Analysis of variance indicated the existence of significant genetic variation (P < 0.01) between the parental genotypes and full-sib families of tall fescue across three harvests for all the measured traits (Additional file 1: Table S1). The effect of harvest and year were also significant for all traits (Additional file 1: Table S1). Mean of dry forage yield ranged from 37.80 to 165.74 g/plant in the parental genotypes and from 73.16 to 352.41 g/plant in the full-sib families (Table 1). Parental genotypes 20L and 21M and full-sib families 1, 26, and 41 had the highest values of dry forage yield and the lowest values belonged to parental genotypes 22M and 3E and full-sib families 6, 29, and 36 (Table 1). The stability parameter based on regression method (b-value) ranged from 0.45 to 2.26 in parental genotypes and from 0.46 to 2.06 in full-sib families (Table 1). Parental genotypes 21M, 23M, 15L, and 1M and full sib families 25, 34, 38, 41, 26, 39, 19, and 12 with regression coefficients for forage yield close to unity can be considered to display high yield stability across years (Table 1).
Table 1
Information about name, mean dry forage yield, and stability parameter of 21 parental genotypes and 42 full-sib families used in this study
Parental genotypes
|
Full sib families
|
Parental genotype name
|
Origin
|
Maternal genotype
|
Paternal genotype
|
Mean dry forage yield (g/plant)
|
Yield stability
(bi)
|
Full-sib family code
|
Parental plants
|
Number of genotype in each full-sib family
|
Mean dry forage yield (g/plant)
|
Yield stability
(bi)
|
Full-sib family code
|
Parental plants
|
Number of genotype in each full-sib family
|
Mean dry forage yield (g/plant)
|
Yield stability
(bi)
|
1E
|
Iran, Isfahan,Yazdabad
|
Yes
|
Yes
|
76.80
|
1.14
|
1
|
♀1E × ♂2E
|
2
|
352.41
|
0.58
|
22
|
♀17M × ♂1M
|
7
|
160.00
|
1.18
|
2E
|
Iran,Yasuj
|
No
|
Yes
|
87.24
|
0.54
|
2
|
♀1E × ♂4E
|
1
|
223.91
|
0.51
|
23
|
♀17M × ♂2L
|
1
|
292.70
|
0.51
|
3E
|
Iran, Isfahan, Mobarake
|
Yes
|
No
|
39.45
|
1.86*
|
3
|
♀1E × ♂1M
|
6
|
135.54
|
1.46
|
24
|
♀21M × ♂14E
|
2
|
158.72
|
1.24
|
4E
|
Iran, Isfahan, Mobarake
|
Yes
|
Yes
|
49.76
|
1.65*
|
4
|
♀3E × ♂10E
|
2
|
159.37
|
1.20
|
25
|
♀21M × ♂1M
|
3
|
200.69
|
0.93
|
10E
|
USA, New Jersy
|
Yes
|
Yes
|
41.47
|
2.09*
|
5
|
♀3E × ♂14E
|
2
|
178.31
|
1.08
|
26
|
♀21M × ♂11M
|
2
|
307.74
|
0.96
|
14E
|
Hungary, unknown
|
Yes
|
Yes
|
88.26
|
0.81
|
6
|
♀3E × ♂1M
|
1
|
73.16
|
1.91*
|
27
|
♀21M × ♂6L
|
1
|
190.62
|
0.46
|
16E
|
Iran, Isfahan, Fozve
|
No
|
Yes
|
77.54
|
0.55
|
7
|
♀3E × ♂11M
|
3
|
149.16
|
1.31
|
28
|
♀22M × ♂4E
|
2
|
144.45
|
1.26
|
1M
|
Iran, Isfahan,Yazdabad
|
Yes
|
Yes
|
132.35
|
1.02
|
8
|
♀4E × ♂11M
|
2
|
294.74
|
0.57
|
29
|
♀22M × ♂10E
|
1
|
92.58
|
2.06*
|
3M
|
Iran, Yasuj
|
Yes
|
No
|
72.27
|
0.57
|
9
|
♀4E × ♂17M
|
3
|
195.9
|
0.87
|
30
|
♀22M × ♂1M
|
2
|
201.70
|
0.73
|
11M
|
Hungary, unknown
|
Yes
|
Yes
|
55.67
|
1.59
|
10
|
♀10E × ♂1M
|
5
|
200.23
|
0.80
|
31
|
♀22M × ♂21M
|
1
|
107.70
|
1.92*
|
17M
|
Iran, Isfahan, Fozve
|
Yes
|
Yes
|
58.57
|
1.24
|
11
|
♀14E × ♂1E
|
1
|
146.41
|
1.14
|
32
|
♀23M × ♂14E
|
2
|
290.45
|
0.55
|
21M
|
Iran, Isfahan, Fozve
|
Yes
|
Yes
|
141.44
|
0.97
|
12
|
♀14E × ♂2E
|
11
|
198.3
|
1.03
|
33
|
♀23M × ♂17M
|
2
|
168.66
|
1.12
|
22M
|
Poland, unknown
