agronomy
Article
Seed Viability, Seedling Growth and Yield in White Guinea Yam
Prince E. Norman 1,2,3,* , Agyemang Danquah 2, Asrat Asfaw 3 , Pangirayi B. Tongoona 2, Eric Y. Danquah 2 and
Robert Asiedu 3
1 Sierra Leone Agricultural Research Institute, Tower Hill, Freetown PMB 1313, Sierra Leone
2 West Africa Centre for Crop Improvement, College of Basic and Applied Sciences, University of Ghana,
PMB LG 30 Legon, Accra, Ghana; adanquah@wacci.ug.edu.gh (A.D.); tongoona@ukzn.ac.za (P.B.T.);
edanquah@wacci.ug.edu.gh (E.Y.D.)
3 International Institute of Tropical Agriculture, Ibadan PMB 5320, Nigeria; a.amele@cgiar.org (A.A.);
r.asiedu@cgiar.org (R.A.)
* Correspondence: pnorman@wacci.ug.edu.gh; Tel.: +232-76-618-454
Abstract: The yam is an economic tuber crop utilized for food, feed, and various industrial applica-
tions. Botanical seed viability, seedling growth, and development are among factors that influence
plant population dynamics, development, structure, and sustainability. However, little is known
about seed viability, growth, and yield potential of seed-progenies developed using different mating
designs. This study assessed seed germination, seedling growth, and yield traits in seed-progenies
developed using North Carolina I (NC-1) and polycross mating designs. For this, seed germination
and seedling nursery trials established using seed-progenies from different yam crosses were used.
Results revealed that days to first seed germination (DAYFG), days to 50% germination (DAYSG),
coefficient of velocity of germination, seed emergence speed (SES), germination index, final germina-
tion percent, and seedling vigor index significantly (p < 0.05) varied within and among NC-1 and
PC-derived families. The mean days to first seed germination (DFSG) and DAYSG seed-progenies of
NC-1 were significantly lower than the polycross progenies. Moreover, the seedling-progenies from
the polycross produced a higher number of stems and more elongate tubers than those originated
from the NC-1 mating. Progenies of family TDr1687 from a polycross mating were among the



 families that had the highest stem number (2.2), longest tuber (7.5 cm), and widest tuber (2.8 cm).


The inter-family means of both NC-1 and polycross had a non-significant variation for mean tuber
Citation: Norman, P.E.; Danquah, A.; weight per plant. Our results suggest the relevance of seed germination and seedling attributes for
Asfaw, A.; Tongoona, P.B.; Danquah, selection of superior progenies at the early generation stage trials in yam breeding.
E.Y.; Asiedu, R. Seed Viability, Seedling
Growth and Yield in White Guinea
Keywords: Dioscorea rotundata; hybrid progeny; seed viability; seedling traits; mating systems
Yam. Agronomy 2021, 11, 2. https://
dx.doi.org/10.3390/agronomy11010002
Received: 16 November 2020
Accepted: 18 December 2020 1. Introduction
Published: 22 December 2020 The white Guinea yam (Dioscorea rotundata Poir) is a valued African food crop grown
for its starchy tubers. The crop is mostly produced and consumed in West Africa, where it
Publisher’s Note: MDPI stays neu- also plays significant roles in people’s social and cultural lives [1]. Fresh and processed
tral with regard to jurisdictional claims white Guinea yam products possess tremendous potential as a source of income and food
in published maps and institutional for over 300 million people in Africa [2]. The fresh tubers also serve as raw materials
affiliations. for various industrial applications. Despite its importance, there is a lack of information
on seed viability, growth and yield of first filial generation white yam developed from
mating designs.
Copyright: © 2020 by the authors. Li- Yam breeding utilizes various mating designs for botanical seed production. The botan-
censee MDPI, Basel, Switzerland. This ical seed production, dispersal, viability, seedling growth and developmental phases are
article is an open access article distributed key factors that influence the plant population dynamics, development, structure and
under the terms and conditions of the sustainability [3,4]. Botanical seed viability is the degree of germination ability of botan-
Creative Commons Attribution (CC BY) ical seeds. The germination ability determines the pathway of germinated and growing
license (https://creativecommons.org/ progeny from their parents. Botanical seed germination is critical in determining plant
licenses/by/4.0/). population size and distribution in communities [5].
