Assessment of Genetic Diversity in Corchorus olitorius Accessions by Simple Sequence Repeat Markers (SSR)



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Submitted Sep 26, 2023
Published Nov 14, 2023
10.24018/ejfood.2023.5.6.745

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Indigenous leafy vegetables such as Corchorus olitorius (jew’s mallow) have potential in contributing to food security as they can provide important nutritional requirements needed for human nourishment. However, in Botswana, this plant is not yet domesticated and its utilization is minimal due to lack of knowledge. To have the crop fully domesticated it is important to document important information on the available landraces and wild species. One of the important information is understanding the variation among the available genotypes as this will help not only in domestication but also in breeding purposes. Thus this study aimed to assess the genetic diversity of 49 accessions of jews mallow collected in Botswana and other African countries. Simple sequence repeats (SSR) markers were used to characterize fourty nine accessions. The results revealed that, out of 49 SSR primer pairs used, 46 showed scorable polymorphism by producing clear amplified products. The average polymorphic loci rate was 82.44% with the lowest rate (33.33%) detected in MJM-536 and the highest was 100% recorded by 27 of the primers. The polymorphism information content (PIC) potential ranged from 0.398 for MJM-475 primer to 0.979 for the primer MJM-623 with an average of 0.719. With the Shannon diversity index, an average of 3.626 was recorded under the studied accessions and this confirmed a very high diversity. In addition, a dendrogram was generated to illustrate the genetic diversity and possible relationships among the 49 Corchorus olitorius accessions using the unweighted pair group method (UPGM) with arithmetic means. This UPGM cluster analysis distinctively divided the accessions into five (5) groups at a cophenetic correlation coefficient 0.977. The total number of accessions per cluster varied from one group to the other. These results reinforced the effectiveness of the SSR markers in discriminating individuals within species even within a narrow genetic background.

Keywords: Allele Botswana Corchorus olitorius polymorphism

Introduction

Corchorus species are popular in the tropics where they are commonly cultivated as vegetable for their fresh or sun dried leaves [1]. They constitute some of the most common indigenous leafy vegetables in Latin America, Asia, Middle East and Africa [2]. Corchorus has been documented as a nutritional and pharmaceutical plant that is rich in minerals such as magnesium, iron, calcium and phytochemicals such as carotene, vitamins, anti-oxidants and anti-cancer agents, which are needed to maintain good health to fight off infections [3]. Reference [1] reported a high genetic variability in the Corchorus species that allows it to be planted in different weather conditions from Africa to Asia and throughout the Middle East countries. Corchorus species populations exist with high genetic variability and fitness to the natural environment where they have originated and been domesticated Ufoegbune [4]. However, in Botswana, this plant is not yet domesticated despite its high genetic variability and fitness to the natural environment and it is underutilized due to lack of knowledge about it’s importance.

Assessment of genetic diversity is a critical factor in the selection of cultivars for plant improvement as it is used to distinguish between genetic similarities and distances among genotypes that are to be used as parent in breeding program [5]. Assessment of genetic diversity includes germplasm collection, characterization and evaluation [6]. Tools for germplasm characterisation include morphological, physiological and molecular markers. Of these tools, the molecular markers have been found to be highly reliable and effective, most importantly they are not affected or influenced by external factors like environment thus making them an ideal tool [7]. Molecular characterization is important in understanding the progressive development among the plant species and to show the genetic heterogeneity within a given taxonomic group [8]. Several molecular markers like Simple Sequence Repeats (SSR), Amplified Fragment Length Polymorphism (AFLP), Random Amplified Polymorphic DNA (RAPD) and Restriction Fragment Length Polymorphism (RFLP) have been successfully used to monitor and characterize some germplasm collections in genetic diversity [6]. Of these markers, the SSRs have been widely used markers for genotyping plants over the past years because they are highly informative, codominant, multi-allele genetic markers that are experimentally reproducible and transferable among related species [9]. Thus, this study utilized the SSR markers to assess the genetic diversity among the Corchorus olitorius accessions from varying regions of the world.