|
Yes
|
No
|
37.8
|
2.26*
|
13
|
♀14E × ♂25L
|
2
|
276.55
|
0.70
|
34
|
♀23M × ♂3L
|
2
|
237.22
|
0.94
|
23M
|
Poland, unknown
|
Yes
|
No
|
133.52
|
1.00
|
14
|
♀14E × ♂11M
|
6
|
181.19
|
1.06
|
35
|
♀23M × ♂15L
|
1
|
194.66
|
0.66
|
2L
|
Iran, Isfahan, Daran
|
No
|
Yes
|
45.58
|
1.43
|
15
|
♀1M × ♂21M
|
3
|
148.85
|
1.13
|
36
|
♀6L × ♂1E
|
2
|
97.51
|
1.94*
|
3L
|
Iran, Isfahan, Yasuj
|
No
|
Yes
|
93.85
|
0.59
|
16
|
♀3M × ♂2E
|
3
|
225.66
|
0.78
|
37
|
♀6L × ♂1M
|
1
|
194.58
|
0.81
|
6L
|
Iran, Isfahan, Daran
|
Yes
|
Yes
|
129.89
|
0.45
|
17
|
♀3M × ♂1M
|
4
|
203.19
|
0.58
|
38
|
♀12L × ♂1E
|
6
|
246.66
|
0.95
|
12L
|
Iran, Isfahan, Daran
|
Yes
|
No
|
117.65
|
0.66
|
18
|
♀3M × ♂6L
|
1
|
102.83
|
1.86*
|
39
|
♀12L × ♂1M
|
4
|
184.42
|
0.97
|
15L
|
Hungary, unknown
|
No
|
Yes
|
64.53
|
1.01
|
19
|
♀11M × ♂2E
|
9
|
195.01
|
1.02
|
40
|
♀12L × ♂2L
|
3
|
287.84
|
0.64
|
20L
|
Iran, Isfahan, Yazdabad
|
Yes
|
No
|
165.74
|
0.59
|
20
|
♀11M × ♂16E
|
1
|
159.41
|
1.19
|
41
|
♀20L × ♂4E
|
4
|
300.85
|
0.95
|
25L
|
Iran, Isfahan, Fozve
|
No
|
Yes
|
121.74
|
0.76
|
21
|
♀11M × ♂1M
|
1
|
130.70
|
1.22
|
42
|
♀20L × ♂14E
|
2
|
288.81
|
0.59
|
*Significantly different from 1 for bi at the 0.05 probability level.
|
In both parental genotypes and full-sib families, the highest forage yield (including SPDFY, SUDFY, AUDFY, and ADFY) was observed in the third year of this experiment compared to the first, second and fourth years (Fig. 1). Mean values of morphological traits for three harvests over four years of experiments are presented in Table 2, in which significant differences can be seen between spring, summer, and autumn harvests for dry forage yield (DFY), plant height (PH), and crown diameter (CD) in both parental genotypes and full-sib families over years (Table 2). The highest and lowest values of DFY, PH, and CD in both parental genotypes and full-sib families were obtained at the spring and summer harvests during four years of experiment, respectively (Table 2).
Table 2
Means of morphological traits in parental genotypes and full-sib families of tall fescue at three harvests (spring, summer and autumn) during 2017-2020
Parental genotypes
|
C Harvest
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
Spring
|
67.97a
|
32.23a
|
15.93a
|
86.12a
|
58.48a
|
23.11a
|
200.19a
|
103.40a
|
27.09a
|
125.77a
|
62.45a
|
16.09a
|
Summer
|
29.46c
|
22.02b
|
9.19b
|
37.62c
|
30.12b
|
15.11b
|
101.85c
|
46.40c
|
18.64b
|
35.92c
|
26.54c
|
5.547c
|
Autumn
|
43.28b
|
29.79ab
|
9.53b
|
50.07b
|
34.04b
|
17.16b
|
173.21b
|
65.90b
|
23.88ab
|
55.91b
|
45.26b
|
10.38b
|
Full-sib families
|
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
DFY (g/plant)
|
PH (cm)
|
CD (cm)
|
Spring
|
104.51a
|
48.28a
|
16.01a
|
426.28a
|
76.92a
|
25.53a
|
471.02a
|
117.20a
|
34.72a
|
215.96a
|
85.07a
|
22.34a
|
Summer
|
57.37b
|
38.53b
|
9.05b
|
140.90c
|
39.20c
|
17.47b
|
188.53c
|
54.92c
|
25.52b
|
57.04c
|
34.78c
|
10.60c
|
Autumn
|
63.54b
|
42.34b
|
11.50b
|
222.49b
|
53.24b
|
19.28b
|
311.14b
|
80.62b
|
31.95ab
|
106.80b
|
64.70b
|
16.69b
|
DFY: dry forage yield, PH: plant height, CD: crown diameter
n each year, in parental genotypes or full-sib families and in each column, means sharing no letter are significantly different at the 5% level by LSD test.
