Problems of low production and sterile pollen in varieties of Vitis vinifera may be tracable to their ancestral relations with dioecious wild grapes.Like V. riparia, the wild summer grape V. aestivalis has dimorphic male and female flowers; but unlike V. riparia it also has dimorphic pollen grains with the pollen from the female flower being significantly smaller.It seems fairly certain that V. aestivalis is truly dioecious

Ambrose, J. D.

Blades, D. C. A.

Kevan, P. G.

Posluszny, U.

English

JKI Open Journal Systems (Julius Kühn-Institut)

Vitis 27, 143-146 (1988) Department of Environmental Biology, Department of Botany, The Arboretum, University of Guelph, Guelph, Ont„ Canada Pollen dimorphism and dioecy in Vitis aestivalis by P. G. KEVAN, D. C. A. BLADES, U. POSLUSZNY and J. D. AMBROSE Dimorphisme du pollen et dioecie chez Vitis aestivalis So mm a i r e : La vigne d'ete, Vitis aestivalis est une plante rare au Canada. Nous avons decouvert que la population sud-ontarienne de cette espece est dimorphique, c'est-a-djre mäle et femelle. Les fleurs des plantes mäles produisent du pollen «tricolporate». Ce pollen est plus gros que le pollen «inaperturate» des plantes femelles. Les fleurs entieres des deux formes sont differentes; chez les mäles, les etamines sont bien developpees et le pistil est sous-developpe, tandis que chez les femelles la situation contraire se produit. Nos conclusions nous portent a croire que cette espece est dioique comme toutes les autres vignes sauvages. Ces resultats sont significatifs en ce qui a trai t a Ja viticulture et aux programmes d'amelioration des vignes. K e y wo r d s : pollen, morphology, flower, sexuality, Vitis, Canada. Introduction Dioecy in grapes is poorly documented and understood. Most commercial varieties of Vitis vinifera L. have hermaphroditic flowers and are thought to be self-pollinating. Vitis 1rinifera ssp. silvestris is functionally dioecious (BRANTJES 1978) as are other wild grapes such as V. riparia, V. cordifolia and V. rotundifolia (see KEVAN et al. 1985). Because commercially grown grapes have their ancestry in various selections and hybridizations of wild grapes, KEVAN et al. (1985) suggested that some of the problems of low production and sterile pollen (e.g. LOMBARDO et al. 1976, 1978; AHMEDULLAH 1983; ME et al. 1984) may be related to the expression of dioecy, which is known to occur occasionally (MEEHAN 1867 a, b). The genetic mechanisms in the expression of sexual polymorphism in grapes are complex and not weil understood (see ANTCLIFF 1980). We believe that a better understanding of sexual expression in wild grapes will assist in understanding the outcomes of breeding programs, hybridizations, and the reasons for some instances of low productivity. Vitis aestivalis, the summer grape, is a rare plant in Canada (ARGUS and WHITE 1977), occurring only in a few locations in southern Ontario. Unlike V. riparia which grows on forest margins, fence rows, and even sandy lake shores, V. aestivalis typically grows within forests . The aim of this study was to investigate the sexual expression in V. aestivalis in Ontario and to compare our findings with those of KEVAN et al. (1985) on V. riparia. Materials and methods Our study site was at Fireman's Park, Niagara-on-the-Lake, Ontario (43° 8' N, 79° 7' W). The plants were !arge, each with numerous, stout vines up to 8 cm in diame-ter, and mostly extending into the forest canopy some 15---20 m overhead. In a few places, where trees had fallen, the vines' foliage and flowers were accessible from the ground. 