
Buckwheat (
Buckwheat is a gluten-free grain crop. It has abundant levels of amino acids, proteins, lipids, saccharides, fiber, minerals, vitamins, and flavonoids (Huang
Seed germination is a complex biological process in which the seed absorbs water and starts to elongate its embryonic axis (Welbaum
Buckwheat sprouts have excellent anti-oxidant activity and are rich in amino acids, minerals, and flavonoids (Kim
One hundred buckwheat germplasms collected from the National Genetic Resource Center (the RDA gene bank), Rural Development Administration (RDA) Jeonju, the Republic of Korea, were used. The germplasm collection included 87 common buckwheat and 13 tartary buckwheat accessions (Table 1). The germplasm was sown at 25℃ ± 1℃ in a greenhouse in the National Institute of Agricultural Sciences (NAS), RDA by placing 100 seeds of each accession between two layers of wet filter papers in Petri plates.
After 10 days of sowing, the buckwheat germplasms were evaluated based on sprout traits such as leaf length, leaf width, fresh shoot weight, and extract weight. For leaf length and width measurement, 10 plants were selected and data were recorded in triplicates. For fresh shoot weight and extract, all sprouts were harvested and used to record the data.
The rutin and quercetin content in buckwheat sprouts was measured using an HPLC system according to the method described by Kim
The values are expressed as milligrams per 100 gram dry weight (mg/100 g DW).
Data were analyzed using the
The morphological comparison of common buckwheat and tartary buckwheat is presented in Table 2. The average leaf length (1.80 cm) of common buckwheat germplasm was significantly higher than that (1.51 cm) of tartary buckwheat germplasm. The leaf length of common buckwheat germplasm ranged from 1.6 to 2.1 cm, while that of tartary buckwheat germplasm ranged from 1.3 to 1.7 cm. Most of the common buckwheat germplasm had leaf length in the category of “1.6-2.0 cm”, whereas most of the tartary buckwheat germplasms in the category of “1.1-1.5 cm” (Fig. 1a). Similarly, the average leaf width (3.08 cm) of common buckwheat germplasm was significantly higher than that (2.16 cm) of tartary buckwheat germplasm. The leaf width of common buckwheat germplasm ranged from 2.6 to 3.6 cm, whereas that of tartary buckwheat germplasm ranged from 1.9 to 2.3 cm. Moreover, we found that most of the common buckwheat germplasm had leaf width of > 3 cm whereas, most of the tartary buckwheat germplasm had leaf width in the category of “2.1-3.0 cm” (Fig. 1b). Furthermore, the average fresh shoot weight (30.75 g) of common buckwheat germplasm was significantly higher than that (20.74 g) of tartary buckwheat germplasm. In common buckwheat germplasm, the fresh shoot weights ranged from 22 to 38 g, whereas that of tartary buckwheat ranged from 17 to 23 g. In common buckwheat, 43% of the accessions had fresh shoot weight in the category of “21-30 g” and 57% had fresh shoot weight in the category of “31-40 g”. Similarly, in tartary buckwheat germplasm, 44% of the germplasm had fresh shoot weight in the category of “10-20 g” and 56% germplasm had fresh shoot weight in the category of “21-30 g” (Fig. 1c). The average extract weight (10.19 g) of common buckwheat germplasm was also significantly higher than that (7.12 g) of tartary buckwheat germplasm. In common buckwheat germplasm, the extract weight ranged from 6.3 to 12.3 g, whereas that of tartary buckwheat germplasm ranged from 6.4 to 8.8 g. Furthermore, 60% of the common buckwheat germplasms had extract weight in the category of “6-10 g” and 40% of the germplasm had extract weight in the category of “11-15 g”. However, in tartary buckwheat, all accessions had extract weight in the category of “6-10 g” (Fig. 1d).
