Induced mutagenesis in breeding of spring barley (Hordeum vulgare L.)

Mutagênese induzida no melhoramento de cevada de primavera (Hordeum vulgare L.)

Abstract

The article presents the results of studies on the creation of new source material based on induced mutagenesis using the pulsed linear electron accelerator ILU-10. Test indicators of the most effective mutagenic effect of radiation treatment in the context of varieties were determined, and highly productive mutant lines were identified that were resistant to abiotic stress factors and retained these indicators in subsequent generations. The most valuable mutants were isolated among the forms obtained under the influence of absorbed doses from 100 to 150 Gy. The excess of productivity over the standard variety Syr Aruy for two years was 6.1 - 11.6 c / ha. Important distinguishing features were their tallness in combination with dense strong straw and resistance to lodging. In general, the reliable increase in yield was determined mainly by the grain weight per ear, due to better grain content per ear and 1000-grain weight. Studies have shown that the use of physical mutagenesis significantly reduces the time for breeding new varieties by direct propagation of mutant lines with a complex of positive traits.

Keywords:
barley; breeding; mutagenesis; line; selection; variability

Resumo

O artigo apresenta os resultados de estudos sobre a criação de novo material fonte com base em mutagênese induzida, usando o acelerador linear de elétrons pulsado ILU-10. Foram determinados indicadores de teste do efeito mutagênico mais eficaz do tratamento por radiação em diferentes variedades, bem como a identificação de inhagens mutantes altamente produtivas, resistentes a fatores de estresse abióticos e que mantiveram esses indicadores em gerações subsequentes. Os mutantes mais valiosos foram isolados entre as formas obtidas sob a influência de doses absorvidas de 100 a 150 Gy. O excedente de produtividade em relação à variedade padrão Syr Aruy por dois anos foi de 6,1 a 11,6 c/ha. Características distintivas importantes foram sua altura combinada com palha densa e forte e resistência ao acamamento. Em geral, o aumento confiável no rendimento foi determinado principalmente pelo peso dos grãos por espiga, devido ao melhor teor de grãos por espiga e peso de 1000 grãos. Os estudos demonstraram que o uso de mutagênese física reduz significativamente o tempo para o desenvolvimento de novas variedades por meio da propagação direta de linhagens mutantes com um conjunto de características positivas.

Palavras-chave:
cevada; melhoramento genético; mutagênese; linhagem; seleção; variabilidade

1. Introduction

Recently, the growth rate of agricultural crop yields has noticeably decreased, which is primarily explained by a qualitatively new environmental situation caused by global warming, which significantly affects the climate of the Kyzylorda region. Given the increasing intensity of global warming, climate change in general, the role of selection in creating stress-resistant varieties increases, where a special role is given to drought-resistant crops such as barley. Scientists note its important economic significance in arid climates (Zhou et al., 2008; Igartua et al., 2008). For practical selection, the Aral Sea region is of particular interest, from the point of view of conducting scientific research on the study of resistance to stress factors (Tokhetova et al., 2022; Tokhetova et al., 2020).

Breeders often face the problem of narrow genetic variability, which has led to the loss of alleles present in wild relatives. The reduction of varietal diversity not only reduces the resistance of agroecosystems to weather fluctuations, but also significantly increases their genetic vulnerability, which is based on the increase in the genetic uniformity of varieties and hybrids, which will lead to the disappearance of traditional local varieties and aboriginal forms and will ultimately threaten food security in the world. Therefore, the source material requires constant updating by introducing new useful genes into it. In achieving the set goals, along with the use of the potential of the world collection, intra- and interspecific hybridization, individual-family selection, induced mutagenesis is one of the effective breeding methods, which is considered throughout the world as a source of creating fundamentally new original forms, which allows expanding the possibilities of synthetic selection through the use of mutant forms in the hybridization process, possessing unique breeding-valuable traits (dwarfism, large grain, high adaptability to stress conditions, resistance to diseases and pests, etc.). In addition, the use of the experimental mutagenesis method reduces the time required to develop new varieties by 3-4 years, since mutant forms are not subject to splitting, which is typical for hybrid lines.

