Assessment of root and vine yields of Sweet potato (Ipomoea batatas (L) Lam.) Landraces as influenced by plant population density in Jos-Plateau, Nigeria.

Abstract

Objective: An investigation was conducted in Kuru (Latitude 09E44’N, longitude 08E47’E and altitude 1350 m a.s.l.) on the Jos-Plateau,
Nigeria to assess the root and vine yields of three landraces and one elite variety of sweet potato (Ipomoea batatas (L.) Lam) as influenced
by plant population density and genotype. Materials and Methods: Sweet potato cultivars (Landraces) sourced from both local farmers
and the National Roots Crops Research Institute (NRCRI), Umudike, Abia state, Nigeria included Kunkudu, Katsina and Dunku, while
TIS.2532.OP.1.13 (An elite variety) served as the check to ensure the purity of the planting material. The parameters tested were the root
and top yields, while the plant population densities under investigation consisted of 50,000, 40,000, 33,333 and 28,570 plants haG1
based on past literature and concurrent studies. These were laid out in a Randomized Complete Block Design (RCBD) consisting of
16 treatments with 3 replications. Data collected were subjected to analysis of variances (ANOVA) according to Snedecor and Cochran,
while the Duncan’s new multiple-range test was used to compare the treatment means. Results: Results obtained indicated that the
highest and lowest mean root yields were observed in Katsina at 33,333 plants haG1 (47.89 t haG1) and Dunku (8.25 t haG1) landraces,
respectively. TIS.2532.OP.1.13 ranked 2nd after Katsina but the difference (p>0.05) was not significant with respect to 50,000 plant
population density but showed significant difference (p<0.05) with respect to the other three plant population densities. The mean vine
yield showed that landrace Dunku had the highest at 33,333 (59.83 t haG1) plants haG1, while the lowest was observed in landrace Katsina
(25.22 t haG1). Conclusion: The study has shown that the optimum plant population density with the most influence on yield
parameters was 33,333 plants haG1 and therefore should guide farmers in making the right choice for maximum yield and breeding
potentials either for forage or root production.

Full text

OPEN ACCESS International Journal of Agricultural Research
ISSN 1816-4897
DOI: 10.3923/ijar.2017.
Research Article
Assessment of Root and Vine Yields of Sweet Potato
(Ipomoea batatas (L.) Lam) Landraces as Influenced by Plant
Population Density in Jos-Plateau, Nigeria
1,2Y.P. Mwanja, 3E.E. Goler and 1,4F.M. Gugu
1Department of Microbiology, Plateau State University, P.O. Box 2012, Bokkos, Nigeria
2Department of Botany and Plant Biotechnology, University of Johannesburg, P.O. Box 524, 2006 Auckland Park, South Africa
3Department of Botany, Federal University Lafiya, Nassarawa State, Nigeria
4Department of Pharmaceutical Microbiology, University of Durham, United Kingdom
Abstract
Objective: An investigation was conducted in Kuru (Latitude 09E44N, longitude 08E47E and altitude 1350 m a.s.l.) on the Jos-Plateau,
Nigeria to assess the root and vine yields of three landraces and one elite variety of sweet potato (
Ipomoea batatas
(L . ) L am ) a s i n fl ue nc e d
by plant population density and genotype. Materials and Methods: Sweet potato cultivars (Landraces) sourced from both local farmers
and the National Roots Crops Research Institute (NRCRI), Umudike, Abia state, Nigeria included Kunkudu, Katsina and Dunku, while
TIS.2532.OP.1.13 (An elite variety) served as the check to ensure the purity of the planting material. The parameters tested were the root
and top yields, while the plant population densities under investigation consisted of 50,000, 40,000, 33,333 and 28,570 plants haG1
based on past literature and concurrent studies. These were laid out in a Randomized Complete Block Design (RCBD) consisting of
16 treatments with 3 replications. Data collected were subjected to analysis of variances (ANOVA) according to Snedecor and Cochran,
while the Duncans new multiple-range test was used to compare the treatment means. Results: Results obtained indicated that the
highest and lowest mean root yields were observed in Katsina at 33,333 plants haG1 (47.89 t haG1) and Dunku (8.25 t haG1) landraces,
respectively. TIS.2532.OP.1.13 ranked 2nd after Katsina but the difference (p>0.05) was not significant with respect to 50,000 plant
population density but showed significant difference (p<0.05) with respect to the other three plant population densities. The mean vine
yield showed that landrace Dunku had the highest at 33,333 (59.83 t haG1) plants haG1, while the lowest was observed in landrace Katsina
(25.22 t haG1). Conclusion: The study has shown that the optimum plant population density with the most influence on yield
parameters was 33,333 plants haG1 and therefore should guide farmers in making the right choice for maximum yield and breeding
potentials either for forage or root production.
Key words:
Ipomoea batatas
(L.) Lam, genotype, planting material, inbreeding, plant density, breeding, replication
Received: Accepted: Published:
Citation: Y.P. Mwanja, E.E. Goler and F.M. Gugu, 2017. Assessment of root and vine yields of sweet potato (
Ipomoea batatas
(L.) Lam) landraces as
influenced by plant population density in Jos-Plateau, Nigeria. Int. J. Agric. Res., CC: CC-CC.
Corresponding Author: Y.P. Mwanja, Department of Microbiology, Plateau State University, P.O. Box 2012, Bokkos, Nigeria
Copyright: © 2017 Y.P. Mwanja
et a l
. This is an open access article distributed under the terms of the creative commons attribution License, which permits
unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Competing Interest: The authors have declared that no competing interest exists.
Data Availability: All relevant data are within the paper and its supporting information files.