Agronomy 2021, 11, 2. https://dx.doi.org/10.3390/agronomy11010002 https://www.mdpi.com/journal/agronomy
Agronomy 2021, 11, 2 3 of 10
The assessment of seed germination and its impact on plant growth and develop-
ment has attracted human interest since the dawn of agriculture (about 10,000 BC) for
the discovery of genotypes or species with physiological and multiplicity potentials [6].
The time, rate, homogeneity, and synchrony of seed germination are important attributes
that inform the dynamics of various progenies’ seedling growth processes [6]. Seed germi-
nation, seedling growth and development traits are critically important to physiologists,
seed technologists, ecologists, geneticists, and breeders due to the possibility of predicting
the extent of species success based on harvested and germinated seeds, establishment and
survival. The theoretical capacity of seeds that express their vital functions and physiologi-
cal potential has been particularly attributed to viability and seedling vigor [6]. Good seed
viability and seedling vigor are among important indices for increased crop productivity [7].
Low seed viability and seedling vigor affect percent germination of seeds, duration of
germination, uniformity of growing seedlings, yield, market quality, and other related
attributes [7]. In yam breeding, many national programs often use an open pollination by
insects to generate sufficient botanic seeds and select superior progenies with desired traits
to release as new varieties [8].
Yam breeding and genetics research are often constrained by low seed viability
and seedling establishment of the progenies from crosses, as well as irregular, low or
non-flowering genotypes, lack of synchronization of flowering and low fruit set [9,10].
Seeds generated from natural and controlled crosses exhibit varying degrees of viability
and seedling vigor due to dormancy, poor embryo and endosperm development [10,11].
Moreover, botanical seeds of yam from different cross combinations possess their peculiar
differences in viability, establishment, survival, yield potential, and other attributes [12].
These attributes determine the adaptability and selection of crops in test environments [13].
Notwithstanding, no comparative studies on different mating designs have been conducted
to assess their effect on seed germination, seedling growth and seed-tuber yield attributes.
Such knowledge is needed to develop and utilize efficient seedling management technique
that enhances seed germination and higher seedling vigor index [14,15]. The objective of
this study was to assess botanical seed viability, seedling growth and tuber yield potential
of progenies developed using North Carolina I and polycross mating designs.
2. Materials and Methods
2.1. Experimental Location
This study was conducted at the glasshouse (pre-nursery) and screen-house (nursery)
facilities of the yam improvement program, International Institute of Tropical Agriculture
(IITA), Ibadan, Nigeria, during the 2017/2018 cropping season.
2.2. Experimental Materials, Layout, Design and Management
The experimental materials were botanical seeds generated using North Carolina I
(NC-I) and polycross mating designs. The crossing blocks of both mating designs were
established at the International Institute of Tropical Agriculture, Ibadan, Nigeria. A total
of 12 clones of D. rotundata comprising nine females and three males with desired com-
plementary traits for the fresh tuber yield, tuber dry matter, tuber shape, earliness and
tolerance to yam mosaic virus were used [8]. The mating schemes targeted crossing three
female parents to a male parent (3:1), producing nine cross combinations. For the polycross
block, staggered planting (at 10-day intervals) was done to facilitate synchronization of
flowering among the parents. However, successful cross of eight and nine families were
generated with the polycross block and NC-1 design hand pollination scheme, respectively.
Female parent, TDr08-21-3 (Ekpe II), did not produce viable seeds in the polycross block.
The botanical seeds from the 17 families were collected from trilobated fruits of the maternal
parents in late February 2017 at the crop’s physiological maturity.
Prior to the establishment of the pre-nursery and nursery experiments, cocopeat and
topsoil substrate samples were collected and analyzed for nutrient composition at IITA soil
analytical lab using standard procedures described by the International Soil Reference and
Agronomy 2021, 11, 2 4 of 10
Information Center (ISRIC) and the FAO [16]. The chemical properties of the two growth
media are shown in Table 1.
Table 1. Chemical attributes of the cocopeat and topsoil growth media.
Macronutrients
Medium pH(H %OC N (%) P (%) K (%) Mg (%) Ca (%)2O)1:1
Cocopeat 4.61 1.401 0.133 0.057 0.380 0.199 1.618
Topsoil 6.08 1.489 0.078 0.0004 0.007 0.019 0.050
Micronutrients
Na (%) Zn (%) Cu (%) Mn (%) Fe (%)
Cocopeat 0.339 0.008 0.002 0.019 0.006
Topsoil 0.003 0.001 0.002 0.043 0.015
OC = organic carbon, N = nitrogen, P = phosphorus, K = potassium, Mg = magnesium, Ca = calcium,
Na = sodium, Zn = zinc, Cu = cupper, Mn = manganese, Fe = iron.
