# Characterization of Morphological Diversity of Jute Mallow(Corchorus spp.)

Authors: Munguatosha Ngomuo; Tsvetelina Stoilova; Tileye Feyissa; Patrick A. Ndakidemi
Journal: International Journal of Agronomy
 (2017)

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## Abstract

Jute mallow is a traditional leaf vegetable that is an important part of daily diet for the majority of people in rural areas in sub-Saharan Africa. Here we employed quantitative and qualitative phenotypic traits to assess the morphological diversity of 90 accessions using univariate and multivariate analyses. Field experiments were conducted for two seasons to identify accessions suitable for leaf yield. The accessions were significantly variable in all traits. Highest variability among accessions was found in harvest index, biomass yield, and weight of 1000 seeds. The traits that significantly correlated with biomass yield include plant height (r=0.448), petiole length (r=0.237), primary branches (r=0.319), and number of leaves per plant (r=0.333). Principal component analysis showed that the first five PCs with eigenvalues ≥1 explained 72.9% of the total variability in the accessions. Pods per plant, primary branches, secondary branches, and number of leaves per plant accounted for highest variability in PC1. Cluster analysis grouped the accessions into five major clusters mainly based on their origin. Thus, the collection displayed high variation in morphological traits, particularly those related to leaf yield. These accessions are therefore useful in breeding for the improvement of the crop and germplasm management.


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## Body

## 1. Introduction

Jute mallow(Corchorus spp.) is a very nutritious African traditional vegetable and has been in use in many households [1–4]. The genusCorchorus is comprised of annual or short-lived perennial herbs and shrubs with many agriculturally useful species [5]. It is widely known for its high genetic diversity and geographical distribution andCorchorus olitoriusis from Africa [6–9]. The vegetable is extensively grown for the sliminess of the leaves used in local dishes. It is one of the leading leafy vegetables in West Africa [10].Crop improvement programs on Jute mallow for selection of varieties with finer and high-quality fiber have received considerable attention over the years in Asian countries such as China, Bangladesh, and India [11–13]. However, improvement programs on the Jute mallow as a vegetable, particularlyC. olitoriusand other wild relatives used as a vegetable in Africa, are very limited [14, 15].Characterization of genetic diversity among accessions of different germplasms by using phenotypic traits is an initial step towards crop improvement [16–18]. The variation in these traits can be used to classify materials into different groups. In Jute mallow, because of variations in local types in traits such as plant height, stem color, pubescence, fruit and leaf shape, and leaf production, Westphal-Stevels [1] proposed a classification of Cameroon materials and other West African countries into three cultivar groups, that is, cv.-groupOlitorius, cv.-groupIncisifolius, and cv.-groupGéant de Bertoua, with the main distinguishing feature being leaf shape.Morphological studies on several accessions have been done in Nigeria to separate segregated populations into different leaf types [19].Nwangburuka and Denton [14] reported significant differences among fifteen genotypes in terms of morphological traits such as plant height at maturity, number of leaves per plant, fresh leaf weight, stem weight, total plant weight, and harvest index. Osawaru et al. [20] used morphological traits and presence of soluble proteins to determine the relationship among threeCorchorusspecies. Traits such as growth habit and stem features appeared to be uniform except for stem color. They also found that determinate growth habit, medium plant branching, and erect stems were the most important traits for production of leaves, which are edible part and are needed by farmers. Nyadanu et al. [15] reported high variability in morphological traits in local cultivars of Ghana. The cultivars were grouped based on their geographical origin and traits such as number of leaves per plant, leaf length, and number of branches per plant were the most informative traits in differentiating the accessions.Few studies on genetics of leaf yield and its components have been conducted on Jute mallow; however, only few accessions have been used [11, 14, 20]. Benor et al. [9] assessed patterns of morphological variation in Jute mallow accessions of Ethiopian origin and compared them with those from other parts of the world. In their study, samples were collected from Ethiopia and compared with the samples from Asia and Africa. They found high genetic diversity among the African accessions and high similarity between North African accessions and Asian accessions. Accessions from West and Southern Africa and some samples from East Africa were not included in this study. These accessions which may be highly diverse remain unexploited for breeding and improvement of jute mallow vegetable.The exploitation of existing diversity of characters of each individual accession forms a major principle in plant improvement. Thus, in order to improve leaf yield of Jute mallow, the knowledge required is not only that of the diversity and genetic variability of the available germplasm but also that of genetic architecture of leaf yield and its components.In view of the above, our study is focused on vegetative, inflorescence, fruit, and seed traits and their contribution towards divergence in these accessions as important step in identifying those which have high yield potential and good adaptation to specific environment.


## 2. Materials and Methods

### 2.1. Study Location

The experimental field was located at Madiira farm at an altitude of 1262 m above sea level, latitude 03.38′S and longitude 36.87°E. The soils are well drained. The center experiences annual average rainfall of 1500–1800 mm and average daily temperature range of 22–27°C.


### 2.2. Experimental Design and Layout

The experiments had two phases: first sowing the accessions in the screen house followed by transplanting of seedling to the field. In the screen house the seeds were sown in plastic trays (with 66 holes; diameter of 4 cm and depth of 4 cm) by using sterilized soil. After 28 days, the seedlings were transplanted to the field. Each plot size was 3 m × 0.6 m with three replications. Each replication contained 90 plots. The plots were arranged according to a completely randomized design. Each accession was planted in two rows, and the space between plants was 0.25 m with 12 plants per row.Fertilizer application was done one week after transplanting, where diammonium phosphate (DAP) and urea fertilizers were applied. DAP was applied at a rate of 143.8 kgP/ha and urea at a rate of 55.2 kgN/ha. The experiments were conducted during the rainfall season; the plants were only supplemented with irrigation when necessary. Manual weeding was carried out when it was necessary to maintain weed-free plots.


### 2.3. The Experimental Materials

Ninety accessions of Jute mallow (Corchorus spp.) were provided by the seed repository of the World Vegetable Center, Eastern and Southern Africa, for these experiments (Table 1). The experiments were carried out for two growing seasons in 2015 and 2016 (from February to June). Jute mallow collection represents one of the different types of traditional vegetables collected from farmers’ field and preserved ex situ for breeding, other research activities, and farmers’ purposes.Table 1
The list of Jute mallow accessions(Corchorus spp.) used in this study.
SN
Accession name
Country of origin
1
HS
Tanzania
2
Bafia
Cameroon
3
Ex-Chamalawi
Malawi
4
IP 5
Kenya
5
IP10
Kenya
6
UG-JM-1
Uganda
7
SUD-1
Sudan
8
TOT 4879
USA
9
ML-JM-1
Malawi
10
TOT 5877
Japan
11
ES
Tanzania
12
ML-JM-14
Malawi
13
SUD-4
Sudan
14
CAMEROON
Cameroon
15
EX-ZIMBABWE
Zimbabwe
16
TOT 4064
Vietnam
17
TOT 0124
Malaysia
18
IP-2
Kenya
19
Aziga
Cameroon
20
ML-JM-5
Malawi
21
TOT 6426
Kenya
22
TOT 5876
Japan
23
UG-JM-2
Uganda
24
TOT 6278
Vietnam
25
SUD-3
Sudan
26
UG-JM-13
Uganda
27
TOT 4157
Vietnam
28
MIX
Tanzania
29
TOT 4885
Japan
30
TOT 5999
Taiwan
31
TOT 4429
Bangladesh
32
ALV MN 059
Unknown
33
KIPUMBULIKO
Unknown
34
ML-JM-2
Malawi
35
TOT 4712
Bangladesh
36
IP 1
Kenya
37
TOT 4721
Bangladesh
38
TOT 7977
Bangladesh
39
ML-JM-4
Malawi
40
TOT 4541
Bangladesh
41
ML-JM-13
Malawi
42
UG
Uganda
43
IP-4
44
GKK 10
Malawi
45
CAMEROON MULA
Cameroon
46
SUD-2
Sudan
47
TOT 4316
Bangladesh
48
TOT 4097
Tanzania, Kenya
49
Local Big Leaves
Mali
50
GKK 25
Malawi
51
ML-JM-12
Malawi
52
CAMEROON EX. CO
Cameroon
53
TOT 4669
Bangladesh
54
TOT 4051
Vietnam
55
TOT 4312
Bangladesh
56
TOT 4352
Bangladesh
57
ML-JM-7
Malawi
58
TOT 4519
Bangladesh
59
TOT 6280
Vietnam
60
TOT 4800
Vietnam
61
TOT 8975
Taiwan
62
TOT 4708
Bangladesh
63
TOT 4670
Bangladesh
64
TOT 7974
Bangladesh
65
TOT 4589
Bangladesh
66
TOT 4713
Bangladesh
67
TOT 3499
Vietnam
68
TOT 4067
Vietnam
69
TOT 4631
Bangladesh
70
TOT 4500
Bangladesh
71
TOT 8532
Unknown
72
TOT 6667
Philippines
73
ML-JM-9
Malawi
74
TOT 6730
Unknown
75
TOT 6425
Uganda
76
TOT 7980
Bangladesh
77
TOT 4413
Bangladesh
78
TZA 3070
Tanzania
79
TOT 9736
Unknown
80
TOT 4624
Bangladesh
81
TOT 6749
Unknown
82
TOT 4701
Bangladesh
83
TOT 4623
Bangladesh
84
TOT 7865
Unknown
85
TOT 7866
Unknown
86
TZA 3002
Tanzania
89
TOT 6427
Kenya
90
TOT 3584
Unknown


