plants are, therefore, a seemingly dormant but effective source o f variation, for heterozygous genotypes are pro duced each time when sexual and apomictic plants hybridize (Bashaw et al. 1970).
Although no reduced embryo sacs (suggesting sexual reproduction) were observed during the current study, chromomosomal and morphological differences were observed in plants representing a specific region. This indicates that a small percentage o f specimens o f C. cil iaris have to be facultative apomicts, for the offspring were not exact replicas o f the maternal plants. It is con cluded that both facultative and obligate apomixis are present in C. ciliaris. This conclusion is based on the presence o f more genetic variation than can be account ed for by mutations alone. There may also be sexual specimens in nature, but they were not found and sam pled during this study.
CONCLUSIONS
Apospory as a mode o f asexual reproduction is com mon fn the Poaceae. It involves the development o f an embryo from an unreduced nucleus, in an embryo sac derived from a somatic cell. Aposporic development in C. ciliaris varies, for this type o f development is initiat ed in various somatic cells simultaneously, and leads to the maturing o f various numbers o f embryo sacs in the ovule.
Em bryological variations regarding em bryo sac developm ent were observed in this species. These aposporous embryo sacs were characterized as unre duced four-nucleated embryo sacs o f the Panicum type. Although the presence o f cytogenetic and morphological variation indicates that this species may be characterized as a facultative apomictic species, all ploidy levels appear to be obligate apomicts. This suggests that the morphological and/or genetic variation originated before obligate apomixis occurred.
ACKNOWLEDGEMENTS
The University o f the Orange Free State and the Foundation for Research and Development are thanked for financial assistance during this study.
REFERENCES
BASHAW, E C. 1962. Apom ixis and sexuality in buffelgrass. Crop Science 2:412^ 415
BASHAW, E.C. 1980. Apomixis and its application in crop improve ment. In W.R. Fehr & H.H. Hadley, Hybridization o f crop plants, ASA Press, Madison, WI, USA.
BASHAW, E.C & HANNA, W.W. 1990. Apomictic reproduction. In G.P. Chapman, Reproductive versatility in the grasses. Cambridge University Press, Cambridge.
BASHAW, E.C. & HOLT, E.C. 1958 Megasporogenesis, embryo-sac development and embryogenesis in dallisgrass, Paspalum dila-tatum Poir. Agronomy Journal 50: 753-756.
BASHAW, E C.. HOVIN, A.W. & HOLT, E.C. 1970. Apomixis, its evo lutionary significance and utilization in plant breeding. Pro ceedings o f the International G rassland Congress 11: 245 -2 4 8 BROWN, W.V. & EMERY, W.H.P. 1958. Apomixis in the Gramineae
Panicoideae. American Journal o f Botany 45: 253-263. CLAUSEN, J. 1954. Partial apomixis as an equilibrium system in evo
lution. C aryologia 6, Suppl : 469-479.
DE LISLE, D.G. 1963. Taxonomy and distribution o f the genus Cenchrus Iowa State Journal o f Science 37: 259-351 EMERY. W.H.P. 1957. A study o f reproduction in Setaria
macro-stachya and its relatives in the Southwestern United States and Northern Mexico Bulletin Torrev Botanical Club 84: 106-121. FISHER, W.D., BASHAW, E.C. & HOLT, E.C. 1954. Evidence for apomixis in Pennisetum ciliare and Cenchrus setigerus. Agro nomy Journal 46: 401-404.
HANNA, W.W. & BASHAW, E.C. 1987. Apomixis: its identification and use in plant breeding. Crop Science 27: 1136-1139.
JOHANSEN, D A 1940. Plant microtechnique McGraw-Hill, New York MOGIE, M. 1992 The evolution o f asexual reproduction in plants.
Chapman & Hall, London
MUNTZING, A 1933 Apomictic and sexual seed formation in Poa Hereditas 26: 115-190.
NOGLER, G.A. 1984. Gametophytic apomixis In B M John. Em bryology o f angiosperm s Springer-Verlag, Berlin
SASS, J.E 1951 Botanical microtechnique Iowa State College Press, Ames
SNYDER, L A. 1957. Apomixis in Paspalum secans American Jour nal o f Botany 44: 318-324.
