the 400 Gray dose, where germination dropped by up to 67%. However, the ability of M1 plants to maintain germination even under the influence of high doses of gamma radiation provided an opportunity to select genotypes as effective sources for further research. Among such genotypes are the Genetik-1 and Selecta-302 varieties (Figure 1). During the study, various soybean varieties and samples were analyzed for certain morpho-agronomic traits, including plant height, number of nodes per plant, number of pods, and number of productive branches. These traits were examined in both the control variant and in variants where the seeds were treated with 50, 100, 200, 300, and 400 Gray doses of gamma (Ƴ) radiation before sowing. According to the results, the plant height in the control variant ranged from 66.0 cm to 154.0 cm. The highest values for plant height were observed in the Ehtiyoj, BK-6, and Gen-25 varieties, with respective measurements of 131.0 cm, 136.0 cm, and 154.0 cm. The lowest plant height was 66 cm, corresponding to the Genetik-1 variety of soybean (Fig. 2).

Figure 2. Indicators of plant height, number of nodes, number of pods, and number of productive branches in the control variant of the experiment

The number of nodes varied in different samples, ranging from 10.8 to 24.0. The highest value for this trait was observed in the Nafis variety (24.0), while the lowest was recorded in the Genetik-1 variety (10.8). The studied soybean varieties also differed from each other in terms of the number of pods per plant. The number of pods per plant in the examined samples ranged from 18.75 to 67.8.

During the study, certain morpho-agronomic traits were analyzed in the varieties treated with a 50 Gray dose of gamma (Ƴ) radiation before sowing. According to the results, in this variant of the experiment, the plant height was 17 cm higher in the Selecta-302 variety and 10.25 cm higher in the Gen-8 variety compared to the control. The number of nodes per plant in the Genetik-1 variety, under the influence of a 50 Gray dose of gamma (Ƴ) radiation, was 15.75, while in the control variant of the experiment, this indicator was 10.8. No significant differences were observed in the other variety samples. When analyzing the number of pods per plant, it can be observed that in almost all of the studied soybean variety samples, the number of pods increased compared to the control. The highest increases were observed in the Selecta-302, Khotira, and Ehtiyoj varieties, with the number of pods rising to 137.5, 80.1, and 45.65, respectively. It can be concluded that as a result of the significant effect of gamma radiation, the number of pods per plant increased in soybeans. No significant differences were observed in the yield branch trait per plant (Fig. 3).

Figure 3. Indicators of plant height, number of nodes, number of pods, and number of productive branches in the variant treated with a 50 Gray dose of gamma (Ƴ) radiation in the experiment

During the research, some morphological traits were analyzed in the variant treated with a 100 Gray dose of gamma (Ƴ) radiation. According to the obtained results, no significant differences were observed in plant height between the experimental variant and the control. The main reason for this is that the effect of gamma radiation did not significantly affect the plant height trait. As for the number of nodes per plant, significant differences were observed in the varieties Selecta-302 and Sochilmas under the 100 Gray gamma radiation dose, while no such differences were found in the other varieties. In the varieties Selecta-302 and Sochilmas of soybean, an increase in the number of nodes was observed, with increases of 2.8 and 3.25 nodes, respectively, compared to the control (Fig. 4).

Figure 4. Indicators of plant height, node number, pod number, and productive branch number in the variant treated with 100 Gray dose of Ƴ-gamma rays

The indicators of pod number per plant were also analyzed in the variant of the experiment treated with 100 Gray doses of Ƴ-gamma radiation. According to the analysis results, the pod number per plant in the studied soybean varieties increased compared to the control for Nafis (72.0 pods), Sochilmas (27.75 pods), and Gen-9 (42.5 pods). The differences in pod number per plant in these samples compared to the control were 4.2, 9.0, and 8.5 pods, respectively. An interesting fact is that in the variant treated with 50 Gray doses of Ƴ-gamma radiation, the pod number per plant also showed significantly higher values compared to the control (figure 4).

In the variant treated with 200 Gray doses of Ƴ-gamma radiation, the indicators of plant height, the number of nodes, pods, and productive branches per plant were compared and analyzed against the control variant. According to the results, the plant height trait in the soybean varieties Genetik-1 (103.67 cm), Selecta-302 (108.0 cm), and Sochilmas (115.0 cm) showed higher values compared to the control, with differences of 37.67 cm, 5.0 cm, and 28.75 cm, respectively.

In this variant of the experiment, the node number per plant in the studied soybean varieties and samples was also analyzed. According to the analysis results, physical mutagens only affected the Genetik-1 and Sochilmas varieties. The node number per plant in the Genetik-1 variety was 12.33, while in the Sochilmas variety, this indicator was found to be 16.0. The differences compared to the control variant were recorded as 1.53 and 3.25, respectively (Fig. 5).