The pre-nursery experiment was laid out in a completely randomized design with
two replicates. The cocopeat medium was put in perforated polyethylene seedling trays
and slightly soaked. About 300 botanical seeds per family were sown in holes created in
the growing medium in early March 2017. The trays were well labeled at planting and
irrigated every other day until four weeks after sowing (WAS). The growing seedlings
were irrigated to field capacity every other day for four WAS. They were also fumigated
with cypermethrin at the rate of 15 mL per 1 L water at six WAS before transplanting in the
seedling nursery at eight WAS.
The nursery experiment was laid out in a randomized complete block design with
five replications. About 100 seedlings per family were transplanted to polythene bag (pot)
in early June, with 20 seedlings planted per replication. The interspatial and intra-spatial
block spaces were 0.5 m apart. Each polythene bag (pot) was filled with sterilized topsoil
and irrigated to field capacity before transplanting. The seedlings were transplanted in
holes created in the crest of the sterilized topsoil and irrigated to field capacity every three
days until six months after transplanting (MAT).
2.3. Data Collection
A total of 11 parameters were assessed, with seven traits studied at the pre-nursery
and four parameters at the nursery trial stages. Data collected during pre-nursery in-
cluded days to first seed germination (DAYFG), days to 50% seed germination (DAYSG),
final germination percent (FGP) and other derived attributes such as coefficient of velocity
of germination (CVG), seed emergence speed (SES), germination index (GI) and seedling
vigor index (SVI). The germination parameters were assessed daily from sowing by count-
ing using germ count pins and continued until the germination ceased. Weekly germination
counts were done from three to eight WAS.
The coefficient of the velocity of germination was estimated as
(N1 + N2 + . . . . . . .. + Nx)CVG = × 100
(T1 N1 + T2 N2 + . . . . . . .. + Tx Nx)
where N1, N2, . . . ., Nx are numbers of seedlings counted on the first day, the second day,
up to the last day (x); and T1, T2, . . . ., Tx are numbers of days after sowing seeds or from
seedling corresponding to N.
The seed emergence speed (SES) was estimated as described by Islam et al. [17]
(No. of germinated seeds at 35 days after sowing)
SES = × 100
(No. of germinated seeds at 49 days after sowing)
Agronomy 2021, 11, 2 5 of 10
The germination index (GI) was estimated using a similar description in the association
of official seed analysis [18] as:
GI (No. of germinated seeds= ) (No. of germinated seeds)
(Days of first count +) (Days of second count + . . .)
(No. of germinated seeds+ )
(Days of last count)
Seedling vigor index (SVI) was estimated as described by Hossain et al. [19] as germi-
nation percent × seedling height.
The data collected during nursery included stem number per plant, length of tubers
per plant, tubers’ width per plant, and weight of tubers per plant. The stem number per
plant was collected at five MAT, and the tuber traits were done at harvest (6 MAT).
2.4. Data Analysis
The phenotypic traits of yam families grown at the pre-nursery and nursery were
analyzed in GenStat version 16 statistical package. The least significant difference (LSD)
was used to compare treatment means at the α = 0.05 level of significance. The residuals
of data for the parameters were first checked for normality and homogeneity using the
Shapiro–Wilk test and Bartlett’s test to ensure that data were normally distributed.
3. Results
3.1. Seed Germination and Related Attributes
Mean days to first seed germination (DFSG), days to 50% germination (DAYSG),
coefficient of the velocity of germination (CVG), seed emergence speed (SES), germination in-
dex (GI), final germination percent (FGP) and seedling vigor index (SVI) were significantly high
(p < 0.05) and varied within and among families developed using NC-1 and polycross designs
(Table 2). Generally, the mean DFSG and DAYSG of NC-1-derived progenies were significantly
lower than that of the polycross-derived progenies.
Mean percent of seed germination significantly (p < 0.05) increased with time in both
the within and between NC-1 and polycross-derived-progeny families (Table 3). The mean
percent germination across the sampling regimes was significantly (p < 0.05) higher in the
NC-1 relative to the polycross-derived progeny-families. The mean percent germination
at 49 days after sowing ranged from the highest of 87.72 in family TDr1679 to the lowest,
27.02 in family TDr1677. The mean percent germination at 49 days after sowing ranged
from the highest of 87.72 in family TDr1679 to the lowest, 0.762 in family TDr1689. Families
with the highest and lowest percent germination values at 49 DAS were also among families
with the highest and lowest percent germination at 21 to 42 DAS (Table 3).