SNYDER, L.A., HERNANDEZ, A R & WARMKE, H E. 1955 The mechanism o f apomixis in Pennisetum ciliare. Botanical G a zette 116: 209-221.
SPIES, J.J & DU PLESSIS, H 1986 The genus Rubus in South Africa. III. The occurrence o f apomixis and sexuality. South African Journal o f Botany 52: 226-232.
TALIAFERRO, C M & BASHAW, E.C. 1966. Inheritance and control o f obligate apomixis in breeding bufTelgrass, Pennisetum cil-tare. Crop Science 6: 473-476.
VISSER, N.C., SPIES, J.J & VENTER, H.J.T 1998a. Uneven segre gation o f chromosomes: a possible source o f aneuploidy in Cenchrus ciliaris (Poaceae: Paniceae). South African Journal o f Botany 64: 130-136
VISSER, N.C., SPIES, J.J. & VENTER, H.J.T. 1998b Meiotic chro mosome behaviour in Cenchrus ciliaris (Poaceae: Panicoi deae). Bothalia 28: 83-90.
VISSER. N.C., SPIES, J.J & VENTER, H J.T. 1998c. Aneuploidy in Cenchrus ciliaris (Poaceae, Panicoideae, Paniceae): truth or fic tion9 South African Journal o f Botany 64 337-345.
N.C. VISSER*. J J SPIES*t and H.J.T. VENTER*
* Department o f Botany and Genetics, University o f the Orange Free State, PO. Box 339, 9300 Bloemfontein
* t To whom correspondence should be addressed
HYACINTHACEAE
CHROMOSOME STUDIES ON AFRICAN PLANTS 13 LACHENALIA MVTABILIS. L PUSTUIATA AND L UNICOLOR
The genus Lachenalia Jacq.f. ex Murray consists of small bulbous geophytes and shows a great potential for use as pot plants (Niederwieser et al. 1997). Various chrom osom e numbers, and even different basic chromo some num bers, have been reported for this genus (M offett 1936; De Wet 1957; Riley 1962; Mogford 1978; O rnduff & Watters 1978; Nordenstam 1982; Crosby
1986; Hancke & Liebcnberg 1990; Hancke 1991; John son & Brandham 1997; Kleynhans 1997; Hancke & Liebenberg 1998; Kleynhans & Spies 1999).
Bothalia 30,1 (2000)
(Ornduff & Watters 1978; Johnson & Brandham 1997) to 2n = 14 (De Wet 1957; Johnson & Brandham 1997) and 56 (De Wet 1957).
Lachenalia pustulata Jacq. and L. unicolor Jacq. are closely related species, growing in the southwestern Cape. Both species are classified as part of the L. unicol or group (Crosby 1986), and Duncan (1988) suggested that these species might be combined, due to their mor phological similarities. Somatic chromosome numbers of 2n = 16 have been reported for both species by De Wet (1957), Hancke (1991), Johnson & Brandham (1997) and Kleynhans (1997).
The aim of this paper is to determine the chromosome numbers of the three species and to determine whether any correlation exists between chromosome number and geographical distribution.
MATERIALS AND METHODS
Specimens were collected in the field throughout the geographical distribution area of each species and vege tative material of each plant collected was grown sepa rately in the nurseries of ARC Roodeplaat and the Department of Botany and Genetics, University of the Orange Free State. Bloemfontein. Voucher specimens are housed in the Geo Potts Herbarium (BLFU) at the uni versity (Table 2).
Bulbs were grown on Deco gel™ and actively grow ing root tips were cut and placed in water at 4°C for 24 hours. The root tips were fixed in C arnoy’s (1886) fixa tive for 24-36 hours, hydrolysed in IN HC1 at 60°C for 7 minutes and stained with 0.5% leucobasic fuchsin for two hours (Darlington & LaCour 1976). Squashes were made in 1% aceto-orcein (Darlington & LaCour 1976). Slides were permanently mounted in Euparal (Darling ton & LaCour 1976).
