Morphological Features and Inheritance of Foliaceous Stipules of ...

Annals of Botany 94: 469–471, 2004
doi:10.1093/aob/mch161, available online at www.aob.oupjournals.org
SHORT COMMUNICATION
Morphological Features and Inheritance of Foliaceous Stipules of Primary Leaves in
Cowpea (Vigna unguiculata)
R. N. PANDEY* and P. DHANASEKAR
Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
Received: 8 March 2004 Returned for revision: 13 May 2004 Accepted: 26 May 2004 Published electronically: 30 July 2004
Background and Aims The presence of connate foliaceous stipules of primary leaves and their inheritance in
cowpea (Vigna unguiculata) genotype EC394736 is reported for the first time.
Methods The development of foliaceous stipules (FS) and their persistence were examined throughout the growth
and developmental stages of the plants of the genotype EC394736. The shape, size, colour, texture and other
parameters were examined in the field during the period 15–50 d after sowing. The area of FS was measured using
image analysis software. The inheritance of FS was studied by making a cross between the genotype EC394763 with
rudimentary stipules (RS) and the genotype EC394736, which has connate foliaceous stipules of primary leaves. The
presence or absence of FS in plants of the F 1,F 2 and F 3 generations was recorded.
Key Results The stipules developed along with the primary leaves in the genotype EC394736. One stipule of each
primary leaf fused with the adjacent stipule of the other primary leaf forming a foliaceous structure. These stipules
persisted on the plants for >50 d, even after the primary leaves had withered off. The F 1 plants showed an absence of
FS indicating the rudimentary stipules to be dominant over foliaceous stipules. The F 2 segregation into 15 (RS) : 1
(FS) indicated that duplicate recessive genes controlled the presence of the FS. This was confirmed from the
segregation pattern in the F 3 generation.
Conclusions The presence of FS is a unique feature in cowpea genotype EC394736 and duplicate recessive genes
govern it. The FS can be used as a morphological marker for identification of cowpea varieties.
ª 2004 Annals of Botany Company
Key words: Cowpea, duplicate recessive genes, foliaceous stipules, inheritance, morphological marker, Vigna unguiculata.
INTRODUCTION
unique type of FS of primary leaves. This prompted us to
Cowpea (Vigna unguiculata), one of the most important
food legume crops, exhibits considerable morphological
variability in its wild as well as cultivated forms. The International
Institute of Tropical Agriculture (IITA), Nigeria,
the main germplasm resource centre for cowpea, maintains
characterize the FS in the genotype EC394736 and study
their inheritance. The details of the connate foliaceous
stipules of primary leaves and their inheritance in cowpea
are reported here for the first time.
over 15 000 germplasm lines (Quin, 1997) that help scientists
all over the world to identify the desired traits and
MATERIALS AND METHODS
combine them to suit their needs. With a view to initiating The development of the FS and their persistence were exam-
an improvement programme for cowpea through mutational ined throughout the growth and developmental stages of
as well as conventional breeding approaches at our Centre, plants of the genotype EC394736. To study the stage
about 130 germplasm accessions were obtained from IITA, at which the FS developed, the unexpanded cotyledonary/
Nigeria through the National Bureau of Plant Genetic primary leaves of the seedlings were forced open and exam-
Resources, New Delhi and used in various field and laborained at 5 d after sowing in Petri dishes. The shape, size,
tory studies. During the course of field studies, a unique colour, texture and other parameters were examined in the
feature in the genotype EC394736 (Pedigree: IT93K-2045- field during the period 15–50 d after sowing. Six stipules
29)—the presence of a pair of foliaceous stipules (FS) from randomly selected plants were excised and studied for
arranged opposite and at about right angle to the primary their shape and size. The area of the stipules was measured
leaves—was noticed. The plants of several other genotypes using image analysis software Biovis image plus, Ver. 1.4
in the germplasm collection belonging to the Nuclear Agri- (Expert Vision Labs Pvt. Ltd, Mumbai, India).
