Advanced Studies in Biology, Vol. 7, 2015, no. 10, 413 - 422
HIKARI Ltd, www.m-hikari.com
http://dx.doi.org/10.12988/asb.2015.5419
Partitioning of Eggplant Cultivars in North
Central Nigeria Using Gross Vegetative and
Reproductive Characters
*C.U.
Aguoru, F. Idakwo and J.O. Olasan
Department of Biological Sciences, University of Agriculture, Makurdi, Nigeria
*
Corresponding author
Copyright © 2015 C.U. Aguoru, F. Idakwo and J.O. Olasan. This article is distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Abstract
Eggplants emanating from a gene bank were studied. The aim was to partition and
separate the cultivars into species level on the basis of their variable characters.
Seeds were obtained from the seed gene bank of the University of Agriculture,
Makurdi, Nigeria, and planted in the university research farm. Forty nine (49)
cultivars at full maturity were examined using thirty (30) vegetative and thirty
three (33 reproductive characters. Among the cultivars, the following characters
remained unvaried: bud position (terminal), leaf type (simple), leaf arrangement
(alternate), pubescence type (puberulent), venation type (pinnately netted), petal
cohesion (fused), ovary position (superior), corolla shape (companulate), anther
type (basifixed), filament adhesion (free) and symmetry of flower
(actinomorphic). Some characters were moderately varied but not important to
separate the cultivars. The prominent variables that formed the basis of
partitioning the species are: leaf sizes, leaf shapes, leaf apices, number of leaf
produced, plant height, number of days to produce flower, number of days to yield
fruit, quantity of fruit produced (yield), fruit sizes, fruit colour, fruit shape, fruit
stripe, fruit groove, fruit taste, fruit position, colour of petal and influorescence
type. Based on these features, the cultivars are separated into eight (8) different
taxonomic groups that may be assigned specific circumscription and named
accordingly by taxonomists.
Keywords: Eggplant, Partitioning, Vegetative character, Reproductive character,
Taxonomy
414
C.U. Aguoru et al.
Introduction
Family solanaceae is well recognized globally as it contains major indispensable
food crops which include; pepper, tomato, potato and eggplant. These crops have
contributed immensely towards the global poverty alleviation and hunger
reduction (FAO, 2014). Eggplant (Genus Solanum) is a vegetable and fruit crop of
wide ecogeographical distributions. However, the genomics of this crop has not
been extensively studied when compared with other solanaceous vegetables
(Agnieska et al., 2007). Studies on eggplant recently attracted global attention due
to its numerous nutritive and medicinal potentials coupled with the diversity in
morphological forms. Many authors have criticized and suggested different
nomenclatures for different eggplant species based on reports on diversity studies.
However, taxonomic difficulties on the crop still persist due to the wide
distribution of varying morphological and sometimes confusing types (Agnieska
et al., 2007). Interspecific hybridization has been reported to be a major challenge
in eggplant studies (Oyelana and Ugborogho, 2008). This is because the overall
effect of this natural process is the emergence of varying hybrid complexes that
possess unique characters that may be totally different from the parental stock.
Hence, the genus Solanum is the most variable among other genera of the
solanaceae family (Doganlar et al., 2002; Frary et al., 2003). Therefore,
systematic investigation and breeding programmes are vigorously being pursued
on eggplant all over the world.
Eggplants have been characterized using morphological, phytochemical and
molecular evidences (Osei et al.,2010; Chinedu et al.,2011; Mariola et al.,2014;
Aguoru et al.,2015abc). Reports have indicated wide variation in major taxonomic
characters even within members of a particular species. Aguoru et al. (2015a)
used population genetic parameters to reveal the level of genetic polymorphism in
eggplant across different populations in Nigeria. They recommended that regions
of high polymorphism should sustain this trend as necessary for improvement
prorammes. Despite the variation on eggplant reported across the globe,
molecular evidences exist that the same genes are conserved as evolution
progresses (Doganlar et al., 2002; Frary et al., 2003; Aguoru et al.,2015b). This
present study is aimed at partitioning and separating mature eggplant cultivars
arising from a pool of germplasm into distinct specific taxa based on their gross
vegetative and reproductive taxonomic characters.
