Analysis of variance
The combined analysis of variance (ANOVA) revealed a significant difference among genotypes for most of the traits recorded (Table 3). Genotype effects accounted for 66.4%, 77.7%, and 65.9% of the total variance for plant height, awns length, and biological yield, respectively. By contrast, year effects accounted for 63%, 89%, and 73% of the total variance for days to heading, days to maturity and grain filling duration, respectively. The same trend was observed for Y, G and G x Y interaction for number of tillers and percent seed emergence. The performances of the populations were stable across the two years and their response patterns were similar in the case of plant height, awns length, and biological yield. The number of tillers and percent seed emergence were less affected by the year variability. The other traits showed relatively distinct patterns of responses corresponding to the years variability. Broad-sense heritability ranged from 0.49 for tiller number to 0.82 for awn length: these are relatively large values resulting from both high additive genetic variance and low residual variance (Table 3).
Table 3 Combined analysis of variance for percent of seed emergence (Em), days to flowering (Dh), days to maturity (Dm), grain filling duration (Gf in days), tiller number (Tn), plant height Ph), awn length (Awl), biological yield (By) and corresponding heritability (H2).
Traits
|
|
df
|
SS
|
MS
|
SS%
|
P-value
|
H²
|
Em
|
Years
|
1
|
8.4
|
8.4
|
3.2
|
0.02
|
|
|
Geno
|
87
|
125.7
|
1.5
|
47.4
|
0.004
|
0.50
|
|
Years. x Geno
|
87
|
131.2
|
1.5
|
49.5
|
0.002
|
|
|
Total
|
157
|
265.4
|
|
|
|
|
Dh
|
Years
|
1
|
373.4
|
373.4
|
62.8
|
<.001
|
|
|
Geno
|
87
|
118.5
|
1.4
|
19.9
|
0.014
|
0.54
|
|
Years x Geno
|
87
|
102.8
|
1.2
|
17.3
|
0.11
|
|
|
Total
|
175
|
594.7
|
|
|
|
|
Dm
|
Years
|
1
|
1719.7
|
1719.1
|
89.10
|
<.001
|
|
|
Geno
|
87
|
119.3
|
1.4
|
6.18
|
0.012
|
0.56
|
|
Years x Geno
|
87
|
91.0
|
1.1
|
4.71
|
0.365
|
|
|
Total
|
175
|
1929.9
|
|
|
|
|
Gf
|
Years
|
1
|
575.7
|
575.7
|
73.2
|
<.001
|
|
|
Geno
|
87
|
124.9
|
1.5
|
15.9
|
0.005
|
0.61
|
|
Years x Geno
|
87
|
85.6
|
0.98
|
10.9
|
0.522
|
|
|
Total
|
175
|
786.2
|
|
|
|
|
Tn
|
Years
|
1
|
274.5
|
274.2
|
27.4
|
<.001
|
|
|
Geno
|
86
|
356.3
|
4.1
|
35.6
|
0
|
0.49
|
|
Years X Geno
|
86
|
370.9
|
4.3
|
37.0
|
0
|
|
|
Total
|
173
|
1001.4
|
|
|
|
|
Ph
|
Years
|
1
|
105.1
|
105.1
|
18.2
|
<.001
|
|
|
Geno
|
86
|
383.2
|
4.5
|
66.4
|
<.001
|
0.80
|
|
Years x Geno
|
86
|
88.8
|
1.1
|
15.4
|
0.395
|
|
|
Total
|
175
|
577.1
|
|
|
|
|
By
|
Years
|
1
|
58.9
|
58.9
|
12.2
|
<.001
|
|
|
Geno
|
86
|
302.5
|
3.6
|
65.9
|
<.001
|
0.75
|
|
Years X Geno
|
86
|
97.1
|
1.2
|
21.2
|
0.195
|
|
|
Total
|
173
|
458.5
|
|
|
|
|
Awl
|
Years
|
1
|
30.6
|
30.6
|
5.4
|
<.001
|
|
|
Geno
|
87
|
437.9
|
5.5
|
77.7
|
<.001
|
0.82
|
|
Years X Geno
|
87
|
94.7
|
1.2
|
16.8
|
0.125
|
|
|
Total
|
175
|
563.4
|
|
|
|
|
The correlation coefficients between the phenotypic traits are shown in Table 4. Number of tillers was positively and significantly correlated with biological yield, plant height, and awns length. Also, awns length, plant height, and biological yield were positively and significantly correlated. Number of days to heading was negatively correlated with grain filling duration (r = − 0.28) and number of tillers (r = − 0.27). By contrast, number of days to maturity was positively and highly correlated with grain filling duration (r = 0.46) and negatively correlated with plant height and biological yield (Table 4).
Table 4 The correlation coefficients among phenotypic traits of wild barley population.