### 2.4. Morphological Study

Thirty-three quantitative and qualitative morphological traits were used to estimate the level of variation among the accessions from seedling stage to seed characterization (Table2). During vegetative growth, measurements of leaves and stem were recorded following Jute mallow descriptor list of WorldVeg [21]. Plant height, flower diameter, and pedicel length together with plant height and plant canopy were measured at flowering. 50% flowering was recorded for each accession. During maturity stage, data on first mature pod, fruit length, and fruit shape and color were recorded. The number of seeds per pod was counted and weight of 1000 seeds was also measured (Table 2).Table 2
Qualitative and quantitative traits used in this study.
SN
Character
Description
(1)
Plant height (PH)
Height of the plant measured at ground surface at 50% flowering (cm)
(2)
Leaf length (LL)
Leaf blade length excluding petiole length (cm)
(3)
Leaf width (LW)
Mature leaf width measured at widest point (cm)
(4)
Leaf length-width ratio (LWR)
The ratio of leaf length to leaf width
(5)
Petiole length (PL)
Length of leaf stalk (cm)
(6)
Days to 50% flowering (50 FLR)
Number of days from sowing to 50% flowering
(7)
Number of primary branches (PB)
Number of branches from main stem
(8)
Number of secondary branches (SB)
Number of branches from the secondary stem
(9)
Plant canopy (PC)
Plant width taken at widest point (cm)
(10)
Flower diameter (FD)
The width of an open flower (mm)
(11)
Pedicel length (PEDL)
The stalk of the flower (mm)
(12)
Fruit length (FL)
Length of mature fruit excluding the pedicel
(13)
Days to first mature pods (DMP)
Number of days from sowing to first mature pod
(14)
Harvest index (HI)
Ratio of total harvestable leaves to total weight of the plant
(15)
Number of leaves (NL)
Counted from individual plant during flowering
(16)
Biomass yield (BY)
Total weight of the plant above the ground surface (gm)
(17)
Number of pods/plant (NPP)
Counted from individual plant at maturity stage
(18)
Weight of 1000 seeds (W1000S)
Measured in weighing balance after counting
(19)
Seeds per pod (SP)
Counted from individual pod
(20)
Cotyledon color (CC)
(3) Light green, (5) green, (7) purplish green
(21)
Stem color (ST)
(3) Brown, (5) green, (7) red-purple
(22)
Leaf color (LC)
(1) Light green, (3) green, (5) dark green, (7) purple, (9) dark purple
(23)
Leaf lobe (LL)
(0)Absent, (1) present
(24)
Setae (S)
(1) Small, (2) large
(25)
Leaf shape (LS)
(1) Ovate, (3) elliptical, (5) cordate, (7) palmate
(26)
Leaf base (LB)
(1) Rounded, (3) sagittate, (5) acute
(27)
Leaf apex (LA)
(1) Acuminate, (3) caudate, (5) acute, (7) palmate
(28)
Leaf margin (LM)
(1) Coarsely serrate, (3) cleft, (5) double serrate, (7) finely serrate, (9) crenate
(29)
Stem pattern (SP)
(1) Erect, (2) semierect
(30)
Stipule color (SC)
(1) Green, (3) green stipule with dark red base, (5) light purple
(31)
Petiole color (PETC)
(1) Green, (3) green with dark red base, (5) purple
(32)
Fruit shape (FS)
(3) Globule, (5) long pod, (7) round pod
(33)
Fruit color (FRC)
(3) Pale brown, (5) brown, (7) brown


### 2.5. Data Analyses

For quantitative data, descriptive statistics, that is, mean and maximum and minimum values, were calculated followed by analysis of variance (ANOVA). The quantitative characters were plotted on box and whisker plots [22] to reveal the dispersion of data set in different populations. Frequency distribution table was used to describe the qualitative traits. Pearson’s simple correlations were used to compare the degrees of association in leaf yield and other traits. The quantitative data were standardized before they were used as an input for PCA and cluster analysis. Descriptive statistics and ANOVA were computed by STATISTICA software version 12, edition 2013 (StatSoft Inc., Tulsa, OK, USA). Multivariate analyses were performed with SAS software.


## 2.1. Study Location

The experimental field was located at Madiira farm at an altitude of 1262 m above sea level, latitude 03.38′S and longitude 36.87°E. The soils are well drained. The center experiences annual average rainfall of 1500–1800 mm and average daily temperature range of 22–27°C.


## 2.2. Experimental Design and Layout

The experiments had two phases: first sowing the accessions in the screen house followed by transplanting of seedling to the field. In the screen house the seeds were sown in plastic trays (with 66 holes; diameter of 4 cm and depth of 4 cm) by using sterilized soil. After 28 days, the seedlings were transplanted to the field. Each plot size was 3 m × 0.6 m with three replications. Each replication contained 90 plots. The plots were arranged according to a completely randomized design. Each accession was planted in two rows, and the space between plants was 0.25 m with 12 plants per row.Fertilizer application was done one week after transplanting, where diammonium phosphate (DAP) and urea fertilizers were applied. DAP was applied at a rate of 143.8 kgP/ha and urea at a rate of 55.2 kgN/ha. The experiments were conducted during the rainfall season; the plants were only supplemented with irrigation when necessary. Manual weeding was carried out when it was necessary to maintain weed-free plots.


