ABSTRACT
This study was carried out at Umudike Longitude-0733E, Latitude -0529N; and altitude of 122m during the2018 and 2019 cropping seasons to evaluate six taro genotypes namely Nce 001, Nce 002, Nce 003, Nce005, Nce 010 and Nce 011. The relationship between their growth, yield and yield stability attributes was studied with a view to determining the most important indices for yield improvement. The experiment was laid out using a randomized complete Block Design (RCBD) with treatments replicated 4 times. Plot size was 2m by 3m. Data collected included plant height (cm), number of leaves per plant, leaf area per plant (cm2), girth size per plant, number of suckers per plant, number of corms per plant, number of cormels per plant, weight of corms per plant, weight of cormels per plant and yield (t/ha). Results obtained indicated the presence of genetic variability among the taro landdraces for the different traits under consideration. Cormel number, cormel weight and corm weight showed significant positive correlation with yield at p<0.05 suggesting that a direct relation for these traits will lead to taro yield improvement. Multiple regression, coefficient of determination R2 and R change (R2) showed that three attributes namely cormels weight, corms weight and plant height were the largest contributor to yield (t/ha). These three attributes significantly predicted and explained 79.8% of total yield observed. The study also showed that Nce 011 (4.45 t/ha, 4.41 t/ha) and Nce 003 (4.38 t/ha, 4.41 t/ha) consistently gave the highest yield in 2018 and 2019; an indication that these two genotypes could be selected in further hybridization.
TABLE OF
CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of contents vi
List of tables viii
Abstract ix
CHAPTER 1 INTRODUCTION 1
CHAPTER
2 LITERATURE REVIEW
4
2.1 History
of Cocoyam Production and Genetics of Taro 4
2.2 Morphology
and Anatomy of Taro 5
2.3 Origin
and Domestication of Taro 8
2.4. Establishment 10
2.4.1 Vegetative Growth and Corm initiation 10
2.4.2 Corm maturation 11
2.5 Uses
of Taro 11
2.5.1 Medicinal 13
2.6 Hybridization
of Taro 14
CHAPTER 3 MATERIALS AND METHODS 19
3.1 Experimental
sites 19
3.2
Soil sample collection and analysis 19
3.3 Planting
materials and experimental design 19
3.4 Agronomic
Practices 19
3.5 Data
collection 19
3.5.1 The plant girth(cm) 19
3.5.2 The plant height (cm) 19
3.5.3 Number of leaves/plant 21
3.5.4 Leaf area (cm2) 21
3.5.5 Number of suckers 21
3.5.6 Number of Cormels 21
3.5.6 Number of corms 21
3.5.7 Corms and cormel weight (kg) 21
3.5.8 Yield(tons/ha) 21
3.6 Statistical
Analysis 21
CHAPTER
4 RESULTS AND DISCUSSION
4.1 Soil
physicochemical properties and meteorological data of
experimental
sites 23
4.1.1 Climatic Data 23
4.1.2 Soil Analysis 25
4.2 Correlation,
Multiple Regression (stepwise) and Path
Coefficient Analysis
of Yield and Associated Traits 35
4.2.1 Correlation Studies 35
4.2.2 Regression Analysis 40
4.2.2.1 Regression Equation 40
4.2.3 Path Coefficient Analysis 40
4.3 Analysis
of Variance 44
4.4 Discussion
44
CHAPTER 5 CONCLUSION AND
RECOMMENDATIONS 47
5.1 Conclusion 47
5.2 Recommendations 47
REFERENCES 52
APPENDICES
52
LIST OF TABLES
4.1 Monthly
Average rainfall (mm), temperature (0C), relative humidity (%)
and sunshine (hrs) at the
experimental site 2018 and 2019 24
4.2 Physicochemical
properties of the soil at the two experimental sites
2018 and 2019 26
4.3 Plant height (cm) of some taro genotypes
at 4, 8, and 12 WAP in 27 two
locations over 2 years .
4.4 Girth size of
some taro genotypes at 4, 8, and 12 WAP in 28 two
locations over 2 years
4.5 Number of
leaves/plant of some taro genotypes at 4, 8, and 12 WAP in two locations over 2
years. 29
4.6 Leaf
area (cm2) of some taro genotypes at 4, 8, and 12 WAP in two
locations over 2 years 30
4.7 Number of
suckers/plant of some taro genotypes at 4, 8, and
12 WAP in two locations over 2 years 31
4.8 Number of
corms/plant, weight [kg] and yield (t/ha) of some taro genotypes in two locations over
2 years 32
4.9 Number of cormels/plant, weight (kg) and
yield(t/ha) of taro genotypes
in two locations over 2 years 33
4.10 Number of corms +cormels, weight (kg), and
total yield [t/ha]
of some taro genotypes in two locations over 2 years 34
4. 11 Pearson’s correlation coefficient of yield and yield component of
six genotypes of taro (Colocasia esculenta) (L) (Schoot
L) in 2018 cropping
season 37
4.12 Pearson’s correlation coefficient of yield and
yield component of six genotypes of Taro (Colocasia esculenta) (L)(Schoot L) in 2021 cropping season .