Materials and Methods

Plant Material

Seeds used for planting were sourced from the Botswana National Genetic Resource Centre (BNGRC) and the World Vegetable Centre, Regional Gene Bank, Tanzania. There were 49 accessions studied of which 40 were obtained from the World Vegetable Centre and 9 from BNGRC (Table I). The seeds were planted in 5 kg soil pots in the greenhouse.

Accession Country of origin
TOT 4316 Bangladesh
TOT 4713 Bangladesh
TOT 4721 Bangladesh
TOT 4670 Bangladesh
AZIGA Cameroon
BAFIA Cameroon
EXCAMEROON Cameroon
TOT 6430 Cameroon
TOT 5876 Japan
IP1 Kenya
IP 10 Kenya
1P 2 Kenya
IP 4 Kenya
IP 5 Kenya
TOT 6426 Kenya
ExMALAWI Malawi
GKK-10 Malawi
ML-JM-14 Malawi
ML-JM-12 Malawi
ML-JM-4 Malawi
ML-JM-3 Malawi
ML-JM-2 Malawi
ML-JM-5 Malawi
ML-JM-13 Malawi
LOCAL LEAVE Mali
TOT 6683 Philipines
TOT 6684 Philipines
SUD1 Sudan
SUD2 Sudan
SUD3 Sudan
SUD4 Sudan
ES Tanzania
HS Tanzania
MIX Uganda
UG-JM-1 Uganda
UG-JM-2 Uganda
UG-JM-13 Uganda
TOT 4879 USA
TOT 6278 Vietnam
ExZIM Zimbabwe
MSB054 Botswana
MSB072 Botswana
MSB082 Botswana
MSB546 Botswana
DELELE1 Botswana
DELELE2 Botswana
DELELE3 Botswana
PANDA Botswana
PANDA1 Botswana
Table I. List of Corchorus Accessions and Their Country of Origin

SSR Primer Selection

Fourty-nine (49) Simple Sequence Repeat (SSR) primers (Table II) were used for screening the accessions. The primer pairs were selected based on the polymorphism information from previous studies on genetic diversity of the Jew’s mallow.

