KEW BULLETIN VOL. 67: 401 Y 411 (2012)
ISSN: 0075-5974 (print)
ISSN: 1874-933X (electronic)
Solanum incanum s.l. (Solanaceae): taxonomic relationships
between S. incanum, S. campylacanthum, S. panduriforme
and S. lichtensteinii
John Samuels1
Summary. In a study designed to elucidate the taxonomy of Solanum incanum sensu lato, S. incanum L., S. campylacanthum
Hochst. ex A. Rich., S. panduriforme E. Mey. ex Dunal and S. lichtensteinii Willd. from Africa and SW Asia were investigated using crossability and morphometric techniques. It is proposed that S. panduriforme is, in fact, a subspecies of
S. campylacanthum (S. campylacanthum subsp. panduriforme) and that S. incanum and S. lichtensteinii are distinct species.
Other information suggests that S. campylacanthum is more closely related to a common ancestor of S. incanum s.l.
S. campylacanthum subsp. panduriforme and S. incanum are believed to have diverged away from S. campylacanthum-type
predecessors in tropical E Africa, moving southwards or towards the Middle East, respectively. S. lichtensteinii probably
evolved from an even earlier ancestor in its migration towards southern Africa.
Key Words. Biosystematics, Georg Bitter, interfertility, numerical taxonomy, series Incaniformia, species concept.
Introduction
Taxonomy of African solanums
The last adequately detailed work on African solanums
was undertaken by Georg Bitter in the first quarter of
the 20th century, when he formulated a revision of the
genus Solanum in Africa, based largely on herbarium
material (Bitter 1913, 1917, 1921, 1923). More recently, Jaeger & Hepper (1986) reviewed the development
of our knowledge of the genus and provided a
conspectus of native African species, totalling around
110, belonging to 16 sections in four subgenera. Levin
et al. (2006) showed that the African solanums formed
part of the distinctive and monophyletic “Old World
clade.” The present paper concerns a few of the
species in series Incaniformia Bitter in sect. Melongena
(Mill.) Dunal of subgen. Leptostemonum (Dunal) Bitter.
Series Incaniformia Bitter
Bitter (1923) grouped several well-known species such
as Solanum incanum L., S. campylacanthum Hochst. ex
A. Rich., S marginatum L. f. and other closely allied
species, along with S. melongena L. into the series
Incaniformia Bitter. Bitter also attempted to expand
upon the particularly narrow species concept prevalent at the time, reducing many of Dammer’s (1905,
1906, 1912, 1915) species to infraspecific taxa or
synonyms. Bitter’s series Incaniformia nevertheless
remained a large group containing 28 species found
throughout much of Africa to SW Asia (Samuels
1996).
Members of series Incaniformia are typical examples
of the subgenus Leptostemonum (the “spiny solanums”)
which comprises 450 species (Levin et al. 2006),
around 80 of which occur in Africa. They are
characterised by stellate pubescence, attenuate
anthers and strong armature. Wherever ground is
disturbed, members of series Incaniformia may successfully establish themselves and become persistent
weeds; they are well-known ruderals and adventives
across much of Africa and parts of SW Asia and are
found growing at altitudes of 250 – 3000 m.
Solanum incanum s.l.
Solanum incanum and its allies have been the subject of
plant breeding and research based on genetic improvement of the brinjal eggplant, S. melongena L. (e.g.
Daunay et al. 1991, 1998, 2001; Lester 1998;
Mohammad et al. 1994; Sakata & Lester 1994). An
accurate understanding of the taxonomy of this group
therefore has important commercial implications.
Previous taxonomic treatments of Solanum incanum s.l.
(Bitter 1923; Jaeger 1985; Lester & Hasan 1991; Whalen
1984) have provided us with surveys based on informal
species groups; they are useful as overviews but do not
commit to detailed taxonomic judgements (see Table 1).
The main taxa representing the Solanum incanum
species complex are: S. campylacanthum (group A in
Lester & Hasan 1991), S. panduriforme E. Mey. ex
Dunal (group B), S. incanum L. s.str (group C) and S.
lichtensteinii Willd. (group D). Their close relationship
has been confirmed by Mace et al. (1999) in their AFLP
Accepted for publication May 2012. Published online 29 June 2012
1
Trezelah Barn, Trezelah, Gulval, Penzance, Cornwall TR20 8XD, UK. e-mail: john.samuels@virgin.net
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
E. S. cerasiferum group
(S. cerasiferum Dunal &
allies)
D. S. campylacanthum group
(S. campylacanthum & allies)
D. S. lichtensteinii & allied
taxa
C. S. incanum L. sensu stricto
only
A. (S. bojeri Dunal, S.
campylacanthum, S. delagoense
Dammer & many other
spp.
