Characteristics of the New Fiber Flax Variety HERA in Terms of Fiber Quality Parameters Regard to Agronomic Assessment and Seeds Quality

ABSTRACT

The work deals characteristics of new flax Hera variety in terms of fiber quality with regard to agronomic assessment and seeds quality. The results of the analyzes were related to the reference varieties Nike, Sara and Modran grown in Poland in 2022 season. The study included evaluation of agrotechnical experiment, flax straw and fiber evaluation taking into account the morphology and surface as well cross section of flax fiber. Moreover, seeds quality assessment were conducted. Hera variety was characterized by the highest total (6.27 t/ha, 0.627 kg/m²) and straw yield (5.16 t/ha, 0.516 kg/m²). Straw of Hera variety was characterized by the best average total (78.5 cm) as well as average technical (66.5 cm) length and average diameter (1.43 mm). In addition, it has fiber to raw straw content (16.42%) at a level comparable to the reference varieties. The metrological analysis of the fiber showed that the Hera variety fiber can be a good raw material for production of yarns.

摘要

从农艺评价和种子质量两个方面研究了亚麻新品种赫拉的纤维品质特征. 分析结果与2022年波兰种植的参考品种耐克、萨拉和莫德兰有关. 该研究包括农业技术试验评估、亚麻秸秆评估和纤维评估，考虑了亚麻纤维的形态、表面和横截面. 此外，还进行了种子质量评估. 赫拉品种的总产量（6.27 t/ha，0.627 kg/m2）和秸秆产量（5.16 t/ha，0.516 kg/m2）最高. 赫拉品种的秸秆具有最佳的平均总长度（78.5 cm）、平均技术长度（66.5 cm）和平均直径（1.43 mm）. 此外，它的纤维含量（16.42%）与参考品种相当. 对纤维的计量分析表明，赫拉品种纤维是生产纱线的良好原料.

KEYWORDS:

• Flax fiber
• new variety
• fiber quality
• Hera
• Modran
• Nike
• Sara

关键词:

• 亚麻纤维
• 新品种
• 纤维质量
• 赫拉
• 莫德兰
• 耐克
• 萨拉人

Introduction

Flax is one of the oldest known cultivated plants. It is also the oldest known spinning plant (Arslanoglu et al. 2022). It belongs to the family Linaceae, which includes about 300 species, and the genus Linum, which includes about 200 species, of which only one - Linum usitatissimum L. - is a cultivated species of economic importance. Two functional forms of flax are in cultivation: fiber flax and linseed. Oily forms are characterized by poor quality fiber, which is not suitable for spinning purposes. However, the seed yield is high (up to more than 2 t/ha). Fibrous forms contain a large amount of long fiber, from which good-quality yarn is obtained. On the other hand, the stems of plants of fibrous forms, have a smaller number of branches and seed capsules, which results in a lower seed yield (Pandey 2016; Sharma, Gawande, and Satpathy 2015). Flax is a versatile plant. All parts of the plant can be used in industry. Flax fiber is used in the production of textiles for fabrics, knitted fabrics, clothing, footwear, table linen, interior design elements (Eberle et al. 2020) and technical textiles such as ropes, cords, nets, thick canvases, carpets, geotextiles (Ahmad and Ullah Ziauddin 2020). It is used in the production of composites and biocomposites as well (Bar et al. 2022; Zimniewska et al. 2014). The shives are used in building materials (boards, acoustic insulation, vibration damping elements) (Bensadoun 2016; Kozłowski et al. 2005), in addition, shives and fiber are used in the production of paper, packaging, banknotes, cigarette paper (Kozłowski et al. 2020). The seeds are an element for the production of high-quality linseed oil. In addition, it can be an ingredient of food, dietary supplements and animal feed (Papadopoulou et al. 2015).