culture and Biotechnology Division (NA&BTD), Bhabha The inheritance of the foliaceous stipules was studied by
Atomic Research Centre (BARC), Mumbai, were examined making a cross between the genotype EC394763 with RS
and no such a feature was found in them, though they had (Fig. 1) and the genotype EC394736 with FS (Fig. 2) of
scaly separate or joint rudimentary stipules (RS). A survey primary leaves. The presence or the absence of the FS in
of the literature, especially on cowpea morphology and
taxonomy (Padulosi and Ng, 1997) and genetics (Fery,
1985; Fery and Singh, 1997), showed no mention of this
plants of the F1,F2 and F3 generations was recorded. The
progenies of only those F2 plants that produced 20 seeds or
more were carried forward in the F3 generation to ensure the
minimum number of plants (16) required for the dihybrid
* For correspondence. E-mail rnpandey@apsara.barc.ernet.in ratio of 15 : 1.
Annals of Botany 94/3, ª Annals of Botany Company 2004; all rights reserved
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470 Pandey and Dhanasekar — Foliaceous Stipules of Primary Leaves in Cowpea
F IG. 1. Rudimentary stipules (RS) of primary leaves in cowpea genotype
EC394763.
FS
F IG. 2. Connate foliaceous stipules (FS) of primary leaves in cowpea
genotype EC394736.
RESULTS
Characteristics of the foliaceous stipules
The stipules developed along with the primary leaves in the
genotype EC394736. One stipule of each primary leaf fused
with the adjacent stipule of the other primary leaf forming a
foliaceous structure. The connate foliaceous stipules were
conspicuous as soon as primary leaves expanded. These
stipules persisted on the plants for >50 d, even after the
primary leaves had withered or dropped off. The characteristics
of the foliaceous stipules present in the genotype
EC394736 are shown in Table 1 and Figs 2 and 3.
Inheritance
The three F1 plants of the cross EC394763 · EC394736
showed absence of the FS indicating the dominance of RS
FS
T ABLE 1. Characteristics of the connate foliaceous stipules of
primary leaves in cowpea genotype EC394736
Parameter Features in foliaceous stipule
Naissance/organogenesis Along with the development
of cotyledonary leaves
Phyllotaxy Opposite
Orientation Horizontal (right angle with
reference to primary leaves)
Petiolate/sessile Sessile
Persistence Persistent
Colour Dark green
Texture Smooth
Venation Reticulate
Shape Ovate to obovate
Apex Obtuse to truncate
Margin Entire
Base Acute
Size (total laminar area) 253 mm 2 (range 114–384 mm 2 )
F IG. 3. Variation in size and shape of the foliaceous stipules.
over FS. In the F2 population of 131 plants, only 12 plants
showed the presence of FS, while 119 had RS (Table 2). The
segregation into RS- and FS-plants indicated a modified
dihybrid ratio of 15 : 1 with a c 2 value of 1 88 (P =
0 10–0 20), i.e. duplicate recessive genes controlled the
presence of FS.
Of the 131 F2 plants, only 93 plants (seven with FS and 86
with RS) were carried forward in the F3 generation as plant
to row progenies. This constituted 50, 31 and 12 plants of
three respective families. The number of plants in the F3
progenies ranged from 18 to 33. In the 40 segregating progenies,
eight progenies had 18–20 plants, 27 progenies had
21–29 plants and five had 30–33 plants each.
All the plants of the seven FS progenies bred true for the
FS-character, while only 46 of the 86 RS-plant progenies
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T ABLE 2. Segregation for foliaceous stipules of primary
leaves in the F 2 generation of the cross EC394763 · EC394736
Observed segregation
Total no.
c
of plants
2
F2 family RS FS (15 : 1) P
1 76 69 7 1.137 0.20–0.30
2 42 38 4 0.768 0.30–0.50
3 13 12 1 0.046 0.80–0.90
Total 131 119 12 1.88 0.10–0.20
T ABLE 3. Segregation for the presence and absence of the
foliaceous stipules in the F3 plant progenies of the cross
EC394763 · EC394736
No. of
progenies
Pandey and Dhanasekar — Foliaceous Stipules of Primary Leaves in Cowpea 471
No. of plants Ratio
Total RS FS O E c 2
7 144 0 144 Tr. Br.
46 1110 1110 0 Tr. Br.