|
Estimations of narrow sense heritability for measured traits and relative selection efficiency (RSE) for improvement of dry forage yield (DFY) in a single harvest and in multiple harvest analysis are given in Tables 3 and 4, respectively. In a single harvest analysis, narrow sense heritability ranged from 0.18 for DFY to 0.29 for number of stems per plant (NS) at the spring harvest, and from 0.16 for DFY to 0.26 for CD at the summer harvest, and from 0.15 for DFY to 0.25 for CD at the autumn harvest (Table 3). Generally, the highest estimates of narrow sense heritability for measured traits were obtained in the spring harvest, whereas the lowest estimates were obtained in the later harvests (summer and autumn) (Table 3). In multiple harvest analysis, low to moderate values of narrow sense heritability were observed for all of the evaluated traits (Table 4). It was 0.22 for DFY, 0.37 for PH, 041 for CD, 0.32 for NS, and 0.22 for flowering time (FLO) (Table 4). In both single and multiple harvest analysis, the narrow-sense heritability of yield related traits consisted of plant height (PH), the number of stems per plant (NS), and CD was greater than the narrow-sense heritability of dry forage yield (Table 3 and 4). In both single and multiple harvest analysis, the highest values of correlated response and relative selection efficiency (more than 1) for genetically improvement of DFY was obtained via selection for PH, CD, and NS (Table 3 and 4).
Table 3
Estimates of variance components and narrow sense heritability of measured traits and relative efficiency of indirect selection (RSE) for improvement of DFY in evaluated genotypes of tall fescue in a single harvest analysis
Variance component
|
DFY
|
PH
|
CD
|
NS
|
FLO
|
DFY
|
PH
|
CD
|
DFY
|
PH
|
CD
|
\({\sigma }_{A}^{2}\)
|
5121.79
|
99.56
|
11.43
|
44.50
|
11.78
|
1384.67
|
35.79
|
9.70
|
4102.92
|
64.52
|
13.53
|
\({\sigma }_{p}^{2}\)
|
28171.93
|
366.01
|
40.67
|
149.71
|
47.57
|
8308.06
|
141.04
|
36.60
|
26202.41
|
278.39
|
52.37
|
\({h}_{n}^{2}\pm \text{S}E\)
|
0.18 ± 0.03
|
0.27 ± 0.03
|
0.28 ± 0.03
|
0.29 ± 0.04
|
0.24 ± 0.04
|
0.16 ± 0.04
|
0.25 ± 0.03
|
0.26 ± 0.04
|
0.15 ± 0.04
|
0.23 ± 0.04
|
0.25 ± 0.05
|
Ry
|
52.87
|
9.03
|
3.12
|
6.20
|
2.89
|
25.52
|
5.19
|
2.75
|
42.49
|
6.71
|
3.16
|
CRy
|
-
|
53.84
|
54.18
|
53.14
|
29.00
|
-
|
24.47
|
26.02
|
-
|
43.88
|
44.67
|
RSE
|
-
|
1.01
|
1.02
|
1.00
|
0.54
|
-
|
1.03
|
1.01
|
-
|
1.03
|
1.05
|
DFY: dry forage yield, PH: plant height, CD: crown diameter, NS: number of stems per plant, FLO: Flowering time
σ2A additive and σ2p phenotypic variance; h2n narrow sense heritability, SE standard error R: response to selection; CR: correlated response to selection.