New varieties of flax must be the basis for obtaining a measurable economic profit (Galinousky et al. 2020). The economic value of fiber flax varieties is determined primarily by straw and fiber yields as well as high fiber quality. Flax fibers are characterized by good mechanical properties, tensile strength 700 MPa, Young’s modulus 70 GPa, elongation at break 3%, density 1.4 g/cm³ (Müssig and Haag 2015; Zhu et al. 2013). Biological, chemical, physical or mechanical processes are used to extract the fiber from the straw. The most popular process of obtaining fibers from the straw is dew retting. However, natural bast fibers are a very small part of the global textile market, therefore the sale of basic raw materials obtained from flax, especially fiber, is currently difficult. Flax is now a minor crop, especially the fibrous form. The total cultivated area of flax in the world in 2021 was 4 384 000 ha, of which only 241 103 ha was used for fiber flax (FAOSTAT 2021). Numerous alternatives for the use of flax straw (biocomposites, second-generation biofuels, the use of lower quality fiber for technical purposes) cause that breeding works are increasingly focused on a high and stable yield of straw and fiber, at the expense of long fiber content. To increase the profitability of fiber flax cultivation, it is possible to use straw and seeds. Flax seeds are a rich source of fat, the content of which is from 33% to 45% (Bhateria, Sood, and Pathania 2006). Flax oil has a favorable composition of fatty acids (e.g. more than 50% are unsaturated fatty acids UFA: alpha-linolenic and linoleic), which shows high healing properties (Buckner et al. 2019; Westcott and Muir 2003). Polyunsaturated fatty acids are necessary for diet and play a vital role in preventing or promoting diet-related diseases.

The variability of cultivated forms of flax is very low, which makes it difficult to breed new varieties with high economic value. To increase the value of the most important functional traits and thus the quality of the fiber obtained from the plant, breeding work also focuses on their direct components, which include: the plant height, technical length of plants, stem diameter, stalks slenderness, number of branches and capsules etc. (Pavelek et al. 2020), but the all traits of fiber flax with significant economic importance are quantitative. They are determined by additive genes and largely modified by environmental factors (Sood et al. 2007). This property makes it difficult to achieve a significant increase in the value of these traits in the obtained hybrids, especially when using standard breeding methods.

The aim of the presented studies was to assess the fiber quality parameters of a new Polish fiber flax variety Hera, including agronomic and seeds quality assessment, in comparison to three reference varieties Nike, Sara and Modran.

Materials and methods

Plant material

The basic research material was flax straw varieties listed in Table 1.

Table 1. List of fiber flax varieties tested in the experiments.

Variety	Year of registration in the list of cultivated plant varieties
Hera	2023
Nike	1987
Sara	2007
Modran	2001

Fiber was extracted from straw of each variety for the assessment of quality parameters (Figure 1). The straw of the tested varieties was also ginned to perform biochemical seeds analysis.

Figure 1. The plants materials in form of flax straw and flax fiber.

Methods

Agrotechnical experiment

Straw and seeds of the tested fiber flax varieties were obtained from the field trial, conducted in 2022 at the experimental station of the Institute of Natural Fibers and Medicinal Plants in Pętkowo (52.2167°N; 17.2667°E), Poland. The tested varieties of flax were sown in three replications, arranging the objects using the random block method. The plot area was 13,5 m², whereas sowing density was 2000 seeds/m². The seeds were sown on 28 April , and the field crops were harvested on 9 August . April 2022 in Poland was extremely cold (the average temperature in the country was 6.7°C). The drought was observed at the time of sowing. The temperature of the topsoil was 7°C. Flax was grown after winter rape, with the use of typical mineral fertilization recommended for flax (N - 34 kg/ha, P - 92 kg/ha, K - 160 kg/ha). After harvesting the plants from the field, biometric measurements were carried out. Compared varieties were evaluated in terms of the following traits:

• Total yield – mass of whole plants with roots.

• Straw yield – mass of plants after removal of seed capsules and roots.

• Seed yield – weight of seeds after extraction from the bolls.

The yields were determined on the basis of testing all plants harvested from each plot. Morphological measurements were made on 30 randomly selected plants from each plot.

Flax straw quality assessment

The following test methods were applied for straw evaluation:

• Total and technical length (cm) according to PN-P-04961:1984.

• Thickness (mm) according to PN-P-04961:1984.

• Fiber content in relation to raw straw according to (%) BN-7511-11:1975.

Fiber quality assessment

Fiber was extracted from each variety of straw on the laboratory scale in water retting process. The process parameters were: time 72 h, temperature of water 32°C. The fiber of compared varieties of flax was evaluated in accordance with the mentioned standards in terms of following parameters:

• Linear mass of fibers (tex) according to PN-EN ISO 1973:2011.

• Length (mm) according to PN-ISO 6989:2000.

• Tenacity (cN/tex) according to PN-P-04676:86.

Additional analysis were performed for a more extensive qualitative assessment:

• Determination of the impurity content in the fiber according to the decree of the Minister of Agriculture and Rural Development of 5th May 2011 on the method of determining the percentage content of impurities in short flax fiber or hemp fiber.