Materials and Methods
Eggplant seeds were obtained from the seed gene bank of the University of
Agriculture, Makurdi, Nigeria. They were planted in the school research farm.
Forty nine (49) cultivars at full maturity were examined using thirty (30)
vegetative and thirty three (33) reproductive characters. Qualitative characters
were physically examined while quantitative measurements were done using
appropriate instruments. Photographs of the various cultivars were taken. Data
were analysed using SPSS software and Microsoft Excel programme.
Partitioning of eggplant cultivars in north central Nigeria
415
Results and Discussion
In all the cultivars, the following vegetative and reproductive features remained
constant and unvaried: stem type (woody), bud position (terminal), leaf type
(simple), leaf arrangement (alternate), pubescence type (puberulent), venation
type (pinnately netted), petal cohesion (fused), ovary position (superior), corolla
shape (companulate), anther type (basifixed), filament adhesion (free) and
symmetry of flower (actinomorphic) (table 1). Similarity recorded in these
qualitative characters therefore corroborates the molecular gene conservation
phenomenon in eggplant as reported by Aguoru et al. (2015b) and Agnieska et al.
(2007). The authors opined that irrespective of the significant variations among
the various eggplant cultivars, certain traits remain unchanged which tend to unify
the species along a common line of ancestry.
However, all the cultivars showed tremendous variations in some quantitative
traits. Some vegetative traits that are important in demarcating the species include:
internode length, leaf sizes, leaf weight, number of leaves produced, stem
diameter and plant height (figure 1). S.anguivi was highly differentiated on the
basis of its tall height. S.aethiopicum Shum and S.anguivi were noted for
producing the highest number of leaves (115). Flower production was fastest in
S.aethiopicum Shum (86 days of planting) while the Gilo Kumba complex was the
first in producing fruits (95 days). Fruit sizes were largest in S.athiopicum Kumba
(9.1cm in diameter). Meanwhile, the highest fruit yield was recorded among three
members of S.aethiopicum Shum (53, 36 and 33 fruits per plant) followed by
S.anguivi (30 fruits). The last two species were therefore highly yielding in terms
of leaf and fruit production though their fruit sizes were relatively tiny. This
quantitative approach therefore agrees with the view of Aguoru et al.(2015b) who
analysed eggplant seedlings using quantitative trait analysis. In their findings,
these traits, which are coded for by polygenes, varied among eggplant species and
they could also form the basis of selection by plant breeders (Mariola et al., 2014;
Aguoru et al., 2015b).
Qualitative inheritance also varied among the cultivars most especially in leaf,
fruit and floral characteristics (table 2 and 3). The combination of qualitative and
quantitative approach in both vegetative and reproductive features has provided a
detailed morphotypic investigation that is sound enough to separate all the
species. Previous studies (Osei et al., 2010; Aguoru et al., 2015c ) that reported
wide variation among the members of eggplant species based on such gross
morphology are strongly supported. The prominent variables that formed the basis
of partitioning the species are: leaf sizes, leaf shapes, leaf apices, number of leaf
produced, plant height, number of days to produce flower, number of days to yield
fruit, quantity of fruit produced (yield), fruit sizes, fruit colour, fruit shape, fruit
stripe, fruit groove, fruit taste, fruit position, colour of petal and influorescence
type. (figure 1 and 4). On this note, the phylogenetic tree has revealed that the
cultivars are separated into eight different species, though some are closely related
416
C.U. Aguoru et al.
along a common ancestral lineage while some appeared to be primitive
progenitors showing a divergent relationship. This finding therefore agrees with
reports of convergent and divergent relationships on eggplant accessions using
molecular marker approach (Sifau et al., 2014; Aguoru et al., 2015b).