3.2. Seedling Growth, Tuber Yield and Related Attribute Assessments
Table 4 presents differences in mean stem number per plant, and mean tuber length
and width per plant within and between NC-1 and polycross-derived-families.
The polycross-derived families generally produced a higher number of stems and more
elongate tubers relative to those produced by NC-1. In contrast, NC-1-derived progeny-
families had wider tubers (2.6 cm) than the polycross (2.2 cm). Polycross-derived-family
TDr1687 (half-sib progenies of clone TDr8902475) was among seed-progenies that had the
highest stem number (2.2), longest tuber (7.5 cm) and widest tuber (2.8 cm). Mean seed-
tuber weight per plant did not show significant difference between the NC-1 and polycross
derived progenies. However, within the NC-1 and polycross derived progenies, the dif-
ference for seed-tuber weight per plant was significant for some families. For instance,
family TDr1687 (half-sib progenies from an open-pollinated female parent TDr8902475)
produced a mean seed-tuber yield of 47.4 g.plant−1, which significantly out-yielded seed-
progeny from other families evaluated. The lowest mean seed-tuber weight per plant
14.2 g.plant−1 was recorded from family TDr1688 (half-sib progenies from an open polli-
nated female parent TDr9700632).
Agronomy 2021, 11, 2 6 of 10
Table 2. Variation in seed germination attributes of white Guinea yam seed-families (crosses) gener-
ated using North Carolina 1 (NC-1) and polycross (PC) designs.
Family DFSG DAYSG CVG SES GI FGP SVI
North Carolina 1
TDr1676 20.5 39.0 2.33 39.7 5.2 81.45 332.0
TDr1677 23.5 74.0 2.30 32.3 0.9 30.16 76.0
TDr1678 26.0 72.0 2.30 26.4 0.8 31.36 87.0
TDr1679 17.5 30.0 2.49 80.4 72.3 88.00 628.0
TDr1680 18.5 33.0 2.47 91.6 17.5 81.37 358.0
TDr1681 23.5 36.0 2.33 55.7 4.0 90.79 304.0
TDr1682 22.0 36.0 2.42 69.5 12.5 73.80 368.0
TDr1683 22.0 42.0 2.36 46.8 6.8 73.05 391.0
TDr1684 18.5 34.0 2.42 61.3 15.2 84.8 689.0
Mean 21.3 44.0 2.38 56.0 15.0 70.5 359.0
LSD(0.05) 2.50 4.13 0.03 2.98 0.77 5.19 140.5
Polycross
TDr1685 19.0 36.0 2.35 53.2 12.2 82.4 438.0
TDr1686 26.5 71.0 2.26 22.9 2.1 40.4 92.0
TDr1687 22.0 69.0 2.28 28.3 4.9 45.0 160.0
TDr1688 19.5 32.0 2.44 69.4 6.2 72.8 378.0
TDr1689 20.5 32.0 2.44 72.3 17.1 91.0 646.0
TDr1690 30.5 43.0 2.27 38.9 1.2 70.5 240.0
TDr1691 25.0 54.0 2.23 18.2 1.1 33.2 72.0
TDr1692 23.0 43.0 2.31 36.0 8.2 63.0 317.0
Mean 23.3 47.5 2.32 42.4 6.6 62.3 292.9
LSD(0.05) 3.46 2.82 0.02 6.99 0.37 5.92 95.30
Between NC-1&PC
LSD 0.98 1.18 0.01 1.72 0.20 1.82 40.05(0.05)
Within all families
LSD 2.85 3.44 0.02 5.00 0.59 5.31 116.57(0.05)
CV(%) 6.1 3.5 0.5 4.8 2.5 3.8 16.8
DFSG = days to first seed germination, DAYSG = days to 50% germination, CVG = coefficient of
velocity of germination, SES = seed emergence speed, GI = germination index, FGP = final germination
percent, SVI = seedling vigor index, CV=coefficient of variation, LSD= least significant difference.
Table 3. Mean percent germination of yam botanical (true) seeds across families and sampling regimes.