Modern mutagenic strategies mainly include physical, chemical mutagenesis. Physical mutagenesis methods include X-ray, gamma (γ) radiation, ultraviolet radiation, ion radiation (neutron and charged ion radiation) including ion and electron beams, laser, and space mutation with the development of aerospace technology (Ahloowalia et al., 2004). The first commercial mutant variety was Nicotiana tabacum developed in 1934 (Tollenaar, 1938; Oladosu et al., 2015). Later, disease-resistant mutants of Saccharum officinarum were successfully bred by several breeders by gamma irradiation and chemical mutagen treatment (Kaur et al., 2016). The yield of rice Oryza sativa has been significantly reduced worldwide by Pyricularia grisea disease, which causes necrotic lesions on leaves, nodes, seedlings, and panicles. Using the induced mutation method, a new combination of genes was created that did not previously exist in the germplasm pool. As a result, a new commercial rice variety with resistance to blast was bred (Miah et al., 2013). Using induced mutagenesis, 263 wheat varieties have been bred worldwide. The maximum varieties were bred using physical mutagens, followed by chemical mutagens. China bred the maximum number of mutant varieties, followed by the Russian Federation and other countries. Advances in induced mutagenesis can modify and characterize a single gene. Thus, using the TILLING and CRISPR genome editing systems, a wide range of allelic variability for agronomically important traits was created and characterized (Bakshi et al., 2021). Radiation mutagenesis is widely used in cotton growing. For example, cotton seeds irradiated with γ-rays were used to obtain heat-resistant and early maturing mutants (Maluszynski et al., 1995; Makhmadjanov et al., 2022). The cotton variety “Lumian 1” with high and stable yield was successfully developed by X-ray mutagenesis of the hybrid progeny of the lines “Zhongmian 2” and “1195”. In recent years, a number of mutants have also been obtained by space mutagenesis (Jia-He et al., 2002). For example, Song et al. (2012) obtained and characterized a leaf yellowing mutant by space mutation. Exposure of seeds to space environment may induce a new spectrum of genetic mutations and can be used in breeding programs. Wang et al. (2012) isolated and characterized one dwarf mutant by atomic energy mutation.

In recent years, many countries have shown interest in the peaceful use of atomic energy, in particular the treatment of agricultural products with ionizing radiation, which is the most modern method that meets the needs of today's agricultural market. It should be noted that in the last decade, the International Atomic Energy Agency of Austria IAEA has widely disseminated mutation methods for creating varieties in the Asian and Latin American regions and achieved very good results. Examples include the high-protein naked mutant barley variety Molina-5, cultivated in the Andes mountainous regions, and the rice variety Zhefu-802, which occupies more than 11 million hectares in China. The Green Revolution, largely based on the use of induced mutants, has doubled rice and wheat yields in developing countries (Dobrovolsky and Kubarev, 2009; Songmei et al., 2019).

The IAEA, in collaboration with the Food and Agriculture Organization of the United Nations (FAO) and the National Institute of Agricultural Sciences of Cuba (INCA), is implementing breeding programs using irradiation and biotechnology to create new crop varieties that can better adapt to growing conditions caused by climate change. Worldwide achievements in induced mutagenesis in crops clearly indicate the role of genotype in the mutation process: crops are classified as highly and low-mutable. Low-mutability crops include rye, oats and durum wheat, while highly-mutable crops include barley, rice and bread wheat (Wang et al., 2020). Induced mutations through physical and chemical mutagens or from cultured cells and tissues are another strategy for expanding the pool of genetic variability (Bo et al., 2019). As world experience shows, the possibilities of experimental mutagenesis in its simple, classical performance have already been largely exhausted, therefore, a constant search is underway for new mutagenic factors and methods of their effects for the identification of utilitarian genotypes. In this regard, at present, there is an urgent need to obtain, using new mutation methods, an original gene pool of the original and breeding material of the most important agricultural crops for the rapid and effective creation of energy-saving varieties. Thus, throughout the world, up to 2004 alone, more than 2,250 varieties were created, obtained either as direct mutants or from their progeny. Mutation induction using radiation was the most frequently used method for directly bred mutant varieties. The main strategy of mutation-based selection was to improve well-adapted plant varieties by changing one or two main traits that limit their productivity or increase the value of their quality. Many mutants have had a transnational impact on increasing the yield and quality of some crops (Thomas, 2020). For example, the high-yielding, low-growing mutant barley varieties “Diamant” and “Golden Promise” had a significant impact on the brewing industry in Europe. Mutants were also used as parents of many leading barley varieties. For example, more than 150 leading barley varieties in several countries in Europe, North America and Asia were derived from crosses involving Diamant. The gamma-induced Diamant variety was officially released in Czechoslovakia in 1965. Diamant was 15 cm shorter than the parent variety Vaticky and had a grain yield that was 12% higher. And already in 1972, 43% of the 600,000 hectares of spring barley in Czechoslovakia were sown with either Diamant or mutant varieties derived from Diamant. The total increase in grain yield is estimated at about 1,486,000 tons. During the same year, spring barley varieties that had the mutant Diamant's denso gene in their pedigree were grown across Europe on an area of ​​2.86 million hectares (Thomas, 2020).

