3. Results and discussion

#### 3.1. Variation in agronomic traits

Characterization and evaluation of crop species is essential in crop improvement programme [29] to identify potential parents according to their traits [22]. In the present study, 50 okra genotypes were characterized for agro-morphological and nutritional traits. The mean squares for the analysis of variance for most of the agro-morphological traits and nutritional values recorded showed highly significant differences (Tables 1 and 2) among the genotypes indicating that there were the existence of wide genetic and phenotypic and nutritional variability among the 50 okra genotypes evaluated. Furthermore, the existence of significant genotype by season interaction showed the influence of the growing season on the agronomic performance of traits. The maximum variation was observed in leaf width, branches, number of fruits closely followed by number internodes. Other characters also showed considerable variability. Even though plant height and leaf length was not significantly different, the genotype VI060803 appeared to have the tallest plant compared to the rest of the genotypes (150 cm) and the shortest genotypes was VI060790 (45.81 cm) (Table 1) and these traits were influenced by the gene factor. It is usually observed that tall and thin plants easily lodge due to environmental factors such as excessive flooding, rain, wind and when they produce high fruit during favorable growing seasons, however, they are also essential for firewood, construction of houses, fences and for livestock feed. Furthermore, selection for tallness gene might be important when the yield performance is low during unfavorable environmental conditions. This okra genotype may produce high dry biomass compared to the rest of the genotypes and can be used as livestock feed during the dry season. Plant height and leaf length were not significantly different which might be due to these traits are controlled by dominant gene. The present values were double higher than the values (17.96–76.65 cm) reported in 21 okra genotypes in Ghana [30]. This might be due to the variation in genetic and environmental factors which prevailed during the growth period. According to Ref. [31], the plant height is controlled by gene. He also reported that it is closely associated with number of flowering nodes, average fruits per plant and number of internodes.

The number of fruits per plant varied from 2.00 in genotype VI055884, VI060313, and VI050956 to 31 in genotype (VI037993) followed by genotypes VI056457 (27) and VI039618 (27). Ref. [30] reported the average mean value of 6.00, which was lower than the values reported in the current study. They also reported 20.00 fruits per plant, which was lower than the values found in the current investigation. Furthermore, [32] reported the number of fruits per plant that varied from 3.22 to 5.67 in Nigeria. The immature fruits of okra are consumed as a vegetable and should be fresh, tender, and green without indication of coloration. Selection of potential parents based on this phenotypic trait would be essential in okra breeding programmes to develop new cultivar in the country.

Mineral analysis: K+

2.3. Data and analysis

emission spectrometric method [26].

80 Rediscovery of Landraces as a Resource for the Future

3. Results and discussion

3.1. Variation in agronomic traits

, Ca2+, P3, Mg2+, Na+

samples of immature fruits were determined using the inductively coupled plasma-optical

The morphological phenotypic and nutritional data were subjected to analysis of variance using Agronomix computer software [27]. The means of all okra genotypes were compared by the least significance difference (LSD) at 0.05 probability level. The mean data were standardized and subjected to multivariate analysis [28] using principal component analysis (PCA). The correlation coefficients were also computed to determine the degree of trait association [28].

Characterization and evaluation of crop species is essential in crop improvement programme [29] to identify potential parents according to their traits [22]. In the present study, 50 okra genotypes were characterized for agro-morphological and nutritional traits. The mean squares for the analysis of variance for most of the agro-morphological traits and nutritional values recorded showed highly significant differences (Tables 1 and 2) among the genotypes indicating that there were the existence of wide genetic and phenotypic and nutritional variability among the 50 okra genotypes evaluated. Furthermore, the existence of significant genotype by season interaction showed the influence of the growing season on the agronomic performance of traits. The maximum variation was observed in leaf width, branches, number of fruits closely followed by number internodes. Other characters also showed considerable variability. Even though plant height and leaf length was not significantly different, the genotype VI060803 appeared to have the tallest plant compared to the rest of the genotypes (150 cm) and the shortest genotypes was VI060790 (45.81 cm) (Table 1) and these traits were influenced by the gene factor. It is usually observed that tall and thin plants easily lodge due to environmental factors such as excessive flooding, rain, wind and when they produce high fruit during favorable growing seasons, however, they are also essential for firewood, construction of houses, fences and for livestock feed. Furthermore, selection for tallness gene might be important when the yield performance is low during unfavorable environmental conditions. This okra genotype may produce high dry biomass compared to the rest of the genotypes and can be used as livestock feed during the dry season. Plant height and leaf length were not significantly different which might be due to these traits are controlled by dominant gene. The present values were double higher than the values (17.96–76.65 cm) reported in 21 okra genotypes in Ghana [30]. This might be due to the variation in genetic and environmental factors which prevailed during the growth period. According to Ref. [31], the plant height is controlled by gene. He also reported that it is closely associated with

number of flowering nodes, average fruits per plant and number of internodes.

