Advances in Agriculture
Volume 2018 (2018), Article ID 8568424, 11 pages
https://doi.org/10.1155/2018/8568424

Research Article

Heritability Analysis and Phenotypic Characterization of Spider Plant (Cleome gynandra L.) for Yield

Ann Kangai Munene,¹ Felister Nzuve,¹ Jane Ambuko,¹ and Damaris Odeny²

¹Department of Crop Science and Crop Protection, University of Nairobi, Kenya
²The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Nairobi, Kenya

Correspondence should be addressed to Ann Kangai Munene; wakaireann@gmail.com

Received 30 November 2017; Revised 30 March 2018; Accepted 12 July 2018; Published 31 July 2018

Academic Editor: Mumtaz Cheema

Copyright © 2018 Ann Kangai Munene et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Knowledge on phenotypic diversity among existing spider plant accessions is a milestone in the improvement of spider plant, which is a highly nutritious indigenous vegetable in Kenya. A study involving agronomic and morphological characterization of 49 spider plant accessions assembled from East and South Africa was carried out at the University of Nairobi Field Station for two seasons in a randomized complete block design with three replications. Phenotypic data was collected on growth habit, flower, petiole, leaf and stem colour, petiole, leaf and stem hairiness, number of leaves per plant, plant height, number of primary branches, leaf length and width, single leaf area, and chlorophyll content according to FAO descriptors with modifications. Data was analyzed using both DARwin software V6 and Genstat Version 14. We observed significant differences among the traits implying great genetic variability among the evaluated spider plant accessions. The high genetic variation was further validated using the Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering method with stem and flower colour as key traits. The 49-spider plant accessions were clustered into 2 major groups, each consisting of Kenyan and South African accessions. Stepwise regression revealed that plant height had the most influence on yield in terms of number of leaves per plant. We also observed high heritability for several traits including days to flowering (91%), number of leaves per plant (99%), plant height (99%), number of primary branches (94%), chlorophyll content (94%), and single leaf area (87%). Our results reveal the high genetic variation between different spider plant accessions, especially from different regions of Africa that could be further exploited to improve productivity in the plant. The high heritability of most of the yield related traits is promising for improving yield in the crop through direct selection.

1. Introduction

Cleome gynandra, also known as “African spider plant”, is among the most important traditional leafy vegetables widely used in Africa [1]. It belongs to the family of Capparaceae. It is also an erect herbaceous annual herb that is mainly self-pollinated [2]. The plant is highly nutritive and contains health promoting bioactive compounds important in combating malnutrition and reducing human degenerative diseases. Spider plant is native to the Southern Africa, Western Africa, Central Africa, Eastern Africa, and South East Asia [3]. In South Africa, spider plant has been found to grow in the wild in KwaZulu-Natal, Free State, Northern Cape, Limpopo, and North West provinces [3]. In Kenya, the plants are mainly found in Western, Rift Valley, Eastern, and Coastal regions. The key counties producing the crop include Kisii, Nyamira, Kericho, Migori, and Siaya [4]. Despite this wide adaptation and continued increase in production and consumption, there have been limited efforts towards its improvement. There is lack of critical information on the extent and structure of phenotypic variation crucial for the breeding and conservation of spider plant [2, 5]. Genetic diversity is particularly useful in characterizing individual accessions and cultivars, in detecting genetic materials with novel genes and thereby rescuing them from genetic erosion, and as a general guide, in selecting appropriate parents in breeding programs. Most of the genetic diversity observed in spider plant in Kenya and South Africa has traditionally been maintained by farmers in situ. This poses the risk of species extinction due to loss of natural habitat as humans continue to exploit and develop land, divert water flow, and change the environment. Secondly, as human population continues to increase, there is pressure on natural land being cleared by human activity. The need for cultivation, conservation, and characterization of spider plant remains imperative in maintaining the integrity of the genetic information and diversity.

Mendelian analysis of discrete morphological traits can be used to estimate genetic diversity in plants [6] and has been successfully used in spider plant [5]. Some of the key traits that have been used as a guide in selection for good genotypes in previous studies included high heritability traits such as days to flowering, plant height, and number of leaves per plant [7]. Omondi [7] observed that higher leaf yield, plant uniformity, longer vegetative phase, late flowering, and drought tolerance could form the best criterion in selection of good performing spider plant accessions. However, for an efficient crop improvement program, information on estimates of heritability for these desirable traits must be established [8]. Due to limited knowledge on the genetic variability, more research remains of the essence to elucidate the genetic and phenotypic diversity of existing spider plant accessions. Thus, the main thrust of this study was to understand the extent of phenotypic diversity and heritability of qualitative traits among 49 spider plant accessions assembled from Kenya and South Africa. Promising spider plant accessions can be utilized in various breeding programs and have the potential of enhancing its utilization while aiding to fight hidden hunger in Kenya.