Traits
|
Em
|
Dh
|
Dm
|
Gf
|
Tr
|
Ph
|
By
|
Awl
|
Em
|
1
|
|
|
|
|
|
|
|
Dh
|
-0.06
|
1
|
|
|
|
|
|
|
Dm
|
-0.17
|
0.67**
|
1
|
|
|
|
|
|
Gf
|
-0.10
|
-0.28*
|
0.46**
|
1
|
|
|
|
|
Tr
|
0.05
|
-0.27*
|
-0.25*
|
-0.04
|
1
|
|
|
|
Ph
|
0.01
|
-0.11
|
-0.13
|
-0.04
|
0.50**
|
1
|
|
|
By
|
0.09
|
-0.19
|
-0.24*
|
-0.04
|
0.74**
|
0.67**
|
1
|
|
Awl
|
0.13
|
-0.09
|
-0.17
|
-0.09
|
0.50**
|
0.45**
|
0.65**
|
1
|
**’* significant ≤ 0.001 and 0.0 5, respectively.
|
In this study, we used principal component analysis to describe the populations distribution by considering both morphological and agronomic data. Considering an eigenvalue greater than one, the PCA results showed that the first three principal components of T1 and two principal components of T2 accounted for 75% and 64% of the overall variation, respectively (Table 5). The variation in PC1, which explained 41% and 38% of the total variation on collection times T1 and T2, was correlated mainly with the number of tillers per plant, plant height, biological yield, and awns length. The grain filling duration showed the most significant loading to PC2, while the number of days to heading and maturity were the traits contributing to PC3, which explained the variation 20% and 14% in PC2 and PC3 of the total variation of collection time T1, respectively. However, these three traits showed the highest contribution to PC2 by explaining 26.2% of the total variations on collection time T2.
Table 5 Eigenvectors and eigenvalues of the first PCs of collection time study traits of wild barley populations.
|
Collection time T1
|
Collection time T2
|
|
Eigenvectors
|
Eigenvectors
|
Traits
|
PC1
|
PC2
|
PC3
|
PC1
|
PC2
|
Em
|
0.09
|
0.02
|
0.24
|
0.01
|
-0.37
|
Dh
|
-0.41
|
-0.79
|
0.43
|
-0.24
|
0.46
|
Dm
|
-0.68
|
0.02
|
0.72
|
-0.08
|
0.71
|
Gf
|
-0.29
|
0.89
|
0.33
|
0.15
|
0.31
|
Tr
|
0.66
|
-0.12
|
0.29
|
0.53
|
0.17
|
Ph
|
0.79
|
0.11
|
0.26
|
0.46
|
-0.01
|
By
|
0.89
|
0.06
|
0.28
|
0.52
|
-0.03
|
Awl
|
0.80
|
-0.13
|
0.19
|
0.38
|
0.14
|
Eigenvalues
|
3.42
|
1.68
|
1.22
|
2.81
|
1.93
|
% of total variance explained
|
41.03
|
20.15
|
14.73
|
38.06
|
26.2
|
% cumulative variance explained
|
41.03
|
61.18
|
75.91
|
38.06
|
64.26
|
The biplot highlighted some notable differences between the eighty populations resulting from two collecting times (Fig. 3). Half of the collected populations, regardless of collection time, were characterized by early heading and maturity, high number of tillers, tall plants, long awns, and high biological yield, were mainly from the northern part of the country. The biplot differentiated the populations in four groups as follows; Group 1 (G1) included 24 populations (collected from the same twelve sites both at T1 and T2) characterized by early heading and maturity, high number of tillers, tall plants, long awns, and high biological yield; Group 2 (G2) included 22 populations (collected from the same eleven sites both at T1 and T2) characterized by late heading and maturity, few tillers, short plant height and awns and low biological yield; the 34 populations representing the remaining 17 collection sites, showed a different performance depending on the collection time. Theses 34 populations were classified in two groups; Group 3 (G3) included 16 populations (representing eight collection sites), of which 8 populations collected at T1 showed the same performance as the populations in Group 1, while the same populations collected at T2 showed a performance similar to the populations classified in Group 2; 2) Group 4 (G4) included 18 populations (representing nine collection sites) of which 9 populations collected at T1 had a performance similar to the populations classified in Group 2, while the same populations collected at T2 had a performance similar to the populations classified in Group 1.
Phenotypic distances assess the differentiation between the population groups, where the smallest phenotypic distances (d = between 2.94 and 3.88) were found within populations for each group, while the largest phenotypic distances (d = between 5.02 and 5.50) were found between populations groups with different performance (Table 6). Cluster analyses of phenotypic distances aggregated the populations into two major groups (Fig. 4). The first cluster included the T1G2, T2G2, T1G4, and T2G3, where all population were characterized by late heading and maturity, few tillers, short plant height and awns and low biological yield. The second cluster included T1G1, T2G1, T1G3, and T2G4, where all population were characterized by early heading and maturity, a high number of tillers, tall plants, long awns, and high biological yield.