The number of fruits per plant varied from 2.00 in genotype VI055884, VI060313, and VI050956 to 31 in genotype (VI037993) followed by genotypes VI056457 (27) and VI039618 (27). Ref. [30]

, Fe2+, Mn2+, B3+, Al3+, Zn2+ and Cu<sup>+</sup> contents in the

Number of branches ranged from 3.83 to 10.44 and the highest value was recorded in genotype VI060313 and closely followed by VI055219. Moreover, the number of leaves ranged from 21.00 in genotype VI055996 to 60.67 in genotype VI050956 followed by VI060131, VI055119 and VI037993 during flowering. Leaves are the primary sources of photosynthesis to produce better yield and yield-related traits in okra genotypes. The values currently reported were higher than the values what [32] reported in Nigeria. Highly significant variation was also observed in the number of internodes, internode length, stem diameter, leaf length and width. The genotype that had tallness gene had highest number of internodes, internode length, and thick stem. The thicker the stem, resists the environmental influences from lodging and can withstand high fruit yield. Days to 50% flowering varied from 46.63 to 74.50 and influenced by genotype and genotype by season interaction. The genotype VI050956 was the first to flower, which is significantly flowered early compared to the rest of the genotypes. Some of the genotypes were expected to be similar in early flowering (Table 1). This genotype could be selected for earliness trait. Early maturing in okra genotypes can be useful to escape drought condition and can be cultivated as climate change crop in drought prone areas of South Africa. Therefore, this trait is potentially very important in okra improvement programmes for earliness and drought escaper genes. Depending on the traits of interest, the user of this crop can select the genotypes for early maturity or late maturity groups for future use. These values reported in the present study were lower than the values reported in Nigeria for days to 50% flowering among the genotypes [30]. Fruit length significantly varied from 10.41 to 32.32 in which the highest value was recorded in genotype VI055777. This trait is the most economically important trait, which affects the yield of okra. As a fruit vegetable crop, the longer pods are very important for consumption and preferred by the consumers in the South Africa, therefore, this trait is important as selection criteria for the improvement programme of okra in the county. Ref. [30] reported that fruit length is the most important determinants in okra production. The wider the size and the longer the fruit is associated with higher number of seeds in the fruit per plant. In this study, the widest fruit was recorded in the genotypes VI037993 and VI039652 with the highest number of seed (67.78) per plant and thousand seed weight, which were the primary determination of the ultimate yield in okra. Hence, widest fruit, highest number of seeds and thousand seed weight were considered as selection criteria for the breeding of okra genotypes for yield and yield related traits. Ref. [33] reported that seed weight is largely a function of seed components such as protein, fat, ash, and nitrogen free extracts. The highest fresh fruit yield, number of seeds per fruit and grain yield per plant were found in the genotypes VI046567 and VI060802. The values reported in the present study were higher than the values reported by [30] in 21 okra genotypes. The genotypes that produced the heaviest pod wall (fruit shell wall) could be selected for parental lines to produce high fodder yield for animal feed compared to the rest of the genotypes where the highest pod wall were recorded in VI037996, VI046567 followed by VI033778 and VI060802. This could help to provide the type of okra which is useful as fodder during the dry season. In this experiment, it is clearly seen that the late maturing genotypes produced significantly higher fodder yield compared to other genotypes. Fruit harvest index is one of the most important trait for drought tolerance and results in yield gains in both drought, irrigated or rain fed environmental conditions. In the present study, the highest fruit harvest index was recorded in the genotypes VI055421 and VI056450 and could be used as parental lines in the development of new cultivar for drought condition in the South Africa.

and strength [42]. Calcium deficiency in plants leads to stunted growth and development of roots [38]. The values detected in this study were higher than the values reported by [43, 44]. The highest concentration of phosphorus was 5246.95 mg kg<sup>1</sup> and found in genotype VI055423; while significantly lowest concentration was recorded in genotypes VI060313

in immature and green fruits of okra determined in this study (expressed in mg kg<sup>1</sup>

) determined in the genotype VI046567 mg kg<sup>1</sup>

had showed significantly highest concentration of aluminum (462.57 mg kg<sup>1</sup>

and mineral elements which are often lacking in the diet in developing countries [44].