2. Materials and Methods

2.1. Plant Materials

The study used 49 spider plant accessions, mainly local landraces assembled from 3 sources: Gene bank of Kenya (25), Gene bank of South Africa (9), and Kenyan farmers’ landraces (15) (Table 1).

Table 1: List of Kenyan and South African spider plant accessions evaluated in the study.

Entry
Accession no.
Country of origin
Region

1
1
Kenya
Siaya

2
2
Kenya
Bungoma

3
3
Kenya
Kakamega

4
4
Kenya
Kitale

5
5
Kenya
Mbale

6
6
Kenya
Bomet

7
7
Kenya
Busia

8
9
Kenya
Marakwet

9
10
Kenya
Kisumu

10
11
Kenya
Homabay

11
12
Kenya
Nandi

12
13
Kenya
Kakamega

13
14
Kenya
Kisii

14
15
Kenya
Mbale

15
16
Kenya
Meru

16
1959
South Africa
Mpumalanga

17
1988
South Africa
Mpumalanga

18
2000
South Africa
Mpumalanga

19
2232
South Africa
Northern province

20
2241
South Africa
Northern province

21
2249
South Africa
Northern province

22
2279
South Africa
Northern province

23
2289
South Africa
Mpumalanga

24
2299
South Africa
Mpumalanga

25
30316
Kenya
Western

26
31990
Kenya
Western

27
31992
Kenya
Western

28
45426
Kenya
Western

29
45446
Kenya
Central

30
45451
Kenya
Central

31
50259
Kenya
Kisii

32
50264
Kenya
Nyamira

33
50265
Kenya
Nyamira

34
50273
Kenya
Nyamira

35
50290
Kenya
Nyamira

36
50296
Kenya
Nyamira

37
50298
Kenya
Nyamira

38
50299
Kenya
Nyamira

39
50307
Kenya
Kisii

40
50319
Kenya
Nyamira

41
50325
Kenya
Kisii

42
50326
Kenya
Nyamira

43
50328
Kenya
Nyamira

44
50330
Kenya
Nyamira

45
50332
Kenya
Kisii

46
50339
Kenya
Nyamira

47
50353
Kenya
Nyamira

48
50584
Kenya
Nyamira

49
50600
Kenya
Kisii

=originated from Kenya; =originated from South Africa.

2.2. Experimental Design and Study Site

The experiments were carried out at the University of Nairobi’s Kabete Field station (Nairobi, Kenya) for two seasons from March 2014 to May 2014 and October 2014 to January 2015. The experiments were laid out in a randomized complete block design with three replications. Kabete Field station lies at 36°41′E and 01°15’S with an altitude of 1737 m above sea level. It receives an average temperature of 23°C with a bimodal rainfall pattern and an annual precipitation of 600 mm to 1800 mm. The soil type is well drained very dark reddish, brown to dark red friable clay locally known as Kikuyu red clay loam with an average pH of 6.2 [9].

2.3. Crop Husbandry

Pregermination for each accession was done for 72 hours under treatment with 0.2% gibberellic acid to break seed dormancy and enhance germination [10]. Each individual accession was planted by hand in two rows comprising ten seeding holes per row (20 plants in a plot). Row plots were 3 m in length with inter-row spacing of 30 cm and intra-row spacing of 30 cm. Farmyard manure was applied to rows at the rate of 10.5 g/accession and mixed with soil at planting. Hand weeding was done throughout the experimental period. The experiment was conducted under rain-fed conditions with supplemental overhead irrigation when required.

2.4. Data Collection and Analysis

There were two sets of data collected in the study, namely, qualitative (morphological) and quantitative (agronomic).

2.5. Qualitative Traits

Spider plant traits that were considered qualitative included growth habit, flower colour, stem colour, stem hairiness, petiole colour, petiole hairiness, leaf colour, and leaf pubescence based on the list of modified spider plant descriptors [11] (Table 2). Three randomly selected plants were tagged per accession per replicate during crop growth, before flowering. The data was subjected to DARwin 5.0 software as described by Perrier and Jacquemoud-Collet [12]. Euclidean distance matrix and hierarchical clustering analyses of Unweighted Pair Group Method of Arithmetic averaging were used to estimate dissimilarities among the accessions and results displayed in a dendrogram. This was followed by the identification of the most significant descriptors contributing to most phenotypic variation among the spider plant accessions through a stepwise regression analysis.