• Surface morphology – longitudinal views and cross sections of fiber examined by means of the scanning electron microscope Hitachi S-3400N Hitachi, Japan. The study was performed in high vacuum SE mode using a secondary electron detector for samples sputtered with gold layer in Sputter Coater 108 auto. Observations of surface morphology were carried out at a magnification of 250×, a table height of 25 mm and an accelerating voltage of 15 kV.

• The statistical evaluation of the test results was performed on the basis of the nonparametric ANOVA Kruskal–Wallis test at a significance level of 0.05 using the Statistica software 8.0.

Seeds quality assessment

The following test methods were applied for seed evaluation:

• Dry mass (%) according to Polish Pharmacopeia XII.

• Ash according to Polish Pharmacopeia XII.

• Swelling index according to Polish Pharmacopeia XII.

• Fat according to PN-R-66164:1973.

• Fatty acid composition (Gromek et al. 2015).

Results and discussion

Agrotechnical experiment results

• Weather conditions

In 2022, the weather was unfavorable for flax cultivation. A very dry spring forced delayed sowing (28.4.2022) and then caused late and uneven emergence of plants. The amount of water available to the plants improved during the summer months, but this did not neutralize the lower crop yields. The average total amount of rainfall during the vegetation period of plants was 81% of the long-term average (Table 2).

Table 2. Average monthly precipitations in 2022 in the period from March 1 to July 31, compared to the average for the years 1996–2021 [mm].

	Month					Total III-VIII	Percentage of multi-year average
Location	III	IV	V	VI	VII
Pętkowo	23	43	31	85	91	273	81

Yields of the HERA variety against reference cultivars. The comparison of HERA variety with reference cultivars, in terms of fiber content and quality, as well as the biochemistry of seeds, was the main aim of the presented investigations. The field experiment was conducted to produce the raw material needed to perform the analyses. The agricultural traits of the HERA variety were determined by Research Centre for Cultivar Testing (COBORU, in a two-year cycle of research (2021–2022), conducted as part of the variety registration process. The results of these studies are reported in the supplement.

Plant emergence was good, and no significant plant loss was found in the plots. No damage caused by diseases and pests was observed during the growing season of the plants. No significant differences in the yield level of the studied cultivars were observed. Total yield of the tested varieties ranged from 5.75 t/ha (0.575 kg/m²) to 6.27 t/ha (0.627 kg/m²) (Table 3). The obtained values are low and differ from the potential of the tested varieties. Undoubtedly, this was due to the lack of rainfall in spring. The total yield of the best fiber flax varieties may exceed 10 t/ha under favorable weather conditions. However, in the absence of sufficient rainfall, the total yield of flax plants may drop to even 3.5 t/ha (Praczyk and Wielgusz 2021). Despite the lack of significance of the differences shown by the statistical test, it should be mentioned that the HERA cultivar had a higher total yield than all reference cultivars (Table 3). A similar situation occurred in the case of straw yield. The yield of the cultivars was low (Diederichsen and Ulrich 2009; Porsev et al. 2020; Praczyk and Wielgusz 2021; Shuvar et al. 2021), and the HERA cultivar surpassed all reference cultivars, although not in a statistically significant way. In terms of seed yield, HERA was slightly inferior to the SARA variety. Even so, seed yield is a trait of less important for fiber flax and does not determine its economic value. The results of the yield-forming traits of the HERA cultivar compared to the reference cultivars are presented in Table 3.

Table 3. Total yield, straw and seed yield of the tested fiber flax varieties.

Variety	Total yield q ha^−1	Straw yield q ha^−1	Seed yield q ha^−1
Hera	62.7	51.6	3.58
Nike	57.5	47.6	2.0
Sara	58.8	48.6	3.95
Modran	59.2	48.1	2.79

Flax straw quality results

The results of flax straw measurement are presented in Table 4.

Table 4. Average total and technical length, average diameter of straw and fiber content in relation to raw straw.