Table 6 Phenotypic distance determined between 8 morphological traits in the Jordanian populations of Hordeum vulgare spp. spontaneum from two collection times.
Population
|
T1G1
|
T1G2
|
T1G3
|
T1G4
|
T2G1
|
T2G2
|
T2G3
|
T2G4
|
T1G1
|
3.70
|
|
|
|
|
|
|
|
T1G2
|
5.09
|
3.55
|
|
|
|
|
|
|
T1G3
|
4.14
|
5.16
|
2.94
|
|
|
|
|
|
T1G4
|
5.11
|
4.47
|
5.50
|
3.49
|
|
|
|
|
T2G1
|
4.48
|
5.14
|
4.52
|
5.06
|
3.88
|
|
|
|
T2G2
|
4.99
|
4.24
|
5.12
|
4.05
|
5.06
|
3.12
|
|
|
T2G3
|
5.10
|
4.30
|
5.43
|
4.28
|
5.22
|
4.22
|
3.32
|
|
T2G4
|
4.09
|
4.95
|
3.80
|
5.02
|
4.16
|
4.89
|
4.77
|
3.05
|
Trait diversity amongst the grouping of population is presented in Table 7. In general, the diversity among each collection times showed that T1 has relatively wider diversity (mean CV across the 8 traits 18.45%) and its groups represent the maximum variations (12.25% to 19.05), while T2 (mean CV across the 8 traits 17.44%) and its groups represent the variations from 11.93–16.23%. The highest variability amongst traits was found within G1T1 (19.05%) followed by G2 T2 (16.23%), followed by G4 T2 (14.9%).
Table 7 Mean, minimum, maximum, SD and CV for emergence plant%, days to flowering and maturity, day of grain filling, tiller number, plant height, biological yield and awn length for wild barley according to collection time.
Collection time
|
|
Em
|
Dh
|
Dm
|
Gf
|
Tr
|
Ph
|
By
|
Awl
|
|
Mean
|
48.5
|
80.2
|
109.2
|
28.9
|
17.6
|
59.1
|
14.9
|
15.0
|
Collection T1
|
Sd
|
12.2
|
3.1
|
3.2
|
2.1
|
4.6
|
11.2
|
6.7
|
2.7
|
|
Cv
|
25.2
|
3.9
|
3.0
|
7.3
|
26.2
|
18.9
|
44.8
|
18.3
|
|
|
|
|
|
|
|
|
|
|
Collection T2
|
Mean
|
51.7
|
81.6
|
109.4
|
27.9
|
17.3
|
62.4
|
16.9
|
15.7
|
|
Sd
|
13.4
|
3.2
|
3.1
|
2.9
|
3.5
|
11.8
|
6.5
|
3.0
|
|
Cv
|
25.9
|
3.9
|
2.8
|
10.4
|
20.1
|
18.9
|
38.3
|
19.2
|
Group1, T1 (T1G1)
|
Mean
|
47.5
|
79.1
|
108.9
|
29.6
|
18.9
|
62.3
|
15.6
|
15.7
|
|
Sd
|
8.6
|
3.2
|
4.1
|
2.4
|
5.2
|
14.5
|
7.3
|
3.3
|
|
Cv
|
18.1
|
4.0
|
3.7
|
8.0
|
27.6
|
23.2
|
47.0
|
20.8
|
Group1, T2 (T2G1)
|
Mean
|
53.8
|
81.8
|
109.0
|
27.3
|
19.5
|
69.6
|
20.8
|
17.3
|
|
Sd
|
10.9
|
3.6
|
2.6
|
3.1
|
3.1
|
8.0
|
4.0
|
1.8
|
|
Cv
|
20.4
|
4.4
|
2.4
|
11.2
|
16.0
|
11.5
|
19.0
|
10.5
|
Group2, T1 (T1G2)
|
Mean
|
53.6
|
80.2
|
108.7
|
28.5
|
14.0
|
53.7
|
10.6
|
13.7
|
|
Sd
|
12.7
|
2.5
|
3.0
|
1.6
|
2.0
|
4.8
|
2.4
|
2.3
|
|
Cv
|
23.6
|
3.1
|
2.8
|
5.7
|
14.4
|
9.0
|
22.6
|
16.8
|
Group2, T2 (T2G2)
|
Mean
|
51.1
|
83.3
|
111.2
|
28.0
|
15.7
|
55.3
|
12.0
|
13.4
|
|
Sd
|
17.2
|
3.0
|
2.9
|
3.1
|
2.9
|
9.5
|
2.8
|
2.7
|
|
Cv
|
33.5
|
3.7
|
2.6
|
11.2
|
18.6
|
17.1
|
23.2
|
19.9
|
Group3, T1 (T1G3)
|
Mean
|
42.8
|
83.4
|
111.5
|
28.5
|
16.1
|
53.0
|
11.6
|
14.0
|
|
Sd
|
16.3
|
2.3
|
2.1
|
2.9
|
3.1
|
4.9
|
2.2
|
0.7
|
|
Cv
|
38.2
|
2.8
|
1.8
|
10.1
|
19.4
|
9.2
|
18.6
|
4.7
|
Group3, T2(T2G3)
|
Mean
|
48.1
|
80.0
|
106.1
|
26.3
|
18.7
|
72.1
|
22.5
|
17.8
|
|
Sd
|
8.7
|
2.1
|
1.3
|
1.3
|
2.8
|
8.4
|
8.2
|
3.0
|
|
Cv
|
18.2
|
2.7
|
1.2
|
5.1
|
15.1
|
11.6
|
36.4
|
17.0
|
Group4, T1(T1G4)
|
Mean
|
48.6
|
79.0
|
108.0
|
28.9
|
21.7
|
66.8
|
22.2
|
16.6
|
|
Sd
|
11.2
|
2.7
|
2.5
|
1.6
|
3.3
|
10.6
|
5.9
|
2.8
|
|
Cv
|
23.0
|
3.5
|
2.3
|
5.6
|
15.0
|
15.9
|
26.7
|
17.1
|
Group4, T2 (T2G4)
|
Mean
|
52.8
|
80.8
|
110.8
|
30.1
|
14.9
|
52.7
|
12.8
|
14.4
|
|
Sd
|
15.8
|
2.9
|
2.9
|
2.4
|
3.0
|
8.5
|
2.9
|
2.3
|
|
Cv
|
30.0
|
3.6
|
2.6
|
7.9
|
20.2
|
16.1
|
22.9
|
16.1
|