No. SSR primers Sequence of primers (5′–3′)
1 HK-2 F: GTTTATCCAACCAATACCAACCA
R: TGCCTCGTTGCTGGACATTGCA
2 HK-4 F: CAAAAGTAGTGAAGAACATGAGCA
R: GCCAAATTCTGATATACGCCTGA
3 HK-5 F: AGTGACTTATAGTCTAATTAGTGA
R: ACAGATAGGATGTTAACGGGA
4 HK-6 F: CTATCTCCCATTGTACCTGCA
R: GCCAGATTGTGTACTATCA
5 HK-10 F: GAACATCAAGACTGAAGACCTA
R: TTGAGGATTTTCATATGCATGCA
6 HK-12 F: CGCTCGCCTAAGTGAAGGCA
R: ATAAAATACAAGGGACACTTAGCA
7 HK-15 F: GAGAGGAATGATGCTGAGATTCA
R: GACACCCTCCGCCTATCTCA
8 HK-18 F: GCTGTTGTCCTATTGGTGA
R: TTCCACGCTCCTTGTTGCCA
9 HK-19 F: TATGAAGGTGAACTACTTGTCACA
R:AGCTTCCATTTCGAACATTCCA
10 HK-20 F: GTAAAGCACAGGATTAGTCCCA
R: GGAAAGTGAACCTCTAGTAGATGA
11 HK-22 F: CTGTTTGTCAATCTCTTTTGAGTCA
R: GTCCAAAACATCGTGCAGTGTGA
12 HK-23 F: GGCCCTTCTAATTAACCTCCA
R: GTTTTGTTTCCAGATATTGCTCA
13 HK-27 F: TTGTGTGCAAACACGAGTGCA
R: GGTAGCCATGTTTACTTCCTGA
14 HK-29 F: CTGAATGAAAGATTGCTTTTAATCC
R: CATGCATCATTTGCATTGCATGCA
15 HK-30 F: GAGTGATTAGAGGGCAGCCA
R: TGCAACAAAGTATCCAAATCGAC
16 HK-38 F: ACCAAGTATGATCTGACCTCT
R: AGCTAAAAACAACACAAAAATATCTTG
7 HK-1 F: CTTTCTTGACCCAAACAATGCCA
R: GGATGATGAAAAACGAAGTGCCTA
18 HK-7 F: AATGATTATGAACCATAGTGGTACA
R: TTATCACAAAGTAGCAGACTAACA
19 HK-9 F: TTACATTATATAATGTCCAGCCA
R: AGTGGCTACTGGTTCCTACA
20 HK-13 F: TTAGGAGTCATTTCTAACAAGAC
R: AATCCCTCCAGCTTTCTCGA
21 HK-16 F: TGGAACCTGAGCATCTCTCCAGA
R: CTTTTTCTTGTTCAGGGACCTGA
22 HK-17 F: AGAGTTTGCAACAAGGTAGCCA
R: TGGCTACTTAAACTTAGTTGTGTGCA
23 HK-21 F: AATCAAATTGAGAATGGACATGCA
R: GAAAGGCAAATGCGCTTGTTGC
24 HK-28 F: AGAGACGAGTAAACATAAAAGTCC
R: CTGGCGAAGCCTTAAAAACTGA
25 HK-33 F: GTTGATATCTTTACGGTGTATAGA
R: GTGATTTTGGTTACTATGACCCA
26 HK-37 F: AATGTGAAATCCAATTAAAGCACA
R: CCAAGATTGTAGCAACAAGCCA
27 MJM 006 F: AATTACAAACTGGAGGTG
R: AATGGAATGGAGCTAACA
28 MJM 217 F: ACGTTTAGCAACTGATATTGG
R: ACTTACAGCGGTTACATCATT
29 MJM 432 F: CAAGCTTCTGCAGGTATGCTC
R: GGACTGAGATGGCAATCT
30 MJM 472 F: CCATTCGTAGCATTAAAGTTTGC
R: GATTGTGTGCAAACACGAGAG
31 MJM 475 F: TTGCTGCTTGATACAACTGGAR: TACGAAACGACAAAGTCCACC
32 MJM 487 F:GGGTTTGCATCATAGTAGCCAR: TAGGTCACGAGAAGAGCGAAG
33 MJM 489 F: GTAGCCAAGTCTGCTTCCTGAR: TAGGTCACGAGAAGAGCGAAG
34 MJM 519 F: AGCATGCTAACTTGAAGACGCR: TGGAAGATCAGAGGGTCAACA
35 MJM 536 F: GTAGCCAAGTCTGCTTCCTGAR: TAGGTCACGAGAAGAGCGAAG
36 MJM 554 F: CTGGTAAGGAGCTGCCTCTCTR: TGCCTGTAAACCAACTTCTGG
37 MJM 563 F: CTTGGTTGTGGTGGTTGAACTR: AAACCCACCATAGTTGTGTGC
38 MJM 566 F: TGCCTGTAAACCAACTTCTGGR: CTGGTAAGGAGCTGCCTCTCT
39 MJM 569 F: CGCCAGAGAAGCAAATGTAACR: TAGAGCTCACCAGAGACTGCC
40 MJM 581 F: CTTATGATTTGCTGGACCCAAR: CACGCTAGCAAGTGATGAATC
41 MJM 609 F: TCAAATCCAAGCACCCATAAAR: AGAATTTGCGAAGTGGGCTAT
42 MJM 618 F: CGTTATCAAGCAAATCCAACCR: CATCTGGTGACTGCTTCGTCT
43 MJM 623 F: TTCTGCAGTTGTCTCCCTGTTR: ACGAGAAGACACAGTGGTGCT
44 MJM 634 F: GGAGAATATAAGGCCGCGTAGR: CAGCGGTGTAAGGCTCTCTC
45 MJM 639 F: CTATCAGACTGCAGGTCAGCCR: ACCTGATTTGCACACCAGAAC
46 MJM 666 F: TTGGTGTGGACCTTACAGGAGR: ATTAGTGGCGACTCCTCCATT
47 MJM 669 F: GGAAGATGGGTAAGCCTGAAGR: ATTTCATGCATCCAACAGAGG
48 MJM 692 F: CCATGAGACCATGCCACTAATR: ATCAATTACAATCCACGCCAG
49 MJM 714 F: ATTGGAAGAGGATATTTGCGAR: GCATTCCCAATGACCAAGTTA
Table II. Primer Sequence of the SSR Primers to Be Used in the Study