Int. J. Agric. Res., 2017
INTRODUCTION
Sweet potato (
Ipomoea batatas
(L.) Lam) is an important
root crop which is extensively cultivated in tropical and
sub-tropical zones1. It is one of the worlds most important
food crops due to its high yield and nutritive value2. The high
nutritive value and performance under resource poor
conditions makes it attractive to farmers and households.
Sweet potato is mainly propagated by vine-cuttings, planted
on mounds and ridges and in single or double rows3. New
shoots and roots arise from the nodes of the vine-cuttings4.
Despite the high potentials of the crop as a short duration
crop (3-4 months) that could be cropped more than
once a year, its production is faced with constraints such
as low yielding varieties, difficulty in maintaining the vines
(p l an t in g m a te r ia l) d ur i ng th e dr y se a so n wh e n wa t er i s s c ar c e,
scarcity of vines as planting material, inbreeding depression as
a result of continuous use of vines as planting material which
is characterized by decrease in vigour and yield5.
African survey reports, Nigeria ranked 2nd in production
of sweet potato in Africa with an annual production output of
2.6 million metric tons, while the global survey reports,
Nigeria ranked 3rd followed by Uganda (2.5 million metric
tons) in global sweet potato production output6. These figures
have changed in the last decade. Presently, Nigeria is the first
largest producer of sweet potato in Africa with 3.46 million
metric tons annually. Globally, Nigeria is now the second
largest sweet potato producer after China at the top of the list
with 106 million metric tons7. The crop ranks 7th among t he
worlds major food crops. In Nigeria, sweet potato is
produced virtually in every part of the country but
predominantly in the Northern Guinea Savannah where many
landraces abound. In the North Central part of the country
large quantities of sweet potato are produced by small scale
farmers but the yields realized are low due to the use of low
yielding varieties and poor agronomic practices. However, this
trend could change if appropriate agronomic practices and
utilization of improved varieties are adopted8-10.
Household income is supplemented by sales of the
roots in local markets and to urban dwellers. Its importance
in starch, alcohol, livestock, pharmaceutical and textile
industries cannot be over emphasized11. The orange-fleshed
varieties with high B-carotene content have been fortified
with vitamin A to reduce its deficiency especially in children.
Several researchers have reported on plant population
density as an index of yield in: Sweet potato12, maize13 and
sesame14. Therefore, the objective of this study was to
determine the most appropriate plant population density for
maximum root and vine yields and breeding potentials in the
test landraces and to also determine the performance of an
elite variety, TIS.2532.OP.1.13 when compared with the test
landraces.
MATERIALS AND METHODS
T he ex p er i me nt w as c ar r ie d ou t in K ur u (L a ti t ud e 0 9 E44N,
longitude 08E47E and altitude 1350 m a.s.l.) on the
Jos-Plateau, Nigeria to investigate root and vine yields of
three local cultivars and one elite variety of sweet potato
(
Ipomoea batatas
(L.) La m) as infl uenc ed by plan t pop ulation
density in Jos-Plateau, Nigeria.
Sweet potato cultivars (Landraces) sourced from both
local farmers and the National Roots Crops Research Institute
(NRCRI), Umudike, Abia state, Nigeria included Kunkudu,
Katsina and Dunku, while TIS.2532.OP.1.13 (An elite variety)
served as the check to ensure the purity of the planting
material. The parameters tested were the root and vine yields,
while the plant population densities under investigation
consisted of 50,000, 40,000, 33,333 and 28,570 plants haG1. The
experiment was laid out in a Randomized Complete Block
Design (RCBD) consisting of 16 treatments and 3 replications.
The agronomic characteristics of some elite varieties are
shown in Table 1.
Land preparation was done manually. The net plot, which
measured 3×3 m, consisted of 3 rows, each measuring
3 ×1 m. Vine-cuttings of about 20 cm long were planted on
each row at 30 cm (within row) and 100 cm (between rows).
The plots were first weeded manually at 40 Days after
Planting (40 DAP). At 41 DAP the plots received a blanket
application of fertilizer NPK (15:15:15) at the rate of 60 kg haG1
each of nitrogen, phosphorus and potassium, which was
equivalent to 360 g plotG1.
Field sampling: Field observations began at 40 DAP and
continued until 140 DAP. The total root yield from 10 sampled
Table 1: Agronomic characteristics of some elite sweet potato varieties
Elite variety Plant population density (plants haG1) No. of days to maturity (WAP) Average yield (t haG1) No. of days to 50% flowering (WAP)
TIS.2532.OP.1.13 33,333 16 10.45 5
TIS.8164 33,333 16 9.58 6
TIS.87/0087 33,333 16 11.65 6
CIPM 3 33,333 16 9.79 6
CIPM 31 33,333 16 1.30 10
Source: National Roots Crops Research Institute (NRCRI) Umudike, Nigeria
2

