Field Evaluation And Virus Indexing Of Selected Hybrid White Yam (Dioscorea rotundata Poir) In Two Selected Locations Of South-Eastern Nigeria
ABSTRACT
Yam (Dioscorea
spp.) is an important crop in tropical and subtropical regions. The
presence of any virus within the vegetative planting material poses a
significant risk. Obtaining virus-free plants are very important for both
international and local germplasm exchange among farmers and breeders, hence
the need to employ sensitive molecular diagnostic tool that will detect the
presence of both DNA and RNA viruses if present in any part of the plant. The
experiment was laid out in Randomized Complete Block Design (RCBD) with nine
treatments of yam genotypes and three replications to assess the three (3)
viral strains: Yam Mosaic Virus
(YMV), Yam Mild Mosaic Virus (YMMV)
and Badnavirus (BaDv). The
experimental layout was carried out in two locations: the National Root Crops
Research Institute (NRCRI) research farm Umudike, Abia State and Faculty
of Agriculture research farm Abakaliki,
Ebonyi State University (EBSU). The
study employed the molecular diagnostic strategy of PCR-based detection tools
targeting the three different yam-infecting viruses. CTAB techniques were used to
extract the total nucleic acid from the leaves samples of the nine genotypes from the two locations, the
nucleic acid were quantified using the Nano Drop 2000
spectrophotometer. RT-PCR was employed for the analysis of YMV with
primer pair YMV- F3x FP: (5ˈ-GACAATGATGGACG GTGCGG-3ˈ) and YMV-B3x RP:(5ˈCTTTGCCATC AAATCCAAACA T- 3ˈ), and YMMV with primer pair YMMV-FP: (5ˈ-GGCACACAT GCA AATGAARGC-3ˈ) and YMMV
RP: (5ˈCACCAGTAGAGTGAACATAG- 3ˈ), while BaDv was subjected to the PCR
with primer pair Badna –FP: (5ˈ–ATGCCITTYGGIIT IAARAAYGCICC-3ˈ) and Badna-RP: (5ˈATGCCITTY
GGIITIAARAAYGCICC–3). The PCR product was
electrophoresed, and then visualized under UV transilluminator.
There were amplifications in the wells containing the positive controls, while
there were no amplifications in the wells of the nine tested genotypes
indicating that the plant tissues are healthy. The genotypes showed some
variations within and across the locations; Genotypes grown in Abakliki were
superior in the length of vines (cm), while those grown in Umudike were
superior in vine girth. At harvest those in Abakaliki recorded total mean yield
of 8 tubers and 3.17kg tuber weight, while those in Umudike recorded mean yield
of 12 tubers and mean weight of 5.20kg. TDr1401785
recorded the highest yield performance with mean yield of 19 tubers while TDr1000021 recorded the least with mean yield of 4 tubers. TDr1400359 recorded the maximum tuber yield with mean weight
of 6.8kg while TDr8902665 recorded the least
with mean weight of 1.17kg. The study demonstrated that environment has a
significant effect on performance of the 9 genotypes as seen across the
locations. The non-detection of viruses among the genotypes screened could be
due to absence of the three year viruses screened for in the two locations.
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of
Contents vi
List of Tables x
List of Figures xi
List of Plates xii
Abstract xiii
CHAPTER
1: INTRODUCTION
1.1
Background of the Study 1
1.2
Statement of the Problem 2
1.3
Aim and Objectives of the Study 3
1.4
Justification of the Study 3
CHAPTER
2: LITERATURE REVIEW
2.1 Origin
of Yam 5
2.2 Nutritional
Value of Yam 11
2.3 Yam
as a Dietary Source of Energy 12
2.4 Yam
as a Mineral Source 17
2.5 Yam
Bioactive Compounds 19
2.6 Therapeutics
Potential of Yam 22
2.7 Antimicrobial
Potential of Yam 25
2.8 Yam
Antioxidant Properties 26
2.9 Yam
Anti-Inflammatory Properties 27
2.10 Anticancer
Activity of Yam 28
2.11 Anti-Diabetic
Properties of Yam 30
2.12 Yams
Future Prospective 32
2.13 Yam
Infecting Viruses 37
12.14 Genus Potyvirus,
Family Potyviridae 40
12.14.1Yam mosaic virus (YMV) 40
12.14.2 Dioscorea
alata virus (DAV) 40
12.14.3 Other potyviridae 41
12.14.4 Family caulimoviridae,
genus badnavirus 41
12.14.5 Cucumber mosaic
virus, genus cucumovirus 42
12.14.6 Dioscorea, genus
of latent viruses 43
12.14.7 Dioscorea mottle
virus genus comovirus
43
CHAPTER
3: MATERIALS AND METHODS
3.1 Study Area 44
3.2 Collection of Planting Material 44
3.3 Experimental Design and Planting 45
3.4 Germination of the Seed Yam 45
3.5 Virus Diseases Incidence 45
3.6 Virus Disease Severity 46
3.7 Tuber Yield at Harvest 46
3.8 Statistical Analysis 46
3.9 Leaves Sampled for
Virus Detections 46
3.10 Molecular Studies for Detecting Viral
Organisms 47
3.10.1 Extraction of total nucleic acid method using hexadecyltrimethyl
