AOBPreview originally published online on July 30, 2004
Annals of Botany 2004 94(3):469-471; doi:10.1093/aob/mch161
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Annals of Botany 94/3, © Annals of Botany Company 2004; all rights reserved
Morphological Features and Inheritance of Foliaceous Stipules of Primary Leaves in Cowpea (Vigna unguiculata)
Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
* For correspondence. E-mail rnpandey{at}apsara.barc.ernet.in
Received: 8 March 2004 Returned for revision: 13 May 2004 Accepted: 26 May 2004 Published electronically: 30 July 2004
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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• 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 F1, F2 and F3 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 F1 plants showed an absence of FS indicating the rudimentary stipules to be dominant over foliaceous stipules. The F2 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 F3 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.
Key words: Cowpea, duplicate recessive genes, foliaceous stipules, inheritance, morphological marker, Vigna unguiculata
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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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 over 15 000 germplasm lines (Quin, 1997
) that help scientists all over the world to identify the desired traits and combine them to suit their needs. With a view to initiating an improvement programme for cowpea through mutational as well as conventional breeding approaches at our Centre, about 130 germplasm accessions were obtained from IITA, Nigeria through the National Bureau of Plant Genetic Resources, New Delhi and used in various field and laboratory studies. During the course of field studies, a unique feature in the genotype EC394736 (Pedigree: IT93K-2045-29)—the presence of a pair of foliaceous stipules (FS) arranged opposite and at about right angle to the primary leaves—was noticed. The plants of several other genotypes in the germplasm collection belonging to the Nuclear Agriculture and Biotechnology Division (NA&BTD), Bhabha Atomic Research Centre (BARC), Mumbai, were examined and no such a feature was found in them, though they had scaly separate or joint rudimentary stipules (RS). A survey 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 unique type of FS of primary leaves. This prompted us to 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. |
MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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The development of the FS and their persistence were examined throughout the growth and developmental stages of plants of the genotype EC394736. To study the stage at which the FS developed, the unexpanded cotyledonary/primary leaves of the seedlings were forced open and examined at 5 d after sowing in Petri dishes. The shape, size, colour, texture and other parameters were examined in the field during the period 15–50 d after sowing. Six stipules from randomly selected plants were excised and studied for their shape and size. The area of the stipules was measured using image analysis software Biovis image plus, Ver. 1.4 (Expert Vision Labs Pvt. Ltd, Mumbai, India).
The inheritance of the foliaceous stipules was studied by making a cross between the genotype EC394763 with RS (Fig. 1) and the genotype EC394736 with FS (Fig. 2) of primary leaves. The presence or the absence of the FS in 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 ratio of 15 : 1.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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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.
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Inheritance
The three F1 plants of the cross EC394763 x EC394736 showed absence of the FS indicating the dominance of RS 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
2 value of 1·88 (P = 0·10–0·20), i.e. duplicate recessive genes controlled the presence of FS.
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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 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 F3 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 2 value of 2·394 (P = 0·30–0·50).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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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 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.
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LITERATURE CITED |
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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, Singh BB. 1997. Cowpea genetics: a review of the recent literature. In: Singh BB, Mohan Raj DR, Dashiell KE, Jackai LEN, eds. Advances in cowpea research. Ibadan, Nigeria: IITA. Co-publication of International Institute of Tropical Agriculture (IITA) and Japan International Research Center for Agricultural Sciences (JIRCAS), 13–29.
Hebard FV. 1994. Inheritance of juvenile leaf and stem morphological traits in crosses of Chinese and American chestnut. Journal of Heredity 85: 440–446.
Josefa L, Antonio DJ, Trinidad R, Ana OO. 1998. Seedling morphology in Genisteae (Fabaceae) from south-west Spain. Botanical Journal of Linnean Society 128: 229–250.[CrossRef]
Mouli C, Kale DM. 1982. An early maturing groundnut (Arachis hypogaea) with foliaceous stipule marker. Current Science 51: 132–134.
Padulosi S, Ng NQ. 1997. Origin, taxonomy, and morphology of Vigna unguiculata (L.) Walp. In: Singh BB, Mohan Raj DR, Dashiell KE, Jackai LEN, eds. Advances in cowpea research. Ibadan, Nigeria: IITA. Co-publication of International Institute of Tropical Agriculture (IITA) and Japan International Research Center for Agricultural Sciences (JIRCAS), 1–12.
Paria P, Basak SL. 1994. Inheritance of some induced mutant characters in jute (Chorchorus olitorius L.). Indian Journal of Genetics and Plant 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: Copublication of International Institute of Tropical Agriculture (IITA) and Japan International Research Center for Agricultural Sciences (JIRCAS), ix–xv.
Stein OL. 1982. Stipule arrangement in the genus Caesalpinia (Leguminosae). Botanical Journal of Linnean Society 84: 289–294.
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