S. incanum sensu lato
groups:
Lester &
Hasan 1991
Jaeger 1985
“Solanum incanum”
group:
“S. incanum L. agg.” —
5 species groups:
Whalen 1984
A. S. incanum group
(S. incanum & allies)
B. S. lichtensteinii group
(S. lichtensteinii & S.
subexarmatum Dammer)
B. S. panduriforme only
C. S. panduriforme group
(S. panduriforme only)
DNA study, by Lester & Hasan (1991) in their biosystematic investigations, and by Lester & Daunay (2003) in
their survey of African vegetable solanums.
3 species collectivae
forming part of series
Incaniformia Bitter:
1. S. campylacanthum
2. S. bojeri (Dunal) sensu
3. S. incanum (L.) sensu ampliore
(Hochst.) sensu ampliore
ampliore Bitter (S. panduriforme Bitter (S. incanum L. & S.
Bitter (S. campylacanthum
Dunal & allies)
incanum L. var. lichtensteinii
& allies)
(Willd.) Bitter
consists of 12 (un-named) spp. of S. incanum and allies; largely based on Bitter’s series Incaniformia with majority of species reduced to synonymy
KEW BULLETIN VOL. 67(3)
Bitter 1923
Table 1. Previous taxonomic treatments of Solanum incanum s.l.
402
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
Objectives
The main objectives of this paper are to consider all
available information, including that produced by the
author, to determine the taxonomic status of groups
A – D in Lester & Hasan (1991) and to designate
species and other taxa appropriately.
Materials and Methods
For the present study, almost all of the species
included in Bitter’s series Incaniformia are considered
under Solanum incanum s.l. However, S. marginatum
and S. melongena, which on the basis of DNA characteristics (Levin et al. 2006; Mace et al. 1999; Sakata &
Lester 1994) and morphological differences (Jaeger
1985; Lester & Hasan 1991) are readily distinguished
from S. incanum and its allies, and must, therefore, be
treated elsewhere. S. cerasiferum Dunal and its allies
were considered by Hasan (1989) to be distinctive
from S. incanum and its near relatives. Although
S. cerasiferum is closely related to S. incanum s.l. (Bitter
1923; Samuels 1996) subsequent DNA analysis (Mace
et al. 1999) and comparative morphology (Samuels, in
prep.) have confirmed Hasan’s (1989) view.
In the present work the scheme for describing the
taxa in Solanum incanum s.l. provided by Lester & Hasan
(1991) has been adopted, but with some modifications.
Two of Lester & Hasan’s Middle Eastern accessions
have been re-located to group C from group D, making
group D a collection of purely southern African
accessions. In addition, S. bojeri Dunal and S. delagoense
Dammer, believed to be distinct species by Lester &
Hasan (1991), are considered to be synonyms of S.
campylacanthum and S. panduriforme respectively, in the
present study. It is also likely that several other species
allied to groups A and D by Lester & Hasan (1991)
are synonyms of S. campylacanthum and S. lichtensteinii
respectively (Samuels, in prep.).
Cultivation of living plants
Seeds of 20 accessions originally collected from Africa
and the Middle East were obtained from the Birmingham University Solanaceae Collection (Lester et al.
2001) and grown on. Plants were cultivated by the
same methods used in other related studies (e.g.
Lester & Hasan 1991; Lester & Niakan 1986). Accessions included eight of group A and four each of
groups B, C and D (Table 2). Crosses between these
accessions produced seed, from which 24 F1 hybrid
lines were grown (Table 3). Voucher specimens were
initially retained at the University of Birmingham and
then transferred to the Radboud University Botanical
and Experimental Garden, Netherlands.
SOLANUM INCANUM S.L. (SOLANACEAE)
403
Table 2. Parental Accessions of Solanum incanum s.l. and methods of study.
Studied by
Accession No.
Group (Hasan 1989)
BIRM/S.0859
0931
1064
1398
b
1512
1518
1692
b
1750
1780
1781
1793
2023
2026
2027
2028
2055
2607
2465
2503
c
RNL337/1432
A
C
A
B
C
D
D
C
A
B
C
A
A
A
A
B
A
D
D
D
a
= unprovenanced;
was employed.
b
Locality, Source/Collector and No.
NTv
Uganda, Kyambogo, Lester s.n. 6 Sept. 1969
Israel, Bot. Gdn. Univ. Tel Aviva
Uganda, Kampala, Anne Kenrick s.n.
Zimbabwe, N.E. Salisbury, Min. Ag. 14 Sept. 1973
Israel, Vadi Pereas, Univ. Jerusalem s.n.
South Africa, Pretoria, P.I. Officer s.n.
South Africa, Transkei, Arnold Q s.n.
Iran, Bandar-Abbas, Wendelbo s.n.
Tanzania, Dar-es-Salaam, Hedberg s.n.
Tanzania, Dar-es-Salaam, Hedberg s.n.
N.E. Ethiopia, Loutfy Boulos s.n.