RESULTS AND DISCUSSION
Lachenalia mutabilis: this species is morphologically extremely variable. It is naturally distributed throughout Nam aqualand to south of Riviersonderend (Duncan
1988). During this study 35 specimens, representing 16 populations have been studied cytogenetically. The spec imens studied represent the central and northern geo graphical distribution area of this species (Figure 2).
Somatic chromosome numbers of 12 (Figure 3A. B), 14 (Figure 3C-CJ) and 24 (Figure 3H) were observed during this study (Table 2). The numbers based on x = 7 confirm a previous report on this species (De Wet 1957). The numbers based on x = 6 present a new basic chro mosome number for this species. Although collected in the same geographical area as the two specimens studied by O rnduff & Watters (1978), no specimens with x = 5 were observed during this study. Six further specimens from unknown localities with 2n = 10 were studied by Johnson & Brandham (1997).
Different specimens collected in a given locality showed no variation in chromosome number. Specimens
FIGURE 2 — Geographical distribution o f the Lachenalia populations. Lachenalia mutabilis specimens, x = 6. • ; x = 7, ■ L pustu lata. ▲ . L unicolor. ♦
with lower chromosome numbers were mostly collected in the northern and western areas of the geographical dis tribution area of this species (Figure 2). However, an insufficient number of specimens has been studied to test the validity of this observ ation.
Three hypotheses regarding the origin of the different basic chromosome numbers in one species can be postu lated: 1. the original basic chromosome number is 5 and the misidentification of B-chromosomes is responsible for the higher basic numbers described; 2, the original basic chromosome number is 7 and dysploidy leads to the formation of lower basic chromosome numbers; or 3. an aneuploid series occurs.
The presence of B-chromosomes in various Lachena lia species has been reported by Hancke & Liebenberg (1990) and Johnson & Brandham (1997). Initial meiotic studies indicate that the same number of chromosomes is present in the anthers and in the root tips used during this study. The initial meiotic study also indicates normal meiosis with the formation of bivalents only. Therefore, we reject the hypothesis that misinterpretation of B-chro mosomes attributed to the ‘different basic chromosome numbers' observed in this species.
TABLE 2.— Somatic chromosome numbers o f Lachenalia specimens with their voucher numbers and localities. Specimens are listed according to their locality from north to south and from west to east
Voucher 2n Locality
L. m utabilis
Spies 6750 24 NORTHERN CAPE.— 3017 (Hondeklipbaai): near Hondeklipbaai, (-A D ). Spies 6744 12 WESTERN CAPE.— 3118 (Vanrhynsdorp): near Vanrhynsdorp, (-D A ). Spies 6748, 6753 14 WESTERN CAPE.— 3118 (Vanrhynsdorp): near Vanrhynsdorp, (-D A ). Spies 6746 12 NORTHERN CAPE.— 3119 (Calvinia): on top o f Vanrhyns Pass, (-A C ). Spies 6757-6761 14 NORTHERN CAPE.— 3119 (Calvinia): along road to Oorlogskloof, (-A C ). Spies 6774, 6775 12 WESTERN CAPE.— 3218 (Clanwilliam): Clanwilliam Nature Reserve, (-A B ) Spies 6751 12 WESTERN CAPE.— 3218 (Clanwilliam): near Elandsbaai, (-A D ). Spies 6747, 6 7 6 7 -6770, 6773, 6 7 7 6 -6 7 7 8 14 WESTERN CAPE.— 3218 (Clanwilliam): near Clanwilliam, (-B B ). Spies 6 7 79-6781 12 WESTERN CAPE.— 3218 (Clanwilliam): near Sandberg, (-B C ). Spies 6745 14 WESTERN CAPE.— 3219 (Wuppertal): near Citrusdal, (-C A ).
Spies 6784, 6785 14 WESTERN CAPE.— 3318 (Cape Town): Langebaan Nature Reserve, (-A A ). Spies 6752 14 WESTERN CAPE— 3318 (Cape Town): near Porterville, (-B B ).