ammonium
bromide (CTAB) 47
3.10.2 Preparation of agarose gel nucleic acid electrophoresis and polymerase
chain reaction
48
3.10.3 Loading
samples and running the agarose gel 49
3.11 Polymerase
Chain Reaction 49
3.11.1 PCR mix components 49
3.11.2 RT-PCR for YMV and YMMV
multiplex
51
3.11.3 PCR detection of badnavirus 52
CHAPTER
4: RESULTS AND DISCUSSION
4.1
Results 53
4.1.1
Sprouting percentage 53
4.1.2
Establishment count 56
4.1.3
Virus disease incidence 58
4.1.4
Virus disease severity 60
4.1.5 Vine girth 62
4.1.6
Vine length 65
4.1.7
Mean number of tubers 68
4.1.8
Tuber weight at harvest 70
4.1.9
Various parameters (variables) assessed across the locations 72
4.1.10
Nucleic acid quantification 74
4.1.11
Molecular studies for virus detections 77
4.1.12
Soil Physiochemical Properties 79
4.2 Discussion 61
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 84
5.2 Recommendations 84
References 85
Appendices 104
LIST OF TABLES
Pages
2.1 The
bioactive compound profile of yam (Dioscorea
species) 21
2.2 The
medicinal applications of yam (Dioscorea
species) 24
2.3 Virus
species infecting yam (Dioscorea species) 39
3.1 Primer
sequences used for the analyses of the three infecting
yam
viruses- YMV, YMMV and Badnavirus 50
3.2 RT-PCR programme showing
Thermal cycling conditions
for YMV and YMMV multiplex 50
3.3 PCR
programme showing thermal cycling conditions for Badnavirus 51
4.1 Mean germination percentage of Umudike genotypes
54
4.2 Mean Germination Percentage of Abakaliki genotypes 55
4.3 Mean comparison of the various parameters (variables)
measured across the
Locations
4.4 Nucleic acid
quantification of the samples collected from the
nine (9) genotypes grown at
the two locations with positive and
negative
controls 78
4.5 Soil chemical properties 83
4.6 Soil physical properties 83
LIST
OF FIGURES
Pages
2.1 Global
Distribution of Yam Production in 2018 7
4.1 Comparison of mean
establishment counts at 4th months of the
genotypes across the locations 57
4.2 Mean comparison of virus disease incidence of the genotypes
across the locations
59
4.3 Comparison
of mean virus disease severity of the genotypes
across the locations
61
4.4 Mean
comparison of vine girth of the genotypes across the locations
(mm) at 4th month 63
4.5 Mean
comparison of vine girth of the genotypes across the locations
(mm) at 5th month 64
4.6 Mean
comparison of length of vine of the genotypes across the
locations at 4th
Month 66
4.7 Mean
comparison of length of vine of the genotypes across the
locations at 5th
Month 67
4.8 Mean
comparison of number of tubers of the genotypes across
the locations 69
4.9 Mean comparison of tuber weight of the genotypes across the locations 71
LIST OF PLATES
Pages
4.1 Gel image of nucleic acid isolated from
the nine (9) samples 76
4.2 Gel
image PCR of YMVand YMMV Multiplex for the nine (9) samples 78
4.3 Gel image of Badnavirus for the nine (9) samples 79
0.0
ALEX, O (2023). Field Evaluation And Virus Indexing Of Selected Hybrid White Yam (Dioscorea rotundata Poir) In Two Selected Locations Of South-Eastern Nigeria. Repository.mouau.edu.ng: Retrieved Apr 29, 2024, from https://repository.mouau.edu.ng/work/view/field-evaluation-and-virus-indexing-of-selected-hybrid-white-yam-dioscorea-rotundata-poir-in-two-selected-locations-of-south-eastern-nigeria-7-2
OCHAI, ALEX. "Field Evaluation And Virus Indexing Of Selected Hybrid White Yam (Dioscorea rotundata Poir) In Two Selected Locations Of South-Eastern Nigeria" Repository.mouau.edu.ng. Repository.mouau.edu.ng, 14 Aug. 2023, https://repository.mouau.edu.ng/work/view/field-evaluation-and-virus-indexing-of-selected-hybrid-white-yam-dioscorea-rotundata-poir-in-two-selected-locations-of-south-eastern-nigeria-7-2. Accessed 29 Apr. 2024.
OCHAI, ALEX. "Field Evaluation And Virus Indexing Of Selected Hybrid White Yam (Dioscorea rotundata Poir) In Two Selected Locations Of South-Eastern Nigeria". Repository.mouau.edu.ng, Repository.mouau.edu.ng, 14 Aug. 2023. Web. 29 Apr. 2024. < https://repository.mouau.edu.ng/work/view/field-evaluation-and-virus-indexing-of-selected-hybrid-white-yam-dioscorea-rotundata-poir-in-two-selected-locations-of-south-eastern-nigeria-7-2 >.
OCHAI, ALEX. "Field Evaluation And Virus Indexing Of Selected Hybrid White Yam (Dioscorea rotundata Poir) In Two Selected Locations Of South-Eastern Nigeria" Repository.mouau.edu.ng (2023). Accessed 29 Apr. 2024. https://repository.mouau.edu.ng/work/view/field-evaluation-and-virus-indexing-of-selected-hybrid-white-yam-dioscorea-rotundata-poir-in-two-selected-locations-of-south-eastern-nigeria-7-2