Kenya, Hepper & Jaeger s.n
Kenya, Lake Naivasha, Jane Parish No. 3
Kenya, 1.6°S 36°E, Jane Parish No. 4
Kenya, Kilifi, Jane Parish No 5
Malawi, Domasi Valley, Blackmore 315A
Belgium, Bot. Gdn. Univ. Liegea
South Africa, TUL, Ngwenyi, Balsinhas 3394
South Africa, Pretoria, Lester s.n.
Zimbabwe, IBPGR, TGR 1432
*
= re-located to group C from group D;
c
*
*
*
*
XX
ST
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
= seed normality/germination data only available; * denotes technique
NTv numerical taxonomy of vegetative characters; XX crossability tests; ST pollen stainability tests.
Interfertility studies
235 cross-pollinations involving accessions representing groups A, B, C and D were performed over four
growing seasons. Each unit cross, its reciprocal cross
and self-pollinations of parents were attempted and
repeated several times wherever possible, according
Table 3. Cross-combinations of Solanum incanum s.l. used in
crossability study.
female parent
group
BIRM/S.0859
0859
0859
1064
0859
0859
1781
1512
1793
1512
1512
1512
1512
1750
1750
1793
1793
1512
1692
1692
2465
1692
1692
2465
A
A
A
A
A
A
B
C
C
C
C
C
C
C
C
C
C
C
D
D
D
D
D
D
×
male parent
group
BIRM/S.2023
2026
2028
2369
1398
1781
2369
2053
2053
0931
1512
1750
1793
1750
1793
1750
1793
2465
0931
1750
1750
1692
2465
2465
A
A
A
A
B
B
B
B
B
C
C
C
C
C
C
C
C
D
C
C
C
D
D
D
to flower availability. The success or failure of
pollinations leading to development of fruit (fruit
set), proportion of normal seeds per cross (seed
normality), the proportion of successful germinations of seed produced per cross-combination
(germination success), and the pollen stainability
of F1 hybrids were investigated according to the
methods employed in similar studies (e.g. Lester &
Hasan 1991; Lester & Niakan 1986). Mean percentage values for each of the crossing programme results
were calculated and crossing success values between 1
and 5 were calculated using a combination of fruit
set, seed production and pollen stainability data (see
Table 4 for details).
Morphometric study of groups A and B
All the morphological characters studied by Lester
& Hasan (1991), Lester & Niakan (1986), Pearce
(1975) and others were considered. During a preliminary study, erratic flowering presented difficulties
with the availability of flowers for study. As a
consequence, a total of 28 purely vegetative characters were chosen for measurement on each plant in
accessions from Group A and Group B (Fig. 1;
Table 5). Focus was given to these two groups as
their distinction is particularly problematic. For each
of six plants of five parental accessions, three habit,
six stem and 19 leaf characters from each of three
leaves, were measured. Each leaf was treated as a
separate OTU (operative taxonomic unit), but all
three leaves from any one plant had the 3 habit and 6
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
404
KEW BULLETIN VOL. 67(3)
Table 4. Solanum incanum s.l. crossing programme results.
A
A
41.4
20.8
B
25.0
73.0
C
0
-
D
0
-
69.0
94.4
5
Male Parent
95.5
95.6
5
1
1
a
= based on 1 value only;
b
Female Parent
B
50.0 98.0a
13.0a 91.9a
5
25.0 0
1
0
1
0
1
C
41.5 6.1
1/1a b
3
16.7 80.0
10.0a 70.3
4
61.8 88.0
37.4 80.4
5
42.8 12.3
a
54.6a
4.0
4
D
81.8a 0
2
75.0a 0
2
75.5 50.8
42.7 69.6
4
57.1 65.0
20.0 83.1
5
= seedling died.
Each block of five values is arranged as:-
c.s.
c.s.
c.s.
c.s.
c.s.
=
=
=
=
=
1
2
3
4
5
–
–
–
–
–
pollinations made, no fruit set
fruit set, no normal seed produced
normal seed produced, no germination of F1
F1 produced from seed, low pollen stainability (0 – 74 %)
F1 produced from seed, high pollen stainability (75 – 100 %)
stem characters in common. The morphological data
were processed and analysed using the CLUSTAN 2.1
numerical taxonomy package (Wishart 1982) as used
in similar analyses (e.g. Lester & Hasan 1991). This
generated phenograms by Euclidean Distance
Squared and Cluster Analysis (Ward’s Method), and
scatter diagrams by Principal Components Analysis (see
Figs 2 and 3).
Results and Discussion
Interfertility Relationships (see Table 4)
In the following discussion, the female parent group is the
first cited of any pair of groups crossed together, whilst
the male parent group (pollen donor) is the second.
In terms of crossing success, there is general
agreement between the present author’s results and
those of Hasan (1989). The present study, however,
was based on a more detailed analysis of A × B, B × A
and C × A crosses, and examined a wide range of
reciprocal crosses, not attempted by the former work.
Within-group crosses Within-group crosses.