Table 2: Character, descriptor, and codes used for characterization of qualitative traits in spider plant accessions.

S/No.
Character
Descriptor and code

1
Growth habit
Erect , semi-erect and prostrate

2
Flower colour
White , purple and pink

3
Stem colour
Green , pink , violet and purple

4
Stem hairiness
Glabrous , weak/sparse , medium and profuse

5
Petiole colour
Green , pink , violet and purple ,

6
Petiole hairiness
Glabrous , weak/sparse , medium and profuse

7
Leaf colour
Dark green and light green ,

8
Leaf hairiness
Glabrous , weak/sparse , medium and profuse

Source: Food and Agriculture Organization of the United Nations (FAO, 1995); numbers in brackets on the right-hand side are the corresponding descriptor codes listed in the FAO publication with modifications during the development of the list.

2.6. Quantitative Traits

All the yield and yield related traits were considered quantitative, including days to 50% flowering, SPAD values, plant height, number of primary branches, leaf length, leaf width, single leaf area, and number of leaves per plant. Using Genstat version 14 software as described by [13], the data was subjected to Analysis of Variance to establish any significance differences among the traits and to obtain genotype means which were then separated using the Fishers protected least significant differences (LSD) at P < 0.05.

To establish the relationship among the traits collected, a two-tail correlation analysis was performed to estimate quantitative relationships among the traits and also to identify those traits that could be of great significance in a spider plant breeding program.

Heritability in the broad sense was estimated as a ratio of genotypic variance to the phenotypic variance and expressed in percentage [14] as per the following equation.

where is the genotypic variance and is the phenotypic variance.

Genotypic variance () was derived by subtracting error mean sum of squares (EMS) from the genotypic mean sum of squares (GMS) and divided by the number of replications as given by the following equation.

where

 GMS is the genotype mean sum of squares, EMS is the error mean sum of squares, and r is the number of replications.

Phenotypic variance () was derived by adding genotypic variance with error variance as per the following equation.

3. Results and Discussions

3.1. Qualitative Traits

There were three distinct flower colours displayed by the spider plant accessions: purple, pink, and white. Among these, the purple flower colour was the most dominant among the Kenyan accessions at 49% (Table 3) while the most dominant flower colour among the South African accessions was white. Most of the South African accessions displayed a green stem with a green petiole as opposed to the Kenyans accessions, which displayed purple stems and pubescence. Previous study by Masuka and Mazarura [15] reported that purple-stemmed plants tended to be more hairy (trichomes) than the green-stemmed plants. Anthocyanins have been implicated as responsible for the stem pigmentation in most herbaceous plants [16] and have also been widely studied for their potential medicinal value [17]. Although spider plants have been traditionally used for medicinal purposes [18], the obvious contrast between South African and Kenyan accessions in their anthocyanin content calls for more studies in order to elucidate the benefits of the variations observed. Presence of trichomes, on the other hand, has been associated with insect resistance in several studies including soybean [19], pigeonpea [20], and Brassicaceae [21]. Trichomes are considered a domestication trait and are often more abundant in unadapted landraces than in improved germplasm. The absence of trichomes in South African accessions may suggest that they have undergone much more intense selection cycles than the Kenyan accessions, although more studies would need to be done to confirm this fact.

Table 3: Morphological descriptors recorded for the 49 field grown spider plant accessions for the combined season.

Entry
Accession no.
Origin
Flower colour
Stem colour
Petiole colour
Stem hairiness
Petiole hairiness
Leaf colour
Leaf hairiness
Growth habit