Sampling for DNA Isolation

Fresh young leaves were collected from seedlings for each accession. The samples were snap frozen in liquid nitrogen and stored in −80 °C until the extraction of DNA. The total genomic DNA was extracted from each sample following [12] with some modifications.

DNA Extraction

The leaves were ground under liquid nitrogen to a fine powder. About 1 g of ground fresh leaves was transferred to a 15 ml tube containing 5 ml preheated (65 °C) CTAB extraction solution (the solution was made up of 3.7 g Ethylenediaminetetraacetic acid (EDTA), 6.05 g Tris base, 40.9 g sodium chloride, 10 g Cetyltrimethylammonium bromide (CTAB), all mixed in distilled water to 500 ml) and mixed thoroughly before incubating for 30 minutes at 65 °C in a water bath with occasional mixing. The homogenate was extracted with an equal volume of 24:1 chloroform/isoamyl alcohol (CI). After centrifuging for 20 minutes at 4000 rpm at room temperature, the top (aqueous) phase was recovered into a fresh tube. This step was repeated four (4) more times with equal volume of CI mixture. One-tenth (1/10th) volume of 65 °C CTAB solution was added to the recovered aqueous phase and mixed well by inversion before extracting with an equal volume of CI. The tubes were mixed well, centrifuged (4000 rpm) and the top phase recovered. Then exactly 1 volume of isopropanol was added, mixed well by inversion and centrifuged for 10 minutes at 4000 rpm at room temperature, then pellet was collected and resuspended in high salt TE buffer (10 mM Tris base mixed with 1mM EDTA) (2–3 ml per gram of starting solution). The suspended extract was treated with DNase free RNase (1/100 vol) and incubated for 20 minutes at 37 °C and the DNA was precipitated by adding 0.6 volume ice cold isopropanol and mixed by inverting slowly and then centrifuging for 10 minutes at 10,000 rpm at 4 °C. The pellet was washed with 80% ethanol, dried and resuspended in a minimal volume of TE buffer and stored at −20 °C.

DNA Quantification and Electrophoresis

DNA quality and quantity were assessed by Nanodrop 2000 spectrophotometer and by the gel electrophoresis on 1% aragose gel.

Polymerase Chain Reaction (PCR) Amplification Analysis

PCR reactions were performed in 25-μL reactions containing 2.5 μL of PCR buffer (10X) containing MgCl2 (15 mM), 10 mM dNTPs, 10 μM of each primer, 0.2 μL of Taq DNA polymerase (5 U/μL) and 50 ng of genomic DNA. PCR amplifications were performed in a Thermal Cycler (Labocon, U.K.) with initial denaturation at 94 °C for 5 mins, followed by 40 cycles of denaturation at 94 °C for 1 min, annealing at 35 °C for 1 min, and extension at 72 °C for 3 mins and a final extension at 72 °C for 7 mins. PCR products was separated on 1.5% agarose gel using 1 × TBE (Tris-Borate-EDTA) running buffer at 5 V/cm and then, the gels were stained with ethidium bromide (0.5 μg/ml) and visualized under UV light. The amplified products were weighed against DNA ladder.

