First Reported Case of Spontaneous Hermaphrodism in Female Date Palm (Phoenix Dactylifera L.), Cv ‘Alligue’
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The Journal of Horticultural Science and Biotechnology ISSN: 1462-0316 (Print) 2380-4084 (Online) Journal homepage: http://www.tandfonline.com/loi/thsb20 First reported case of spontaneous hermaphrodism in female date palm (Phoenix dactylifera L.), cv ‘Alligue’ Ahmed Othmani, Myriam Collin, Amel Sellemi, Shri Mohan Jain, Noureddine Drira & Frédérique Aberlenc To cite this article: Ahmed Othmani, Myriam Collin, Amel Sellemi, Shri Mohan Jain, Noureddine Drira & Frédérique Aberlenc (2017): First reported case of spontaneous hermaphrodism in female date palm (Phoenix dactylifera L.), cv ‘Alligue’, The Journal of Horticultural Science and Biotechnology To link to this article: http://dx.doi.org/10.1080/14620316.2017.1280379 Published online: 28 Feb 2017. Submit your article to this journal Article views: 6 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=thsb20 Download by: [othmani ahmed] Date: 10 March 2017, At: 01:59 THE JOURNAL OF HORTICULTURAL SCIENCE AND BIOTECHNOLOGY, 2017 http://dx.doi.org/10.1080/14620316.2017.1280379 First reported case of spontaneous hermaphrodism in female date palm (Phoenix dactylifera L.), cv ‘Alligue’ Ahmed Othmania, Myriam Collinb, Amel Sellemia, Shri Mohan Jainc, Noureddine Drirad and Frédérique Aberlencb aLaboratoire de culture in vitro, Centre Régional de Recherches en Agriculture Oasiennes, Degache, Tunisia; bUnité Mixte de Recherche DIADE (diversité, adaptation, développement des plantes), IRD Montpellier, France; cDepartment of Agricultural Sciences, University of Helsinki, Helsinki, Finland; dLaboratoire des Biotechnologies Végétales Appliquées à l’Amélioration des Cultures, Faculté des Sciences de Sfax, Sfax, Tunisia ABSTRACT ARTICLE HISTORY The date palm (Phoenix dactylifera L.) is dioecious with male flowers deficient in functional Accepted 4 January 2017 gynoecium and female flowers deficient in functional androecium borne on separate palms. KEYWORDS The presence of male and female flowers on the same plant, a phenomenon known as Date palm; cv Alligue; monoecy, is unusual in male date palms. flowers; hermaphroditism; This study reports for the first time on hermaphrodite (bisexual) flowers borne by two female inflorescence; date palms, ‘Alligue’, that were found growing in an open field in Degache, southern Tunisia. The parthenocarpy; rachilla observations on these two female palms were compared with hermaphrodite male date palms growing in the same location. Hermaphrodite female date palm inflorescence branches bear female flowers predominantly near their base, in contrast to the hermaphrodite flowers that are found primarily toward their upper part. The position of the hermaphrodite flowers in hermaphrodite male date palms is reversed: inflorescence branches bear male flowers toward the upper part while the hermaphrodite flowers are found at the base. Histological examination of female hermaphrodite flowers revealed that they had three carpels and 1–6 stamens. Hermaphrodite flowers on male plants were usually also composed of three carpels of variable size, and six stamens. Hermaphrodite flowers on both female and male palm trees turn generally into parthenocarpic fruits. The present data support the theory that dioecious plants are derived from a common hermaphrodite ancestor. Floral hermaphroditism in date palm should be investigated in relation to the in planta self- fertilization process to identify sex markers and genes that control sex organ development. Introduction A typical date palm inflorescence consists of numer- ous unbranched rachillae spirally arranged on a single The genus Phoenix or pinnate-leaved palms is comprised flattened rachis. Both male and female flowers are ses- of 17–19 dioecious species (Carpenter & Ream, 1976), sile on the rachilla and enclosed in its early stages in a native to the tropical or subtropical regions of Africa or hard, fibrous envelope known as a spathe that protects southern Asia (Old World), including Phoenix dactyli- the delicate flowers from the intense heat and sunlight fera L. (Munier, 1973).Thelatteristhemosteconomic- during the early stage of flower development ally important palm next to the coconut palm and is the (ChihCheng & Robert, 2007). The spathe splits open mainstay of agriculture in oasis zones where many other as the flowers mature, exposing the entire inflorescence food crops can be grown in combination. Recently, ser- for pollination (Zaid & De Wet, 2002). The spathes are ious efforts have been geared toward understanding of shorter and wider in male compared to female trees. the genetic basis and the sex determination mechanism Generally, the female inflorescence has fewer florets in date palm, with the aim of identifying sex before per rachilla compared to that of the male inflorescence. reproductive age through the employment of molecular Each spikelet carries a large number of tiny flowers, as marker tools (Al-Dous et al., 2011;Cherifetal.,2013; many as 8000–10,000 in female and even more