Spies 6749, 6 7 5 4 -6756. 6782, 6783 14 Unknown. L. pustulata
Spies 6806, 6807 16 NORTHERN CAPE — 3119 (Calvinia): Oorlogskloof, (-A C ). Spies 6792 16 WESTERN CAPE — 3218 (Clanwilliam): Algeria, (-B B ). Spies 6789 16 NORTHERN CAPE — 3220 (Sutherland): near Aurora, (-D C ). Spies 6788 16 WESTERN CAPE.— 3317 (Saldanha): near Saldanha. (-B B ). Spies 6808-6811 16 WESTERN CAPE — 3318 (Cape Town): Langebaan. (-A A ).
Spies 6798-6804, 6 8 1 6 -6 8 2 3 16 WESTERN CAPE.— 3318 (Cape Town): Langebaan Nature Reserve, (-A A ). Spies 6790 16 WESTERN CAPE.— 3318 (Cape Town): near Postberg, (-A A ).
Spies 6791 16 WESTERN CAPE — 3318 (Cape Town): near Darling, (-A D ). Spies 6797 16 WESTERN CAPE — 3318 (Cape Town): Mamre Road, (-B C ). Spies 6787 16 WESTERN CAPE — 3318 (Cape Town): near Kampsbaai, (-C D ). Spies 6786, 6793, 6795, 6796, 6805, 6 8 12-6815 16 Unknown.
Spies 6794 16/32 Unknown.
L. unicolor
Spies 6827 16 WESTERN CAPE — 3118 (Vanrhynsdorp): Vredendal, (-C B ). Spies 6828 16 WESTERN CAPE — 3118 (Vanrhynsdorp): Umonskraal, (-D B ). Spies 6831 16 NORTHERN CAPE — 3119 (Calvinia): Nieuwoudtville, (-A C ). Spies 6 8 5 3 -6 8 5 6 16 WESTERN CAPE — 3217 (Vredenburg): Abdolsbaai, (-D D ). Spies 6829 16 WESTERN CAPE.— 3218 (Clanwilliam): Verlorevlei, (-A D ). Spies 6857 16 WESTERN CAPE.— 3218 (Clanwilliam): near Clanwilliam, (-B B ) Spies 6837, 6838 16 WESTERN CAPE — 3218 (Clanwilliam): Velddnf, (-C C ). Spies 6825 16 WESTERN CAPE — 3218 (Clanwilliam): Piketberg, (-D D ). Spies 6 8 4 4 -6 8 4 6 16 NORTHERN CAPE.— 3220 (Sutherland): Aurora, (-D C ). Spies 6835 16 WESTERN CAPE.— 3318 (Cape Town): Darling, (-A D ) Spies 6833, 6834, 6843 16 WESTERN CAPE — 3318 (Cape Town): Porterville, (-B B ). Spies 6830 16 WESTERN CAPE — 3319 (Worcester): Tulbach, (-A C ). Spies 6824, 6826, 6832, 6836, 6839-6842, 6 8 47-6852 16 Unknown.
sonian translocations) in any specimen or in specimens with a particular basic chromosome number. Therefore, no evidence supports the second hypothesis.
At this stage it seems as if an aneuploid series exists in L mutabilis. To test this hypothesis, thorough meiotic studies, including hybrids between some of these speci mens, should be completed. The use of in situ hybridiza tion techniques will also help to determine the mode of chromosome evolution in this species. Simultaneously, the species delimitation should be investigated to determine whether L. mutabilis represents one variable species or more than one species, each with its own basic chromo some number.
Bothalia 30,1 (2000)
FIGURE 3.— Mitotic chromosomes in some Lachenalia mutabilis specimens. A, Spies 6751, 2n = 12; B, Spies 6744, 2n = 12; C, Spies 6760, 2n = 14; D, Spies 6748, 2n = 14; E, Spies 6757, 2n = 14; F, Spies 6789, 2n = 14; G, Spies 6749, 2n = 14; H, Spies 6750, 2n = 24. Scale bar: 6.5 pm.