Data Analysis

The detected bands were scored as 1 (present) and 0 (absent). Cluster analysis was carried out using the unweighted pair group method with arithmetical average (UPGMA) and dendrogram was constructed based on Jaccard’s genetic similarity index (1908).

Resolving power (Rp) of each primer was calculated using (1). According to Jaccard's genetic similarity index (1908): (1)Rp=∑Ib (Band in formativeness)

Whereas, Ib was calculated by (2): (2)Ib=1−(2×|0.5−p|)

where p is the percentage of genotypes containing the band.

PIC was calculated according to (3): (3)PIC=1−p2−q2

where p is frequency of present band and q is the frequency of the absent band.

Shannon diversity index was calculated according to (4): (4)H=−∑Pi ln (Pi)

where Pi is the frequency of a particular allele i and ln is the symbol of natural logarithm.

Results

The efficiency of SSR markers in discriminating between the distinct accessions was demonstrated on the 49 accessions. Out of 49 SSR primer pairs used, 46 showed scorable polymorphism by producing clear amplified products which were used to evaluate the diversity of the accessions. Three primers (HK-13, HK-37 and MJM-714) did not give any scorable products thus were not used in this study as only reproducible and distinct bands were scored and used for analysis. Though SSR are believed to be locus specific and expected to amplify single or twin bands with a single SSR primer, multiple alleles were observed (Table III). The 46 SSR primers pairs yielded a total of 204 different alleles with an average of 4.16 alleles per locus. Out of the total alleles observed, only 177 are polymorphic. The number of alleles per locus varied amongst the accessions. The minimum allele (1) was revealed by primers MJM 472 and MJM 623 while the maximum was detected by MJM 569 (10). A total of 2758 bands were generated by the 46 SSR primers used. All the bands produced were polymorphic in nature with alleles assigned based on different fragments size (base pair). The recorded scored fragment size varied from 100-700 base pair in size. The maximum number of amplified polymorphic bands was 122 produced by HK-6, while the minimum (3) was produced by MJM-623.