144 P. G. KEVAN, D. c. A. BLADES, U. POSLUSZNY and J. D. AMBROSE In June and July 1987, we visited Fireman's Park to inspect the vines for flowers. A population survey and a collection of flowers was dorre during peak flowering on 19 June, 1987. Flowers of each sex were preserved in FAA (10 % formalin: glacial acetic acid : 95 % ethanol 1 : 1 : 9) and taken to the laboratory for examination. Some flowers were prepared by critical point drying and sputter coating with gold-palladium for scanning electron microscopy by Hitachi S-570. Pollen from each kind of flowers was placed on microscope slides and wet mounted under a cover slip for examination by light microscopy. Results Two kinds of flowers were found on separate individuals of V aestivalis. One flower type had weil developed stamens with a small ovary (Fig. 1), and the other poorly developed stamens and a !arge ovary with prominent stigma (Fig. 2). This dimorphism is identical to that found in V. riparia so the forms were designated male and female respectively. The tangles of vines and the inaccessibility of the flowers in the canopy made it impossible to determine sex ratio of the population. However, we were confident that we found six different male plants and one female plant. Further evidence of sexual dimorphism in V aestivalis came from examination of pollen from the two flower types collected. We found the same clear differences as were found in V riparia (KEVAN et al. 1985); the pollen of male flowers was spherical and tri-colporate (mean diameter = 26.3 µm, 95 % confidence interval ± 0.5, N = 100; Fig. 3), whereas pollen from female flowers was spherical, but completely inaperturate (mean diameter = 23.7 µm ± 0.4, N = 100; Fig. 4). The sizes of the pollen grains from the two sexes are highly significantly different (t = 7.65, P < 0.001). Revisiting Fireman's Park on August 19, 1987, we were unable to find any fruit on the plants we had seen before. Because the males would not be expected to set fruit, and the single female had had only a few inflorescences within sight, we are unable to offer the corroborating evi-dence of dioecy. Discussion Although we have not undertaken definitive experiments, like those used for V riparia (KEVAN et al. 1985) to prove dioecy in V aestivalis, we find the dimorphism of structural characteristics of the flowers and of the pollen grains similar to those of V. riparia and indicate the same breeding system. The sex ratio of the dioecious plants Fig. 1-4: Photographies prises a l'aide d'un microscope electronique a balayage. L'echelle des bar-res dans les Fig. 1 et 2 est de 1 mm. Celle des barres dans les Fig. 3 et 4 est de 6 µm . Fig. 1: Vue superieure oblique d'une fleur mäle demontrant un gynecee avorte (G) et des etamines (S) aux filaments droits. Une etamine a ete enlevee (rS) pour mieux montrer Je gynecee. Fig. 2: Vue superieure oblique d 'une fleur femelle demontrant un gynecee completement developpe (G) et des etamines (S) aux filaments recurves. Fig. 3: Vue superieure d'un grain de pollen «tricolporate» provenant de l'etamine d'une fleur mäle. Fig. 4: Un grain de pollen «inaperturate» provenant de l'etamine d'une fleur femelle. Pollen dimorphism and dioecy 145 is usually skewed in favour of males (OPLER and BAWA 1978) as is the case of V. riparia (KEVAN et al. 1985) and is suggested by our minimal data on V. aestivalis. The difference in the sizes of the pollen grains in V. aestivalis is unlike the situation in V. riparia with pollen grains of each sex being the same size (KEVAN et al. 1985). Perhaps the small, but noteworthy difference in pollen dimorphism between V. riparia and V. aestivalis signi-fies a greater development of dioecy ih the latter. Certainly, we conclude that V. aesti-valis, like V. riparia, is truly dioecious. Figs. 1-4: Scanning electron micrographs. The scale bars in Figs. 1 and 2 equal 1 mm, in Figs. 3 and 4 the bars equal 6 µm. Fig. 1: An oblique top view of a male flower showing the aborted gynoecium (G) and Stamens (S) with upright filaments. One stamen has been removed (rS) in order to show the gynoecium. Fig. 2: An oblique top view of a female flower showing a fully developed gynoecium (G) and stamens (S) with recurved filaments. Fig. 3: A top view of a tricolporate polten grain from the stamen of a male flower. Fig. 4: An inaperturate polten grain from the stamen of a female flower. 