Thus, induced mutations will continue to play an important role in the development of crop varieties with such traits as oil, protein and starch quality, increased absorption of certain metals, deeper root system and resistance to drought, diseases and salinity, which is a key component of environmental safety and sustainable agriculture (Bo et al., 2019). It should be noted that in the breeding work of scientists in the Aral Sea region, the only classical method for creating these varieties is intraspecific hybridization based on the “pedigri” method. Therefore, the expansion of breeding methods in the creation of fundamentally new source material based on induced mutagenesis, which significantly reduces the time for breeding new varieties by direct propagation of mutant lines with a complex of positive traits, has become the main focus of this research. Seed treatment with ionizing radiation was performed using a pulsed linear electron accelerator ILU-10 of the JSC “Park of Nuclear Technologies” (Kurchatov, East Kazakhstan Region). The aim of the research is to study the effectiveness of ionizing radiation on barley varieties of local selection, to solve methodological issues of mutagenic effects on plant ontogenesis, and to obtain promising mutants as source material for breeding varieties adapted to stressful, soil and climatic conditions of the Kazakh Aral Sea region. The scientific results will find wide application in theoretical and practical breeding, which will help to identify the genetic nature of complex polygenic traits and enhance the effectiveness of genetics and breeding projects in Kazakhstan. The research was carried out within the framework of the program-targeted financing of scientific research of the Ministry of Agriculture of the Republic of Kazakhstan under the scientific and technical program “Creation of highly productive varieties and hybrids of grain crops based on the achievements of biotechnology-genetics-physiology-biochemistry of plants for their sustainable production in various soil and climatic zones of Kazakhstan”, BR10765056, Agreement No. 111-2 dated September 30, 2015.

2. Objects and Methods of the Study

In 2015, seeds of two locally bred barley varieties, Syr Aruy and Inkar, were subjected to radiation treatment, 500 grains in each variant. The ILU-10 electron accelerator was used with the following parameters of the radiation treatment technological process:

• electron energy – 5 MeV;

• average electron beam current – ​​0.04; 0.08; 0.12; 0.16; 0.2 mA;

• conveyor beam section speed – 9 m/min;

• absorbed dose range – 50±10% Gy; 100±10% Gy; 200±10% Gy; 250±10% Gy.

The analysis of growth parameters was carried out in laboratory conditions by determining the germination energy, laboratory seed germination, measuring the length of roots and shoots of 10- and 15-day-old seedlings and other auxiliary parameters (Udovenko, 1968; VIR, 1989).

The sowing of treated and control seeds was carried out manually with a marker with row spacing of 15 cm in seven-row plots with an area of ​​1 ${\text{m}}^2$(Dospekhov, 1973). In subsequent years with an increase in the area of ​​plots depending on the number of seeds obtained (Figure 1).

Figure 1
Establishment of breeding nurseries for the study of mutant lines of barley.

Starting with the M₂ generation, we carried out individual ear selection. That is, we sowed each whole ear separately in a square-nest manner. Then, in the fourth generation after culling, we selected the best families and propagated them to the seventh generation. That is, we selected those lines that stably retained economically useful traits (Figure 2).

Figure 2
Square-nest method of sowing ears M3.

The studies were conducted in the Kyzylorda region of the Republic of Kazakhstan. Kyzylorda region is located in the south of the republic along the lower reaches of the Syr Darya River, occupies a significant part of the Turan Lowland with a flat relief. In the west it includes the northern and eastern parts of the Aral Sea, in the south - the northern part of the Kyzylkum Desert, in the north - the Aral Karakum, Aryskum and desert plateaus of the outskirts of Central Kazakhstan. The climate of the Kyzylorda region is sharply continental, hot dry summers and cold winters with unstable snow cover. The average annual air temperature is 9.8 ° C. The climate of the region is very arid. The average annual precipitation is 129 mm. In some dry years, only 40-70 mm can fall. The soil of the experimental site is meadow-marsh, typical for rice crop rotations of the region. The humus content is 1.73% and a high value of dense residue of 1.15%. Salinity type - sulfate, highly saline. Mechanical composition - medium loam (Table 1).