38
4.13a: Multiple Regression (B, stepwise), coefficient of determination (R2),
R2 change (∆R2), between total yield (t/ha) and other
attributes of some taro genotypes evaluated in
2018
4.13b: Multiple Regression (B, stepwise), coefficient of determination (R2), R2 change (∆R2),
between total yield (t/ha) and other attributes of
some taro genotypes evaluated in 2019 39
CHAPTER 1
INTRODUCTION
Cocoyam is the
common name for two tuber crops. Taro (Colocasia
esculenta (L) Schott) and tannia (Xanthosoma
sagittitoluim (L) (Schott) also refers to new cocoyam) are the most
important species (Green and Oguzor, 2009). Cocoyam is found throughout the
tropics and is of economic interest within tropical regions of the world. .
Taro have been in existence for over five centuries ago and its domestication
is likely to have occurred more than 10,000 years ago. Cocoyam forms one of the
major source of carbohydrates after cassava and yam in Nigeria.
A crop initially
referred to as a minor crop in the traditional intercropping system and often regarded
by the local indigenous people as a "woman crop" has presently
assumed significant economic importance due to the discovery of its qualities
and industrial uses. Nigeria is presently the world's highest producer of
cocoyam, producing about 180000 tons of cocoyam per annum accounting for about
30% of worlds total and 48% of Africa's total production (Onwueme and Sinha,
1991). This is produced in an estimated land area of 350000ha. Inspite of this
however, yield is still very low in Nigeria (5143kg/ha) compared with what is
obtained in Japan (13493kg/ha) and China (13333kg/ha) (Onwueme and Sinha,
1991). This very low yield may be attributed to poor production techniques,
such as the overuse of agrochemicals or the choice of low-yielding cultivars,
may be blamed for the extremely low productivity. (Fadina and Ogunyem 2002;
Akpantaku, 2000), Taro is an important traditional staple crop in many
sub-Saharan African countries, but its potential contribution to food security
is partly harnessed by lack of research and development on its agronomy and
commercialization (Mare, 2009). Taro is used mostly as food, and prepared in
the same way as potato. Its flour is considered good for formulation of baby
food because its starch is easily digestible, helps with digestive problems as
well as iron supplement (Onwueme, 1999", Shanye, 2004; RanWyk, 2003).
However, taro is a difficult crop to grow because of its high requirements for
soil nutrients moisture and labour. It is also affected by numerous pests and
diseases, which can have a drastic impact on yield. Farmers have lost interest
in farming as a result of these causes
acting in consonance (Okpul et al,
2002).
Cocoyam has provided colonies that helped to sustain most
especially the rural and poor segements of the population which incidentally is
the most threatened in terms of food security (Osuji and Nsaka, 2009; Amadi et al., 2015). Almost all parts of a
cocoyam plant are utilized; corms and cormels are boiled or roasted as a source
of carbohydrates, leaves are frequently consumed as vegetables representing an
important source of vitamins and even petioles and flowers are consumed in
certain parts of the world (Singh et al.,
2012). Cocoyam is nutritionally superior to major competitors roots and tubers
like cassava and yam in terms of digestibility, content of crude protein and
essential minerals such as Calcium, Magnesium and Phosphorus (Chukwu, et al., 2011).
The use of cocoyam is rooted in the culture of the people
that are involved in its production. It was introduced into West Africa around
1840 (Doku, 1980). In Nigeria C.
esculenta first became established as a staple in the Southeast followed much later by xanthosoma sagittitoluim
(L) Schoot) (Ezedinma, 1987) which became the main cocoyam grown in
the southwest (Ogwueme, 1987).
OBJECTIVES
OF THE STUDY
Thus, the objectives of the study will
include;
•
To determine the growth and yield of
different taro genotypes.
•
Identifying the taro genotype with
highest stability in yield.
•
Evaluation of yield stability of
different genotypes of taro.
JUSTIFICATION OF THE STUDY
Yield
improvement have been a major concern for farmers. Growth and attributes
evaluated in this study have explianed the criterial and the best indices for
proper selection for breeding purposes and for the farmers. This study justified
interest of farmers on the genotypes that produces consistent yield under their
growing conditions and breeders also want to fulfill these needs.
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