Figure 5. Indicators of plant height, node number, pod number, and productive branch number in the experimental variant treated with 200 Gray dose of gamma radiation

During the research, some morphological characteristics of the soybean samples treated with a 300 gray dose of γ-rays were analyzed. According to the results obtained, the plant height indicator generally showed lower values compared to the control variant. Only in the Gen-8 variety did the plant height reach 160.0 cm, showing a difference of 36.0 cm compared to the control. No significant differences were observed in the other studied samples. It should be noted that during the experiment, the plants of the Ehityoj and Gen-25 soybean varieties treated with a 300 gray dose of γ-rays perished during the vegetative period. This can be explained by the strong effect of physical mutagens at high doses (Fig. 6).

Figure 6. Indicators of plant height, number of nodes, number of pods, and number of productive branches for the soybean varieties treated with a 300 gray dose of gamma rays

During the research, the number of nodes per plant in the soybean varieties treated with a 300 gray dose of gamma rays was also analyzed. The analysis results showed that the number of nodes per plant in the soybean varieties Sochilmas and Gen-8 exhibited higher indicators compared to the control, with differences of 3.25 and 3.0 nodes, respectively. No significant differences were observed in the other soybean varieties studied. The number of pods per plant was also analyzed. The analysis results showed that the number of pods per plant exhibited significant positive differences when compared to the control variant. Specifically, in the soybean variety Selecta-302, the number of pods in the control variant was 35.0, while in the variant treated with a 300 gray dose of gamma rays, this indicator increased to 52.1. In the soybean variety Sochilmas, the number of pods was 101.5, in Gen-8 it was 130.0, in Gen-9 it was 85.0, and in the BK-6 variety, it was 84.0. The differences compared to the control variant were as follows: in Selecta-302, +17.1 pods; in Sochilmas, +82.75 pods; in Gen-8, +80.6 pods; in Gen-9, +51.0 pods; and in BK-6, +39.8 pods. These positive results in the number of pods per plant in the studied soybean varieties can be attributed to the effect of the 300 gray dose of gamma radiation (Fig. 6).

During the research, the morphometric indicators of the varieties treated with a dose of 400 gray of Ƴ-gamma rays were analyzed by comparing them with the control group of the experiment (Fig. 7).

Figure 7. Indicators of plant height, number of nodes, number of pods, and number of productive branches in the variant treated with a dose of 400 gray of Ƴ-gamma rays in the experiment

The data presented in Figure 7 show that under the influence of a 400 gray dose of gamma rays in the experiment, only the plants of the varieties Gen-8, Gen-9, BK-6, and Kol-17 survived. The plants of the remaining varieties were destroyed. This situation occurred due to the effect of high doses of physical mutagens. In this experimental variant, a positive difference in plant height was observed only in the Gen-9 variety, with an increase of +16.0 cm. As for the number of pods per plant, differences were observed in the Gen-8, BK-6, and Kol-17 varieties, with changes compared to the control group being +31.11, +41.98, and +11.0, respectively.

4. Conclusions

Thus, in the experiment with control and pre-sowing variants treated with Ƴ-gamma rays at doses of 50, 100, 200, 300, and 400 gray, it was observed that as the dose of physical mutagens increased, the productivity decreased. In the studied soybean varieties, a significant decrease in productivity was observed in the variants treated with a 400 gray dose of Ƴ-rays, where productivity decreased by up to 67%. However, even under the influence of the high dose of gamma rays in the M1 plants, the retention of productivity provided the possibility of identifying genotypes for further research as a valuable source. In the experiment, various morphological traits, including plant height, number of nodes, number of pods, and number of yield branches per plant, were analyzed for variants treated with different doses of Ƴ-gamma rays before sowing and in the control group. The results showed that the physical mutagens had varying effects on the morphological characteristics of the studied soybean varieties. Specifically, a 50 gray dose of Ƴ-gamma rays had an impact on plant height and the number of nodes per plant, a 100 gray dose influenced the number of nodes and pods per plant, a 200 gray dose affected plant height and the number of nodes per plant, a 300 gray dose influenced plant height and the number of pods per plant, and a 400 gray dose positively affected plant height and the number of pods per plant. These positive effects were observed in comparison to the control variants of the experiment. Based on the positive indicators, M2 generation seeds were collected from the plants for further research.

ACKNOWLEDGEMENTS

This article was prepared based on scientific research conducted within the framework of state scientific programs of the Academy of Sciences of the Republic of Uzbekistan, which is funded by the state budget of the Republic of Uzbekistan.

Conflict of Interest

The authors of this article have no conflicts of interest.