Crossing success for crosses A × A, C × C and D × D were
high, as expected; however, B × B cross-combinations
yielded no viable seed, which was surprising, especially as
parental group B accessions showed high pollen
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
fertility (Samuels 1994). Some B × B cross-combinations were self-pollinations, and the possibility of selfincompatibility arises here. This is rare in subgenus
Leptostemonum (Whalen 1984), and neither Hasan (1989)
working on related taxa, nor the present author (Samuels
1994) found any evidence for this phenomenon.
Within-group crosses did not consistently demonstrate better fruit set than between-group crosses,
which is surprising, since greater success might be
expected between more closely related taxa. Furthermore, Daunay et al. (1999) also noted low fruit set in
crosses within groups A and B and erratic fruit set in
related species of Solanum.
Wider Crosses Wider Crosses.
Out of 32 attempts only one seed was produced (seed
normality of 6.1%) by C × A cross-pollinations, but the
resultant seedling died. Such very low seed normality
values are probably an indication of the more distant
taxonomic relationship between group C and group A
plants. The seed normality value compares closely with
6.9% noted by Hasan (1989). Lester & Kang (1998)
suggested that incongruity between the two parental
genomes in C × A crosses leads to the breakdown of
endosperm and sporophyte tissues.
Hasan’s (1989) pollen stainability results for the C ×
A combination (77%) are surprising, since groups C
SOLANUM INCANUM S.L. (SOLANACEAE)
405
Fig. 1. Leaf morphology characters used for morphometric study.
and A are believed to be taxonomically distinct.
Furthermore, any interfertility between the two groups
is at best only one way, as a total of 16 attempts at crosspollination in the present study (and Hasan’s (1989)
results) showed that the reciprocal cross failed to
produce any fruit.
Although some other wide cross-combinations (C ×
B, C × D and D × C) provided substantially fertile
pollen (although less than 75% stainability) there may
well be genomic incongruities (which parallel taxo-
nomic disparity) whereby the fertility and viability of
subsequent generations could be seriously impaired.
In addition, cross-combinations involving allopatric
groups (such as those above) are unlikely to take
place in nature because of geographical isolation.
Certain cross-combinations resulted in no fruit
being set, whereas the reciprocal crosses did. E.g. no
fruits were produced when flowers of groups A or B
were used as female parents to cross with groups C or
D as the male parents, whereas many of the reciprocal
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
406
KEW BULLETIN VOL. 67(3)
Table 5. Definitions and abbreviations of gross vegetative morphology characters employed for numerical taxonomy (see Fig. 2).
No.
Character definitions
(a) Plant habit characters
1.
Plant height at highest point, cm
2.
Plant breadth at broadest point, cm
3.
Plant habit, height/breadth, ratio × 100
(b) Stem characters
4.
Stem width at 10 cm from ground, mm × 10
5.
Prickle number at half way up, all round the stem for 10 cm
6.
Length of longest prickle, at half way up stem for 10 cm, mm × 10
7.
Width of longest prickle, at half way up stem for 10 cm, mm × 10
8.
Prickle length/prickle width, ratio × 100
9.
Stem prickle shape (coded: 1 straight; 2 curved; 3 hooked)
(c) General leaf lamina characters
10.
Leaf blade attitude (coded: 1 erect; 3 semi-erect; 5 horizontal; 7 semi-pendent; 9 pendent)
11.
Leaf lamina shape (coded: 1 elliptic; 3 elliptic ovate; 5 ovate; 7 ovate lanceolate; 9 lanceolate)
(d) Individual petiole characters
12.
Petiole length, mm
13.
Petiole width, in middle, mm × 10
14.
Petiole length/petiole width, ratio × 10
(e) Individual leaf lamina characters
15.
Total number of prickles on the petiole
16.
Leaf lamina length, cm × 10
17.
Leaf width at widest part, cm × 10
18.
Leaf lamina length/width, ratio × 100
19.
Distance from the widest part of the leaf to the tip of the leaf, cm × 10
20.
Widest to the tip/length, ratio × 100
21.
Leaf blade tip angle
22.
Leaf base angle
23.
Total leaf lobe number
24.
Length of the greatest leaf lobe, mm
25.
Width of the base of the greatest leaf lobe, mm
26.
Distance from the greatest leaf lobe to the tip, cm × 10
27.
Prickle number on the upper lamina surface
28.
Leaf undulation, height at highest undulation, mm Lf. undu
crosses did set fruit. Hasan (1989) and Lester & Hasan
(1991) also noted the complete failure of fruit set of
group A flowers pollinated by groups C or D pollen
donors.
These results may be explained by a one-way prezygotic barrier. The hermaphrodite flowers of groups
A and B have long, robust styles and large stigmas,
whereas those of groups C and D tend to have thinner,
shorter styles, with smaller stigmas. Pollen from group
A or group B pollen is more likely to produce pollen
tubes that penetrate the stylar tissue of the less robust,
shorter styles of groups C and D, than the reverse.