) and the lowest in VI060802 (26.77 mg kg<sup>1</sup>

higher than the values reported by [44] in the previous study. Furthermore, the genotype VI055423 showed the highest concentration of micronutrients such as zinc, manganese and copper are the essential micro-elements that plays a great role in the human growth and development. Ref. [45] reported that zinc is one of the essential trace mineral nutrient for human nutrition. The values reported in current study for zinc content in okra fruits was higher than the values reported previously by [43]. This genotype also contributed to the substantial concentration of magnesium next to the genotype VI049632 (4544.91 mg kg<sup>1</sup>

reported by [43]. The sodium concentration varied from 244.87 to 778.83 mg kg<sup>1</sup> (Table 2). The highest significant concentration was found in VI060313 and VI060131, respectively, com-

the other genotypes studied, while genotypes VI060824, VI060802 and VI056450 had the highest concentration compared to the rest of the genotypes evaluated for this mineral element which is higher than the values reported by [43, 44]. In similar fashion, the genotype VI060824

genotypes, significantly highest concentration of boron was recorded in the genotype VI050957

mean values in the order of K > Ca > P > Mg > Na > Fe > Al > Zn > B > M > Cu, that magnifies the importance of macro- and micro-elements in health, growth and development of human body. The existence of mineral elements such as iron, zinc, manganese and nickel has been reported in the immature pods of okra [44, 46]. Okra provides an important source of vitamins

Protein is an essential component of the diet of animals and human and supplies the required amino acids [47]. Protein played a significant role in growth, development and replacement of lost tissues in the human body. It is an important nutritional component in the body to build and repair body tissues that is a building block of bones, muscles, cartilage, skin and blood. Protein is a macronutrient, which the human body needs relatively in a large amount. In this experiment, the crude protein content of immature fruits of okra was analyzed and it varied from negligible amount, of which nitrogen was not detected in genotypes VI055996, VI056450 and VI060678 to 21.45% in VI041210 followed by VI049632 and VI039618 (Table 2) indicating that there was a high significant variation among the genotypes due to the effect of genes they carry. Similarly, [48] reported 21.40% of crude protein in the fruits of okra. Ref. [49] also found 21% protein content in okra pods. Moreover, the current value was also almost similar to the

) (Table 2). The concentration of phosphorus

http://dx.doi.org/10.5772/intechopen.70813

). The overall concentration of mean value of magnesium

Agronomic Performance, Nutritional Phenotyping and Trait Associations of Okra…

) were

83

) with

). Among all

) was higher than the values

) was significantly lower than that of

). Okra had a mineral concentration

) and VI056457 (2992.73 mg kg<sup>1</sup>

(3187.60 mg kg<sup>1</sup>

(3506.61 mg kg<sup>1</sup>

(48.96 mg kg<sup>1</sup>

the concentration of 4346.06 (mg kg<sup>1</sup>

The iron content of genotype VI060822 (118.28 mg kg<sup>1</sup>

pared to other okra genotypes.