in male Siljak-Yakovlev et al., 1996). These studies indicate that inflorescence (Chandler, 1958). Zaid and De Wet (2002) date palm is one of the rare monocotyledonous dioecious reported that the female flower has a diameter of about species that employs heteromorphic XY sex chromo- 3–4 mm and has rudimentary stamens and three carpels somes of gender inheritance. DeMason and Tisserat closely pressed together, and the ovary is superior (hypo- (1980) were the first to report that, in certain cases, gynous). The three sepals and three petals are united some male date palm trees give rise to apparent bisexual together so that only tips diverge. On opening, the female flowers. flowers show more yellow color while the male ones CONTACT Ahmed Othmani [email protected] Laboratoire de culture in vitro, Centre Régional de Recherches en Agriculture Oasiennes, P.O. Box 2260, Degache, Tunisia © 2017 The Journal of Horticultural Science & Biotechnology Trust 2 A. OTHMANI ET AL. show white-colored dust, produced on shaking. The spathe anthesis and followed in the course of all their pollen sacs usually open within an hour or two after the phenological stages. This study was repeated 3 times bursting of the spathe. Only one ovule per flower is during 3 successive years (2012, 2013, and 2014). fertilized, leading to the development of one carpel which in turn gives a fruit called a date. The other ovules Histological study abort and persist as two brown spots in the calyx of ripe fruits. The male inflorescences are densely packed with For histological analysis, 20 bisexual female flowers were flowers and the rachillae nod at the time of anthesis fixed in fixation buffer (10% paraformaldehyde, 25% −1 (Munier, 1973). glutaraldehyde, 1% caffeine, and 0.1 mol L 21 phos- We are reporting for first time two cases of a phate buffer, and pH 7). Flowers were then dehydrated spontaneous bisexuality in female date palm, cv through a graded ethanol series (30, 50, 70, 80, 90, 95, and Alligue, in Tunisia with the aim to add further infor- 100%) and stored at 4°C. The dehydrated inflorescences mation on this important phenomenon. were transferred to a 50% ethanol:50% butanol solution for 1 h, then to 100% butanol for 2 h, followed by a transfer for 2 days to several months to a 100% butanol Materials and methods solution. For their inclusion, inflorescences were Materials embedded in the resin, Technovit 7100 (Heraeus Kulzer GmbH, Germany) and impregnated with a solution of The vegetal material used in this study consisted of resin and butanol (50%:50%). Then, Hardener II of flowers and fruits at different phenological stages col- Technovit 7100 kit was added to the resin. The blocks ≈ lected from a clone of a ( 45-year-old) female date obtained were stacked with cold-curing resin of ‘ ’ ≈ palm Alligue ,havingthree 30-year-old offshoots Technovit 3040 kit. The resin was allowed to polymerize ‘ ’ (Figure 1); four 25-year-old male date palms ( P7 , for a few hours at room temperature. ‘ ’ ‘ ’ ‘ ’ Abd1 , Abd2 ,and Abd3 );anda27-year-oldbisexual Sections (3.5–4.0 mm thick) were obtained using a ‘ ’ male date palm ( P8 ). The sampled source plants grow in microtome (Microm). Finally, the sections were double- the oasis field of Degache, a region in the southwest of stained with periodic acid (Sigma P-7875) and protein- Tunisia. The bisexual flowers collected from the studied specific Naphthol Blue Black (Sigma N-3005) and then plants were counted in every inflorescence just after observed under a light microscope. Pollen fertility M Two methods were used. First, inflorescences were cov- ered with craft paper before anthesis to avoid cross- pollination. Secondly, stamens of bisexual flowers were transferred to the flowers of another female date palm variety, ‘Deglet nour’, before anthesis. After this transfer, the latter inflorescence was also covered with craft paper. Seed germination Germination of date palm seeds requires soaking them in a solution of sodium hypochlorite (20%) for 24 h followed by transfer to an empty Petri dish containing three sterile filter paper disks imbibed by water and placed in air conditioned culture room at 2 1 28 ± 2°C with 16/8 h photoperiod providing 80 μmol − − m 2 s 1 fluorescent light for 3 weeks. 3 Results Structure of inflorescences produced by the bisexual female tree The inflorescences of offshoots 2 and 3 appeared Figure 1. Photo of a clone of date palm variety ‘Alligue’ similar to those produced by ordinary female trees. composed of a mother plant (M) and offshoot 1 producing The rachillae of these inflorescences are divided into only female flowers, and offshoots 2 and 3 producing both two groups: the first one is dominant and includes female and bisexual flowers. Scale bar 20 cm. completely typical female flowers, and the second one THE JOURNAL OF HORTICULTURAL SCIENCE AND BIOTECHNOLOGY 3 is composed of both typical female flowers and apparent bisexual flowers (Figure 2). b f Structure of flowers produced by the two bisexual female date palms m Macroscopic scale As described, date palm has dimorphic flowers pro- duced by separate male or female palms.