Family Sampling Regime
21 DAS 28 DAS 35 DAS 42 DAS 49 DAS
North Carolina 1
TDr1676 1.61 8.06 30.24 58.87 76.21
TDr1677 0.00 3.20 8.74 19.05 27.02
TDr1678 0.00 4.25 7.64 16.98 28.85
TDr1679 2.98 40.95 70.48 84.54 87.72
TDr1680 1.51 28.04 70.68 76.99 77.16
TDr1681 0.00 4.58 48.06 81.67 86.32
TDr1682 0.00 21.20 48.20 61.00 69.40
TDr1683 0.00 13.65 32.87 65.25 70.47
TDr1684 1.60 26.40 51.40 78.40 83.80
Mean 0.86 16.70 40.92 60.31 67.44
Within NC-1 family LSD(0.05) 0.69 3.92 6.02 8.49 9.44
Polycross
TDr1685 0.40 9.20 42.80 70.20 80.40
Agronomy 2021, 11, 2 7 of 10
Table 3. Cont.
Sampling Regime
Family
21 DAS 28 DAS 35 DAS 42 DAS 49 DAS
TDr1686 0.00 2.06 7.53 20.89 32.86
TDr1687 0.20 2.80 11.40 29.40 40.20
TDr1688 1.38 25.00 50.74 71.44 73.30
TDr1689 1.00 29.20 65.60 84.20 90.80
TDr1690 0.00 0.00 25.83 49.17 68.12
TDr1691 0.00 0.83 4.20 13.02 23.10
TDr1692 0.00 6.20 22.40 48.80 62.20
Mean 0.37 9.41 28.81 48.40 58.90
Within PC family LSD(0.05) 0.71 1.64 4.95 11.54 16.40
Between NC-1 and PC LSD(0.05) 0.23 1.02 1.83 3.29 4.31
Between all families LSD(0.05) 0.65 2.85 2.43 9.26 12.12
CV(%) 48.7 10.2 6.9 8.3 9.1
DAS = days after sowing, NC-1 = North Carolina design 1 and PC = polycross design.
Table 4. Mean seedling traits of first filial generation yam populations developed using North Carolina 1
and polycross designs.
Family Pedigree SN TL TW TWT(cm) (cm) (g)
North Carolina 1
TDr1676 TDr9700793 × TDr9902789 1.8 6.0 2.6 28.8
TDr1677 TDr8902157 × TDr9902789 2.2 6.4 2.7 27.4
TDr1678 TDr8902475 × TDr9902789 2.2 6.9 2.8 33.8
TDr1679 TDr9700632 × TDr9902607 2.0 6.6 2.8 31.5
TDr1680 TDr9700205 × TDr9902607 1.6 5.3 2.0 19.2
TDr1681 TDr08-21-3 × TDr9902607 2.3 5.5 2.5 25.9
TDr1682 TDr9519158 × TDr9501932 1.9 5.9 2.3 23.9
TDr1683 TDr9518988 × TDr9501932 1.5 4.9 1.9 15.1
TDr1684 Ojuiyawo × TDr9501932 1.6 6.1 2.3 24.0
Mean 1.7 6.0 2.6 25.7
LSD(0.05) 0.46 1.22 0.3 8.3
Polycross
TDr1685 TDr9700793 1.6 6.6 2.5 29.7
TDr1686 TDr8902157 2.0 6.3 2.4 28.5
TDr1687 TDr8902475 2.2 7.5 2.8 47.4
TDr1688 TDr9700632 1.9 4.8 1.9 14.2
TDr1689 TDr9700205 1.7 5.4 2.8 16.2
TDr1690 TDr08-21-3 1.8 5.3 2.0 17.2
TDr1691 TDr9519158 1.8 5.6 2.2 20.0
TDr1692 TDr9518988 1.8 5.6 2.1 19.5
Mean 2.0 6.2 2.2 26.7
Within PC family LSD(0.05) 0.24 0.78 0.26 7.56
Between NC-1 and PC LSD(0.05) 0.06 0.19 0.06 1.81
Between all families LSD(0.05) 0.28 0.90 0.31 8.58
CV(%) 44.4 43.4 36.9 96.6
NC-1 = North Carolina design 1 and PC = polycross, SN = stem number per plant, TL = tuber length,
TW = tuber width, and TWT = tuber weight per plant.
4. Discussion
High rate of seed germination is an important factor in the process of yam breeding.
The rate of seed germination varies among cross-seeds of different clones. For instance,
family TDr1679 took the lowest duration to germinate, highest germination index, and was
among the families that exhibited the highest coefficient of the velocity of germination,
Agronomy 2021, 11, 2 8 of 10
seed emergence speed, final germination percent and seedling vigor index. Seed germina-
tion and seedling emergence are the most important and vulnerable phases of a crop cycle.