Dendrogram (figure 3) therefore shows that S.anguivi is an old stock of eggplant
species which diverged in the course of evolution followed by S.aethiopicum
Shum. It has been revealed that these two divergent species yielded the highest
number of leaves and fruits though with small fruit sizes. The S.athiopicum
Kumba and the unidentified species are more closely related than S,macrocarpon
but the three species are related by common ancestry. In the same manner, S.gilo
is more closely related to the Gilo-Kumba than the Gilo-Shum hybrid. This
confirms that the Gilo-Kumba was a hybrid product of the S.gilo. However, all the
eggplant species are well separated and they may be named accordingly. A similar
approach of species separation was adopted by Shalom (2011) who used
proximate and phytochemical analysis to dermacate S.aethiopicum and
S.macrocarpon and concluded that the two species are distinctly different in terms
of the quality (types) and quantity of their active ingredients.
In conclusion, the roles of gross and total morphological analysis in revealing the
phylogenetic relationships among eggplant species cannot be over-emphasized. It
forms the basis of all other criteria used in plant taxonomic studies as the
characters are easily obtainable, observable and measurable. In this analysis, leaf
sizes, number of leaf produced, plant height, number of days to produce flower
and fruits, fruit sizes and colours, quantity of fruit yielded and other qualitative
and quantitative variables are important features in separating the eggplant species
into eight distinct groups. The notable and prominent species that showed traits of
interest may be acted upon by plant breeders and growers for continuous
propagation or be improved upon.
Table 1: Constant characteristics in all species
Species
S.a Kumba
Bud P
Leaf T
Lf A
Pub T
Ven T
Pet Co
Ov P
Cor S
Anther T
Flwr S
Fil Ad
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
S. a Shum
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
S.gilo
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
Gilo-Kumba complex
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
S.anguivi
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
S.macrocarpon
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
Gilo-Shum complex
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
Unidentified species
Term
Simple
Alt
Pubr
P/netted
Fused
Sup
Comp
Basifixed
Reg
Free
Partitioning of eggplant cultivars in north central Nigeria
417
Legend:
T=type
Bud P=Bud position; Term=terminal; Pub =Pubescent; Pubr=Puberulent; Ven=Venation;
P/netted=Pinnately netted
Pet Co=Petal cohesion; Ov P=Ovary position; Sup=Superior; Cor S=Corolla shape;
Comp=Companulate;
Flwr S= Flower symmetry; Reg=Regular; Fil Ad=Filament adhesion
Table 2: Variable vegetative features (qualitative)
Species
Leaf shape
Leaf surface
Leaf apex
Leaf base
Leaf pub
Stem Position
S.aethiopicum Kumba
Cordate/Ovate
Rough
Cusp/Acc
Ob/Tr/Rd
P
Erect
S. aethiopicum Shum
Cordate/Ovate
Rough/Smooth
Cusp/Acc/Acute
Ob
P/A
Erect/Branched
Cordate/Obovate
Rough/Smooth
Cusp/Acute
Ob
P
Erect/Branched
Cordate/Ovate
Rough
Cusp
Ob
P
Erect/Branched
S.gilo