1
1
Kenya
Purple
Purple
Green
Profuse
Medium
dark green
Medium
Erect

2
2
Kenya
White
Purple
Pink
Profuse
Medium
light green
Sparse
Erect

3
3
Kenya
Pink
Purple
Pink
Profuse
Medium
dark green
Sparse
Erect

4
4
Kenya
Pink
Purple
Pink
Profuse
Medium
light green
Medium
Erect

5
5
Kenya
White
Purple
Purple
Profuse
Profuse
light green
Profuse
Erect

6
6
Kenya
Pink
Purple
Pink
Profuse
Profuse
dark green
Medium
Erect

7
7
Kenya
Pink
Purple
Purple
Profuse
Medium
dark green
Medium
Erect

8
9
Kenya
White
Purple
Purple
Profuse
Profuse
dark green
Sparse
Erect

9
10
Kenya
Purple
Purple
Purple
Medium
Medium
light green
Sparse
Erect

10
11
Kenya
Pink
Purple
Purple
Medium
Medium
dark green
Medium
Erect

11
12
Kenya
Pink
Purple
Purple
Profuse
Medium
light green
Sparse
Erect

12
13
Kenya
Purple
Purple
Purple
Medium
Medium
light green
Sparse
Erect

13
14
Kenya
Purple
Green
Purple
Profuse
Profuse
dark green
Medium
Erect

14
15
Kenya
Pink
Purple
Purple
Medium
Sparse
dark green
Sparse
Erect

15
16
Kenya
Pink
Purple
Pink
Medium
Sparse
light green
Sparse
Erect

16
1959
S. Africa
Pink
Purple
Pink
Profuse
Medium
light green
Medium
Erect

17
1988
S. Africa
White
Green
Green
Sparse
Sparse
light green
Sparse
Semi erect

18
2000
S. Africa
White
Green
Green
Glabrous
Glabrous
light green
Glabrous
semi erect

19
2232
S. Africa
White
Green
Green
Glabrous
Glabrous
dark green
Glabrous
Erect

20
2241
S. Africa
White
Green
Pink
Sparse
Sparse
light green
Sparse
Erect

21
2249
S. Africa
White
Green
Pink
Glabrous
Glabrous
light green
Glabrous
Erect

22
2279
S. Africa
White
Green
Green
Glabrous
Glabrous
light green
Glabrous
Semi erect

23
2289
S. Africa
White
Green
Pink
Medium
Sparse
dark green
Sparse
Erect

24
2299
S.Africa
White
Green
Green
Glabrous
Sparse
light green
Glabrous
Erect

25
30316
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

26
31990
Kenya
Purple
green
Green
Medium
Sparse
light green
Sparse
Erect

27
31992
Kenya
Pink
purple
Green
Profuse
Medium
dark green
Medium
Erect

28
45426
Kenya
Purple
Purple
Green
Profuse
Sparse
dark green
Sparse
Erect

29
45446
Kenya
White
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

30
45451
Kenya
Pink
Purple
Purple
Profuse
Profuse
dark green
Medium
Erect

31
50259
Kenya
Pink
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

32
50264
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

33
50265
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
Erect

34
50273
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

35
50290
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
Semi erect

36
50296
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
Erect

37
50298
Kenya
Purple
Purple
Purple
Medium
Sparse
light green
Sparse
Semi erect

38
50299
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
Erect

39
50307
Kenya
Purple
Purple
Purple
Medium
Medium
dark green
Sparse
Erect

40
50319
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
erect

41
50325
Kenya
Pink
Purple
Purple
Medium
Medium
dark green
Sparse
erect

42
50326
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
erect

43
50328
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
erect

44
50330
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
erect

45
50332
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
erect

46
50339
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
erect

47
50353
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Medium
erect

48
50584
Kenya
Purple
Purple
Purple
Medium
Medium
dark green
Sparse
erect

49
50600
Kenya
Purple
Purple
Purple
Profuse
Medium
dark green
Sparse
erect

Erect growth habit was more dominant and was observed in 90% of the accessions as opposed to the semi-erect growth habit observed among 10% of the accessions. This observation agrees with earlier findings [22], which reported over 80% erect growth in the studied spider plant accessions. Other past research has also shown that majority of the spider plant morphotypes present an erect type of growth [5]. Growth habit is crucial in vegetable breeding as reported in other indigenous vegetables [23]. Bushy growth habit results in many small leaves arising from numerous shoots that are not a preference trait to producers while the erect growth habit with only primary and secondary branches maximizes the leaf area. This implies that yield improvement in spider plant could be exploited through selection of genotypes exhibiting erect growth habit and therefore large leaf size. Further reports have suggested that, in mixed cropping, farmers could adopt the semi-erect type whereas the erect types are ideal for intercrop adaptability [14].