Duration to emergence and percent emergence may influence crop yield by altering plant
population density, spatial arrangement, and effective crop growth duration. The coeffi-
cient of the velocity of germination (CVG) indicates the rapidity of seed germination where
the highest number of seeds germinate in shortest possible time [20]. Families with high
seedling vigor index are indicative of consistent growth of emergent seedlings and optimal
emergence. Moreover, families with low seedling vigor index lacked optimal emergence
and uniform growth of emergent seedlings. The delayed and poor germination of the
botanical yam seeds of some families were possibly attributable to dormancy caused by
genetic factors [17,21]. Knowledge of existing variations in the degree of seed viability and
dormancy permits selection for either dormancy or non-dormancy [22]. This information
also helps in devising robust, practical strategies that overcome dormancy. Seed dormancy
has been overcome in many crops using physical and chemical seed-treatment techniques
with resultant early and increased germination and seedling vigor [17,23]. Moreover,
Feike et al. [21] and Islam et al. [17] have demonstrated that water soaking of seeds prior
to sowing greatly enhances germination and seedling vigor. Improvement of viability,
vigor and related seedling growth traits would probably enhance the identification of
superior progenies at the early-stage yam breeding trials. Finch-Savage and Bassel [24]
suggested that improvement of seed vigor would enhance the crop establishment for
better yield in the agricultural industry and the seed/breeding companies [24]. Besides the
agronomic seed treatments, genetic studies to identify loci controlling seed weight, size and
seedling traits are also critically important for combating poor seed germination in yam
compared to other crops such as tomato, where similar studies have been done. Botanical
seeds of yam vary in size [8]. Understanding the genetic basis underlying variability in
seed weight, size, and seedling traits will contribute to the yam’s breeding efforts. Many
researchers have demonstrated that higher seedling survival and competitiveness depend
on seed traits such as quality, size and weight [7,25–27]. The reserved food energy and
nutrients accrued in seeds during the seed filling phase are released to the viable embryo
during germination. This suggests the significance of the seed filling phase in address-
ing the nutrient and energy gap needed in combating early germination of seeds and
establishment of cotyledons prior to initiation of their photosynthetic potentials [28].
The significant within and between NC-1 and PC derived family variations for the
measured traits indicate inherent genetic differences in the yam seed-progenies for ger-
mination and seedling attributes. The highest and lowest mean seed-tuber weights per
plant were obtained from a polycross-derived family TDr1687 and TDr1688, respectively.
The wider variability for seed-tuber weights in the polycross-derived family was expected
as the progenies were half-sibs from a wider gene pool of putative male parents (three
males) relative to the full-sib progenies from the bi-parental cross in the NC-1 design.
The wide variability of tuber size among families could be attributed to the differences
in the effective individual plant growth periods after emergence. The higher coefficient
of variation of the seedling traits measured in the nursery (screen-house stage) indicates
a higher level of dispersion around the mean. Our findings concur with the results of
Cornet et al. [29], who reported a high coefficient of variation of 42–71% for fresh tuber
yield caused by uneven emergence in D. alata and D. rotundata.
5. Conclusions
The slow rate of germination decreased the effective growth and development du-
ration of the seedling progenies in yam. The use of appropriate physical or chemical
treatment techniques should be exploited to break dormancies that could contribute to
increased and consistent seed germination, good seedling growth and development traits
in yam population improvement. The polycross-derived progenies possess higher pheno-
typic plasticity with a higher potential of creating more useful variability in seedling traits.
Agronomy 2021, 11, 2 9 of 10
Our results suggest the relevance of seed germination and seedling attributes for selection
of superior progenies at early generation yam breeding populations.
Author Contributions: P.E.N. and A.A. designed the experiment. P.E.N., A.A., A.D., P.B.T., E.Y.D. and
R.A. supervised the work. P.E.N. and A.A. performed the data analysis and drafted the manuscript.
All the authors contributed to writing the article, read and approved its submission. All authors have
read and agreed to the published version of the manuscript.
Funding: The work was financially supported by Bill and Melinda Gates Foundation (BMGF) through
the AfricaYam project (OPP1052998) to IITA and the International Development Research Center
(IDRC) under the IDRC/CORAF-WECARD/IITA sub-grant agreement for developing capacity for
Agricultural Research in Sub-Saharan Africa (PJ-2126) to PEN (Ph.D. student) at the West African
Center for Crop Improvement (WACCI), University of Ghana.
Acknowledgments: The authors are grateful to IITA for the glasshouse and screenhouse facilities
provided for the study. The technical support from the entire yam breeding team, IITA, Ibadan,
Nigeria, is also duly acknowledged.
Conflicts of Interest: The authors declare no conflict of interest.
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