Table 1
Characteristics of the soil of the experimental site (research and production station of the Kazakh Research Institute of Rice Growing named after I. Zhakhaev, map No. 4).

Horizon (cm)	рН	Humus content %	Anions, %/mg-eq in 100g of soil			Cations, % / mg.eq in 100 g of soil			Total salts %	Type of salinization
			HCO3	Cl	SO4	Ca	Mg	Na
0-20	8.1 slightly alkaline	1.18	0.023	0.055	0.849	0.17	0.021	0.023	0.825	sulfate highly saline
			0.250	0.122	14.23	8.2	1.25	0.758
20-40	8.3 slightly alkaline	1.15	0.028	0.059	0.835	0.18	0.024	0.028	0.862	sulfate highly saline
			0.252	1.806	15.95	8.41	1.82	0.712

Global warming has a noticeable impact on the climate of the Kyzylorda region, in addition, the deficit of water resources, which is increasing from year to year, as well as salinization, depletion of the humus layer of local soils necessitate a reduction in rice crops with their replacement with other less water-consuming crops. As part of ensuring food security in our country at the government level, during a meeting of the operational headquarters for anti-crisis measures, the primary task was set as soon as possible to develop a Program for the selection of domestic drought-resistant varieties to reduce import dependence.

3. Results of the Research

The effect of radiation treatment of the seeds of the barley variety Syr Aruy on the industrial electron accelerator ILU-10 on the germination energy and germination of seeds was insignificant and their indicators in all doses were at the same level, with the exception of the first variant of seed treatment. It is interesting to note that with a minimum radiation dose of 50 Gy, a significant decrease in germination to 85.4% was observed, while in other variants with an increased dose this indicator was at the control level in the range from 94.4 -94.9%. A different pattern was observed for the barley variety Inkar, in which the laboratory germination decreased in direct proportion with an increase in the dose of ionizing radiation to 75.2% and the differences in comparison with the control were reliably significant. The study of the effect of ionizing radiation on the length of 10- and 15-day-old sprouts showed that as the absorbed doses increase, the length of 10-day-old sprouts decreases slightly to 12.6 and 9.8 cm in barley varieties, and the length of 15-day-old sprouts decreases to 14.9 and 11.3 cm, with 18.3 and 17.2 cm in the control variants, respectively, for the varieties Syr Aruy and Inkar. A similar picture is observed for the weight of 15-day-old sprouts and roots. The obtained data from the analysis of plant growth processes in the context of barley varieties at different levels of seed radiation treatment on the industrial accelerator ILU-10 are presented in Tables 2.

Table 2
Analysis of growth processes of plants of the barley variety Syr Aruy at different levels of radiation treatment of seeds on the industrial accelerator ILU-10.

Range of absorbed doses, Gy	Number of germinated seeds, unit (after 4 days)	Laboratory germination, %	Length of 10-day sprouts, cm	Indicators of 15-day sprouts
				sprout length, cm	mass of sprouts, g	root length, cm	mass of roots, g
50±10%	42.7	85.4±0,98	14.4±0,21	17.1±0.56	0.165±0.004	5.12±0.08	0,087±0.021
100±10%	47.3	95.6±0.56	14.2±0.46	17.4±0,53	0.171±0,009	7.07±0.15	0.123±0.015
150±10%	46.7	94.4±0.89	13.0±0.32	16.3±0.91	0.152±0.012	7.92±0.21	0.112±0.011
200±10%	46.3	96.9±0.57	14.5±0.51	17.8±0.89	0.167±0.003	7.96±0.27	0.128±0.018
250±10%	45.8	94.6±0.92	12.6±0.95	14.9±1.86	0.157±0.016	6.31±0.31	0.117±0.021
unprocessed	48.3	96.6±0.98	14.4±0.85	18.3±0.97	0.173±0.006	8.55±0.05	0.139±0.004