There were different levels of variations in both collection times for the traits we recorded (Table 7). A). The two collection times T1 and T2 showed a coefficient of variation ranging from 10.4–44.8% for all traits, except for days to heading and days to maturity for which the coefficient of variation varied from 2.8–3.9%. The populations collected at T1 in G1 were diversified in the stable traits more than populations from collection T2 except in emergence percentage and grain filling. The populations from collection T2 in both G 2 and G3 diversified in all traits more than the population from collection T1 except in the emergence percentage and grain filling where the populations from collection T1 showed more variation in G3. Also, the populations’ collected at T2 in group 4 diversified in plant height and the number of tillers more than those collected at T1, though the populations collected at T1 diversified in percent emergence, biological yield, and awn lengths more than those collected at T2.
Phenotypic variation and the impact of environmental conditions
Mantel test showed significant relationship between bioclimate variables and altitudes within the four sub population groups (G1, G2, G3 and G4) collected at T1 and T2 (r = 0.76, p < 0.0001; r = 0.81, p < 0.0001; r = 0.70, p < 0.0001; r = 0.76, p < 0.0001, respectively), and among populations (r = 0.79, p < 0.001). On the other hand, no relationship was found between all groups with geographical variables, except for populations in group G2 and among populations were bioclimatic variables correlated moderately with altitudes (r = 0.33, p= 0.01; r = 0.30, p= 0.01, respectively).
The correlations between agronomic traits, bioclimatic variables, and altitude for both collection time T1 and T2 are shown in Figure 5. The populations biological yield and awns length relatively correlated significantly and positively with the bioclimate variables in collection times T1 and T2. The correlations between agronomic traits and bioclimate variables showed a more varied pattern among populations in G3 and G4 than G1 and G2 in both collection times. Indeed, the grain filling period of populations in G1 collected at T1 correlated positively with precipitation variables and significantly with precipitation seasonality, and days to heading correlated positively with temperature variables at T2. In the case of populations of G2 collected at T1, their days to heading, days to maturity were significantly correlated with temperature variables, while in the same populations collected at T2, tiller number was positively correlated with precipitations variables. In the populations of G3 collected at T1, only grain filling periods was positively correlated with precipitation variables, and negatively with the bioclimate variables. By contrast, days to heading and days to maturity were significantly and positively correlated with temperature variables. In the populations of G4 collected at T2, percent emergence and biological yield were positively correlated with precipitations variables.
A principal component analysis of the phenotypic data including control varieties is shown in Figure 6. In the case of the population collected at T1, the first two axes accounted for 34.29% and 24.25% of the total variation, respectively. In the case of the populations collected at T2, the first two axes accounted for 33.18% and 28.69% of the total variation, respectively. The PCA separated the control varieties in two groups (Figure 6). The biological yield and tiller number of the H. spontaneum populations, namely collected at T2 were higher than the improved cultivars as compared with the H. spontaneum populations collected at T1. They were also taller and with a longer grain filling period