#### 3.2. Variation in nutritional traits

Vegetables are major sources of essential minerals and vitamins and are often low in calories, fat, and sugar that are an important addition to any diet consumed, particularly for resource poor community. Deficiency of mineral elements and crude protein content is a wide problem in alarmingly growing human populations in the world. The mineral elements play an important role in the development of the human body [34]. The existence of wide genetic differences among the crop plants for the nutritional quality would assist the improvement of the crop of interest for high quality through breeding in the available germplasm collection/gene pool [34–36]. Identification of okra genotypes based on selected mineral elements and crude protein content will help in the selection of the best parents for breeding nutritionally enhanced okra for food and nutritional security in South Africa [36]. Calcium and phosphorus are very important in the formation of strong bones and teeth, for growth, blood clotting, heart function and cell metabolism [37, 38]. In the present study, the mean squares for the analysis of variance for the concentration of mineral elements and protein content recorded showed highly significant differences for all the nutritional traits (Table 2) in the immature fruits of okra genotypes indicating that there was a wide genetic variability among the genotypes evaluated. It was reported that potassium is the major cation of intracellular fluid, which helps to regulate the acid base balance, osmotic pressure and water balance [39, 40]. The concentration of potassium varied from 17983.32 to 30384.65 mg kg<sup>1</sup> and the highest concentration and uptake of potassium was observed in the genotype VI050958 closely followed by genotype VI033803, while significantly the lowest uptake was observed found in the genotype VI060679, respectively (Table 2). The overall mean value of the genotypes recorded in this study was much higher than the values what [41] reported in okra in Cameroon. Okra is a good source of potassium for human health. The predominant mineral element in the current study was potassium and the concentration of this mineral element is superior to that of the rest of the elements evaluated. It is a primary mineral element found in the body and plays an important role in maintaining fluid balance.

Genotypes VI055423 (8242.49 mg kg<sup>1</sup> ), VI041763 (7854.91 mg kg<sup>1</sup> ) and VI055996 (23505.800 mg kg<sup>1</sup> ) were significantly higher in calcium content compared to all other genotypes (Table 2), respectively. The mineral element, calcium plays a significant function in the growth and development of plant meristems, root hairs and root tips as well as for bone development and strength [42]. Calcium deficiency in plants leads to stunted growth and development of roots [38]. The values detected in this study were higher than the values reported by [43, 44].

yield for animal feed compared to the rest of the genotypes where the highest pod wall were recorded in VI037996, VI046567 followed by VI033778 and VI060802. This could help to provide the type of okra which is useful as fodder during the dry season. In this experiment, it is clearly seen that the late maturing genotypes produced significantly higher fodder yield compared to other genotypes. Fruit harvest index is one of the most important trait for drought tolerance and results in yield gains in both drought, irrigated or rain fed environmental conditions. In the present study, the highest fruit harvest index was recorded in the genotypes VI055421 and VI056450 and could be used as parental lines in the development of new cultivar

Vegetables are major sources of essential minerals and vitamins and are often low in calories, fat, and sugar that are an important addition to any diet consumed, particularly for resource poor community. Deficiency of mineral elements and crude protein content is a wide problem in alarmingly growing human populations in the world. The mineral elements play an important role in the development of the human body [34]. The existence of wide genetic differences among the crop plants for the nutritional quality would assist the improvement of the crop of interest for high quality through breeding in the available germplasm collection/gene pool [34–36]. Identification of okra genotypes based on selected mineral elements and crude protein content will help in the selection of the best parents for breeding nutritionally enhanced okra for food and nutritional security in South Africa [36]. Calcium and phosphorus are very important in the formation of strong bones and teeth, for growth, blood clotting, heart function and cell metabolism [37, 38]. In the present study, the mean squares for the analysis of variance for the concentration of mineral elements and protein content recorded showed highly significant differences for all the nutritional traits (Table 2) in the immature fruits of okra genotypes indicating that there was a wide genetic variability among the genotypes evaluated. It was reported that potassium is the major cation of intracellular fluid, which helps to regulate the acid base balance, osmotic pressure and water balance [39, 40]. The concentration of potassium varied from 17983.32 to 30384.65 mg kg<sup>1</sup> and the highest concentration and uptake of potassium was observed in the genotype VI050958 closely followed by genotype VI033803, while significantly the lowest uptake was observed found in the genotype VI060679, respectively (Table 2). The overall mean value of the genotypes recorded in this study was much higher than the values what [41] reported in okra in Cameroon. Okra is a good source of potassium for human health. The predominant mineral element in the current study was potassium and the concentration of this mineral element is superior to that of the rest of the elements evaluated. It is a primary mineral element found in the body and plays an important role in

), VI041763 (7854.91 mg kg<sup>1</sup>

) were significantly higher in calcium content compared to all other genotypes

(Table 2), respectively. The mineral element, calcium plays a significant function in the growth and development of plant meristems, root hairs and root tips as well as for bone development

) and VI055996 (23505.800

for drought condition in the South Africa.