## 2.3. The Experimental Materials

Ninety accessions of Jute mallow (Corchorus spp.) were provided by the seed repository of the World Vegetable Center, Eastern and Southern Africa, for these experiments (Table 1). The experiments were carried out for two growing seasons in 2015 and 2016 (from February to June). Jute mallow collection represents one of the different types of traditional vegetables collected from farmers’ field and preserved ex situ for breeding, other research activities, and farmers’ purposes.Table 1
The list of Jute mallow accessions(Corchorus spp.) used in this study.
SN
Accession name
Country of origin
1
HS
Tanzania
2
Bafia
Cameroon
3
Ex-Chamalawi
Malawi
4
IP 5
Kenya
5
IP10
Kenya
6
UG-JM-1
Uganda
7
SUD-1
Sudan
8
TOT 4879
USA
9
ML-JM-1
Malawi
10
TOT 5877
Japan
11
ES
Tanzania
12
ML-JM-14
Malawi
13
SUD-4
Sudan
14
CAMEROON
Cameroon
15
EX-ZIMBABWE
Zimbabwe
16
TOT 4064
Vietnam
17
TOT 0124
Malaysia
18
IP-2
Kenya
19
Aziga
Cameroon
20
ML-JM-5
Malawi
21
TOT 6426
Kenya
22
TOT 5876
Japan
23
UG-JM-2
Uganda
24
TOT 6278
Vietnam
25
SUD-3
Sudan
26
UG-JM-13
Uganda
27
TOT 4157
Vietnam
28
MIX
Tanzania
29
TOT 4885
Japan
30
TOT 5999
Taiwan
31
TOT 4429
Bangladesh
32
ALV MN 059
Unknown
33
KIPUMBULIKO
Unknown
34
ML-JM-2
Malawi
35
TOT 4712
Bangladesh
36
IP 1
Kenya
37
TOT 4721
Bangladesh
38
TOT 7977
Bangladesh
39
ML-JM-4
Malawi
40
TOT 4541
Bangladesh
41
ML-JM-13
Malawi
42
UG
Uganda
43
IP-4
44
GKK 10
Malawi
45
CAMEROON MULA
Cameroon
46
SUD-2
Sudan
47
TOT 4316
Bangladesh
48
TOT 4097
Tanzania, Kenya
49
Local Big Leaves
Mali
50
GKK 25
Malawi
51
ML-JM-12
Malawi
52
CAMEROON EX. CO
Cameroon
53
TOT 4669
Bangladesh
54
TOT 4051
Vietnam
55
TOT 4312
Bangladesh
56
TOT 4352
Bangladesh
57
ML-JM-7
Malawi
58
TOT 4519
Bangladesh
59
TOT 6280
Vietnam
60
TOT 4800
Vietnam
61
TOT 8975
Taiwan
62
TOT 4708
Bangladesh
63
TOT 4670
Bangladesh
64
TOT 7974
Bangladesh
65
TOT 4589
Bangladesh
66
TOT 4713
Bangladesh
67
TOT 3499
Vietnam
68
TOT 4067
Vietnam
69
TOT 4631
Bangladesh
70
TOT 4500
Bangladesh
71
TOT 8532
Unknown
72
TOT 6667
Philippines
73
ML-JM-9
Malawi
74
TOT 6730
Unknown
75
TOT 6425
Uganda
76
TOT 7980
Bangladesh
77
TOT 4413
Bangladesh
78
TZA 3070
Tanzania
79
TOT 9736
Unknown
80
TOT 4624
Bangladesh
81
TOT 6749
Unknown
82
TOT 4701
Bangladesh
83
TOT 4623
Bangladesh
84
TOT 7865
Unknown
85
TOT 7866
Unknown
86
TZA 3002
Tanzania
89
TOT 6427
Kenya
90
TOT 3584
Unknown


## 2.4. Morphological Study

Thirty-three quantitative and qualitative morphological traits were used to estimate the level of variation among the accessions from seedling stage to seed characterization (Table2). During vegetative growth, measurements of leaves and stem were recorded following Jute mallow descriptor list of WorldVeg [21]. Plant height, flower diameter, and pedicel length together with plant height and plant canopy were measured at flowering. 50% flowering was recorded for each accession. During maturity stage, data on first mature pod, fruit length, and fruit shape and color were recorded. The number of seeds per pod was counted and weight of 1000 seeds was also measured (Table 2).Table 2
Qualitative and quantitative traits used in this study.
SN
Character
Description
(1)
Plant height (PH)
Height of the plant measured at ground surface at 50% flowering (cm)
(2)
Leaf length (LL)
Leaf blade length excluding petiole length (cm)
(3)
Leaf width (LW)
Mature leaf width measured at widest point (cm)
(4)
Leaf length-width ratio (LWR)
The ratio of leaf length to leaf width
(5)
Petiole length (PL)
Length of leaf stalk (cm)
(6)
Days to 50% flowering (50 FLR)
Number of days from sowing to 50% flowering
(7)
Number of primary branches (PB)
Number of branches from main stem
(8)
Number of secondary branches (SB)
Number of branches from the secondary stem
(9)
Plant canopy (PC)
Plant width taken at widest point (cm)
(10)
Flower diameter (FD)
The width of an open flower (mm)
(11)
Pedicel length (PEDL)
The stalk of the flower (mm)
(12)
Fruit length (FL)
Length of mature fruit excluding the pedicel
(13)
Days to first mature pods (DMP)
Number of days from sowing to first mature pod
(14)
Harvest index (HI)
Ratio of total harvestable leaves to total weight of the plant
(15)
Number of leaves (NL)
Counted from individual plant during flowering
(16)
Biomass yield (BY)
Total weight of the plant above the ground surface (gm)
(17)
Number of pods/plant (NPP)
Counted from individual plant at maturity stage
(18)
Weight of 1000 seeds (W1000S)
Measured in weighing balance after counting
(19)
Seeds per pod (SP)
Counted from individual pod
(20)
Cotyledon color (CC)
(3) Light green, (5) green, (7) purplish green
(21)
Stem color (ST)
(3) Brown, (5) green, (7) red-purple
(22)
Leaf color (LC)
(1) Light green, (3) green, (5) dark green, (7) purple, (9) dark purple
(23)
Leaf lobe (LL)
(0)Absent, (1) present
(24)
Setae (S)
(1) Small, (2) large
(25)
Leaf shape (LS)
(1) Ovate, (3) elliptical, (5) cordate, (7) palmate
(26)
Leaf base (LB)
(1) Rounded, (3) sagittate, (5) acute
(27)
Leaf apex (LA)
(1) Acuminate, (3) caudate, (5) acute, (7) palmate
(28)
Leaf margin (LM)
(1) Coarsely serrate, (3) cleft, (5) double serrate, (7) finely serrate, (9) crenate
(29)
Stem pattern (SP)
(1) Erect, (2) semierect
(30)
Stipule color (SC)
(1) Green, (3) green stipule with dark red base, (5) light purple
(31)
Petiole color (PETC)
(1) Green, (3) green with dark red base, (5) purple
(32)
Fruit shape (FS)
(3) Globule, (5) long pod, (7) round pod
(33)
Fruit color (FRC)
(3) Pale brown, (5) brown, (7) brown


## 2.5. Data Analyses

For quantitative data, descriptive statistics, that is, mean and maximum and minimum values, were calculated followed by analysis of variance (ANOVA). The quantitative characters were plotted on box and whisker plots [22] to reveal the dispersion of data set in different populations. Frequency distribution table was used to describe the qualitative traits. Pearson’s simple correlations were used to compare the degrees of association in leaf yield and other traits. The quantitative data were standardized before they were used as an input for PCA and cluster analysis. Descriptive statistics and ANOVA were computed by STATISTICA software version 12, edition 2013 (StatSoft Inc., Tulsa, OK, USA). Multivariate analyses were performed with SAS software.


## 3. Results

### 3.1. Variation in Qualitative Characters

Fourteen qualitative characters of this study are summarized in a frequency distribution (Table3). At the seedling stage, three types of cotyledon colors were observed in our studied accessions in which 67% were light green, 30.9% were green, and 2.1% were purplish green. During vegetative growth, green stem color was predominant among the accessions (52%), while brown and red-purple colors were shared among the remaining accessions (24% each). Most accessions were characterized by light green and green leaf color. The presence of leaf lobe was only observed in 8.5% of accessions. These accessions were also characterized by palmate leaf shape and cleft leaf margins. The remaining accessions had no leaf lobes. For leaf shape, ovate and cordate leaf shapes were observed in 38.3% and 35.1%, respectively. Leaf margins and stem pattern displayed little variation; that is, 62.8% of accessions were coarsely serrate and 87.2% had erect stems. At maturity stage, among all the accessions, 62.8% possessed long pods, while 9.5% had globule fruits and the remaining accessions had round pods. Three types of fruit color were also observed: pale brown (67%), brown (11.7%), and dark brown (21.3%). The accessions were also highly variable in terms of stipule color and petiole color.Table 3
Frequency distribution table of qualitative morphological traits.
SN
Plant traits
Percentage
(1)
Cotyledon color
Light green
67
Green
30.90
Purplish green
2.10
(2)
Stem color
Brown
24
Green
52
Red-purple
24
(3)
Leaf color
Light green
38.30
Green
45.70
Dark green
5.30
Purple
8.50
Dark purple
1.10
(4)
Leaf lobe
Absent
91.50
Present
8.50
(5)
Setae
Small
72.30
Large
27.70
(6)
Leaf shape
Ovate
38.30
Elliptical
16
Cordate
35.10
Palmate
8.50
(7)
Leaf base
Round
87.20
Sagittate
6.40
Acute
6.40
(8)
Leaf apex
Acuminate
33
Caudate
10.60
Acute
46.80
Palmate
7.40
(9)
Leaf margin
Coarsely serrate
62.80
Cleft
9.60
Double serrate
13.80
Finely serrate
10.60
Crenate
3.20
(10)
Stem pattern
Erect
87.20
Semierect
12.80
(11)
Stipule color
Green
46.80
Green stipule with dark red base
26.60
Light purple
25.50
(12)
Petiole color
Light green
43.60
Dark green
28.70
Light purple
21.30
Purple
5.30
(13)
Fruit shape
Globule
9.50
Long pod
62.80
Round
27.70
(14)
Fruit color
Pale brown
67
Brown
11.70
Dark brown
21.30