Lachenalia pustulata and L. unicolor: during this study somatic chromosome numbers of 38 L. pustulata specimens, representing at least 10 different localities, and 34 L. unicolor specimens, representing at least 12 localities, were determined (Table 2). All specimens were diploid with 2n = 2x = 16 (Figure 4), except one L. pustulata specimen, Spies 6794, which was diploid (19 cells) and a single tetraploid cell was observed. This study confirms published reports on a chromosome num ber for L. pustulata (Johnson & Brandham 1997; Kleynhans 1997) and L. unicolor (De Wet 1957; Hancke 1991; Johnson & Brandham 1997; Kleynhans 1997).
The karyotypes of the two species correspond. Both species have four chromosomes that are significantly
longer than the other chromosomes. The chromosome numbers of the species are the same. In order to deter mine whether Duncan's (1988) suggestion of combining the two species is correct, meiotic chromosome behav iour of crosses between these species and pollen viabili ty of the hybrids should be studied.
ACKNOWLEDGEMENTS
The University of the Orange Free State, the National Research Foundation and the Roodeplaat Vegetable and Ornamental Plant Institute are thanked for financial assis tance during this study. The latter Institute is also thanked for collecting and providing the bulbs used in this study.
REFERENCES
CARNOY, J.B. 1886. La cytodierese de l’oeuf. Cellule 3: 1-92. CROSBY, T.S. 1986. The genus Lachenalia. The Plantsman 8:
129-166.
DARLINGTON, C.D. & LACOUR, L.F. 1976. The handling o f chro mosomes. Allen & Unwin, London
DE WET, J.M.J. 1957. Chromosome numbers in the Scilleae. Cytologia 22: 145-159.
DUNCA N, G.D. 1988. The Lachenalia handbook. National Botanical Gardens, Cape Town.
HANCKE, F.L. 1991. 'n Sitotaksonomiese ondersoek van sewe Lache nalia spesies vir gebruik in n blomteeltprogram. M.Sc. thesis. University o f Pretoria.
HANCKE. F.L. & LIEBENBERG, H. 1990. B-chromosomes in some Lachenalia species and hybrids. South African Journal o f Botany 56: 6 5 9 -6 6 4 .
HANCKE, F.L. & LIEBENBERG, H. 1998. Meiotic studies o f inter specific Lachenalia hybrids and their parents. South African Journal o f Botany 64: 250-255.
JOHNSON, M A T. & BRANDHAM , PE. 1997. New chromosome numbers in petaloid monocotyledons and other miscellaneous angiosperms. Kew Bulletin 52: 121-138.
KLEYNHANS, R. 1997. Genetic variation in Lachenalia bulbifera M.Sc. thesis. University o f the Orange Free State.
KLEYNHANS, R & SPIES, J.J. 1999. Chromosome number and mor phological variation in Lachenalia bulbifera (Hyacinthaceae).
South African Journal o f Botany 65: 357-360.
MOFFETT, A. A. 1936. The cytology o f Lachenalia. Cytologia 7: 4 9 0 -498.
MOGFORD, D.J. 1978. Centromeric heterochromatin in Lachenalia tricolor (L.) Thunb. South African Journal o f Botany 44:
111-117.
NIEDERWIESER, J.G., ANANDAJAYASEKERAM. P., COETZEE. M„ MARTELLA. D„ PIETERSE, B & MARASAS, C. 1997. Socio-economic impact o f the Lachenalia research program. SACCAR, Gaborone.
NORDENSTAM, B 1982. Chromosome numbers o f southern African plants. 2. Journal o f South African Botany 48: 273-275. ORNDUFF, R. & WAITERS, PJ. 1978. Chromosome numbers in
Lachenalia (Liliaceae). Journal o f South African Botany 44: 387-390.
RILEY, H P. 1962. Chromosome studies in some South African mono cotyledons. Canadian Journal o f Genetics and Cytology 4: 4 0 -55.
J.J. SPIES*, J.L. DU PREEZ*, A MINNAAR* and R KLEYNHANS** * Department o f Botany and Genetics (106), University o f the Orange Free State, P.O. Box 339, 9300 Bloemfontein