23 546 515 31 16.6:1 15:1 0.305 0.50–0.70
17 408 315 93 3.39 : 1 3 : 1 1.06 0.30–0.50
O, Observed; E, expected; Tr. Br., true breeding.
FS and RS indicate the plants with foliaceous stipules and rudimentary
stipules, respectively.
bred true for the RS character (Table 3). Of the remaining
40 progenies, 23 segregated into a ratio of 15 RS : 1 FS, and
17 into 3 RS : 1 FS. The segregation of the 86 RS plant
progenies in the F 3 generation fitted in the expected genetic
ratio of 7 (true breeding for RS) : 4 (segregating into 15 RS :
1 FS) : 4 (segregating into 3RS : 1 FS) with the c 2 value of
2 394 (P = 0 30–0 50).
DISCUSSION
The segregation pattern of the foliaceous stipules observed
in the F2 and F3 generations confirmed the involvement of
duplicate recessive genes in their development.
It is proposed that the gene symbols for foliaceous
stipules of primary leaves be fos1 and fos2. The genotype
EC394736 with foliaceous stipules can thus be represented
as fos1fos1fos2fos2. Studies on the inheritance of stipules in general, and
foliaceous stipules of primary leaves in particular, are
very few and reports are scanty. Small stipule size in
American chestnut has been reported to be incompletely
dominant over large stipule size in Chinese chestnut and
is controlled by two genes (Hebard, 1994), implying that the
large stipule size is a recessive character. This conforms
with the present authors’ findings that recessive genes
control the large size of the foliaceous stipules. In jute
also, the foliaceous stipule character has been reported to
P
be recessive though inherited monogenically (Paria and
Basak, 1994).
The stipules have been recognized as an important morphological
character for identification of species or varieties.
Mouli and Kale (1982) reported foliaceous stipules
to be a good identifying marker for the early maturing
groundnut TGE-1. The presence or absence of foliar stipules
was used to describe various tribes of the family Genisteae
(Josefa et al., 1998). Information on stipule development
is useful to the taxonomists (Stein, 1982).
The foliaceous stipules of the primary leaves in the cowpea
genotype EC394736 will be used as a morphological
marker in the breeding programme of the NA&BTD,
BARC. The phenotypic behaviour of the stipule in the F1
could be very useful in detecting successful crosses involving
the genotype EC394736 as a female parent. As this
genotype is endowed with the presence of foliaceous stipules
of primary leaves, a cross between this parent and
those with rudimentary stipules as male can be taken as
successful if the F1 shows the absence of foliaceous stipules,
a recessive character. The FS character can also be transferred
to any variety for identification. It could be used
during seed multiplication of cowpea varieties to check
for any inadvertent, undesirable out-crossing to other cowpea
genotypes that would reduce the purity of the seed.
LITERATURE CITED
Fery RL. 1985. The genetics of cowpeas: a review of the world literature. In:
Singh SR, Rachie KO, eds. Cowpea research, production and utilization.
Chichester, UK: John Wiley and Sons, 25–62.
Fery RL, SinghBB. 1997. Cowpea genetics:a review of the recent literature.
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in cowpea research. Ibadan, Nigeria: IITA. Co-publication of
International Institute of Tropical Agriculture (IITA) and Japan
International Research Center for Agricultural Sciences (JIRCAS),
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Hebard FV. 1994. Inheritance of juvenile leaf and stem morphological traits
in crosses of Chinese and American chestnut. Journal of Heredity
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in Genisteae (Fabaceae) from south-west Spain. Botanical Journal of
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hypogaea) with foliaceous stipule marker. Current Science 51:
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Padulosi S, Ng NQ. 1997. Origin, taxonomy, and morphology of Vigna
unguiculata (L.) Walp. In: Singh BB, Mohan Raj DR, Dashiell KE,
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Paria P, Basak SL. 1994. Inheritance of some induced mutant characters in
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Breeding 54: 347–350.
Quin FM. 1997. Introduction. In: Singh BB, Mohan Raj DR, Dashiell KE,
Jackai LEN, eds. Advances in cowpea research. IITA, Ibadan, Nigeria:
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Stein OL. 1982. Stipule arrangement in the genus Caesalpinia (Leguminosae).
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