Straw	Average total length	SD	CV	Average technical length	SD	CV	Average diameter	SD	CV	Fiber content in raw straw
	cm	cm	%	cm	cm	%	mm	mm	%	%
Hera	78.5	3.1	3.9	66.5	1.5	2.3	1.43	0.10	6.96	16.42
Nike	70.5	2.5	3.5	58.7	1.8	3.1	1.33	0.10	7.47	11.50
Sara	72.0	3.1	4.2	61.3	1.7	2.8	1.31	0.07	5.66	16.51
Modran	67.8	3.2	4.7	58.7	1.8	3.1	1.38	0.06	4.70	16.64

The value of the total length is in the range 67.8–78.5 cm. The straw Nike varieties were the shortest, Hera varieties were the longest. The value of the average technical length is in the range 58.6–66.5 cm. Hera variety was characterized by the highest technical length, while the lowest values were observed for the Nike and Modran varieties. Różańska indicated that for another Agatha variety the total length is 74 cm and technical length is 67 cm (Różańska 2022).

The statistical analysis of the results of both total and technical length (ANOVA), tested at the significance level of 0.05, showed differences (p = .0000). In order to check which samples were statistically different from each other, a post hoc test was carried out, which showed remarkable differences between the varieties: Hera and Nike, Hera and Modran.

The value of average diameter of straw is in the range between 1.31 and 1.43 mm. The statistical analysis of the results (Kruskal – Wallis test), tested at the significance level of 0.05, demonstrated statistically significant differences between Hera and Sara (p = .6709).

Fiber content in relation to raw straw is within the range 11.50% for Nike variety and 16.64% for Modran variety. The fiber content of the Hera variety (16.4%) is almost similar to the fiber content in two reference varieties: Sara (16.5%) and Modran (16.6%), whereas Nike variety was definitely worse than the above-mentioned genotypes, with a fiber content in straw of 11.5% (Table 2). The performed tests indicate that the Hera variety is characterized by a fiber content at the level of the best Polish varieties included in the register. The content of fiber in all tested samples was typical for varieties cultivated in Poland. Mańkowski et al. reported that fiber content in straw for Luna variety is 16.55% (Mańkowski et al. 2015), for other varieties it could be 14–24% depending on the year (Mańkowski and Pudełko 2015; Strażyński and Mrówczyński 2017; Zimniewska et al. 2021). The average fiber content in the straw of fiber could be higher e.g. Diederichsen and Ulrich reported that the fiber content of fiber flax in their study, it is around 34% (Diederichsen and Ulrich 2009). Similar results were obtained by Khan et al. (Khan et al. 2021) and Shuvar et al. (Shuvar et al. 2021).

Fiber quality results

The results of length of fiber, linear mass, impurity content, breaking force, elongation and tenacity of flax fiber are presented in Table 5. Figures 2–5 present microphotographs of longitudinal views and cross sections of flax fibers, taken with a scanning electron microscope.

Figure 2. Microphotographs - longitudinal views and cross sections of Hera flax fibre.

Figure 3. Microphotographs - longitudinal views and cross sections of Nike flax fibre.

Figure 4. Microphotographs - longitudinal views and cross sections of Sara flax fibre.

Figure 5. Microphotographs - longitudinal views and cross sections of modran flax fibre.

Table 5. Length of fibre, linear density, impurity content, breaking force, elongation and tenacity of flax fibre.

Fibre	Length of fibre	Linear density	SD	Impurity content	Breaking force	SD	CV	Elongation	SD	CV	Tenacity
	mm	Tex	tex	%	N	N	%	%	%	%	cN/tex
Hera	411.8	0.5	0.10	0.8	11.24	7.35	65.35	8.57	3.10	36.16	5.70
Nike	262.7	0.4	0.05	0.9	9.73	5.87	60.30	6.36	2.39	37.60	4.83
Sara	360.1	0.5	0.13	0.9	13.08	9.28	70.91	9.24	3.78	40.92	6.54
Modran	453.5	0.5	0.08	0.8	14.69	6.27	42.66	11.24	5.11	45.45	7.47

Features that dedicated fibers to spinning process are characterized by low linear density, higher length, higher strength and low content of impurities. The average fiber length is from 262.7 mm for Nike and 453.5 mm for Modran varieties. The fiber obtained from the new Hera variety is characterized by a high length of 411.8 mm. The only variety with a longer length is the fiber obtained from the Modran variety - 453.5 mm. The length of the Hera fiber will therefore ensure adequate fiber strength and stream uniformity during the classical spinning process.

The linear density of the Hera variety is 0.5 tex. This result does not differ from the linear density values of the other analyzed fibers. Comparing the research results with literature (Mańkowski et al. 2015; Różańska 2022), where it was shown that linear mass for flax fiber is 3.3–4.7 tex, it can be concluded that all tested varieties of flax fiber are properly divided into smaller complex of fiber. This is also a result that can provide assurance to obtain thin yarns dedicated to light summer clothing.