3.2. Cluster Analysis

Sufficient phenotypic variation was observed among the accessions as revealed by the cluster analysis (Figure 1). Two major clusters, namely, clusters 1 and 2, were distinguished using the eight morphological descriptors. Cluster 1 included 9 accessions of South African origin with an exception of one Kenyan accession 1959 while cluster 2 is comprised of 40 Kenyan accessions inclusive of one South African origin. Stem and petiole colour were the major traits that contributed to the Kenyan accession 31990 grouping together with the South African accessions that were mainly green stemmed with green petiole. The exceptional South African accession grouped together with the Kenyan accessions due to the purple stem colour and profuse pubescence that were predominant among the Kenyan accessions. This clearly revealed the differences in the genetic makeup of the accessions from the two regions. However, the South African accessions 2279 and 2000, which were collected from the Northern Province, showed similarity in their phenotypic traits. Most of the Kenyan gene bank accessions, namely, 50339, 50330, 50328, 50326, 50299, and 50273, from Nyamira region clustered closely together with accession 30316 from Western region despite being collected from different regions. Additionally, Kenyan accession 45451 from central region and Kenyan accession 14 collected from Kisii region grouped together suggesting some degree of similarity in their morphological traits. Most of the Kenyan farmers’ landraces clustered together based on their origin. There were major overlaps with the accessions assembled from the gene bank implying that they could have same genetic makeup. A study by K’opondo [5] has demonstrated a close relationship among spider plant genotypes following the evaluation of the variability in seed proteins among them. In addition, this uniformity could also arise from the self-pollination status of spider plant. However, more characterization needs to be done to validate such findings. The cluster analysis, which clearly grouped the accessions according to their geographical origin, suggests that crop improvement of spider plant could be achieved through exploiting the variation revealed. However, the current cluster analysis was done using morphological traits, which can be influenced by several environmental factors. There will be need to undertake a more detailed genetic analysis using molecular markers to confirm the existence of genetic variation across the different geographical regions. There is need for specific regional breeding efforts to target preferred traits [24, 25].

Figure 1: Phenogram showing relationship among accessions characterized using morphological traits.

3.3. Quantitative Traits

3.3.1. Analysis of Variance

Spider plant accessions showed significant differences (P<0.05) with no seasonal effect for all the traits, namely, days to 50% flowering, single leaf area, leaf length and width, chlorophyll content, number of leaves per plant, number of primary branches, and plant height (Table 4), implying the existence of variability for the respective traits among spider plant accessions. Accessions that exhibited longer days to 50% flowering also yielded more leaf count. Late flowering enables a plant to have a longer vegetative phase during growth period [7]. Past research has associated late flowering with increased leaf yield and consequently early flowering as a limit to leaf yield in other indigenous vegetables [23]. This suggests that late flowering would be a good selection criterion for yield improvement in spider plant.

Table 4

(a) Analyses of variance showing the mean squares for the agronomic traits in Cleome gynandra season one (April-July 2014).

Source of variation
d.f.
DTF
LL
LW
NPB
NLPP
PH
SLA
SPAD

Rep
2
4.3
0.6
1.7
1.6
27.9
6.5
0.4
1

Genotype
48
34.7
5.2
16.3
14.7
6895.6
2734.0
8.1
165.4

Residual
96
1
0.2
1.4
0.3
13.4
8.2
0.4
2.1

Total
146

(b) Analyses of variance showing the mean squares for the agronomic traits in Cleome gynandra season one (October-July 2014).

Source of variation
d.f.
DTF
LL
LW
NPB
NLPP
PH
SLA
SPAD

Rep
2
5
0.5
0.5
0.4
1.5
3.2
0.6
3.6

Genotype
48
31.1
5.1
16.5
11.9
6961.3
2723.8
7.9
139.5

Residual
96
0.8
0.1
0.5
0.5
17.6
6.4
0.2
4.3

Total
146

(c) Analyses of variance showing the mean squares for the agronomic traits in Cleome gynandra for the combined seasons.

Source of variation
d.f.
DTF
LL
LW
NPB
NLPP
PH
SLA
SPAD

Rep
2
9.1
1
1.2
1.6
16
4.7
0.9
3.2

Genotype
48
64.6
10.3
32.6
26.1
13840.2
5451.1
15.9
300.8

Season
1
161.6
1.0
4.1
2.1
54
33.4
2.1
4.8

Genotype Season
48
1.2
0.1
0.2
0.4
16.7
6.7
0.1
4.1

Residual
194
0.9
0.2
0.9
0.4
15.5
7.3
0.3
3.2

Total
293

Significant at P <0.05, DTF: days to 50% flowering, SLA: single leaf area (cm²), LL: leaf length (cm), LW: leaf width (cm), NLPP: number of leaves per plant, NPB: number of primary branches, PH: plant height (cm), and SPAD: soil plant analysis development.