Marker At Bands PA P He Base pair range PIC I
HK-23 8 69 6 75 0.231 100–500 0.538 0.127
MJM-432 5 61 4 80 0.33 100–500 0.527 0.091
MJM-475 3 61 3 100 0.313 100–200 0.398 0.062
MJM-487 3 89 2 66.67 -0.643 100–200 0.462 0.062
MJM-519 4 53 3 100 0.597 100 0.896 0.077
MJM-554 7 79 5 71.42 0.393 100–400 0.699 0.116
MJM-566 7 110 7 100 0.081 100–300 0.837 0.116
MJM-569 10 81 9 90 0.562 200–500 0.832 0.148
MJM-581 4 81 4 100 0.258 200–300 0.483 0.077
MJM-609 9 62 6 66.67 0.743 100–700 0.971 0.137
MJM-618 7 62 7 100 0.648 100–200 0.9 0.116
MJM-666 6 42 4 66.67 0.685 100–200 0.947 0.104
MJM-669 4 56 3 75 0.438 100–200 0.784 0.077
MJM-692 3 56 2 66.67 0.353 100 0.646 0.062
MJM-714 0 0 0 0 0 0 0 0
HK-9 7 99 6 85.71 0.094 100–200 0.871 0.116
MJM-217 5 66 5 100 0.604 100 0.921 0.091
HK-6 6 122 6 100 -0.432 100 0.799 0.104
HK-33 4 86 3 100 -0.044 100 0.739 0.077
HK-20 5 47 4 80 0.742 100–250 0.948 0.091
HK-7 3 52 2 66.67 0.411 100 0.686 0.062
MJM-006 7 76 6 85.71 0.467 100–250 0.856 0.012
HK-5 5 73 5 100 0.362 100–300 0.596 0.091
HK-2 7 72 7 100 0.659 100 0.948 0.116
HK-29 5 75 5 100 0.312 100–150 0.485 0.091
HK-4 5 52 4 80 0.715 100 0.942 0.091
HK-10 3 35 3 100 0.819 100 0.936 0.062
HK-19 5 92 5 100 0.213 100 0.575 0.091
HK-38 5 40 5 100 0.822 100 0.964 0.091
HK-18 4 63 4 100 0.599 100 0.898 0.077
HK-21 4 48 4 100 0.739 100 0.935 0.077
HK-27 2 46 2 100 0.543 100 0.771 0.045
HK-22 3 44 3 100 0.729 100 0.813 0.062
HK-12 3 52 3 100 0.438 100 0.727 0.062
HK-16 3 54 3 100 0.554 100 0.816 0.062
HK-28 4 52 4 100 0.699 100 0.777 0.077
HK-1 2 43 2 100 0.555 100 0.735 0.045
HK-15 3 44 2 66.67 0.539 100 0.802 0.062
HK-30 4 58 4 100 0.522 100 0.835 0.077
HK-17 4 58 4 100 0.513 100 0.642 0.077
HK-37 0 0 0 0 0 0 0 0
HK-13 0 0 0 0 0 0 0 0
MJM-472 1 32 1 100 0.574 100 0.631 0.026
MJM-634 2 35 1 50 0.518 100 0.574 0.045
MJM-489 3 24 2 66.67 0.796 100–200 0.812 0.062
MJM-536 3 42 1 33.33 0.333 100–250 0.598 0.062
MJM-563 3 66 3 100 0.035 100–500 0.778 0.062
MJM-623 1 3 1 100 0.963 500 0.979 0.026
MJM-639 3 45 2 66.67 0.513 100–300 0.936 0.062
Mean 4.163 3.612 82.439 0.719 3.626
Table III. Level of Genetic Diversity of 49 Simple Sequence Repeat (SSR) Primers Tested on 49 Corchorus olitorius Accessions

The average polymorphic loci rate was 82.44% with the lowest rate (33.33%) detected by MJM-536. The highest was 100% recorded by 27 of the primers. There was a recorded negative expected heterozygosity of value −0.0044, −0.423 and −0.643 exhibited by the primers, HK-33, HK-6 and MJM-487, respectively. MJM-563 recorded 0.035 while HK-10 recorded the highest at 0.819. The polymorphism information content (PIC) potential ranged from 0.398 for MJM-475 primer to 0.979 for the primer MJM-623 with an average of 0.719 and the average for Shannon diversity index was 3.626 and this suggested a very high diversity. The lowest index was recorded at 0.012 for primer MJM-006 followed by 0.026 for primer MJM-623 while the highest value of 0.148 was recorded on primer MJM569 and 0.127 was recorded on HK-23.

A dendrogram was generated to illustrate the genetic diversity and possible relationships among the 49 Corchorus olitorius accessions based on 46 simple sequence repeats (SSR) primer analysis using the unweighted pair group method (UPGM) with arithmetic means. This UPGM cluster analysis distinctively divided the accessions into five (5) groups at a cophenetic correlation coefficient 0.977 (Fig. 1). The total number of accessions per cluster varied from one group to the other where Cluster II and IV had only one accession each, cluster I and V had 16 accessions and cluster III had 15 accessions. Cluster I was further sub-divided into 13 sub clusters indicating enough diversity within it while Cluster V was further sub divided into 12 sub clusters. The second main cluster III which contained 15 accessions was also subdivided into 12 sub-clusters. Cluster II and IV were composed of Ex Zimbabwe from Zimbabwe and Big Local leaves from Mali, respectively. These two accessions appeared to be the most divergent amongst the lot, probably demonstrating that they are genetically dissimilar from other accessions possibly because of their demonstrated distinctiveness of the genetic background compared to all accessions under study.