Such unilateral fertility barriers are of considerable
significance in Solanum incanum and its allies. Baksh &
Iqbal (1979, cited in Daunay et al. 1991) reported that
many crosses between S. incanum and S. melongena
were only successful with S. incanum as the female
parent. Olet & Bukenya-Ziraba (2001) noted similar
unidirectional success in crosses between S. incanum
from Uganda (probably S. campylacanthum) and
S. cerasiferum, in which fruit was produced only in crosses
in which S. incanum was the female parent. Similar
unilateral fertility barriers were noted by Daunay et al.
(1991) and Daunay et al. (1999) in crosses between
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
Abbreviations
Pl. ht.
Pl. br.
Pl. ht./Pl. br.
St .wid.
St. pric.
St. pric.
St. pric.
St. pric.
St. pric.
no.
len.
wid.
l/w
sh.
Lf. att.
Lf. shape
Pet. len.
Pet. wid.
Pet. len./wid.
Pet. pric. no.
Lf. len.
Lf. wid.
Lf. len./lf. wid.
Lf. w-tip.
Lf. w-tip./Lf. len.
Lf. tip. ang.
Lf. base ang.
Lf. lobe no.
Lf. lobe len.
Lf. lobe wid.
Lf. lobe-tip
Lf. pric. no.
Lf. undul.
S. melongena and other Solanum species. Furthermore,
this phenomenon is well-known and relatively common in several genera in the Solanaceae, including
Solanum, Nicotiana and Petunia (Onus & Pickersgill
2004).
Interfertility of groups A and B InterfertilityofgroupsAandB.
Prolonged seed dormancy, erratic seed germination, unilateral pre-zygotic and complex postzygotic fertility barriers seem to have a strong
influence on fertility relationships in Solanum
incanum s.l. Therefore, two groups must show full
two-way crossing success (i.e. crossing success score
of “5”) to be safely regarded as fully interfertile and
thereby members of the same biological species. On
this basis, only groups A and B show full interfertility
and are conspecific.
A study performed by Sakata et al. (1991) involving
the analysis of chloroplast DNA (cpDNA) from plants in
accessions of groups A and B, showed that these groups
were closely related. This was later confirmed by Mace
et al. (1999) using AFLP analysis. This close genetic
relationship tallies with the results of the interfertility
study.
SOLANUM INCANUM S.L. (SOLANACEAE)
407
Fig. 2. Dendrogram for analysis of 28 vegetative characters of 3 leaves of 6 plants in 5 parental accessions of Solanum incanum s.l.,
groups A and B. (Accessions are as follows: 0859, 2026, 2028 — group A; 1398, 1781 — group B).
Morphological Variation in Solanum incanum s.l
Differentiation of groups A and B DifferentiationofgroupsAandB.
In Fig. 2 the various individual accessions were shown
to be more or less distinctive. However, separation
between group A accessions on the one hand, and
group B on the other, was unclear, indicating that their morphological distinction is unclear. For example, group B accession S.1781
showed considerable phenetic affinity with group
A accession S.2028. A similar situation in Fig. 3
shows that OTUs from individual accessions were
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
408
KEW BULLETIN VOL. 67(3)
Fig. 3. Principal Components Analysis of 28 vegetative characters of 3 leaves of 6 plants in 5 parental accessions of Solanum
incanum s.l.
more or less tightly clustered, but that group A and
group B accessions overlap, with S.2028 and S.1781
on the one hand, and S.2026 and S.1398 on the
other, partly intermerging. Again, this suggests a
lack of morphological distinction between the
respective accessions. Lester & Hasan (1991) also
found that groups A and B were morphologically
very close, and that several group A and group B
accessions showed considerable morphological
similarity.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
Variation in Group A Variation in Group A.
Fig. 3 shows that group A OTUs (S.0859, S.2026 and
S.2028) were generally quite dispersed within their clusters,
indicating greater variability, whereas group B OTUs
(S.1398 and S.1781) clustered more tightly, indicating
greater homogeneity. Observations by Gianoli &
Hannunen (2001), Olet & Bukenya-Ziraba (2001) and
Robinson (1993) substantiate the view that morphological variation in group A plants is considerable and covers
a broad range of vegetative and reproductive characters.
SOLANUM INCANUM S.L. (SOLANACEAE)
The wider variation of one of the group A accessions,
S.0859, is well demonstrated in Fig. 2, as the majority of
the S.0859 OTUs were clustered together at D2 = 12.4,
compared with much tighter clustering in other
accessions (D2 = 8 or less). This accession also seems
to be quite dissimilar to other group A (and B)
accessions, as the majority of its component plants
only linked up with other accessions at D2 = 29.0.
Furthermore, one plant (S.0859-1) was so dissimilar that
it clustered with different accessions. The cluster
analysis in Fig. 3 confirmed that accession S.0859 is
quite distinctive, whereby it formed a cluster that is quite
removed from the other four accessions. This particular
accession displays a range of morphological characteristics
that lies near the boundaries of typical group A plants.