82 Rediscovery of Landraces as a Resource for the Future

3.2. Variation in nutritional traits

maintaining fluid balance.

mg kg<sup>1</sup>

Genotypes VI055423 (8242.49 mg kg<sup>1</sup>

The highest concentration of phosphorus was 5246.95 mg kg<sup>1</sup> and found in genotype VI055423; while significantly lowest concentration was recorded in genotypes VI060313 (3187.60 mg kg<sup>1</sup> ) and VI056457 (2992.73 mg kg<sup>1</sup> ) (Table 2). The concentration of phosphorus in immature and green fruits of okra determined in this study (expressed in mg kg<sup>1</sup> ) were higher than the values reported by [44] in the previous study. Furthermore, the genotype VI055423 showed the highest concentration of micronutrients such as zinc, manganese and copper are the essential micro-elements that plays a great role in the human growth and development. Ref. [45] reported that zinc is one of the essential trace mineral nutrient for human nutrition. The values reported in current study for zinc content in okra fruits was higher than the values reported previously by [43]. This genotype also contributed to the substantial concentration of magnesium next to the genotype VI049632 (4544.91 mg kg<sup>1</sup> ) with the concentration of 4346.06 (mg kg<sup>1</sup> ). The overall concentration of mean value of magnesium (3506.61 mg kg<sup>1</sup> ) determined in the genotype VI046567 mg kg<sup>1</sup> ) was higher than the values reported by [43]. The sodium concentration varied from 244.87 to 778.83 mg kg<sup>1</sup> (Table 2). The highest significant concentration was found in VI060313 and VI060131, respectively, compared to other okra genotypes.

The iron content of genotype VI060822 (118.28 mg kg<sup>1</sup> ) was significantly lower than that of the other genotypes studied, while genotypes VI060824, VI060802 and VI056450 had the highest concentration compared to the rest of the genotypes evaluated for this mineral element which is higher than the values reported by [43, 44]. In similar fashion, the genotype VI060824 had showed significantly highest concentration of aluminum (462.57 mg kg<sup>1</sup> ). Among all genotypes, significantly highest concentration of boron was recorded in the genotype VI050957 (48.96 mg kg<sup>1</sup> ) and the lowest in VI060802 (26.77 mg kg<sup>1</sup> ). Okra had a mineral concentration mean values in the order of K > Ca > P > Mg > Na > Fe > Al > Zn > B > M > Cu, that magnifies the importance of macro- and micro-elements in health, growth and development of human body. The existence of mineral elements such as iron, zinc, manganese and nickel has been reported in the immature pods of okra [44, 46]. Okra provides an important source of vitamins and mineral elements which are often lacking in the diet in developing countries [44].

Protein is an essential component of the diet of animals and human and supplies the required amino acids [47]. Protein played a significant role in growth, development and replacement of lost tissues in the human body. It is an important nutritional component in the body to build and repair body tissues that is a building block of bones, muscles, cartilage, skin and blood. Protein is a macronutrient, which the human body needs relatively in a large amount. In this experiment, the crude protein content of immature fruits of okra was analyzed and it varied from negligible amount, of which nitrogen was not detected in genotypes VI055996, VI056450 and VI060678 to 21.45% in VI041210 followed by VI049632 and VI039618 (Table 2) indicating that there was a high significant variation among the genotypes due to the effect of genes they carry. Similarly, [48] reported 21.40% of crude protein in the fruits of okra. Ref. [49] also found 21% protein content in okra pods. Moreover, the current value was also almost similar to the values what [41] reported in the fruits of okra; while higher than the values reported by [43] in Nigeria. Ref. [50] reported 19.5% crude protein content in the fruits of okra, which is lower than the values reported in the current study. This difference might be due to genetic and environmental conditions prevailed during the growth period. Ref. [51] reported 23.40% of crude protein in the fruits of okra in dry basis in Nigeria, which is relatively higher than the current study. Similarly, [52] reported that 23.68% of protein content in two okra genotypes in Pakistan. The green okra fruit showed slightly lower protein content, when compared to the protein contents reported in the immature green pods and fresh young leaves of cowpea genotypes [53, 54] evaluated in South Africa, and hence, okra could be considered as protein fruit vegetable in the dietary requirements. It was earlier reported that okra is a good source of protein among a few protein vegetables such as spinach, cauliflower, broccoli, asparagus and others. The genetic variation existed in this study would assist the breeders in selection of potential parental okra lines for the development of new okra cultivars with high protein content. Okra pre-breeding for nutritional quality would start with the selection of potential parents based on their individual nutritional values determined in the current evaluation. Due to the current prevalence of malnutrition in the world, particularly in sub-Saharan Africa and South Africa, breeding for higher nutritional quality which is suitable for human are so quite important for end users. Therefore, quantification and identification of the nutritional composition in the immature and green fruits of collection of okra genotypes is important to develop new okra cultivar with high nutritional composition of interest in the South Africa.