Fig. 1. Dendrogram of 49 Corchorus olitorius accessions showing genetic similarities using UPGM cluster analysis of Jaccard similarity coefficient based on 49 SSR markers.

Discussion

The detected level of polymorphism among the 49 accessions demonstrated the efficiency of SSR markers in discriminating amongst the accessions. It was revealed that 46 SSR markers showed scorable polymorphism. The current study attained 82.44% polymorphism. These results are comparable to the high polymorphism of 92.20% with SSR attained in Corchorus olitorius studies by [10]. Similarly, [13] reported 92.45% and [14] observed 91.11% polymorphism. Furthermore, [15] reported a 92.19% polymorphism rate, which indicated a high level of polymorphism of the SSR markers used in Corchorus olitorius. These similar levels of polymorphism reported by different researchers proves that SSR markers are an excellent tool for cultivar identification, pedigree analysis and the evaluation of genetic distances among many plant species [16] in addition to its ability to discriminate individuals within a species even within a narrow genetic background.

Polymorphism information content (PIC) average of 0.719 was recorded in this study where the PIC values ranged from 0.527–0.979 suggesting the primers used in this study were highly informative. In genetic studies, the primers with PIC values ≥ 0.5 are regarded as highly informative and very effective in distinguishing the polymorphism rate of a primer at a specific rate [17]–[19]. These results are significantly higher than findings reported by [15], who found that in 16 SSR markers used for the estimation of genetic diversity among 96 accessions of Corchorus olitorius, PIC values varied from 0.11–0.49 with an average of 0.32. The low PIC value may be due to a low level of diversity within the species. Reference [1], also reported a PIC value ranging from 0.07–0.33 on seven landraces of Corchorus olitorius evaluated basing on RADP primers. A great proportion of the polymorphic primers demonstrated in the current study could be beneficial in monitoring flow of desirable genes of promising accessions of Jews’ mallow.

The average number of alleles amplified per locus was 4.16 in the current study. These results are in close agreement with [15], [13] and [14], who found an average of 3.31, 4.61 and 3.04 alleles per locus, respectively. The differences in average number of alleles might arise from using different combination of genotypes and different loci in the present study.

An average of 3.626 Shannon diversity index of the accessions under study was attained. The values were directly proportional to the number of polymorphic alleles at corresponding loci. Reference [10] reported a lower value of 1.73 which was also directly proportional to the number of polymorphic alleles. The Shannon diversity index is commonly used to characterize species diversity in a community. The higher the index, the more diverse the species are in the population. This average is higher than 1.5, which confirms a high diversity among the accessions under study.

The study demonstrated genotypic variation indicated by clustering of Corchorus olitorius accession through SSR. This could possibly be related to the genetic differentiation among the individual accession rather than the geographical origins. A fair representation of accessions from different geographical locations was observed in each cluster. This clustering showed a close relationship among some accessions which may help identify some duplicates within the evaluated accessions since molecular markers represent a portion of the genome that is not subjected to environmental influence. This is in agreement with [20] who evaluated 140 accessions and found that despite the higher number of markers and more diverse geographical origins of all the accessions used by the latter, only three groups of genetic clusters were generated. Similarly, [15] generated only two distinctive groups. Contrary to [10], classified the evaluated seven landraces into two main clusters. The constructed dendrogram was able to separate the landraces according to their geographic location.

Conclusion

There exists a genetic variation among the studied 49 Jews’ mallow accessions using the 49 simple sequence repeats markers. A significantly high genetic diversity within the studied accessions was confirmed by the clustering analysis as well the genetic variables determinants that were observed during the study. This genetic diversity of the accessions was independent of their geographical origin as well as the primer type used.

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