We also found that at a dose of 200±10% Gray, both varieties showed more intensive growth of seedlings, compared to other options, that is, a stimulating effect of this dose of mutagen on growth processes was noted, which indicates the effectiveness of using this radiation power for pre-sowing seed treatment, in order to accelerate the first phases of ontogenesis, reduce the vegetation period of barley varieties grown in rice crop rotation mainly as a cover crop for perennial legumes, which will allow obtaining a high yield in the stressful conditions of the Aral Sea region. Analysis of the growth processes of barley plants showed that the selected radiation doses did not have a lethal effect on barley seeds, however, in the process of ontogenesis, in particular, the radiation dose power of 250±10% Gray leads to reliable inhibition of the development of the sprout and roots, and subsequently to the death of the entire sprout. The loss of seedlings at this radiation dose was the highest and amounted to 65-70%. The data obtained indicate that the maximum permissible dose of barley irradiation using the ILU-10 industrial electron accelerator is the dose at an average electron beam current of 0.2 mA or 250 Gray. Varietal differences in the effect of the mutagen dose on laboratory seed germination were revealed, indicating the dependence of the effect of ionizing radiation on the genetic nature of the varieties.

Laboratory studies have revealed a reliable decrease in the length and weight of the roots with increasing radiation doses compared to the control variant, indicating significant differences between the experimental variants; therefore, these features can serve as one of the informative (test) indicators in assessing the effective doses of ionizing radiation (Table 3).

Table 3
Analysis of growth processes of barley variety Inkar plants at different levels of radiation treatment of seeds on the industrial accelerator ILU-10.

Range of absorbed doses, Gy	Number of germinated seeds, unit (after 4 days)	Germination rate, %	Length of 10-day sprouts, cm	Indicators of 15-day sprouts
				sprout length, cm	mass of sprouts, g	root length, cm	mass of roots, g
50±10%	42.2	84.4±0.87	13.5±0.51	16.5±0.15	0.152±0.009	6.15±0.12	0.119±0.012
100±10%	40.3	80.6±0.34	13.3±0.44	15.2±0.24	0.148±0.012	6.22±0.18	0.129±0.002
150±10%	40.8	81.6±0.29	13.0±0.52	14.8±0.32	0.144±0.015	6.57±0.04	0.127±0.004
200±10%	39.8	89.6±0.48	14.0±0.61	16.0±0.27	0.145±0.012	7.52±0.16	0.135±0.009
250±10%	37.6	75.2±0.31	12.9±0.91	14.5±0.31	0.140±0.019	5.15±0.09	0.108±0.018
unprocessed	48.7	97.4±0.23	13.8±0.34	17.2±0.29	0.157±0.003	9.27±0.04	0.151±0.009

Field studies considered factors such as field germination, plant survival rate, length of the vegetation period, the onset of the heading stage, productivity components, grain yield per unit area, and the range of modified forms in M1-2.

In М₁ plants of the Syr Aruy variety, the field germination fluctuations for the mutagenic effect variants ranged from 38.0% (250±10%) to 50.0% (50±10%) with the indicator for the original plants (control - non-irradiated seeds) being 69.3%. In М₁ plants of the Inkar variety, the field germination value varied from 33.6% (250±10%) to 44.8% (50±10%).

The survival of plants for harvesting in М₁ in the studied varieties did not differ significantly from the indicators of the control variant, and the doses applied did not have an inhibitory effect on plant survival. But during plant growth, mutagens had a stimulating effect on the duration of individual phases of ontogenesis, in particular on “sowing-earing” (Table 4).

Table 4
Effect of different doses of ionizing radiation on biological traits of plants of М_1-2 varieties of spring barley, (2016-2018).

Nº	Range of absorbed doses, Gy	Field germination, %	Plant survival rate for harvesting, %	Sowing-earing period, days	Growing season, days
Syr Aruy variety
	Initial variety - control	69.3	81.7	36	75
1. 1	50±10%	50.0	80.0	40	79
2. 2	100±10%	44.4	81.7	40	79
3. 3	150±10%	41.6	80.8	40	79
4. 4	200±10%	42.8	80.0	44	82
5. 5	250±10%	38.0	79.5	49	84
Inkar variety
	Initial variety - control	67.6	88.7	40	79
6. 1	50±10%	44.8	86.9	44	82
7. 2	100±10%	32.2	84.5	42	82
8. 3	150±10%	31.4	83.1	44	82
9. 4	200±10%	33.8	82.7	47	84
10. 5	250±10%	33.6	79.6	49	86

Thus, the duration of the “sowing-earing” period varied from 40 to 49 days for the Syr Aruy variety and from 42 to 49 days for Inkar. The latest onset of the earing phase was noted in the variant with a high radiation dose of 250±10%, in which the deviation from the control variant was 13 days (Syr Aruy) and 9 days (Inkar). Accordingly, this phenomenon was reflected in the final indicator of ontogenesis - this is the vegetation period. In the early-ripening Syr Aruy variety with a vegetation period of no more than 75 days, the duration of vegetation lengthened proportionally to the increase in the radiation dose from 4 to 9 days. A similar picture was observed in the mid-season Inkar variety.