Sakata & Lester (1994) in their study of cpDNA
reported the Ugandan accession S.0859 and several
other east African group A accessions to be distinct from
409
the main mass of other group A (and B, C and D)
accessions. This diversity in cpDNA suggests that group A
is a more ancient group than groups B, C, or D (Sakata
& Lester 1994) which all have homogeneous cpDNA
profiles. Group A genotypes may have become more
diverse through the development of more numerous
mutations over a greater period of time. This greater
genetic diversity in group A parallels its greater morphological diversity.
Differentiation of groups C and D
Groups C and D accessions were investigated using
morphometric techniques by Jayawickrama (1990). His
study revealed a clear distinction between groups C and D;
this was later confirmed by the findings of Lester & Hasan
(1991) and Samuels (1996). Furthermore, the distinction
evident between group D chloroplast DNA and that from
group C was demonstrated by Sakata & Lester (1994).
Key to the species and subspecies
1. Shrubs or sub-shrubs, less than 2 m high; branches robust, up to 7 mm diam., densely tomentose with stellate
hairs; always armed on shoots, leaves, inflorescence axes, and calyces and pedicels of hermaphrodite flowers;
leaf lamina ovate; corolla violet, purple, or white
2. Leaf lamina narrowly ovate, margin repand; inflorescence 1 – 5-flowered; corolla white (rarely violet),
2.5 – 3 cm across; fruiting calyx manifestly robust, heavily armed, lobes strongly reflexed; berry 3.5 – 4.5 cm
diam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. lichtensteinii
2. Leaf lamina broadly ovate, margin subentire to repand; inflorescence 1 – 15-flowered; corolla violet to
purple, 2.5 – 3 cm across; fruiting calyx enlarged, ± armed, lobes slightly reflexed; berry 3 – 3.5 cm
diam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. incanum
1. Shrubs, sub-shrubs or herbaceous perennials up to 2 m or more high; branches approx. 4 mm diam., sparsely
tomentose with stellate hairs; armed or unarmed; leaf lamina lanceolate to elliptic; corolla violet or purple
3. Leaf lamina ovate-lanceolate or lanceolate, margin subentire to lobed; inflorescence 3 – 15 (– 50)flowered, 1 – 5 (–15) lowest flowers hermaphrodite; corolla violet or purple, 2 – 3.5 cm across;
berry 2.5 – 3.5 cm diam . . . . . . . . . . . . . . . . . . . . S. campylacanthum subsp. campylacanthum
3. Leaf lamina elliptic, margin entire to subentire; inflorescence 3 – 12-flowered, lowest flower only
(more rarely 1 – 3 lowest flowers) hermaphrodite; corolla violet, 1.5 – 3 cm across; berry 2 –
2.5 cm diam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. campylacanthum subsp. panduriforme
Range of variation and distribution of the taxa
http://www.ipni.org/urn:lsid:ipni.org:names:77120311-1
Solanum campylacanthum Hochst. ex A. Rich. subsp.
campylacanthum
Solanum panduriforme Drège ex Dunal in DC., Prodromus 13 (1): 370 (de Candolle 1852).
Highly polymorphic group of more or less tomentose,
more or less armed shrubs, up to 2 m or more high, with
ovate-lanceolate to lanceolate, more-or-less lobed leaves.
Flowers up to 50 in each inflorescence, violet or purple,
often with several to many hermaphrodite flowers. Infructescence of several to many fruits, up to 3.5 cm diam.
Finely tomentose, sparsely armed or unarmed shrubs,
sub-shrubs or herbaceous perennials; up to 2 m or more
high; with elliptic, entire to sub-entire leaves; up to
12 violet flowers in each inflorescence, usually only
one flower (more rarely up to 3) hermaphrodite;
infructescence of up to 3 fruits, up to 2.5 cm diam.
DISTRIBUTION. Centred around tropical eastern Africa
DISTRIBUTION. Centred on eastern and south-eastern Africa.
and extending across to Madagascar.
Solanum incanum L.
Solanum campylacanthum subsp. panduriforme (Drège
ex Dunal) J. Samuels stat. nov.
Densely tomentose, armed perennial shrubs; up to 2 m
high; with broadly ovate, sub-entire to repand leaves; up to
15 purple or violet flowers in each simple inflorescence,
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
410
usually only one flower (more rarely up to 3) hermaphrodite; infructescence of up to 3 fruits, up to 3.5 cm diam.
DISTRIBUTION. Across north-eastern Africa, extending
southwards into Somalia and Kenya, westwards to
Senegal, across the Middle East, and as far eastwards
as northern Pakistan and northern India.
Solanum lichtensteinii Willd.
Densely tomentose, armed shrubs or sub-shrubs, 0.5 – 2 m
high; with narrowly ovate, repand leaves; up to 5 white (or
more rarely violet) flowers in each simple inflorescence,
usually only one flower (more rarely up to 3) hermaphrodite; infructescence of up to 3 fruits, up to 4.5 cm diam.