#### 3.3. Trait association

#### 3.3.1. Morphological phenotypic traits

The results of the association analysis for 18 morphological phenotypic traits are presented in Table 3. A strong positive and highly significant association was observed between grain yield and number of fruit per plant (r = 0.85), fruit length (r = 0.75), and fruit diameter (r = 0.73). Grain yield was also positively and significantly associated with number of seeds per plant as well as thousand seed weight, which indicates that all yield components are important for the improvement of grain yield in okra genotypes. Number of fruit was positively and significantly associated with yield contributing traits such as fruit length, fruit diameter, fruit yield, grain yield, number of seeds per fruit, thousand seed weight as well as shelled fruit weight without seeds. Moderately positive and significant association was also observed between grain yield and fruit yield (r = 0.48) and plant height (r = 0.34). Plant height was moderately and positively significantly associated with number of fruits per plant, number of internodes, number of seeds per fruit, internode length, and thousand seed weight. Moreover, fruit length was also positively and significantly associated with grain yield and its related traits. The strong positive association between the different phenotypic traits would allow the breeder for simultaneous selection and improvement of these traits. In this study, plant height, number of fruits per plant, fruit length, fruit diameter, fruit yield, grain yield, number of seeds per fruit, and thousand seed weight were identified as selection criteria for obtaining potential and good parents for the development of new cultivar in the okra breeding programme in the South African condition.

Phenotypic

PH

 NFP

 NB

 NL

 NI

 IL

 SD

 LL

 LW

 D50%F FL

 FD

 FYLD

 GY

 NSF

 TSwt Swt

traits

PH NFP

NB NL

NI

IL SD LL LW

D50%F

FL FD FYLD

GY NSF TSwt

Swt FHI \*, \*\*: significant at 0.05 and 0.01,

length; SD: stem diameter; LL: leaf length; LW: leaf width; D50%F: days to 50% flowering; number of seed per fruit; TSwt: thousand seed weight; Swt: shell weight; FHI: fruit harvest index.

Table 3.

Association

 analysis for 18

morphological

 phenotypic

 traits of okra genotypes.

0.17

 0.02

0.11

respectively;

 PH: plant height; NFP: number of fruit; NB: number of branch; NL: number of leaves; NI: number of internodes;

0.07

 0.02

 0.15

 0.09

0.14

0.13

 FL: fruit length; FD: fruit diameter; FYLD: fruit yield; GY: grain yield; NSF:

0.24

0.10

0.22

0.58

0.04

0.24

 0.15

 IL: internode

http://dx.doi.org/10.5772/intechopen.70813

85

0.39\*\*

0.15

 0.61\*\*

 0.00

0.07

 0.03

 0.10

0.14

 0.00

 0.02

0.21

 0.55\*\*

 0.70

 0.86\*\*

 0.67\*\*

 0.67\*\* 0.67\*\*

 1.00

0.40\*\*

 0.61\*\*

0.03

0.16

 0.16

 0.31\*

 0.02

0.04

0.06

0.40

 0.60\*\*

 0.61

 0.47\*\*

 0.71\*\*

 0.65\*\* 1.00

Agronomic Performance, Nutritional Phenotyping and Trait Associations of Okra…

0.34\*\*

 0.51\*\*

 0.08

0.08

 0.16

 0.24

 0.09

 0.00

0.01

0.12

 0.53\*\*

 0.76\*\*

 0.51\*\*

 0.67\*\*

 1.00

0.34\*\*

 0.85\*\*

0.10

0.20

 0.20

 0.22

0.13

0.22

0.28\*

0.44

 0.75\*\*

 0.73\*\*

 0.48\*\*

 1.00

0.03

 0.48\*\*

 0.10

0.02

0.03

 0.06

0.14

 0.03

 0.02

0.03

 0.40\*\*

 0.61\*\*

 1.00

0.18

 0.71\*\*

0.07

0.24

 0.00

 0.03

0.20

0.18

0.13

0.22

 0.58

 1.00

0.26

 0.66\*\*

 0.00

0.23

 0.04

 0.21

0.13

 0.04

0.16

0.46\*\*

 1.00

0.23

0.52\*\*

 0.22

 0.19

 0.05

0.27

 0.20

 0.27

 0.28

 1.00

0.06\*\*

0.33\*\*

 0.33\*\*

 0.34\*\*

 0.16

 0.06

 0.27

 0.53\*\*

 1.00

0.12

0.30\*

 0.27

 0.08

 0.10

 0.13

 0.30\*

 1.00

0.25

0.24

 0.41\*\*

 0.37\*\*

 0.31\*

 0.21

 1.00

0.52\*\*

 0.20

 0.15

0.03

 0.29\*

 1.00

0.47\*\*

 0.05

 0.35\*\*

 0.10

 1.00

0.14\*\*

0.18

 0.60\*\*

 1.00

0.17

0.18

 1.00

0.33\*

 1.00

1.00


values what [41] reported in the fruits of okra; while higher than the values reported by [43] in Nigeria. Ref. [50] reported 19.5% crude protein content in the fruits of okra, which is lower than the values reported in the current study. This difference might be due to genetic and environmental conditions prevailed during the growth period. Ref. [51] reported 23.40% of crude protein in the fruits of okra in dry basis in Nigeria, which is relatively higher than the current study. Similarly, [52] reported that 23.68% of protein content in two okra genotypes in Pakistan. The green okra fruit showed slightly lower protein content, when compared to the protein contents reported in the immature green pods and fresh young leaves of cowpea genotypes [53, 54] evaluated in South Africa, and hence, okra could be considered as protein fruit vegetable in the dietary requirements. It was earlier reported that okra is a good source of protein among a few protein vegetables such as spinach, cauliflower, broccoli, asparagus and others. The genetic variation existed in this study would assist the breeders in selection of potential parental okra lines for the development of new okra cultivars with high protein content. Okra pre-breeding for nutritional quality would start with the selection of potential parents based on their individual nutritional values determined in the current evaluation. Due to the current prevalence of malnutrition in the world, particularly in sub-Saharan Africa and South Africa, breeding for higher nutritional quality which is suitable for human are so quite important for end users. Therefore, quantification and identification of the nutritional composition in the immature and green fruits of collection of okra genotypes is important to develop

new okra cultivar with high nutritional composition of interest in the South Africa.

The results of the association analysis for 18 morphological phenotypic traits are presented in Table 3. A strong positive and highly significant association was observed between grain yield and number of fruit per plant (r = 0.85), fruit length (r = 0.75), and fruit diameter (r = 0.73). Grain yield was also positively and significantly associated with number of seeds per plant as well as thousand seed weight, which indicates that all yield components are important for the improvement of grain yield in okra genotypes. Number of fruit was positively and significantly associated with yield contributing traits such as fruit length, fruit diameter, fruit yield, grain yield, number of seeds per fruit, thousand seed weight as well as shelled fruit weight without seeds. Moderately positive and significant association was also observed between grain yield and fruit yield (r = 0.48) and plant height (r = 0.34). Plant height was moderately and positively significantly associated with number of fruits per plant, number of internodes, number of seeds per fruit, internode length, and thousand seed weight. Moreover, fruit length was also positively and significantly associated with grain yield and its related traits. The strong positive association between the different phenotypic traits would allow the breeder for simultaneous selection and improvement of these traits. In this study, plant height, number of fruits per plant, fruit length, fruit diameter, fruit yield, grain yield, number of seeds per fruit, and thousand seed weight were identified as selection criteria for obtaining potential and good parents for the development of new cultivar in the okra breeding programme in the South

3.3. Trait association

African condition.

3.3.1. Morphological phenotypic traits

84 Rediscovery of Landraces as a Resource for the Future

Table 3. Association analysis for 18 morphological phenotypic traits of okra genotypes.