Other traits that contributed to increased leaf count were plant height and number of primary branches. Kenyan accessions were taller than the South African accessions with plant height varying from 21 cm for accession 2249 to 113 cm for accession 50296. The Kenyan accessions performed better than South African genotypes for the number of leaves per plant, number of primary branches, leaf length, leaf width, plant height, single leaf area, and chlorophyll content conforming to past research by Wasonga [22]. The best 5 outstanding accessions with regard to yield related traits like 50% flowering, single leaf area, and number of leaves per plant included Kenyan accessions: 3, 7, 45451, 50296, and South African accession 2241 (Table 5).

Table 5: Mean comparison of the quantitative traits of 49 spider plant accessions from Kenya and South Africa grown in the University of Nairobi Field at Kabete, for the two combined seasons.

Entry
Accession No.
Origin
DTF
LL
LW
NPB
NLPP
PH
SLA
SPAD

1
1
Kenya
39.7
5.1
14.2
6.3
105
38.3
8.7
56.4

2
2
Kenya
45.7
6.4
11.5
5.7
58.8
31.5
8.8
57.6

3
3
Kenya
45.3
6.7
17
7
112.2
41
10.9
50.3

4
4
Kenya
43.8
5.2
13.8
7.5
75.8
36.7
8.7
56.9

5
5
Kenya
45.3
5
13.2
7.5
53.8
46.8
8.3
57.6

6
6
Kenya
39.7
5
11.7
7.5
57.2
47.8
7.8
56.9

7
7
Kenya
45
5.9
16
7.7
91.3
51.2
9.9
53

8
9
Kenya
45.5
6.2
14.3
6.5
94.3
39
9.6
56.6

9
10
Kenya
41.5
5.6
11.7
5.7
68
40.7
8.3
58.3

10
11
Kenya
45
3.6
10.6
5.5
100.5
40.1
6.3
56.8

11
12
Kenya
46
4.6
11.9
7.5
61
42.2
7.6
58.8

12
13
Kenya
37.8
5
13.1
6.2
64.8
38.3
8.3
55.9

13
14
Kenya
39.8
4.7
11.3
7.8
83.3
63.2
7.4
53.3

14
15
Kenya
38.7
3.7
9.3
5.7
55.7
37.8
6
46.7

15
16
Kenya
45.2
7.8
15.6
9
75.7
75.5
11.2
61.6

16
1959
S. Africa
43.8
5.8
12
6.7
89.2
34.3
8.5
54.3

17
1988
S. Africa
34.2
6.8
12.6
5.7
50.7
45.2
9.5
49.9

18
2000
S. Africa
32.8
6.5
13.6
4.2
19.7
30.8
9.6
53.1

19
2232
S. Africa
39.8
5.3
10
4.7
56
26.3
7.4
24.3

20
2241
S. Africa
45.3
7.8
15.4
7.8
41
42.3
11.2
44

21
2249
S. Africa
39.3
6.2
13.2
4.2
20.3
21.2
9.2
42.9

22
2279
S. Africa
53.2
6.3
12.3
6.7
23.2
22.1
9
39.6

23
2289
S. Africa
44
7.2
13.9
6.3
31.3
41.7
10.2
43

24
2299
S. Africa
40
5.1
9.8
7.3
78
30.3
7.2
43.7

25
30316
Kenya
37.7
5.9
10.3
10
146
83
8
57.1

26
31990
Kenya
41
5.7
13.2
8.5
109.3
91.3
8.8
55.4

27
31992
Kenya
42
8
11
9.2
201
91.7
9.9
59.5

28
45426
Kenya
43
7.4
11.5
10
97
97
9.5
58.4

29
45446
Kenya
42.3
8.8
13
8.3
68
111.7
11.1
57.3

30
45451
Kenya
47.7
7.2
16.1
9.2
247.5
109.3
10.9
53.9

31
50259
Kenya
44
5.7
10.6
9.2
182
101.3
7.9
58.1

32
50264
Kenya
40.2
4.4
10.5
11.7
172.2
108.8
6.9
60.8

33
50265
Kenya
44.3
5.5
11.6
10.3
78.7
92.2
8.2
60.1

34
50273
Kenya
40.3
5.1
9.5
8.7
92.8
89.7
7.1
57.5

35
50290
Kenya
40.3
4.8
10.4
9.3
105.2
93.2
7.1
62.2

36
50296
Kenya
40
10.5
18.3
10.7
109.5
113
14.2
57.9

37
50298
Kenya
40
4.4
7.9
11.5
140
82.7
6.1
59.5

38
50299
Kenya
41.7
4.8
9.4
10.5
101.3
99.8
6.9
58.9

39
50307
Kenya
40
6
12
8.3
140.7
93.8
8.7
58.4

40
50319
Kenya
40.3
6.2
12.5
9.5
101
77.8
9
62.5

41
50325
Kenya
40
6.8
12.1
10
94.8
95