Int. J. Agric. Res., 2017
plants in each plot was used in the analysis of variance to
determine the mean root yield for each landrace. Similarly, the
total vine yield from 10 sampled plants in each plot was used
in the analysis of variance to determine the mean vine yield for
each landrace and the check.
Statistical data analysis: Data collected were subjected to
analysis of variances (ANOVA) according to Snedecor and
Cochran15. Duncans new multiple-range test was used to
compare between means of treatments according to Duncan16
at probability of 5% (Duncans new multiple-range test).
RESULTS
Mean root yield (t haG1): The results showed that the
influence of genotype (Landrace) at 50,000 plants haG1
population density on mean root yield was highest and lowest
in Katsina (39.96 t haG1) and Kunkudu (11.10 t haG1),
respectively. TIS.2532.OP.1.13 ranked 2nd after Katsina
and the difference (p>0.05) was not significant (Table 2).
However, it showed significant difference (p<0.05) when
compared with Dunku in the 3rd position at 40,000 plant
population (Table 2). The influence of genotype (Landrace)
at 40,000 plants haG1 population density indicated that the
highest and lowest mean root yields were recorded in Katsina
(41.22 t haG1) and Dunku (8.83 t haG1), respectively. Similarly,
TIS.2532.OP.1.13 ranked 2nd after Katsina but this time
showed significant difference (p<0.05) with both Dunku
and Kunkudu in the 3rd position (Table 2). The influence
of genotype and 33,333 plants haG1 population density on
mean root yield showed that the highest and lowest mean
root yields were observed in Katsina (47.89 t haG1) and
Dunku (8.25 t haG1), respectively. TIS.2532.OP.1.13 maintained
the 2nd spot showing significant difference (p<0.05)
amongst the landraces (Table 2). The influence of genotype
and 28,570 plants haG1 population density showed that the
highest and lowest were observed in Katsina (40.00 t haG1) and
Dunku (8.70 t haG1), respectively with TIS.2532.OP.1.13 in the
2nd position showing significant difference (p<0.05) with the
others.
Mean vine yield (t haG1): The influence of genotype and
50,000 plants haG1 population density on vine yield indicated
that the highest and lowest mean vine yields were observed
in Dunku (58.91 t haG1) and Katsina (25.22 t haG1), respectively.
TIS.2532.OP.1.13 ranked 2nd after Dunku and the difference
was not significant (p>0.05) but showed significant difference
(p<0.05) with both Katsina and Kunkudu (Table 3). Genotype
Table 2: Mean root yield (t haG1) of sweet potato landraces as influenced by
population density
Population density (plants haG1)
-------------------------------------------------------------------
Sweet potato landrace 50,000 40,000 33,333 28,570
Kunkudu 11.10c15.46c11.62c12.34c
Katsina 39.96a41.22a47.89a40.00a
Dunku 21.74b8.83d8.25d8.70d
TIS.2532.OP.1.13 39.11a37.80b37.53b30.99b
CV (%) 6.74 14.45 12.54 12.27
Means followed by the same letter(s) within the same column are not
significantly different at 5% level of probability (Duncans new multiple-range
test)
Table 3: Mean vine yield (t haG1) of sweet potato landraces as influenced by
population density
Population density (plants haG1)
-------------------------------------------------------------------
Sweet potato landrace 50,000 40,000 33,333 28,5 70
Kunkudu 33.55b33.24b26.21c37.44b
Katsina 25.22c31.11c40.16b25.41d
Dunku 58.91a34.67b59.83a31.06c
TIS.2532.OP.1.13 55.32a45.33a41.95b42.82a
CV (%) 2.72 2.47 4.63 16.24
Means followed by the same letter(s) within the same column are not
significantly different at 5% level of probability (Duncans new multiple-range
test)
and 40,000 plants haG1 population density influence
showed that the highest and lowest mean vine yields
were recorded in TIS.2532.OP.1.13 (45.33 t haG1) and Katsina
(31.11t haG1), respectively, Dunku and Kunkudu ranked 3rd
and 4th, respectively with no significant difference (p>0.05)
between them (Table 3). The highest and lowest mean vine
yields with respect to genotype and 33,333 plants haG1
population density were observed in Dunku (59.83 t haG1) and
Kunkudu (26.21 t haG1), respectively. TIS.2532.OP.1.13 ranked
2nd after Dunku and showed significant difference (p<0.05)
with both Dunku and Kunkudu but did not differ significantly
(p>0.05) with Katsina (Table 3). The influence of genotype and
28, 570 plants haG1 population density revealed that the
highest and lowest were recorded in TIS.2532.OP.1.13
(42.82 t haG1) and Katsina (25.41 t haG1), respectively with
Kunkudu and Dunku ranking 2nd and 3rd showing significant
difference (p<0.05) amongst all the landraces (Table 3).
DISCUSSION
Variation in the mean root and vine yields could be
attributed to both genotype and environmental influences.
The variation in root and vine yields within and between
landraces attributable to genotype could be due to planting
densities and genotype respectively. Similarly, variation within
and between planting densities attributable to genotype
3