DISTRIBUTION. Across southern East Africa and much of
southern Africa.
Acknowledgements
Firstly, my gratitude for expert advice and guidance
given by the late Dr R. Lester and the late Prof. J.
Hawkes OBE must be recorded here. My thanks also
go to Mr A. Esquilant, Dr S. Hasan, Mr H. Jayawickrama
and Dr J. Kang for their practical assistance. I would also
like to thank Dr M. Vorontsova for assistance at K, Mr E.
Thewlis who typed the original manuscripts and Mr J.
Tennant for his encouragement. I am indebted to the
many herbaria and plant collectors who provided the
dried plant specimens used in this study. Lastly, I am
grateful to the Annals of Botany journal for their research
fellowship which funded the early part of this study, and
also to the National Science Foundation (USA) for
funding recent research on the PBI Solanum: a
Worldwide Treatment project at K and BM.
References
Bitter, G. (1913). Solana Africana Part I. Bot. Jahrb. Syst.
49: 560 – 569.
——— (1917). Solana Africana Part II. Bot. Jahrb. Syst.
54: 416 – 507.
——— (1921). Solana Africana Part III. Bot. Jahrb.Syst.
57: 248 – 286.
——— (1923). Solana Africana Part IV. Repert. Spec.
Nov. Regni Veg. 16: 1 – 320.
Dammer, U. (1905). Solanaceae Africanae. Repert. Spec.
Nov. Regni Veg. 38: 57 – 60.
——— (1906). Solanaceae Africanae I. Repert. Spec.
Nov. Regni Veg. 38: 176 – 195.
——— (1912). Solanaceae Africanae II. Repert. Spec.
Nov. Regni Veg. 48: 236 – 260.
——— (1915). Solanaceae Africanae III. Repert. Spec.
Nov. Regni Veg. 53: 325 – 352.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012
KEW BULLETIN VOL. 67(3)
Daunay, M.-C., Dalmon, A. & Lester R. N. (1999).
Management of a Collection of Solanum Species for
Eggplant (Solanum melongena) Breeding Purposes.
In: M. Nee, D. E. Symon, R. N. Lester & J. P. Jessop
(eds), Solanaceae IV: Advances in Biology and Utilization,
pp. 369 – 383. Royal Botanic Gardens, Kew.
———, Lester, R. N., Dalmon, A., Ferri, M., Kapilima,
W., Poveda-Aguilar, M. M. & Jullian, E. (1998). The
use of wild genetic resources for eggplant (Solanum
melongena) breeding. II: crossability and fertility of
interspecific hybrids. In: A. Palloix & M.-C. Daunay
(eds), Proceedings of the Xth Eucarpia Meeting on Genetics
and Breeding of Capsicum and Eggplant, 7 – 11
Sept 1998, Avignon, France, pp.19 – 24. INRA, Paris.
———, ———, Gebhardt, C., Hennart, J. W., Jahn,
M., Frary, A. & Doganlar, S. (2001). Genetic
resources of eggplant (Solanum melongena) and
allied species: a new challenge for molecular
geneticists and eggplant breeders. In: R. G. van
den Berg, G. W. M. Barendse, G. M. van der
Weerden & C. Mariani (eds), Solanaceae V: Advances
in Taxonomy and Utilization, pp. 251 – 274. Nijmegen
University Press, Nijmegen.
———, ——— & Laterrot, H. (1991). The use of wild
species for the genetic improvement of brinjal
(Solanum melongena L.) and tomato (Lycopersicon
esculentum Mill.). In: J. G. Hawkes, R. N. Lester, M.
Nee & N. Estrada (eds), Solanaceae III: Taxonomy,
Chemistry, Evolution, pp. 389 – 412. Royal Botanic
Gardens, Kew,
de Candolle, A. P. (1852). Prodromus systematis naturalis
regni vegetabilis 13. Sumptibus Victoris Masson,
Parisis.
Gianoli, E. & Hannunen, S. (2001). Plasticity of leaf
traits and insect herbivory in Solanum incanum L.
(Solanaceae) in Nguruman, S.W. Kenya. Afr. J. Ecol.
38: 183 – 187.
Hasan, S. M. Z. (1989). Biosystematic Study of Solanum
melongena L. in Asia and Africa. Unpublished Ph.D.
Thesis, University of Birmingham.
Jayawickrama, H. D. (1990). Study of the Diversity of
Solanum incanum agg. Unpublished M.Sc Thesis,
University of Birmingham.
Jaeger, P.-M. L. (1985). Systematic Studies in the Genus
Solanum in Africa. Unpublished Ph.D. Thesis,
University of Birmingham.
——— & Hepper, F. N. (1986). A review of the genus
Solanum in Africa. In: W. G. D’Arcy (ed.), Solanaceae:
Biology and Systematics, pp. 41 – 55. Columbia
University Press, New York.