9.3
57.9

42
50326
Kenya
44.3
5.6
11.1
12.5
165.8
101.2
8.1
57.5

43
50328
Kenya
40.2
5.4
8.6
8.7
96.5
75.7
7.1
58.6

44
50330
Kenya
39.8
5.7
10.4
9.8
172
104.3
7.8
60.8

45
50332
Kenya
40.5
4.2
8.8
9.2
115.8
110.5
6.2
62.5

46
50339
Kenya
42.7
5.2
12.8
12.5
149.8
101.7
8.3
61.6

47
50353
Kenya
42.3
4.5
8.4
11
146.8
86
6.3
57.8

48
50584
Kenya
39.7
4.8
9.8
9.7
88.8
78.7
7
57.9

49
50600
Kenya
38.8
5.9
8.8
9.5
78.8
98.8
7.5
56.2

Mean

41.8
5.8
12
8
97
68.4
8.5
55.1

LSD

1.5
0.7
1.6
1
6.3
4.4
0.9
2.9

(p<0.05)

CV

2.2
7.4
8.1
7.8
4
4
6.5
3.3

DTF: days to 50% flowering, SLA: single leaf area (cm²), LL: leaf length (cm), LW: leaf width (cm), NLPP: number of leaves per plant, NPB: number of primary branches, PH: plant height (cm), and SPAD: soil plant analysis development.

3.3.2. Correlation among the Traits

Knowledge of the correlations among yield and the yield related traits is of considerable importance in crop improvement because it aids in indirect selection [26]. There was positive and significant correlation between leaf length, leaf width, and leaf area with number of days to 50% flowering Table 6. This agrees with the findings of Kiebre et al. [27] who also reported a positive significant correlation between number of days to 50% flowering with leaf length and width. This further suggests that the late flowering genotypes could be selected for their big size, which is a crucial trait to the producers who regard leaf biomass as key in leafy vegetables production.

Table 6: Correlation in combined seasons.

DTF
LL
LW
NPB
NLPP
PH
SLA
SPAD

DTF
-

LL
0.12
-

LW
0.28
0.62
-

NPB
0.09
0.02
-0.20
-

NLPP
0.1
-0.01
-0.11
0.63
-

PH
-0.07
0.16
-0.19
0.82
0.69
-

SLA
0.21
0.92
0.88
-0.08
-0.06
0.01
-

SPAD
-0.04
-0.07
-0.11
0.54
0.45
0.59
-0.1
-

implies significance difference at P<0.05; implies significance difference at p<0.001 (2-tailed), DTF- days to 50% flowering, SLA- single leaf area (cm²), LL- leaf length (cm), LW- leaf width (cm), NLPP- number of leaves per plant, NPB- number of primary branches, PH- plant height (cm), SPAD- soil plant analysis development.

There was a significant positive correlation between plant height and number of primary branches conforming to the results of Kiebre et al. [27] indicating the taller the plant, the more the number of primary branches. This is further supported by the observed correlations, where yield in terms of number of leaves per plant had a positive and significant correlation with plant height (r = 0.69) and number of primary branches (r = 0.63) implying that the higher the number of the branches and the taller the plant, the higher the number of leaves. Single leaf area correlated positively with leaf length, width, and days to 50% flowering at r = 0.92, r = 0.88, and r = 0.21, respectively. As expected, the leaf area would be determined by its length and width suggesting the longer and wider the leaf, the bigger the leaf area. This suggests leaf length and width as important traits in selecting for vegetative yield in spider plant.