### 3.2. Variation in Quantitative Characters

Significant (p<0.001) variation was revealed for vegetative, floral, and seed traits. Harvest index, biomass yield, and weight of 1000 seeds showed highly significant variation (Table 4). There was a wide range of values in traits such as numbers of primary and secondary branches, weight of 1000 seeds, number of pods per plant, and number of seeds per pod. Number of days to 50% flowering varied significantly, ranging from 52 days to 110 days; this grouped the accessions into three categories: early, mid, and late flowering. Days to first mature pod also corresponded to 50% flowering, which ranged from 73 days to 135 days; thus there were earlier and late maturing accessions in terms of seed yield. Similarly, plant canopy exhibited a wide range resulting from the growth habit of the accessions; some had bushy canopy with many primary and secondary branches, while others had small canopy with few primary and secondary branches. The wide range observed in fruit length from 0.5 cm to 18.2 cm is attributed to differences in fruit shapes; the accessions with round pods belong toC. capsularis species. They had very small fruit size as compared toC. olitorius species. Other traits such as petiole length, leaf length and width, flower diameter, and pedicel length, though had a fairly narrow range, differed significantly (p<0.001) among the accessions, indicating highly significant variation among the accessions.Table 4
The results of descriptive statistics for quantitative traits.
SN
Trait
Mean ± SE
Max.
Min.
(1)
Plant height (cm)
78.08
±
0.96
∗
∗
137.50
52
(2)
Leaf length (cm)
11.63
±
0.15
∗
∗
20.97
6.50
(3)
Leaf width (cm)
5.41
±
0.07
∗
∗
10.05
2.73
(4)
Leaf length-width ratio
2.22
±
0.08
∗
∗
3.16
1.12
(5)
Petiole length (cm)
4.85
±
0.08
∗
∗
10.22
1.99
(6)
Days to 50% flowering
64.93
±
0.54
∗
∗
110
52
(7)
Number of primary branches
12.16
±
0.19
∗
∗
21.60
1.00
(8)
Number of secondary branches
15.22
±
0.92
∗
∗
79.80
0
(9)
Plant canopy (cm)
71.88
±
1.18
∗
∗
125.10
10
(10)
Flower diameter (mm)
11.22
±
0.13
∗
∗
15.20
5.52
(11)
Pedicel length (mm)
2.28
±
0.03
∗
∗
4.22
1.14
(12)
Fruit length (cm)
5.05
±
0.13
∗
∗
18.20
0.50
(13)
Days to first mature pod
107.60
±
0.58
∗
∗
135
72.50
(14)
Harvest index
24.08
±
0.65
∗
∗
∗
61.35
0.90
(15)
Number of leaves
288.82
±
11.41
∗
∗
1329
15
(16)
Biomass yield
332.40
±
7.62
∗
∗
∗
1001
43
(17)
Number of pods/plant
111.96
±
6.48
∗
∗
660
0
(18)
Weight of 1000 seeds
1.48
±
0.04
∗
∗
∗
4.50
1
(19)
Number of seeds per pod
136.42
±
3.69
∗
∗
275
8
⁢Significant∗∗ at p<0.01. Significant∗∗∗ at p<0.001.Box and whisker plots are displayed in Figure1 for selected quantitative traits. The accessions were divided into seven subpopulations based on their origin. Populations A, B, C, and E were from Africa, while populations F and G were from Asia. In terms of plant height, the highest interquartile ranges were observed in a group of accessions originating from Southeast Asia.Figure 1
Box and whisker plots showing the variation in quantitative traits of the accessions from different parts: (A) West Africa, (B) East Africa, (C) South Africa, (D) unknown, (E) North Africa, (F) Southeast Asia, and (G) East Asia.All accessions from Africa showed almost the same average plant height irrespective of which part of the continent they originated from. West African and North African accessions had high interquartile ranges for both leaf length and leaf width. Southeast Asian accessions had highest interquartile ranges for number of leaves per plant as compared with the rest of other populations. 50% flowering period did not vary much across all populations. Harvest index and plant canopy traits indicated high variability among the accessions, which were reflected in leaf yield. The highest plant canopy was observed in accessions from East Africa.


### 3.3. Simple Correlations

Biomass yield was statistically significant (p=0.05) and positively correlated with plant height (r=0.448), petiole length (r=0.237), primary branches (r=0.319), days to first mature pods (r=0.306), and number of leaves per plant (r=0.333) (Table 5). Harvest index was positively and significantly correlated to leaf width (r=0.355), petiole length (r=0.310), and days to 50% flowering (r=0.270). It was also negatively correlated with secondary branches (r=0.350). Positive and significant correlation was observed between number of leaves per plant and plant height (r=0.505), petiole length (r=0.261), 50% flowering (r=0.378), primary and secondary branches (r=0.577 and 0.559), pods per plant (r=0.582), and number of days to first mature pods (r=0.433). On the other hand, seed yield components such as number of pods per plant were positively and significantly correlated with plant height (r=0.357), 50% flowering (r=0.307), and primary and secondary branches (r=0.620 and 0.680). Fruit length was positively correlated to plant canopy (r=0.378) and flower diameter (r=0.561). It was negatively correlated to 50% flowering and primary and secondary branches. Number of seeds per pod was positively correlated with leaf width (r=0.307), plant canopy (r=0.271), flower diameter (r=0.694), and fruit length (r=0.658).Table 5
Simple correlation matrix for the 19 quantitative traits ofCorchorusspp.
PH
LL
LW
LWR
PL
50 FLR
PB
SB
PC
FD
PED L
FL
NPP
DMP
NL
SP
HI
W1000S
BY
PH
LL
0.10
LW
−0.01
0.50
∗
LWR
0.14
0.46
∗
-
0.52
∗
PL
0.35
∗
−0.07
0.38
∗
-
0.42
∗
50 FLR
0.38
∗
−0.06
0.07
−0.09
0.29
∗
PB
0.47
∗
-
0.23
∗
-
0.23
∗
0.11
0.25
∗
0.38
∗
SB
0.28
∗
-
0.32
∗
-
0.57
∗
0.33
∗
-
0.22
∗
0.13
0.48
∗
PC
−0.03
−0.19
-
0.24
∗
0.05
−0.15
-
0.58
∗
0.02
0.18
FD
−0.06
0.27
∗
0.48
∗
-
0.26
∗
0.31
∗
-
0.24
∗
-
0.24
∗
-
0.61
∗
0.10
PEDL
0.29
∗
0.23
∗
0.40
∗
−0.14
0.30
∗
0.03
0.20
−0.06
−0.18
0.27
∗
FL
−0.02
0.01
0.13
−0.18
−0.04
-
0.42
∗
-
0.23
∗
-
0.44
∗
0.38
∗
0.56
∗
0.16
NPP
0.38
∗
−0.19
-
0.45
∗
0.34
∗
−0.01
0.31
∗
0.62
∗
0.68
∗
0.01
-
0.66
∗
−0.12
-
0.57
∗
DMP
0.44
∗
−0.01
0.23
∗
−0.20
0.53
∗
0.65
∗
0.47
∗
0.15
-
0.51
∗
−0.09
0.40
∗
-
0.39
∗
0.32
∗
NL
0.52
∗
-
0.23
∗
−0.18
0.03
0.26
∗
0.38
∗
0.58
∗
0.56
∗
0.06
-
0.44
∗
0.12
-
0.32
∗
0.58
∗
0.43
∗
SP
-
0.27
∗
0.15
0.31
∗
-
0.23
∗
0.09
-
0.45
∗
-
0.29
∗
-
0.45
∗
0.27
∗
0.69
∗
0.16
0.66
∗
-
0.66
∗
-
0.31
∗
-
0.42
∗
HI
-
0.22
∗
−0.05
0.36
∗
-
0.36
∗
0.31
∗
0.27
∗
0.04
-
0.35
∗
−0.11
0.21
−0.05
−0.15
−0.15
0.14
−0.05
0.06
W1000S
−0.19
−0.18
−0.19
0.01
−0.03
-
0.26
∗
−0.07
−0.03
0.29
∗
0.14
0.00
0.17
−0.12
−0.21
−0.09
0.13
0.04
BY
0.45
∗
−0.11
0.11
-
0.21
∗
0.24
∗
0.01
0.32
∗
0.14
0.16
0.07
0.17
0.14
0.10
0.31
∗
0.33
∗
−0.02
−0.16
−0.15
S
i
g
n
i
f
i
c
a
n
t
∗ at p<0.05. PH: plant height; LL: leaf length; LW: leaf width; LWR: leaf width ratio; PL: petiole length; 50 FLR: 50% flowering; PB: primary branches; SB: secondary branches; PC: plant canopy; FD: flower diameter; PEDL: pedicel length; FL: fruit length; NPP: number of pods per plant; DMP: days to first mature pods; NL: number of leaves per plant; SP: number of seeds per pod; HI: harvest index; W1000S: weight of 1000 seeds; BY: biomass yield.