Lester, R. N. (1998). Genetic resources of capsicums
and eggplants. In: A. Palloix & M.-C. Daunay (eds),
Proceedings of the Xth Eucarpia Meeting on Genetics and
Breeding of Capsicum and Eggplant, 7 – 11 Sept. 1998,
Avignon, France, pp. 25 – 30. INRA, Paris.
——— & Daunay, M.-C. (2003). Diversity of African
vegetable Solanum species and its implications for a
SOLANUM INCANUM S.L. (SOLANACEAE)
better understanding of plant domestication. In: H.
Knuppfler & J. Ochsmann (eds), Rudolf Mansfield and
Plant Genetic Resources; Schriften zu Genetischen Ressourcen
(DEU) Symposium Dedicated to the 100th Birthday of Rudolf
Mansfield. Gatersleben (DEU) 22: 137 – 152.
——— & Hasan, S. M. Z. (1991). Origin and
domestication of the brinjal eggplant, Solanum
melongena from S. incanum in Africa and Asia. In:
J. G. Hawkes, R. N. Lester, M. Nee & N. Estrada
(eds), Solanaceae III: Taxonomy, Chemistry, Evolution,
pp. 369 – 387. Royal Botanic Gardens, Kew.
———, Hawkes, J. G., Daunay, M.-C., van der Weerden,
G. M. & Barendse, G. W. M. (2001). The sources,
successes and successors of the Birmingham University Solanaceae Collection (1964-2000). In: R. G. van
den Berg, G. W. M. Barendse, G. M. van der Weerden
& C. Mariani (eds), Solanaceae V: Advances in Taxonomy and Utilization, pp. 391 – 412. Botanical Garden
of Nijmegen, Nijmegen University Press.
——— & Kang, J. (1998). Embryo and endosperm
function and failure in Solanum species and
hybrids. Ann. Bot. 82 (4): 445 – 453.
——— & Niakan, L. (1986). Origin and domestication
of the scarlet eggplant, Solanum aethiopicum, from S.
anguivi in Africa. In: W. G. D’Arcy (ed.), Solanaceae:
Biology and Systematics, pp. 433 – 456. Columbia
University Press, New York.
Levin, R. A., Myers, N. R. & Bohs, L. (2006).
Phylogenetic relationships among the “spiny solanums” (Solanum subgenus Leptostemonum, Solanaceae). Amer. J. Bot. 93 (1): 157 – 169.
Mace, E. S., Lester, R. N. & Gebhardt, C. G. (1999). AFLP
analysis of genetic relationships among the cultivated
eggplant, Solanum melongena L., and wild relatives
(Solanaceae). Theor. Appl. Genet. 99: 626 – 633.
Mohammad, A., Baksh, S. & Iqbal, M. (1994). Cytogenetic studies on on the F1 hybrid Solanum incanum
411
X S. melongena var. American Wonder. Cytologia 59
(4): 433 – 436.
Olet, E. A. & Bukenya-Ziraba, R. (2001). Variation
within the Solanum incanum complex in Uganda
and its relationship with Solanum cerasiferum. In:
R. G. van den Berg, G. W. M. Barendse, G. M. van der
Weerden & C. Mariani (eds), Solanaceae V: Advances
in Taxonomy and Utilization, pp. 97 –108. Botanical
Garden of Nijmegen, Nijmegen University Press.
Onus, A. N. & Pickersgill, B. (2004). Unilateral
incompatibility in Capsicum (Solanaceae): occurrence and taxonomic distribution. Ann. Bot. 94
(2): 289 – 295.
Pearce, K. G. (1975). Solanum melongena L. and
Related Species. Ph.D. Thesis, University of
Birmingham.
Robinson, R. W. (1993). Variability of Solanum incanum
in Kenya. Solanaceae Newslett. 3 (3): 4 – 7.
Sakata, Y. & Lester, R. N. (1994). Chloroplast DNA
diversity in Eggplant (Solanum melongena) and its
related species S. incanum and S. marginatum.
Euphytica 80: 1 – 4.
———, Nishio, T. & Mathews, P. J. (1991). Chloroplast
DNA analysis of Eggplant (Solanum melongena) and
related species for their taxonomic affinity. Euphytica 55: 21 – 26.
Samuels, B. J. (1994). Solanum incanum sensu lato
(Solanaceae): A Taxonomic Survey. M.Sc. Thesis,
University of Birmingham.
——— (1996). Solanum incanum sensu lato (Solanaceae):
Taxonomy, Phylogeny and Distribution. Ph.D Thesis,
University of Birmingham.
Whalen, M. D. (1984). Conspectus of species groups in
Solanum subgenus Leptostemonum. Gentes Herb. 12:
179 – 282.
Wishart, D. (1982). CLUSTAN User Manual. Edinburgh
University Library Program Unit, Edinburgh.
© The Board of Trustees of the Royal Botanic Gardens, Kew, 2012