In addition to visible changes in the biological development of plants, the use of mutagenesis causes the appearance of quantitative changes in various varieties and lines, which are the main criterion for the breeder's search. The results showed that the productivity of the M1 populations was significantly lower than that of the original varieties and also decreased proportionally with an increase in the dose of ionizing radiation (Table 5).

Table 5
The effect of different doses of ionizing radiation on the productivity of plants of М_1-2 varieties of spring barley (2016-2018).

Nº	Range of absorbed doses. Gy	Productive bushiness, unit/plant	Number of grains in an ear, unit	Weight of 1000 grains, g	Grain weight per ear, g/m2	±, deviation from control, g/m2
Syr Aruy variety
	Initial variety - control	1.7±0.04	24.7±0.92	45.0	504.9	0.0
11. 1	50±10%	2.1±0.03	21.1±0.53	45.8	379.9	-125.0
12. 2	100±10%	2.4±0.02	20.0±0.23	45.4	357.5	-147.4
13. 3	150±10%	2.8±0.03	19.8±0.08	46.0	337.3	-167.6
14. 4	200±10%	2.8±0.05	19.2±0.25	45.2	336.8	-168.1
15. 5	250±10%	3.3±0.06	16.5±0.87	46.0	318.1	-186.8
Inkar variety
	Initial variety - control	1.8±0.03	25.2±0.86	45.4	514.9	0.0
16. 1	50±10%	2.3±0.03	20.1±0.68	46.7	291.6	-223.3
17. 2	100±10%	3.5±0.04	16.0±0.74	47.9	268.7	-246.2
18. 3	150±10%	3.5±0.05	21.0±0.38	45.2	257.1	-257.8
19. 4	200±10%	3.8±0.04	21.2±0.57	45.9	254.2	-260.7
20. 5	250±10%	3.4±0.05	16.7±0.14	47.1	231.8	-283.1

Thus, the grain weight per 1 m² in Syr Aruy decreased by 125.0 g (50±10%) and 186.8 g (250±10%); in Inkar by 223.3 g (50±10%) and 283.1 g (250±10%), compared with the original genotypes.

It was revealed that the Inkar variety, compared with the Syr Aruy variety, significantly reduces productivity under the influence of mutagens, which indicates a significant contribution of the genotype itself, i.e. the dependence of the mutagen effect on the genetic nature of the genotype.

Different doses of ionizing radiation had a stimulating effect on productive tillering and 1000-grain weight, but slightly reduced the grain content of an ear (Table 3). Productive tillering in both varieties increased to 3.3 unit/plant (Syr Aruy) and 3.8 unit/plant (Inkar) with an increase in the radiation dose. Although ionizing radiation had a stimulating effect on increasing this trait, it led to the appearance of empty grains in ears of lateral shoots and their under-ripening. In general, the decrease in the productivity of barley varieties under the influence of different doses of ionizing radiation is caused, first of all, by low field germination due to inhibition of growth processes already in the germination (swelling) phase of the grain or their non-viability.

Throughout the growing season, work was carried out to select modified plants based on traits that differ from the original control variety. In the М₂ generation, modified forms were found: by density and shape of the ear, awns, plant height, branching of the ear and others (Table 6, Figure 3).

Table 6
Modified forms in М₂ in barley varieties under the influence of ionizing radiation.