### 3.4. Principal Component Analysis

Principal component analysis (PCA) of the 19 quantitative traits is summarized in Table6. The first five PCs had eigenvalues > 1 and they explained 72.97% of the total variation for the morphological traits of the accessions. Numbers of primary and secondary branches, number of pods per plant, and number of leaves per plant loaded highly in PC1 and they accounted for 27.33% of the total variation of the studied samples.Table 6
Eigenvalues, proportion of variance, and morphological traits that contributed to the first five PCs.
Traits
PC1
PC2
PC3
PC4
PC5
Plant height
0.22
0.19
0.28
0.28
−0.02
Leaf length
−0.11
0.09
−0.19
0.60
0.16
Leaf width
−0.19
0.38
−0.09
0.09
−0.10
LW ratio
0.12
−0.28
−0.08
0.48
0.31
Petiole length
0.03
0.39
0.13
−0.17
0.17
50% flowering
0.24
0.27
−0.24
−0.07
0.01
Primary branches
0.30
0.11
0.24
−0.03
0.23
Secondary branches
0.33
−0.19
0.15
0.01
0.00
Plant canopy
−0.08
−0.25
0.44
−0.11
0.06
Flower diameter
−0.32
0.21
0.16
0.07
0.17
Pedicel length
−0.02
0.29
0.18
0.26
0.26
Fruit length
−0.29
−0.00
0.36
0.06
−0.07
Pods per plant
0.38
−0.09
0.02
0.01
0.09
Days to first mature pods
0.23
0.38
−0.04
0.02
0.06
Number of leaves
0.33
0.09
0.22
−0.06
0.03
Seeds per pod
−0.34
0.05
0.22
0.02
0.05
Harvest index
−0.07
0.22
−0.22
−0.39
0.25
Weight of 1000 seeds
−0.09
−0.14
0.15
−0.22
0.66
Biomass yield
0.09
0.17
0.41
0.05
−0.40
Eigenvalues
5.19
3.54
2.24
1.81
1.08
Proportion variance
(
%
)
27.33
18.65
11.81
9.51
5.66
Cumulative variance
(
%
)
27.33
45.98
57.79
67.30
72.97PC2 accounted for 18.65% of the total morphological variation among the accessions. Leaf width, petiole length, and days to first mature pods loaded more in PC2. PC3 accounted for 11.81% of the total variation. Traits such as plant canopy, fruit length, and biomass yield loaded more in PC3. PC4 contributed 9.51% of the total morphological variation in these accessions with only leaf length and leaf length-width ratio loading highly. PC5 accounted for 5.66% of total variation with weight of 1000 seeds loading highly. Generally, for the 19 morphological traits studied, PC1 and PC2 constituted 45.9% of the total morphological variation with most vegetative traits and seeds related traits. This indicated that these traits can be used to classify the accessions under this study.Three-dimensional principal component analysis showing the relationship among quantitative traits of studied accessions is presented in Figure2. Accessions from West Africa, East Africa, and North Africa recorded higher values for PC2; traits related to leaves and days to first mature pods were found at the center of PCA scatter plot. Accessions from Asia had higher values for PC1, those related to branching habit, pods per plant, and number of leaves per plant. These accessions were most dispersed and diverse as compared to other accessions.Figure 2
Three principle components showing relationship among quantitative traits of studied accessions.


### 3.5. Cluster Analysis

Dendrogram for complete linkage cluster analysis of quantitative and qualitative traits is presented in Figure3. The results indicated that the accessions were grouped into five major clusters. Cluster 1 contained 7 accessions from Bangladesh and Vietnam. These are characterized by stems and leaves that are purple in color and have round pods. Also these accessions had high number of branches (Table 7). Cluster 2 contained 7 accessions from Bangladesh and Vietnam with addition of two accessions from Malaysia and one from Taiwan. These were characterized by both green stems and purple stems and the leaves were green. Accessions in this cluster belong toC. capsularis except three accessions on top of the cluster. They are also characterized by highest plant height compared to all other accessions. Cluster 3 contained 12 accessions: 7 from Bangladesh and Japan, four from unknown origin, and 1 from Kenya. These were classified with semierect stems and few pods and high plant canopy compared with other clusters. All had long pods and belong to speciesC.olitorius. Cluster 4 was the largest one with 33 accessions from almost all countries. These had both erect and semierect stem patterns. Cluster 5 contained 29 accessions: 9 from East and Southern Africa, 8 from Asia, 4 from an unknown origin, 2 from North Africa, and 6 from West Africa. The accessions (8) in the upper cluster are characterized by palmate leaves with cleft margins. The other 10 accessions are characterized by big leaves. In this cluster, accessions such as Bafia and Aziga had globule pods as compared to other accessions which had long and round pods. These had erect stems and have late flowering. Generally, clusters 1 and 2 contained accessions from Asia, while cluster 5 contained accessions from Africa. This grouping pattern indicates their distinct centers of origin and ecological adaptation. Clusters 3 and 4 contained mixed accessions from different countries.Table 7
Cluster analysis for 19 quantitative traits ofCorchorusspp. accessions.
Traits
C1
C2
C3
C4
C5
Plant height
83.51
98.50
63.88
76.43
78.38
Leaf length
10.38
11.36
10.60
11.24
12.85
Leaf width
3.94
4.63
4.96
5.16
6.43
LW ratio
2.70
2.48
2.18
2.22
2.04
Petiole length
4.70
4.36
3.45
4.74
5.75
50% flowering
72.79
75.28
62.21
59.73
67.20
Primary branches
16.81
14.06
9.22
11.95
11.92
Secondary branches
37.18
33.26
10.10
14.28
7.03
Plant canopy
73.10
57.98
73.59
79.77
65.30
Flower diameter
7.49
8.28
10.29
11.96
12.63
Pedicel length
1.85
2.48
1.93
2.32
2.44
Fruit length
2.13
4.01
5.32
5.97
4.95
Pods per plant
351.38
222.41
74.60
77.70
74.29
Day to first mature pod
112.48
116.48
99.44
103.69
111.65
Number of leaves
502.85
505.12
182.66
245.00
264.49
Seeds per pod
29.88
50.69
134.95
166.32
155.23
Harvest index
28.47
15.65
23.85
22.94
28.33
Weight of 1000 seeds
1.55
1.06
1.38
1.62
1.49
Biomass yield
344.29
377.27
250.29
347.56
332.24Figure 3
Dendrogram of 90 accessions ofCorchorusspp. explained by complete linkage clustering of 19 quantitative traits and 14 qualitative traits. The source of accessions is indicated by the country code of respective accession and UKN represents unknown accession.