#### 3.3.2. Nutritional traits

Moderate to highly significant association was observed for the mineral and protein content determined in the okra genotypes (Table 4). Highly to moderate significant positive associations were observed between K and Ca, P, Mg, Zn, Mn, and Cu; while negative and moderate correlation was observed between K and Na. Similarly, there were significantly positive association between Ca and P, Mg, Na, B, Zn, Mn and Cu. It was also observed that there were highly significant associations between P and Mg, Zn, Mn, and Cu. These results suggested that high P content might be accompanied with increased concentration of Mg, Zn, Mn, and Cu contents of okra fruits and vice-versa. Na was negatively and significantly associated with all micronutrients except B indicating that high Na content associated with the low contents of the Fe, Al, Zn, Mn, and Cu. An extremely strong association was observed between Al and Fe (0.91) which might be the indication of the existence of genetic control compared to the rest of the traits evaluated. Strong association was also found between K and P as well as K and Mg. Significantly, negative association was observed between protein and Fe, and between protein and Mn. In general, in the current study most of the traits evaluated showed highly and significantly positive and moderate associations among them indicating that there were some functional interaction existed among the mineral elements and protein content. Ref. [55] reported the positive correlation among the mineral elements in rice was due to the interaction between ions whose chemical properties were sufficiently similar, and they compete for site of absorption, transport, and function in plant tissues. Hence in the present study, positive association between and among the mineral elements and protein contents showed that selecting and improving the primary traits of interest would have a positive effect on the

Agronomic Performance, Nutritional Phenotyping and Trait Associations of Okra…

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The principal component analysis (PCA) was used for the reduction of data set and transforming the available raw data set into principal components or component factors, which are equal to the number of evaluated morphological phenotypic traits (Table 5). From the current experiment, the PCA transformed 18 raw set of data into 18 factors loadings or principal components with the pattern that the first principal component (PC1) contributed the most variability and the last principal component (PCn) contributed the lowest variability, which accounted for the entire (100%) variability. However, the PC1, PC2, PC3, and PC4 showed high significant variability compared to the rest of the PCs (Table 5) with the eigenvalues greater than one and cumulatively accounted for 68.49% of the total variation among the okra genotype. These PCs had eigenvalue more than 1 [56, 57]; while the rest of the PCS had eigenvalue less than 1 [58], and would not be considered in the interpretation of the results obtained and removed, as they were not significantly influencing and contributing to the variability among the genotypes. Morphological phenotypic traits showed different pattern of contribution to the variability in the principal components loading suggesting the existence of genetic variability that would be used in the okra improvement programme. The current cumulative variation explained by the first four PCs was comparable with what [59, 60] reported in contributing to the variations among different okra genotypes. In the first principal component, grain yield, number of fruits, fruit diameter, shelled pod weight, thousand seed weight, number of seeds per fruit and fruit length, respectively, contributed high variability with positive loading compared to the rest of the traits. This principal component alone explained 33.10% of the total variability among the okra genotypes with the eigenvalue of 5.96. The PC2 accounted for 16.10% of the total variation and was mainly influenced by vegetative growth traits such as number of branches, stem diameter, leaf width, leaf length, number of internodes and number of leaves with positive loading. The PC3 with 12.72% variance distinguished the okra genotypes based on fruit harvest index, plant height, fruit yield, and internode length with all positive loading except fruit yield. Similarly, the PC4 was associated and dominantly influenced by the number of leaves, leaf length and number of branches with all positive loadings except leaf length and this PC accounted 6.58% variances. The remaining phenotypic traits had no any significant contribution to the variation in the four

PCs and hence were of minor importance in the characterization of okra genotypes.

Biplot analysis was carried out based on the first two PCs. The genotypes and morphological phenotypic traits were shown on a biplot to clearly visualize their associations and differences (Figure 1). This PCA biplot more explained the 49.20% of total variability among the genotypes, displaying that number of branches, number of seeds, grain yield, number of fruit, fruit harvest index, and days to 50% flowering were considered as the most discriminating parameters (Figure 1). The genotypes that were positioned on the right top quadrant were closely associated and characterized by longest fruit, largest seed size, heavy fruit shell, highest fruit yield, highest number of seeds per fruit, tallest plant, longest internode, and highest number of

secondary traits in the breeding programme for nutritional quality.

3.4. Multivariate analysis

3.4.1. Morphological phenotypic traits


\*\* significant at the 0.01 probability level.

Table 4. The correlation coefficients between mineral elements and total protein contents evaluated in immature fruits of okra genotypes.

selecting and improving the primary traits of interest would have a positive effect on the secondary traits in the breeding programme for nutritional quality.