Nº	Range of absorbed doses, Gy	Number of plants	Number of changes, units	Number of types of morphological changes, pcs
				Tall-growing	Short-growing	loose ear	erect ear	branching of ears	short awns	Ear with developed lateral spikelets	Total types of changes
Syr Aruy
21. 1	50±10%	250	2	-	1	-	-	-	-	1	2
22. 2	100±10%	222	7	-	-	-	4	-	1	2	3
23. 3	150±10%	208	5	1	-	2	1	-	-	1	4
24. 4	200±10%	214	6	2	-	1	2	-	1	-	4
25. 5	250±10%	190	24	5	3	4	8	1	-	2	6
26.	Inkar
27. 1	50±10%	224	3	-	-	2	-	-	1	-	2
28. 2	100±10%	161	4	-	-	-	3	-	1	-	2
29. 3	150±10%	157	6	2	-	2	-	-	-	2	3
30. 4	200±10%	169	8	3	-	2	2	-	-	1	4
31. 5	250±10%	168	23	12	-	3	2	1	1	4	6

Figure 3
Modification of the ear – branching: barley variety Inkar, option No. 5 – 250±10%.

In the second-generation populations, the variability coefficient increased by 1.5–2.5 times for different parameters and variants compared to the control. The detected altered forms were marked with flags and removed separately. Then, in laboratory conditions, the selection of ears with visible morphological changes was repeated. Each selected ear in 2018 was sown in a square-nest manner (hole/ear).

The main factor in the effectiveness of mutagenesis is the search for quantitative changes in mutant lines. As a result of the research, we identified populations that have a set of productive traits and, most importantly, have retained these indicators in subsequent generations. Since 2021, the selected lines have been studied as part of a control nursery on plots with an area of ​​10 m² (Table 7).

Table 7
Yield and grain quality of mutant spring barley varieties in the control nursery (2021 - 2024).

Standard variety and mutant lines	Growing season, days	Plant height, cm	Ear length, cm	Number of grains in an ear, pcs	Weight of 1000 grains, g	Grain weight per ear, g	Number of produced ears, unit/m2	Grain yield, c/ha	Protein content, %
Syr Aruy, St	79	72.0	8.0	20.5	42.8	0.95	338	18.4	14.2
М 1/15-3-2И	82	82.0	9.0	28.0	44.0	1.66	330	25.1	15.5
100±10% Gy.
М 1/15-2-3И	82	80.0	10.5	26.5	43.5	1.68	332	27.8	15.9
150±10% Gy.
М 1/15-5-3И	82	85.3	8.9	28.0	42.5	1.64	320	26.5	16.0
150±10% Gy.
М 1/15-5-3СА	79	82.7	8.5	22.0	45.0	1.72	325	24.5	15.5
150±10% Gy.
М1/15-3-3 СА	81	83.0	9.0	26.0	48.0	1.98	340	30.0	15.5
150±10% Gy
LSD05		1.36	0.34	0.65	0.31	0.08	2.25	1.38	0.75

As can be seen from Table 7, the most productive were mutant lines, the original varieties of which were treated in the range of absorbed doses from 100 to 150 Gy. The excess of yield over the standard variety Syr Aruy for two years was 6.1 - 11.6 c / ha. A noticeable elongation of the ear length and an increase in the number of grains in an ear to 28 units per ear are observed. Important distinguishing features were their tallness in combination with dense strong straw and resistance to lodging. In general, a reliable increase in yield was determined mainly by the weight of grain per ear, due to better grain content of the ear and the weight of 1000 grains.

4. Conclusion

Many modern breeding methods have practical limitations due to complex operations and high cost. In this study, we developed a new method of radiation mutagenesis using a linear electron accelerator. The collection of barley mutants created during this study is of practical interest for the genetic improvement of barley germplasm. Thus, within the framework of creative cooperation with JSC “Park of Nuclear Technologies”, research on the use of induced mutagenesis as a source for creating fundamentally new initial forms will expand the capabilities of synthetic selection, obtain mutant lines that are resistant to abiotic stress factors, and significantly reduce the time for breeding new varieties by direct propagation of mutant lines with a set of positive traits.

Acknowledgements

The work was carried out within the framework of program-targeted funding under the scientific and technical programs for 2024-2026 years of the Ministry of Agriculture of the Republic of Kazakhstan “Breeding and primary seed production of cereal crops to increase the potential of productivity, quality and stress resistance in different soil-climatic zones of Kazakhstan” IRN BR24892821.

Data Availability Statement

The entire data set that supports the results of this study was published in the article itself.

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Edited by

• Editor:
  Takako Matsumura Tundisi

Publication Dates

• Publication in this collection
  06 Oct 2025
• Date of issue
  2025

History

• Received
  27 Dec 2024
• Accepted
  28 June 2025