Int. J. Agric. Res., 2017
could be due to genotype and planting densities. The
variation in the mean root and vine yields among landraces
and planting densities could be largely due to genotype even
when the difference (p>0.05) is not significant. A similar
observation has been reported by Tewe
et al
.17. Landrace
Katsina had the highest mean root yield but also had the least
vine yield, whereas the landrace Dunku which had the least
mean root yield ended up with the highest mean vine yield.
This suggests an interplay of a negative correlation existing
among the landraces with respect to root and vine yield
parameters. Some researchers have reported a negative
relationship existing in the sweet potato landraces in which
they showed that clones which have a prolonged vegetative
phase tend to have a low root-top ratio since most of the
assimilates produced will be used in leaf and stem growth
instead of tuber growth or flower production18. Several other
researchers including Ifenkew
et al
.19 have also reported on
this type of relationship.
The study has shown that different planting densities and
genotypes favour different yield parameters among the
landraces tested. This is an indication that farmers desire and
needs should guide their choice of genotypes and planting
density rates to be utilized in order to realize maximum yields
from their harvest. For example, one may want to consider the
landrace Katsina which had the highest root yield in all
planting densities and may be recommended for root
production (Table 2), whereas Dunku the planting density of
33,333 and 50,000 plants haG1 may be m ore adv anta geo us
if the purpose is vine yield in the event of scarcity of
planting material and it may also be recommended for
forage production (Table 3). In this study TIS.2532.OP.1.13
ranked 2nd in all yield parameters and population
densities suggesting that it is an improved variety. However,
Iwama
et al
.20 have discouraged its production if the aim is
industrial processing because of the low dry matter content of
its tubers.
CONCLUSION
In conclusion, one may want to consider the landrace
Katsina because it did well in all the planting densities if the
purpose is root yield, whereas Dunku the planting densities
of 33,333 and 50,000 plants haG1 may be more advantageous
if the purpose is vine yield. Thus, it can be concluded from this
study that landraces and planting densities have played a lot
of influence on root and vine yields exploitable potentials
of the sweet potato through breeding that can enhance the
production of this crop in the Jos-Plateau agro-ecological zone
of Nigeria.
SIGNIFICANCE STATEMENT
CPlant population density and genotype should serve as a
guide for farmers in making the right choices to meet
specific needs for maximum yield and breeding
potentials
CThe production of TIS. 2532.OP.1.13 (An elite variety) may
not be advantageous if the aim is for industrial processing
because of the low dry matter content of its tubers, it may
however be profitable if the aim is for consumption as
food because of its average root and vine yields
ACKNOWLEDGMENTS
The authors are grateful to the administration of the
National Root Crops Research Institute, Kuru sub-station for
the logistic and technical assistance during the field work.
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