Chromosome numbers in African and Madagascan Loranthaceae and Viscaceae

Wiens, Delbert

doi:10.1111/j.1095-8339.1975.tb01206.x

Cited by 22 publications

(22 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The unusual translocation heterozygosity in this species was previously described and illustrated by Wiens andBarlow (1973, 1975). Male plants were found to have a somatic chromosome number of 2n = 23, and at first meiotic metaphase the chromosomes consistently associated as seven bivalents and an open multivalent chain of nine chromosomes.…”

Section: Introductionsupporting

confidence: 66%

“…In other species of Viscum studied karyologically, there are no indications of identifiable sex chromosomes (Wiens and Barlow, 1971;Wiens, 1976). Sex is probably determined in a genetically simple fashion, as mentioned earlier.…”

Section: Discussionmentioning

confidence: 64%

“…(vii) Uniqueness of the V. fischeri system Translocation heterozygosity is of widespread occurrence in dioecious African Visca Barlow and Wiens, 1975;Wiens, 1976 and unpublished data), but none is known in monoecious species.…”

Section: Discussionmentioning

confidence: 98%

“…Data for many species are severely limited, but of the 21 dioecious African Visca for which chromosome numbers are now known (Wiens, 1976), 11, or 57 per cent, exhibit translocation heterozygosity. Of the remaining 10, five appeared to have no translocations and for the remaining five insufficient material was available to determine meiotic pairing relationships.…”

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Translocation heterozygosity and sex ratio in Viscum fischeri

Barlow

Wiens

1976

Heredity

View full text Add to dashboard Cite

SUMMARYMale plants of V. fischeri have 2n = 23 and constantly produce seven bivalents and a multivalent chain of nine chromosomes at meiosis. Regular assortment results in transmission of 11-and 12-chromosome genomes via the pollen. Female plants have the chromosome number 2n = 22 and are homozygous for the 11-chromosome genome. The multivalent chain in the males is a consequence of reciprocal translocations, one of which was Robertsonian and one of which involved the chromosome carrying the sex determination factors. There is a constant female-predominant sex ratio of approximately 1:2 in V. fischeri, possibly maintained by gamete selection; the genes involved may have been linked with the sex determination mechanism through the translocation system.

show abstract

Section: Introductionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Translocation heterozygosity and sex ratio in Viscum fischeri

Barlow

Wiens

1976

Heredity

View full text Add to dashboard Cite

show abstract

“…The most common chromosome number among the African species is x = 14, and this appears to be the basic number for the genus (Wiens, 1975).…”

Section: Introductionmentioning

confidence: 99%

Translocation heterozygosity and the origin of dioecy in Viscum

Wiens

Barlow

1979

Heredity

View full text Add to dashboard Cite

SUMMARYSex-associated and floating translocation complexes are characteristic of dioecious species of Viscum, but are virtually absent in monoecious species. In most of the dioecious species, fixed sex-associated translocation complexes are present, with the male being the heterozygous sex. The sex-associated multivalent is usually 04 (ring-of-four) or 06, rarely 08. In only a few of the dioecious species are sex-associated translocations not apparent. Most of the dioecious species are also polymorphic for floating translocations, producing one or more additional multivalents ranging from 04 to 012. Floacing translocations may be more frequent in species which do not have sex-associated translocations. Supernumerary chromosomes are also present in several species. Sex ratios are at unity in most dioecious species, but female-biased ratios as low as 052 and male-biased ratios as high as 140 may occur in some species. The high correlation between dioecy and translocation heterozygosity suggests that translocations are primarily associated with the origin and establishment of dioecy, and any role they play in the maintenance of biased sex ratios through meiotic drive is probably secondary. A model is presented in which male-and female-determining factors are non-alIelic, and sex-associated translocations serve to stabilise dioecy by bringing the sex factors into linkage.Subsequent structural rearrangements within a sex-associated translocation complex may bring the sex factors together in one chromosome pair, releasing floating translocations. The high frequencies of floating translocation heterozygosity in some species indicate that such heterozygosity has adaptive value.

show abstract

Fine Structure of Mistletoe Pollen. Iv. Eurasian and Australian Viscum L. (Viscaceae)

Feuer

Kuijt

1982

American J of Botany

View full text Add to dashboard Cite

Fifteen Eurasian and Australian species of Viscum L. were examined by light, scanning, and transmission electron microscopy. Pollen characters divide the species into two groups, each correlated with differences in habit and inflorescence structure: Group I (12 spp.) characterized by psilate or slightly sculptured exines and a non‐uniform ektexine pattern and Group II (3 spp.) possessing highly sculptured (echinate, rodlet) surfaces and uniform ektexine patterns. Within each of the groups, pollen characters divide the species into several subgroups. Among Group I, species V. nepalense, V. heyneanum and V. ovalifolium are particularly close. The Group I species, V. trilobatum, is placed in its own subgroup primarily because of its uniform ektexine pattern—a unique feature among Asian and Australian Viscum. Of the three Group II species, V. album and V. alniformosanae are palynologically almost indistinguishable. Pollen of the Group II V. cruciatum, though exomorphologically similar to V. album, is closest ultrastructurally to the Indian V. trilobatum. Overall, the most common and probably basic pollen characters among the Eurasian and Australian species include: subprolate, rounded convex almost spherical shapes; tricolporate apertures, and non‐uniform sculpturing and ektexine patterns. Oblate‐spheroidal or prolate‐spheroidal shapes, prominent sculpturing, and a uniform ektexine pattern are derived characters largely restricted to the Eurasian and Asian Group II species (V. album, V. alniformosanae, V. cruciatum).

show abstract

Chromosome numbers in African and Madagascan Loranthaceae and Viscaceae

Cited by 22 publications

References 12 publications

Translocation heterozygosity and sex ratio in Viscum fischeri

Translocation heterozygosity and sex ratio in Viscum fischeri

Translocation heterozygosity and the origin of dioecy in Viscum

Fine Structure of Mistletoe Pollen. Iv. Eurasian and Australian Viscum L. (Viscaceae)

Contact Info

Product

Resources

About