However, there was a nonsignificant negative correlation between leaf size and leaf yield indicating the more the number of leaves in the plant, the smaller the leaves. Yield is influenced by complex soil plant interactions in many crops. In this study, the chlorophyll content measured in SPAD value had a positive significant correlation with number of leaves per plant (r = 0.45), number of primary branches (r = 0.54), and plant height (r = 0.59). This contradicts the findings of [28] who reported negative correlations between chlorophyll readings with yield related traits except for plant height in beans. This positive significance correlation between SPAD values and yield related traits calls for more studies to elucidate this phenomenon. Leaf yields may be improved through selection of accessions that showed high leaf count as well as large single leaf area.

3.4. Stepwise Regression

The most important traits that have a considerable effect on the dependant variable are verified through a stepwise regression analysis. The traits selected through the regression model can then be used as a selection criterion for indirect selection in a breeding program [29]. A multiple linear regression analysis was calculated by considering the number of leaves as the dependent variable and other characters as the independent variables. Results of regression analysis showed that plant height had a significant influence on yield (R² = 46.7, P value ≤ 0.05) (Table 7). This implies that selection based on plant height will influence and increase vegetative yield in C. gynandra. This further agrees with other findings by Nwangburuka et al. [30] in vegetable C. olitorius where plant height was found to significantly increase leaf yield.

Table 7: Stepwise regression analysis of the 7 evaluated traits.

Step
Variable
Partial R square
Adjusted R square
F-test

1
Plant height
0.48
0.47
43.00

Significant at p≤ 0.05 y = 1.102x + 21.947, y = number of leaves per plant, and x = plant height.

3.5. Heritability Estimates for Yield and Yield Related Traits

The estimates of heritability in broad sense for all the traits ranged from 78% to 99% (Table 8). High percentages of broad sense heritability were estimated for number of leaves per plant, plant height at 99%, and SPAD value at 96%. Leaf width exhibited a moderately lower percentage at 78% followed by single leaf area and leaf length at 86% and 89%, respectively (Table 8). High heritability plays a great role in selection for crop improvement as the traits to be improved depend immensely on their heritability and variability [27]. In this study, the genotypic variance of all traits was higher than the environmental variance implying that much of the phenotypic variation among the accessions was attributed to variation in genotype as opposed to the environment. The high estimates of heritability displayed in the study suggest that selection for yield improvement in spider plant could be based on traits like number of leaves per plant and plant height.

Table 8: Estimates of yield and yield related components of 49 spider plant accessions.

Traits

VE
VG
VP
HBS ()

DTF
Season 1
1.0
11.2
12.2
91.8

Season 2
1.0
10.1
11.1
91.0

LL
Season 1
0.2
1.7
1.9
89.3

Season 2
0.2
1.7
1.9
89.3

LW
Season 1
1.4
5.0
6.4
78.0

Season 2
1.4
5.3
6.7
79.2

NPB
Season 1
0.3
4.8
5.1
94.1

Season 2
0.3
3.8
4.1
92.7

NLPP
Season 1
13.4
2294.1
2307.5
99.4

Season 2
13.4
2314.6
2328.0
99.4

PH
Season 1
8.2
908.6
916.8
99.1

Season 2
8.2
905.8
914.0
99.1

SLA
Season 1
0.4
2.6
3.0
86.5

Season 2
0.4
2.6
3.0
86.5

SPAD
Season 1
2.1
54.4
56.5
96.3

Season 2
2.1
45.1
47.2
95.5

VE = environmental variance, VG = genotypic variance, VP = phenotypic variance, HBS = broad sense heritability, NLLP = number of leaves per plant, NPB = number of primary branches, LL = leaf length, LW = leaf width, PH = plant height, SLA = single leaf area, and SPAD = soil plant analysis development.

4. Conclusions and Recommendations

This study reported the existence of significant phenotypic variation in Cleome gynandra as evidenced by the morphological characterization which clearly distinguished the accessions from the two regions. The new knowledge generated on the spider plant morphological structure could offer a great potential in developing relevant genetic and genomic resources for spider plant breeding programs. It is also clear that indirect selection for improved spider plant accessions could be based on the yield related traits like number of leaves per plant, plant height, number of primary branches, and days to flowering which exhibited high heritability. This study recommends the complementation of morphological characterization with the use of molecular markers for germplasm characterization and genetic diversity since they are under little influence from the environment.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

Acknowledgments

The authors would like to acknowledge the University of Nairobi for the opportunity to undertake the research. This paper is part of the M.S. thesis entitled “Genetic Characterization and Nutrition Analysis of Eastern and South African Cleome gynandra (Spider Plant) Accessions” submitted to the University of Nairobi towards achievement of an M.S. degree in plant breeding and biotechnology.

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