The results presented in Table 2 revealed that the mean content of rutin (2729.9 mg/100 g DW) and quercetin (12.23 mg/100 g DW) was significantly higher in tartary buckwheat germplasm than in common buckwheat germplasm (553.5 mg/100 g DW and 0.78 mg/100 g DW, respectively). The content of rutin in common buckwheat sprouts ranged from 323.7 to 750.6 mg/100 g DW, whereas that in tartary buckwheat sprouts ranged from 2220.0 to 3185 mg/100 g DW. Similarly, the content of quercetin in common buckwheat sprouts ranged from 0.27 to 1.82 mg/ 100 g DW and that in tartary buckwheat sprouts ranged from 5.51 to 30.41 mg/100 g DW. In common buckwheat, 24% of the germplasm had rutin content in the category of “1-500 mg/100 g DW” and 76% of the germplasm had rutin content in the category of “501-1000 mg/100 g DW”. However, in tartary buckwheat, all accessions had rutin content in the category of “> 2000 mg/100 g DW” (Fig. 2a). Similarly, 78% of the common buckwheat germplasm had quercetin content in the category of “< 1 mg/100 g DW” and 22% of the germplasm had quercetin content in the category of “1-2 mg/100 g DW”, whereas 100% of the tartary buckwheat germplasm had quercetin content in the category of “> 4 mg/100 g DW” (Fig. 2b).
The correlation results of buckwheat sprouts revealed that there was a significant correlation between the leaf length, leaf width, fresh shoot weight, and extract weight. In addition, there was also a significant correlation between the content of rutin and quercetin. However, the leaf length, leaf width, fresh shoot weight, and extract weight showed a non-significant correlation with the rutin content. Similarly, the leaf length and leaf width also showed non-significant correlation with quercetin content; however, the fresh shoot weight and extract weight were significantly correlated with the quercetin content (Fig. 3a). In tartary buckwheat sprouts, the leaf length showed a significant correlation with the leaf width, extract weight, and rutin content, and a non-significant correlation with the fresh shoot weight and quercetin content. Similarly, the leaf width showed a significant correlation with the fresh shoot weight and non-significant correlation with the extract weight, rutin content, and quercetin content. Similarly, the extract weight was non-significantly correlated with the rutin and quercetin content. In addition, there was no significant correlation between rutin and quercetin content (Fig. 3b).
In the PCA, we observed that the maximum variation was explained by the first two principal components (PC1 and PC2), showing 78.61% and 8.71% of the total variation. The 3rd, 4th, 5th and 6th component of PCA exhibited 5.93%, 3.30%, 2.38%, and 1.05% of the total variability. The PCA biplot confirmed the high variability between species and within species, based on sprout growth traits and rutin and quercetin content (Fig. 4). Moreover, all variables (loading > 0.385) contributed significantly to PC1. Analysis of loading (Table 3) revealed that PC1 had the highest eigenvalue (4.72). The leaf width, fresh shoot weight, and rutin content were the main contributors of variability to PC1. The rutin and quercetin content was the major contributor and positive loading in PC2 and negative loading in PC1, and significantly correlated with each other.
Based on the content of rutin and quercetin, germplasms with high and low rutin and quercetin content have been identified from both species (Table 4). In common buckwheat germplasm, five accessions (302328, 278145, 141448, 141447, and 100801) had the highest rutin content (> 700 mg/ 100 g DW) and three accessions (179846, 187867, and 288929) had the lowest rutin content (< 400 mg/100 g DW). Similarly, two accessions (302329 and 101282) had the highest quercetin content (> 1.5 mg/100 g DW) and six accessions (141458, 160602, 179843, 179846, 187869, and 288929) had the lowest content of quercetin (< 0.5 mg/ 100 g DW). Similarly, in tartary buckwheat germplasm, two accessions (226674 and 224676) had the highest rutin content (> 3000 mg/100 DW) and two accessions (301236 and 301238) had the lowest rutin content. Similarly, one accession (226673) had the highest content of quercetin (> 30 mg/100 DW) and five accessions (224676, 301235, 301236, 301240, and 301244) had the lowest content of quercetin (< 5 mg/100 g DW).
Buckwheat sprouts are excellent source of amino acids, minerals, and flavonoids; however, sprout growth and flavonoid content may vary among buckwheat germplasms. Regardless of the high nutritional value of buckwheat sprouts, there is limited research on the association between morphological diversity of sprouts and flavonoid content. In this study, we evaluated 87 accessions of common type and 13 tartary type buckwheat germplasms for sprout growth traits and rutin and quercetin content and their association. In our results, sprout growth traits of common buckwheat were significantly higher than those of tartary buckwheat. Our results are in good agreement with those of Woo
Moreover, in both species, the content of rutin and quercetin were in higher range than that of reported in buckwheat seeds. The content of flavonoids depends on the developmental stage, cultivation conditions, and cultivated species (Park
In order to investigate the relationship between sprout growth traits and rutin and quercetin content, we performed a correlation analysis. Correlation is a statistical method for investigating the strength of a relationship among quantitative traits, and a high correlation value between two traits indicates that the variables have a strong relationship with each other and a low value indicates that the variables have a weak relationship with each other (Franzese and Luliano 2019). In our results we did not find any strong relationship between sprout growth traits of common buckwheat germplasm; however, leaf length and rutin content of tartary buckwheat showed a considerable relationship. In addition, the extract weight was non-significantly correlated with the rutin and quercetin content. This information could be helpful for plant breeders in selecting useful morphological traits for crop improvement.