146 P . G. KEVAN, D. c. A. BLADES, U. POSLUSZNY and J. D. AMBROSE Summary 1. Problems of low production and sterile pollen in varieties of Vitis vinifera may be tracable to their ancestral relations with dioecious wild grapes. 2. Like V. riparia, the wild summer grape V. aestivalis has dimorphic male and fe-male flowers; but unlike V. riparia it also has dimorphic pollen grains with the pol-len from the female flower being significantly smaller. 3. lt seems fairly certain that V. aestivalis is truly dioecious. Acknowledgements This work was supported in part by a Strategie Grant from the Natural Sciences and Engineer-ing Research Council of Canada to UsHER PosLUSZNY and PETER G. KEVAN and from the World Wild-life Fund to JOHN D. A~IBROSE and PETER G. KEVAN. We would like to thank the excellent technical ass istance of PAMELA F. JACOBS and LESLEY S. SMITH in the preparation of the S.E.M . micrographs. As weil, we are grateful to TERRY G. GR!GNON who helped with the statistieal analysis and the prepara-tion of the manuseript and CHRISTIAN R. LACROIX who did the freneh translation. Literature cited AmIEDULLAH, M.; 1983: Pollen morphology of seleeted Vitis cultivars. J. Amer. Soc. Hort. Sei. 108, 155--'-l 60. ANTCLIFF, A. J.; 1980: Inheritanee of sex in Vitis. Ann. Amelior. Plantes 30, 113-122. ARGUS, G. W.; WHITE, D. J.; 1977: The rare vaseular plants of Ontario. Syllogeus (Can. Natl. Mus. Nat. Sei.) 14. BRANTJES, N. B. M.; 1978: Pollinator attraetion to Vitis vinifera ssp. silvestl"is. Vitis 17, 229-233. KEVAN, P. G .; LoNGAIR, R. W.; GADAIVSKY, R. M.; 1985: Dioecy and pollen dimorphism in Vitis riparia (Vitaceae) . Can. J. Bot. 63, 2263-2267. Lo~IBARDO, G.; CARGNELLO, G.; BASSI, M.; CARRARO, L.; 1978: Pollen ultrastrueture in different vine eul-tivars with low productivity. Vitis 17, 221-228 . - - ; CARRARO, L.; CARGNELLO, G.; BASSI, M.; 1976: Ultrastructure of pollen of Vitis vinifera L. ev. 'Picolit giallo' and its behaviour in experiments of seif- and eross-pollination. Vitis 15, 73-81. ME, G.; SACERDOTE, S.; VALLANIA, R.; 1984: Osservazioni sulla meiosi in cellule madri de! polline di Vitis vinifera L. (ev. Barbera) diploide e tetraploide. Vitis 23, 195-201. MEEHAN, T.; 1867 a: Note on dioecious forms of Viti s vinifera L. Proc. Aead. Nat. Sei. Philadelphia 1867 (April), 42. - - ; 1867 b: Additional note on dioecious forms of Vitis vinifera L. Proc. Aead. Nat. Sei. Philadel-phia 1867 (April), 98-99. ÜPLER, P. A.; BAwA, K. S.; 1978: Sex ratios in tropieal forest trees. Evolution (Lawrenee, Kansas) 32, 812-821. Eingegangen am 28. 4. 1988 Note added in proof: Dr. P. G. KEVAN Department of Environmental Biology University of Guelph Guelph, Ontario NlG 2Wl Canada In 1988, we found a small population of V. aestivalis in La Salle, Ontario. The .plants were clearly male or femaie with flowers eorresponding to those deseribed from plants at Fireman's Park. 

Pollen dimorphism and dioecy in Vitis aestivalis

https://ojs.openagrar.de/index.php/VITIS/article/download/5891/5620

Pollen dimorphism and dioecy in Vitis aestivalis

Abstract

Similar works

Full text

Available Versions

JKI Open Journal Systems (Julius Kühn-Institut)