Gilo-Kumba complex
Ovate/Obovate
Rough/Smooth
Cusp/Acc
Ob
P/A
Erect/Branched
Obovate/Cordate
Rough/Smooth
Cusp
Ob/Rd
P/A
Erect/Branched
Gilo-Shum complex
Cordate
Rough
Cusp
Ob
P
Erect/Branched
Unidentified species
Cordate
Rough
Cusp/Acc
Ob
P
Erect/Branched
S.anguivi
S.macrocarpon
Legend
Cusp/Acc=Cuspidate/Accuminate
Ob/Tr/Rd=Oblique/Truncate/Rounded
Leaf pub= Leaf pubescence (P=present; A=absence)
Table 3: Variable reproductive features (qualitative)
Petal
colour
Infl/type
Fruit colour
Fruit
stripe
Fruit
groove
Fruit shape
Fruit position
Fruit taste
S.aethiopicum Kumba
W/C
CC
White
yes/no
yes
Obl/Obv
Int
Bt
S. aethiopicum Shum
W/Cy
CC/AX/ST
Green
yes/no
yes
Sph/Obl
Term/Base
Bt/Sw/VBt
S.gilo
W/C
CC/AX
Gr/Yel/Wt
yes/no
yes/no
Pyr/Ova/Obv/Obl
Term/Base/Int
Bt/Sw
Gilo-Kumba complex
W/C
CC
White
yes/no
yes
Obv/Ova
Int
Bt
W
CC/ST
Green
no
no
Rounded
Term/Base
Bt
P/W
CC
Green
yes
yes
Obl
Term
Bt
Gilo-Shum complex
W
ST
Green
yes
yes
Sph
Int
Bt
Unidentified species
W/Wy/C
CC/ST
NF
NF
NF
NF
NF
NF
Species
S.anguivi
S.macrocarpon
Legend
W/C/Cy/Wy/P= white/creamy/cream-yellow/white-yellow/purple
Infl/type=Influorescence type (CC/AX/ST=compound cyme/auxillary/solitary)
NF= No fruit within 150 days
Gr/Yel/Wt= green/yellow/white
Sph/Pyr/Ova/Obv/Obl=spheroid/ pyriform/oval/obovate/oblate
Term/Base/Int= terminal/base/intermediate
Bt/Sw/VBt= bitter/sweet/very bitter
418
C.U. Aguoru et al.
160
140
120
100
80
60
40
20
0
SaKumba
SaShum
Sgilo
Gilokumba
Sangv
Smacro
GiloShum
Unid
Fig. 1: Some vegetative features of the cultivars
IL= Internode length; LL= Leaf length; LB= Leaf breadth; LW= Leaf weight; LS= Leaf shape;
LA= Leaf apex; LBASE= Leaf base; LPU= Leaf pubescence; PL= Petiole length; NOL= Number
of leaves; STD= Stem diameter; PLTH= Plant height
160
140
120
100
80
60
40
20
Plant Height
No of leaves
Leaf size
0
Fig.2: Species differentiation on the basis of three important vegetative characters
Legend:
Sakumba= Solanum aethiopicum Kumba
SaShum= Solanum aethiopicum Shum
Sgilo= Solanum gilo
Gilokumba= Solanum gilo- Solanum aethiopicum Kumba complex
Sangv= Solanum anguivi
Smacro= Solanum macrocarpon
GiloShum= Solanum gilo- Solanum aethiopicum Shum complex
Unid= Unidentified species
Partitioning of eggplant cultivars in north central Nigeria
419
Fig.3: Phylogenetic relationships to demarcate the cultivars into species
140
120
SaKumba
100
SaShum
Sgilo
80
Gilokumba
60
Sangv
40
Smacro
20
GiloShum
0
Unid
Fig.4: Floral and fruit features of the cultivars
Legend:
FL= Flower length; PC= Petal colour; NP= number of petals; NS= number of sepals; LP=length of
petal; LS=length of sepal; LF=length of filament; PL= pedicel length; Day F= number of day to
flowering; Nsta= number of stamen; FrtL= fruit length; FrtD=fruit diameter; FrtC=fruit colour;
Yield= number of fruits produced.
420
C.U. Aguoru et al.
140
120
100
80
Day of flowering
60
Fruit weight
40
Fruit size
20
Yield
0
Fig.5: Species differentiation on the basis of floral and fruit characters.
Gilo-Kumba
Gilo-Shum
S.anguivi
S.macrocarpon
Partitioning of eggplant cultivars in north central Nigeria
421
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Received: April 17, 2015; Published: October 1, 2015