In addition, fiber from Hera variety contains a low content of impurities, 0.8%, the same level as the other analyzed fiber variety. Low content of impurities accommodates a more efficient spinning process and reduces the production of waste generation during spinning.

The breaking force for all tested varieries is from 9.73 N at elongation 6.36% to Nike and 14.69 N at elongation 11.24% to Modran. Breaking force and elongation at Hera (11.24 N, 8.77%) are at the level of the other tested samples. Statistical analysis of strength results showed no significant differences between trials. Strength results of the tested fibers are at a level that enables the production of high-quality, durable yarns.

The microscopic analysis of the longitudinal and cross-sectional views of the fibers showed that the fibers were present in bundles (Figures 2–5). In the longitudinal view, elementary bast fibers usually take the shape of polyhedrons stretched along the length; moreover, they have characteristic elbows. In the cross-section, the bast fibers can take the form of oval, through strongly flattened and polygonal, to completely irregular, the fibers have a visible medulla. Both the longitudinal and cross-section views of the analyzed samples showed that the fiber complexes are well divided into elementary fibers and fiber complexes of very low linear mass (Table 5). No damage was observed on the fibers.

Seeds quality results

Flaxseed has been known as a rich source of oil. Flaxseed oil has good ratio of unsaturated fatty acid content. Results presented typical parameters tested for flaxseeds intended for food and pharmaceutical purposes (Table 6). Fibrous flaxseed Modran had the highest oil content (33.51%). Hera and Nike were lower oil content than Sara. The few major fatty acids were identified and qualified (Table 7) for four varieties: Hera, Nike, Sara and Modran. Notable differences in the values of individual fatty acids among flaxseed variety Nike and the other three varieties were observed. The highest SFA/UFA ration was observed in Nike (0.12), followed by other three varieties (0.10–0.09).

Table 6. Dry mass, ash, swelling index and fat content in seeds.

Parameter, unit	Hera	Nike	Sara	Modran
Dry mass,(%)	7.55	8.17	7.97	8.08
Ash, (%)	4.06	4.20	4.28	4.32
Swelling index, (ml)	4.0	4.0	3.0	3.0
Fat, (%)	32.17	32.16	32.42	33.51

Table 7. Composition of fatty acids.

Parameter, unit (%)	Hera	Nike	Sara	Modran
Fatty acids with chain shorter than C16	0.15	0.13	0.10	0.07
Palmitic acid	4.60	4.70	4.67	4.30
Palmitoleic acid	0.04	0.06	0.04	0.04
Stearic acid	4.21	5.59	3.86	3.55
Oleic acid	16.95	22.74	16.59	18.07
Linoleic acid	15.94	15.40	13.64	14.44
Alfa -linolenic acid	55.15	48.11	58.08	56.48
Arachidic acid	0.20	0.16	0.17	0.18
SFA	9.01	10.45	8.70	8.03
UFA	88.08	86.31	88.35	89.03
SFA/UFA	0.10	0.12	0.10	0.09

Conclusions

• The new fiber flax variety Hera was characterized by the highest total and straw yield. Hera exceeded all the tested reference varieties in terms of these traits.

• Straw of Hera variety was characterized by the best total and technical length, and the straw was also the thickest compared to the reference varieties Nike, Sara and Modran.

• Fiber content in relation to raw straw for Hera variety was similar to fiber content in reference varieties.

• Metrological assessment of Hera variety fiber in the context of length, impurity content and strength parameters in comparison with the reference varieties dedicates the Hera variety fiber to the production of yarns intended for clothing products.

• Fatty acid composition and other tested parameters in flaxseed of Hera were not significant differences to the other tested varieties.

Highlights

1. In 2023, a new fiber flax variety HERA was added to the national register of agricultural plant varieties in Poland.

2. Variety HERA exceeds the reference genotypes in terms of important agricultural traits.

3. The quality parameters of the fiber predispose the HERA variety to be used in various textile directions.

4. Cultivation of the HERA variety is an interesting proposition for fiber flax farmers.

Ethical approval

We confirm that all the research meets ethical guidelines and adheres to the legal requirements of the study country. The research does not involve any human or animal welfare related issues.

Acknowledgments

The authors gratefully acknowledge the funding by Polish Ministry of Education and Science under the smart development program financed by the European Union.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15440478.2023.2301669

Additional information

Funding

This research was supported by the Polish Ministry of Education and Science under the smart development program financed by the European Union.