Moreover, PCA has been suggested as a significant tool for plant breeders in order to group the diverse germplasms and evaluate the relationship among breeding materials, and to identify genetic diversity for crop improvement. We performed PCA to distinguish buckwheat germplasm based on type, sprout growth, and rutin and quercetin content. The first principal component, with the highest variability, showed an eigenvalue greater than 1. In general, the principal components whose eigenvalue is greater than 1 are considered significant. The components with higher eigen value have a greater variability than that of components whose eigenvalue is less than 1 (Girden 2001). The leaf width, fresh shoot weight, and rutin content were the main contributors of variability to PC1. The variability in tartary buckwheat germplasm was higher than that in common buckwheat germplasm. This could be due to the wider range of rutin and quercetin content in tartary buckwheat germplasm. The genotypic difference is one of the key factors that influence the content of flavonoids. Earlier, serval scientists have reported variation among genotypes for particular traits by PCA in buckwheat and many other plants (Yao
Hence, we conclude that the difference in rutin and quercetin content in common and tartary buckwheat sprouts is not associated with morphological traits, but could be due to genetic difference and expression of flavonoid biosynthesis-related genes. In the future, comprehensive research is needed to evaluate diverse germplasms for diversity in the flavonoid content in sprouts. Moreover, extensive research is needed to compare the differential expression of flavonoid biosynthesis-related genes in both species. These selected accessions could be further used to investigate the genetic basis of rutin and quercetin content in common and tartary buckwheat using RNA-Seq analysis. Additionally, sprouts of the identified accessions with higher content of rutin and quercetin can be used as a dietary source of phenolic components to reduce the risk of various chronic diseases.
This study was supported by the “Research Program for Agricultural Science & Technology Development (Project No. PJ012478)” of the National Institute of Agricultural Sciences, Rural Development Administration.
List of common and tartary buckwheat accessions used to study sprout growth traits and rutin and quercetin content.
S. No. | Accessions IT | Type | S. No. | Accessions IT | Type | S. No. | Accessions IT | Type | S. No. | Accessions IT | Type |
---|---|---|---|---|---|---|---|---|---|---|---|
1 | 28843 | ESZ) | 26 | 141444 | ES | 51 | 189663 | ES | 76 | 278145 | ES |
2 | 28844 | ES | 27 | 141447 | ES | 52 | 194511 | ES | 77 | 288928 | ES |
3 | 100801 | ES | 28 | 141448 | ES | 53 | 199279 | ES | 78 | 288929 | ES |
4 | 101006 | ES | 29 | 141450 | ES | 54 | 199280 | ES | 79 | 288931 | ES |
5 | 101022 | ES | 30 | 141453 | ES | 55 | 199281 | ES | 80 | 289118 | ES |
6 | 101091 | ES | 31 | 141458 | ES | 56 | 199282 | ES | 81 | 301213 | ES |
7 | 101271 | ES | 32 | 148424 | ES | 57 | 199286 | ES | 82 | 301231 | ES |
8 | 103026 | ES | 33 | 148427 | ES | 58 | 200686 | ES | 83 | 302264 | ES |
9 | 103633 | ES | 34 | 148429 | ES | 59 | 208852 | ES | 84 | 302327 | ES |
10 | 104461 | ES | 35 | 158263 | ES | 60 | 210198 | ES | 85 | 302328 | ES |
11 | 105453 | ES | 36 | 160602 | ES | 61 | 220413 | ES | 86 | 302329 | ES |
12 | 105506 | ES | 37 | 175920 | ES | 62 | 220676 | ES | 87 | 310514 | ES |
13 | 105543 | ES | 38 | 175975 | ES | 63 | 225054 | ES | 88 | 201753 | TA |
14 | 105649 | ES | 39 | 178415 | ES | 64 | 225055 | ES | 89 | 224676 | TA |
15 | 105699 | ES | 40 | 178417 | ES | 65 | 250614 | ES | 90 | 225088 | TA |
16 | 105997 | ES | 41 | 179841 | ES | 66 | 250617 | ES | 91 | 226673 | TA |
17 | 108852 | ES | 42 | 179843 | ES | 67 | 250622 | ES | 92 | 226674 | TA |
18 | 108885 | ES | 43 | 179844 | ES | 68 | 250624 | ES | 93 | 226675 | TA |
19 | 108889 | ES | 44 | 179846 | ES | 69 | 250626 | ES | 94 | 301235 | TA |
20 | 108892 | ES | 45 | 185685 | ES | 70 | 101282 | ES | 95 | 301236 | TA |
21 | 108934 | ES | 46 | 185686 | ES | 71 | 261919 | ES | 96 | 301238 | TA |
22 | 109175 | ES | 47 | 185704 | ES | 72 | 261921 | ES | 97 | 301240 | TA |
23 | 121461 | ES | 48 | 187867 | ES | 73 | 261923 | ES | 98 | 301241 | TA |
24 | 134978 | ES | 49 | 187869 | ES | 74 | 261925 | ES | 99 | 301242 | TA |
25 | 138108 | ES | 50 | 187871 | ES | 75 | 278144 | ES | 100 | 301244 | TA |
Z)ES:
Means and ranges of sprout growth traits and rutin and quercetin content in common and tartary buckwheat germplasm.