|
Table 4
Estimates of variance components and narrow sense heritability of measured traits and relative efficiency of indirect selection (RSE) for improvement of DFY in evaluated genotypes of tall fescue in multiple harvest analysis
Variance component
|
DFY
|
PH
|
CD
|
NS
|
FLO
|
\({\sigma }_{A}^{2}\)
|
4350.66
|
75.60
|
12.61
|
71.22
|
9.50
|
\({\sigma }_{p}^{2}\)
|
19102.97
|
223.52
|
30.22
|
189.56
|
31.22
|
\({h}_{n}^{2}\pm \text{S}E\)
|
0.22 ± 0.04
|
0.32 ± 0.04
|
0.41 ± 0.04
|
0.37 ± 0.02
|
0.30 ± 0.03
|
Ry
|
53.21
|
8.37
|
3.94
|
8.91
|
2.93
|
CRy
|
-
|
54.12
|
60.55
|
56.17
|
30.47
|
RSE
|
-
|
1.01
|
1.13
|
1.05
|
0.57
|
DFY: dry forage yield, PH: plant height, CD: crown diameter, NS: number of stems per plant, FLO: flowering time
σ2A additive and σ2p phenotypic variance; h2n narrow sense heritability, SE standard error, R: response to selection; CR: correlated response to selection..
|
Genetic correlation between traits ranged from 0.20 (between PH and FLO) to 0.86 (between DFY and PH) (Table 5). The higher correlation values were obtained between DFY with PH, CD, and NS (Table 5). Flowering time (FLO) had medium correlation with DFY (0.50), PH (0.38), CD (0.44), and NS (0.36) (Table 5).
Table 5
Genetic correlation coefficients using best linear unbiased predictions (BLUPs) for measured traits across three harvest and four years in the evaluated tall fescue germplasm
Traits
|
DFY
|
PH
|
CD
|
NS
|
FLO
|
DFY
|
1
|
|
|
|
|
PH
|
0.86 ± 0.09
|
1
|
|
|
|
CD
|
0.85 ± 0.09
|
0.65 ± 0.11
|
1
|
|
|
NS
|
± 0.12 0.83
|
± 0.10 0.69
|
0.59± 0.13
|
1
|
|
FLO
|
± 0.14 0.50
|
± 0.18 0.38
|
± 0.15 0.44
|
0.36 ± 0.19
|
1
|
DFY: dry forage yield, CD: Crown diameter, PH Plant height, NS: Number of stems per plant, FOL: flowering time
|
A broad range of breeding value was observed for all measured traits in both parental genotypes and their clonal progenies (Additional file 1: Table S2 and S3). The breeding value for DFY varied from -70.29 to 37.45 in parental genotypes and from -45.79 to 159.90 in progenies (Additional file 1: Table S2 and S3). In general, the highest values of DFY, PH, CD, NS, and FLO was observed in the parental genotypes 21M and 1M. However, genotypes 23M, 25L, and 20L had also the high values of DFY, CD, and FLO, respectively (Additional file 1: Table S2). Parental genotypes 22M and 3E had the lowest breeding values of DFY, PH, and CD. Parental genotypes 2E and 2L had the low breeding values of NS and parental genotypes 2E and 22M had the low breeding values of FLO (Additional file 1: Table S2). In progenies, the highest breeding values of DFY was obtained in genotypes 154 and 133 (Additional file 1: Table S3). Genotypes 133, 168, and 53 with high breeding values of PH, and genotypes 135, 157, 53, and 167 with high breeding values of CD, and genotypes 133, 135, and 168 with high breeding values of NS, and genotypes 167, 154, 135, and 133 with high breeding values of FLO were distinguished in the progenies (Additional file 1: Table S3). Genotypes 65 and 127 had the lowest breeding values of DFY, PH, CD, ND, and FLO in the progenies (Additional file 1: Table S3).
Principal component analysis (PCA) revealed that the first two components explained more than 83%, 72%, and 69% of the genetic variation in the parental genotypes, full-sib families, and individual progenies of tall fescue, respectively (Fig. 2). A broad range of variation was observed for the studied germplasm for all the evaluated traits across harvests. In all three groups (parental genotypes, full-sib families, and individual progenies) dry forage yield (DFY) and crown diameter (CD) at three harvest and flowering time most towards the variation in the first component, while plant height at three harvests (PH) and number of stems per plant (NS) contributed more towards second component (Fig. 2). Therefore, selection based on moderate to high PC1 and PC2 value would lead to genotypes or families with favorable forge yield production and its related traits (Fig. 2). In this respect, parental genotypes 23M, 21M, 20L, and 1M, and full-sib families 25, 26, 35, 40, and 41 and individual progenies 53, 60, 115, 116, 118, 133, 167, and 168 were identified as the superior genotypes. In contrast, parental genotypes 2L, 17M, 22M, and 3E, and full-sib families 2, 6, 14, 16, 17, 27, and 37, and individual progenies 57, 65, 78, 83, 94, 127, 137, and 139 had low values of yield production and its related traits (Fig. 2).