## 3.1. Variation in Qualitative Characters

Fourteen qualitative characters of this study are summarized in a frequency distribution (Table3). At the seedling stage, three types of cotyledon colors were observed in our studied accessions in which 67% were light green, 30.9% were green, and 2.1% were purplish green. During vegetative growth, green stem color was predominant among the accessions (52%), while brown and red-purple colors were shared among the remaining accessions (24% each). Most accessions were characterized by light green and green leaf color. The presence of leaf lobe was only observed in 8.5% of accessions. These accessions were also characterized by palmate leaf shape and cleft leaf margins. The remaining accessions had no leaf lobes. For leaf shape, ovate and cordate leaf shapes were observed in 38.3% and 35.1%, respectively. Leaf margins and stem pattern displayed little variation; that is, 62.8% of accessions were coarsely serrate and 87.2% had erect stems. At maturity stage, among all the accessions, 62.8% possessed long pods, while 9.5% had globule fruits and the remaining accessions had round pods. Three types of fruit color were also observed: pale brown (67%), brown (11.7%), and dark brown (21.3%). The accessions were also highly variable in terms of stipule color and petiole color.Table 3
Frequency distribution table of qualitative morphological traits.
SN
Plant traits
Percentage
(1)
Cotyledon color
Light green
67
Green
30.90
Purplish green
2.10
(2)
Stem color
Brown
24
Green
52
Red-purple
24
(3)
Leaf color
Light green
38.30
Green
45.70
Dark green
5.30
Purple
8.50
Dark purple
1.10
(4)
Leaf lobe
Absent
91.50
Present
8.50
(5)
Setae
Small
72.30
Large
27.70
(6)
Leaf shape
Ovate
38.30
Elliptical
16
Cordate
35.10
Palmate
8.50
(7)
Leaf base
Round
87.20
Sagittate
6.40
Acute
6.40
(8)
Leaf apex
Acuminate
33
Caudate
10.60
Acute
46.80
Palmate
7.40
(9)
Leaf margin
Coarsely serrate
62.80
Cleft
9.60
Double serrate
13.80
Finely serrate
10.60
Crenate
3.20
(10)
Stem pattern
Erect
87.20
Semierect
12.80
(11)
Stipule color
Green
46.80
Green stipule with dark red base
26.60
Light purple
25.50
(12)
Petiole color
Light green
43.60
Dark green
28.70
Light purple
21.30
Purple
5.30
(13)
Fruit shape
Globule
9.50
Long pod
62.80
Round
27.70
(14)
Fruit color
Pale brown
67
Brown
11.70
Dark brown
21.30


## 3.2. Variation in Quantitative Characters

Significant (p<0.001) variation was revealed for vegetative, floral, and seed traits. Harvest index, biomass yield, and weight of 1000 seeds showed highly significant variation (Table 4). There was a wide range of values in traits such as numbers of primary and secondary branches, weight of 1000 seeds, number of pods per plant, and number of seeds per pod. Number of days to 50% flowering varied significantly, ranging from 52 days to 110 days; this grouped the accessions into three categories: early, mid, and late flowering. Days to first mature pod also corresponded to 50% flowering, which ranged from 73 days to 135 days; thus there were earlier and late maturing accessions in terms of seed yield. Similarly, plant canopy exhibited a wide range resulting from the growth habit of the accessions; some had bushy canopy with many primary and secondary branches, while others had small canopy with few primary and secondary branches. The wide range observed in fruit length from 0.5 cm to 18.2 cm is attributed to differences in fruit shapes; the accessions with round pods belong toC. capsularis species. They had very small fruit size as compared toC. olitorius species. Other traits such as petiole length, leaf length and width, flower diameter, and pedicel length, though had a fairly narrow range, differed significantly (p<0.001) among the accessions, indicating highly significant variation among the accessions.Table 4
The results of descriptive statistics for quantitative traits.
SN
Trait
Mean ± SE
Max.
Min.
(1)
Plant height (cm)
78.08
±
0.96
∗
∗
137.50
52
(2)
Leaf length (cm)
11.63
±
0.15
∗
∗
20.97
6.50
(3)
Leaf width (cm)
5.41
±
0.07
∗
∗
10.05
2.73
(4)
Leaf length-width ratio
2.22
±
0.08
∗
∗
3.16
1.12
(5)
Petiole length (cm)
4.85
±
0.08
∗
∗
10.22
1.99
(6)
Days to 50% flowering
64.93
±
0.54
∗
∗
110
52
(7)
Number of primary branches
12.16
±
0.19
∗
∗
21.60
1.00
(8)
Number of secondary branches
15.22
±
0.92
∗
∗
79.80
0
(9)
Plant canopy (cm)
71.88
±
1.18
∗
∗
125.10
10
(10)
Flower diameter (mm)
11.22
±
0.13
∗
∗
15.20
5.52
(11)
Pedicel length (mm)
2.28
±
0.03
∗
∗
4.22
1.14
(12)
Fruit length (cm)
5.05
±
0.13
∗
∗
18.20
0.50
(13)
Days to first mature pod
107.60
±
0.58
∗
∗
135
72.50
(14)
Harvest index
24.08
±
0.65
∗
∗
∗
61.35
0.90
(15)
Number of leaves
288.82
±
11.41
∗
∗
1329
15
(16)
Biomass yield
332.40
±
7.62
∗
∗
∗
1001
43
(17)
Number of pods/plant
111.96
±
6.48
∗
∗
660
0
(18)
Weight of 1000 seeds
1.48
±
0.04
∗
∗
∗
4.50
1
(19)
Number of seeds per pod
136.42
±
3.69
∗
∗
275
8
⁢Significant∗∗ at p<0.01. Significant∗∗∗ at p<0.001.Box and whisker plots are displayed in Figure1 for selected quantitative traits. The accessions were divided into seven subpopulations based on their origin. Populations A, B, C, and E were from Africa, while populations F and G were from Asia. In terms of plant height, the highest interquartile ranges were observed in a group of accessions originating from Southeast Asia.Figure 1
Box and whisker plots showing the variation in quantitative traits of the accessions from different parts: (A) West Africa, (B) East Africa, (C) South Africa, (D) unknown, (E) North Africa, (F) Southeast Asia, and (G) East Asia.All accessions from Africa showed almost the same average plant height irrespective of which part of the continent they originated from. West African and North African accessions had high interquartile ranges for both leaf length and leaf width. Southeast Asian accessions had highest interquartile ranges for number of leaves per plant as compared with the rest of other populations. 50% flowering period did not vary much across all populations. Harvest index and plant canopy traits indicated high variability among the accessions, which were reflected in leaf yield. The highest plant canopy was observed in accessions from East Africa.