Traits | Common buckwheat | Tartary buckwheat | ||
---|---|---|---|---|
Mean | Range | Mean | Range | |
Leaf length (cm) | 1.80 Az) ± 0.09 | 1.6-2.1 | 1.51 B ± 0.09 | 1.3-1.7 |
Leaf width (cm) | 3.08 A ± 0.16 | 2.6-3.6 | 2.16 B ± 0.12 | 1.9-2.3 |
Fresh shoot weight (g) | 30.75 A ± 3.14 | 22.0-38.0 | 20.74 B ± 2.02 | 17-23 |
Extract weight (g) | 10.19 A ± 1.0 | 6.3-12.3 | 7.12 B ± 0.78 | 6.4-8.8 |
Rutin (mg/100 g DW) | 553.5 B ± 86.27 | 332.7-750.6 | 2729.9 A ± 274.14 | 2220-3185 |
Quercetin (mg/100 g DW) | 0.78 B ± 0.29 | 0.27-1.82 | 12.23 A ± 7.37 | 4.76-30.41 |
Values are presented as mean ± standard deviation.
z)Different letters indicate significant differences at the 0.05 probability level.
Loadings, eigenvalue and % variance of buckwheat germplasm for the diversity in sprout growth traits and the content of rutin and quercetin.
PC 1 | PC 2 | PC 3 | PC 4 | PC 5 | PC 6 | |
---|---|---|---|---|---|---|
Leaf length | 0.398 | 0.393 | 0.593 | −0.382 | 0.253 | −0.355 |
Leaf width | 0.441 | 0.010 | 0.298 | 0.002 | −0.287 | 0.797 |
Fresh shoot weight | 0.411 | 0.347 | −0.117 | 0.814 | 0.100 | −0.154 |
Extract weight | 0.389 | 0.322 | −0.737 | −0.433 | 0.083 | 0.087 |
Rutin | −0.422 | 0.391 | 0.045 | 0.056 | 0.676 | 0.455 |
Quercetin | −0.385 | 0.685 | 0.036 | −0.022 | −0.616 | −0.031 |
Eigenvalue | 4.72 | 0.52 | 0.36 | 0.20 | 0.14 | 0.06 |
% variance | 78.62 | 8.71 | 5.93 | 3.30 | 2.38 | 1.05 |
Selected germplasm with the highest and lowest content of rutin and quercetin.
Species | Flavonoids | Description | Accessions IT |
---|---|---|---|
Common buckwheat | Rutin | Highest (> 700 mg/100 g DW) | 302328, 278145, 141448, 141447, 100801 |
Lowest (< 400 mg/100 g DW) | 179846, 187867, 288929 | ||
Quercetin | Highest (> 1.5 mg/100 g DW) | 302329, 101282 | |
Lowest (< 0.5 mg/100 g DW) | 179846, 288929, 141458, 187869, 160602, 179843 | ||
Tartary buckwheat | Rutin | Highest (> 3000 mg/100 g DW) | 226674, 224676 |
Lowest (< 2500 mg/100 g DW) | 301236, 301238 | ||
Quercetin | Highest (> 30 mg/100 g DW) | 226673 | |
Lowest (< 5 mg/100 g DW) | 301240, 301235, 224676, 301236, 301244 |
![]() |
![]() |