## 3.3. Simple Correlations

Biomass yield was statistically significant (p=0.05) and positively correlated with plant height (r=0.448), petiole length (r=0.237), primary branches (r=0.319), days to first mature pods (r=0.306), and number of leaves per plant (r=0.333) (Table 5). Harvest index was positively and significantly correlated to leaf width (r=0.355), petiole length (r=0.310), and days to 50% flowering (r=0.270). It was also negatively correlated with secondary branches (r=0.350). Positive and significant correlation was observed between number of leaves per plant and plant height (r=0.505), petiole length (r=0.261), 50% flowering (r=0.378), primary and secondary branches (r=0.577 and 0.559), pods per plant (r=0.582), and number of days to first mature pods (r=0.433). On the other hand, seed yield components such as number of pods per plant were positively and significantly correlated with plant height (r=0.357), 50% flowering (r=0.307), and primary and secondary branches (r=0.620 and 0.680). Fruit length was positively correlated to plant canopy (r=0.378) and flower diameter (r=0.561). It was negatively correlated to 50% flowering and primary and secondary branches. Number of seeds per pod was positively correlated with leaf width (r=0.307), plant canopy (r=0.271), flower diameter (r=0.694), and fruit length (r=0.658).Table 5
Simple correlation matrix for the 19 quantitative traits ofCorchorusspp.
PH
LL
LW
LWR
PL
50 FLR
PB
SB
PC
FD
PED L
FL
NPP
DMP
NL
SP
HI
W1000S
BY
PH
LL
0.10
LW
−0.01
0.50
∗
LWR
0.14
0.46
∗
-
0.52
∗
PL
0.35
∗
−0.07
0.38
∗
-
0.42
∗
50 FLR
0.38
∗
−0.06
0.07
−0.09
0.29
∗
PB
0.47
∗
-
0.23
∗
-
0.23
∗
0.11
0.25
∗
0.38
∗
SB
0.28
∗
-
0.32
∗
-
0.57
∗
0.33
∗
-
0.22
∗
0.13
0.48
∗
PC
−0.03
−0.19
-
0.24
∗
0.05
−0.15
-
0.58
∗
0.02
0.18
FD
−0.06
0.27
∗
0.48
∗
-
0.26
∗
0.31
∗
-
0.24
∗
-
0.24
∗
-
0.61
∗
0.10
PEDL
0.29
∗
0.23
∗
0.40
∗
−0.14
0.30
∗
0.03
0.20
−0.06
−0.18
0.27
∗
FL
−0.02
0.01
0.13
−0.18
−0.04
-
0.42
∗
-
0.23
∗
-
0.44
∗
0.38
∗
0.56
∗
0.16
NPP
0.38
∗
−0.19
-
0.45
∗
0.34
∗
−0.01
0.31
∗
0.62
∗
0.68
∗
0.01
-
0.66
∗
−0.12
-
0.57
∗
DMP
0.44
∗
−0.01
0.23
∗
−0.20
0.53
∗
0.65
∗
0.47
∗
0.15
-
0.51
∗
−0.09
0.40
∗
-
0.39
∗
0.32
∗
NL
0.52
∗
-
0.23
∗
−0.18
0.03
0.26
∗
0.38
∗
0.58
∗
0.56
∗
0.06
-
0.44
∗
0.12
-
0.32
∗
0.58
∗
0.43
∗
SP
-
0.27
∗
0.15
0.31
∗
-
0.23
∗
0.09
-
0.45
∗
-
0.29
∗
-
0.45
∗
0.27
∗
0.69
∗
0.16
0.66
∗
-
0.66
∗
-
0.31
∗
-
0.42
∗
HI
-
0.22
∗
−0.05
0.36
∗
-
0.36
∗
0.31
∗
0.27
∗
0.04
-
0.35
∗
−0.11
0.21
−0.05
−0.15
−0.15
0.14
−0.05
0.06
W1000S
−0.19
−0.18
−0.19
0.01
−0.03
-
0.26
∗
−0.07
−0.03
0.29
∗
0.14
0.00
0.17
−0.12
−0.21
−0.09
0.13
0.04
BY
0.45
∗
−0.11
0.11
-
0.21
∗
0.24
∗
0.01
0.32
∗
0.14
0.16
0.07
0.17
0.14
0.10
0.31
∗
0.33
∗
−0.02
−0.16
−0.15
S
i
g
n
i
f
i
c
a
n
t
∗ at p<0.05. PH: plant height; LL: leaf length; LW: leaf width; LWR: leaf width ratio; PL: petiole length; 50 FLR: 50% flowering; PB: primary branches; SB: secondary branches; PC: plant canopy; FD: flower diameter; PEDL: pedicel length; FL: fruit length; NPP: number of pods per plant; DMP: days to first mature pods; NL: number of leaves per plant; SP: number of seeds per pod; HI: harvest index; W1000S: weight of 1000 seeds; BY: biomass yield.


## 3.4. Principal Component Analysis

Principal component analysis (PCA) of the 19 quantitative traits is summarized in Table6. The first five PCs had eigenvalues > 1 and they explained 72.97% of the total variation for the morphological traits of the accessions. Numbers of primary and secondary branches, number of pods per plant, and number of leaves per plant loaded highly in PC1 and they accounted for 27.33% of the total variation of the studied samples.Table 6
Eigenvalues, proportion of variance, and morphological traits that contributed to the first five PCs.
Traits
PC1
PC2
PC3
PC4
PC5
Plant height
0.22
0.19
0.28
0.28
−0.02
Leaf length
−0.11
0.09
−0.19
0.60
0.16
Leaf width
−0.19
0.38
−0.09
0.09
−0.10
LW ratio
0.12
−0.28
−0.08
0.48
0.31
Petiole length
0.03
0.39
0.13
−0.17
0.17
50% flowering
0.24
0.27
−0.24
−0.07
0.01
Primary branches
0.30
0.11
0.24
−0.03
0.23
Secondary branches
0.33
−0.19
0.15
0.01
0.00
Plant canopy
−0.08
−0.25
0.44
−0.11
0.06
Flower diameter
−0.32
0.21
0.16
0.07
0.17
Pedicel length
−0.02
0.29
0.18
0.26
0.26
Fruit length
−0.29
−0.00
0.36
0.06
−0.07
Pods per plant
0.38
−0.09
0.02
0.01
0.09
Days to first mature pods
0.23
0.38
−0.04
0.02
0.06
Number of leaves
0.33
0.09
0.22
−0.06
0.03
Seeds per pod
−0.34
0.05
0.22
0.02
0.05
Harvest index
−0.07
0.22
−0.22
−0.39
0.25
Weight of 1000 seeds
−0.09
−0.14
0.15
−0.22
0.66
Biomass yield
0.09
0.17
0.41
0.05
−0.40
Eigenvalues
5.19
3.54
2.24
1.81
1.08
Proportion variance
(
%
)
27.33
18.65
11.81
9.51
5.66
Cumulative variance
(
%
)
27.33
45.98
57.79
67.30
72.97PC2 accounted for 18.65% of the total morphological variation among the accessions. Leaf width, petiole length, and days to first mature pods loaded more in PC2. PC3 accounted for 11.81% of the total variation. Traits such as plant canopy, fruit length, and biomass yield loaded more in PC3. PC4 contributed 9.51% of the total morphological variation in these accessions with only leaf length and leaf length-width ratio loading highly. PC5 accounted for 5.66% of total variation with weight of 1000 seeds loading highly. Generally, for the 19 morphological traits studied, PC1 and PC2 constituted 45.9% of the total morphological variation with most vegetative traits and seeds related traits. This indicated that these traits can be used to classify the accessions under this study.Three-dimensional principal component analysis showing the relationship among quantitative traits of studied accessions is presented in Figure2. Accessions from West Africa, East Africa, and North Africa recorded higher values for PC2; traits related to leaves and days to first mature pods were found at the center of PCA scatter plot. Accessions from Asia had higher values for PC1, those related to branching habit, pods per plant, and number of leaves per plant. These accessions were most dispersed and diverse as compared to other accessions.Figure 2
Three principle components showing relationship among quantitative traits of studied accessions.


## 3.5. Cluster Analysis

Dendrogram for complete linkage cluster analysis of quantitative and qualitative traits is presented in Figure3. The results indicated that the accessions were grouped into five major clusters. Cluster 1 contained 7 accessions from Bangladesh and Vietnam. These are characterized by stems and leaves that are purple in color and have round pods. Also these accessions had high number of branches (Table 7). Cluster 2 contained 7 accessions from Bangladesh and Vietnam with addition of two accessions from Malaysia and one from Taiwan. These were characterized by both green stems and purple stems and the leaves were green. Accessions in this cluster belong toC. capsularis except three accessions on top of the cluster. They are also characterized by highest plant height compared to all other accessions. Cluster 3 contained 12 accessions: 7 from Bangladesh and Japan, four from unknown origin, and 1 from Kenya. These were classified with semierect stems and few pods and high plant canopy compared with other clusters. All had long pods and belong to speciesC.olitorius. Cluster 4 was the largest one with 33 accessions from almost all countries. These had both erect and semierect stem patterns. Cluster 5 contained 29 accessions: 9 from East and Southern Africa, 8 from Asia, 4 from an unknown origin, 2 from North Africa, and 6 from West Africa. The accessions (8) in the upper cluster are characterized by palmate leaves with cleft margins. The other 10 accessions are characterized by big leaves. In this cluster, accessions such as Bafia and Aziga had globule pods as compared to other accessions which had long and round pods. These had erect stems and have late flowering. Generally, clusters 1 and 2 contained accessions from Asia, while cluster 5 contained accessions from Africa. This grouping pattern indicates their distinct centers of origin and ecological adaptation. Clusters 3 and 4 contained mixed accessions from different countries.Table 7
Cluster analysis for 19 quantitative traits ofCorchorusspp. accessions.
Traits
C1
C2
C3
C4
C5
Plant height
83.51
98.50
63.88
76.43
78.38
Leaf length
10.38
11.36
10.60
11.24
12.85
Leaf width
3.94
4.63
4.96
5.16
6.43
LW ratio
2.70
2.48
2.18
2.22
2.04
Petiole length
4.70
4.36
3.45
4.74
5.75
50% flowering
72.79
75.28
62.21
59.73
67.20
Primary branches
16.81
14.06
9.22
11.95
11.92
Secondary branches
37.18
33.26
10.10
14.28
7.03
Plant canopy
73.10
57.98
73.59
79.77
65.30
Flower diameter
7.49
8.28
10.29
11.96
12.63
Pedicel length
1.85
2.48
1.93
2.32
2.44
Fruit length
2.13
4.01
5.32
5.97
4.95
Pods per plant
351.38
222.41
74.60
77.70
74.29
Day to first mature pod
112.48
116.48
99.44
103.69
111.65
Number of leaves
502.85
505.12
182.66
245.00
264.49
Seeds per pod
29.88
50.69
134.95
166.32
155.23
Harvest index
28.47
15.65
23.85
22.94
28.33
Weight of 1000 seeds
1.55
1.06
1.38
1.62
1.49
Biomass yield
344.29
377.27
250.29
347.56
332.24Figure 3
Dendrogram of 90 accessions ofCorchorusspp. explained by complete linkage clustering of 19 quantitative traits and 14 qualitative traits. The source of accessions is indicated by the country code of respective accession and UKN represents unknown accession.


## 4. Discussion

Germplasm collections from underutilized traditional vegetables such as Jute mallow can be an important step in breeding for improvement of the crop [23, 24]. Accessions, particularly those from East and Southern Africa, remain unexploited. The accessions under this study are morphologically very diverse according to the multivariate analysis of both quantitative and qualitative traits. The accessions demonstrated high variation in harvest index, biomass yield, and weight of 1000 seeds. These are important aspects to consider during selection of accessions with high leaf yield. Adebo et al. [7] and Nwangburuka and Denton [14] reported number of leaves per plant, plant height at maturity, and harvest index as discriminating traits amongC. olitorius accessions. In breeding for leafy vegetable, these materials can be used as parental stock. Variation in primary and secondary branches is an important informative trait in differentiating accessions, particularly those desirable for leaf production. Accessions from East Africa had high plant canopy, which is a result of high branching habit and large leaves. These traits are attributes of leaf yield. Similar results are reported by Benor et al. [9] and Shukla et al. [25] in Jute mallow and amaranth, respectively. Accessions from East Asia show lowest interquartile ranges for leaf length, leaf width, and number of leaves. This indicates accessions more desirable for fiber than leaf production.The analysis of simple correlations among the traits revealed that accessions with high plant height, petiole length, and number of primary branches had high biomass yield as well as fruits. Positive correlations recorded among the accessions suggest that these traits can be used as selection criteria for accessions with high leaf yield. Plant height was also positively and significantly related to number of days to 50% flowering. Similar to our study, Ojiewo et al. [26] reported significant correlation between days to 50% flowering and plant height in lentil. These traits can be transferred to desired accessions through breeding due to high heritability. Positive correlation between harvest index and 50% flowering is a challenge for leaf harvesting of these accessions. The most limiting and significant factors to leaf production and yield are early and prolific flowering and berry production [27].Traits such as number of primary branches, pods per plant, and number of leaves per plant accounted for the variations recorded in the accessions in PC1. Similar to our study, Nyadanu et al. [15] reported leaf length and numbers of branches per plant and leaves per plant as traits that defined PC1 in their study. On the other hand, leaf width, days to first mature pods, and petiole length accounted for the variation observed in the accessions in PC2. Total cumulative variance was 45.98%, indicating the high degree of diversity among the traits under study. Furthermore, the traits can be used as phenotypic markers in differentiating the accessions.Cluster analysis grouped the accessions into five clusters. Clusters 1 and 2 contained accessions from Asia only. These accessions are fromC. capsularis species. Few numbers of branches (5–8 branches), high plant height, and low number of leaves characterized these accessions (Figure 2). This is attributed to unique selection pressure that aimed to improve fiber yield. Palit et al. [11] reported greater homogeneity in accessions from Asia, which was due to uniformity in selection pressure from commercial considerations. It is interesting that one accession from East Africa clustered with accessions from Asia. This pattern of clustering indicates, on one hand, the diversity of population within these geographical areas and, on the other hand, similarity of accessions from different geographical areas. These results agree with the report of Alemayehu and Becker [28] inBrassica carinata. This is due to some level of similarity in other quantitative traits, though the accession belongs toC. olitorius species. Cluster 4 contained mixed accessions from all countries under study. Twenty-five out of thirty-three accessions were from Africa; the remaining accessions from Asia and USA indicate frequent exchange of germplasm across the countries [29]. Similarly, cluster 5 contained most accessions from Africa, a clustering pattern that indicates the distinct nature of the accessions. Most of these accessions were from East and Southern Africa. Some materials with uncertain origin appeared in clusters 3, 4, and 5. However, the origins of the accessions can be traced through their clustering pattern. Generally, the clustering of all accessions in our study indicates significant difference in diversity among their origins as most of Asian accessions are clustered at lower part of dendrogram, that is, clusters 1, 2, and 3. Accessions from Africa are mostly found in the upper part of the dendrogram, that is, clusters 4 and 5.


## 5. Conclusion

Morphological diversity studies on leaf vegetable Jute mallow(Corchorus spp.) were carried out in 90 accessions. The results from ANOVA, simple correlations, and multivariate analyses indicated high variation among the studied materials. Significant and positive correlation between biomass yield and other leaf yield-related attributes indicates the potential of using these accessions for improvement of foliage yield. Traits such as plant height, primary branches, and number of leaves per plant proved to be superior in contributing to biomass yield. Based on biomass yield and harvest index traits, accessions Aziga, TOT 8532, UG-JM-13, UG-JM-2, GKK 25, TOT 7980, ML-JM-1, UG-JM-1, Local Big Leaves, and Ex-Chamalawi had highest yields and could be used as potential parental lines for improvement of leaf yield. On the other hand, principal component analysis showed that the variations observed in the accessions are mainly caused by traits such as number of leaves per plant, petiole length, leaf width, days to first mature pods, and branching habit, indicating that their contribution was important in discriminating the accessions. Cluster analysis grouped the accessions based on their origin into five clusters that showed high diversity for most of the traits, demonstrating the homogeneity of accessions from specific location, except for cluster 4. This clustering pattern can be exploited for identification of highly diverse accessions falling in different clusters for future genetic improvement of this crop. Direct selection can also be made for the accessions with high harvest index and biomass yield based on the recorded performance of these accessions during the field experiments. These results can further be confirmed by molecular diversity analysis, as it has been confirmed by other studies using different materials. In our study, the accessions from this germplasm showed another allele diversity that has remained unexploited for improvement of this vegetable. Therefore, plant breeders can use these germplasms for improvement of Jute mallow.



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*Source: 6460498-2017-08-08.xml*