Triploid Races Research Articles

Cytological studies in Moraceae (III) The triploid races

Cytological studies in Moraceae (III) The triploid races

Additional Taxa in Astrolepis

A biosystematic study of the star-scaled cloak ferns (Benham, 1989), led to the description of the new genus Astrolepis Benham & Windham (Benham & Windham, 1992) and elucidated several new taxa. Because of the preparation of several new floristic treatments, it is necessary to describe these new taxa within Astrolepis. Based upon isozyme patterns from starch gel electrophoresis and chromosome pairing relationships (Benham, 1989), one new species was discovered and is described below. Additional results from the study also reveal that two races of A. sinuata exist at diploid and triploid levels, and three races of A. cochisensis exist at diploid, triploid and tetraploid levels. These races can be easily distinguished from one another on the basis of spore number per sporangium and spore size. These races will be recognized at the subspecific level in the following taxonomic revision. 1. Astrolepis sinuata (Lagasca ex Sw.) Benham & Windham la. Astrolepis sinuata subsp. sinuata This subspecies represents the apogamous 32-spored, triploid race (n = 87). Spore diameters for this subspecies range from 50-65 gim. It is widely distributed from South America through Mexico into the southwestern United States, Georgia, and the West Indies.

Sporobolus virginicus (L.) Kunth in Coastal Australia: the Reproductive Behaviour and the Distribution of Morphological Types and Chromosome Races

Sporobolus virginicus (L.) Kunth is essentially a littoral grass distributed over much of the coastline of Australia. It occupies a number of different habitats, and exists as morphologically distinct variants and chromosomally distinct races. Four morphological forms are here recognised (designated types 1-4) that do not conform to currently defined subspecific taxa. Cytological investigation of somatic cells has determined six different chromosome numbers: 2n = 20, 30, 3 1, 40, 50 and 60. The counts of 2n = 31, 50 and 60 are the first records of these numbers for the species. Races, defined by morphological type and chromosome number, were found to be discretely distrib- uted, with diploid populations (2n = 20) occurring only in the southern regions and polyploid popu- lations predominantly (but not solely) in the northern half of the continent. This pattern is presumed to reflect a high level of local evolution, with substantial physiological adaptation to climatic and ecological conditions. Whilst all races were found to reproduce asexually, by way of stolons and rhizomes, instances of sexual reproduction were recorded only from the diploid and tetraploid cytotypes. Possible subsexual reproduction by way of agamospermy was observed in the triploid race and also in one diploid plant and inflorescence proliferation was found to be a feature of one pentaploid clone.

Karyological Races and Ecology of the Brazilian Duguetia furfuracea as Compared With Xylopia aromatica (Annonaceae)

Summary D. fufurcaea , a highly adapted pyrophyte of the Central Brazilian savanna vegetation contains three karyological races (2n = 16, 24, 32) which are to some extent geographically and ecologically differentiated. The forest species D. cf. lanceolata and D. cf. salicifolia have chromosome numbers of 2n = 16. The triploid race of D. furfuracea is probably apomictic. X. aromatica (South Brazil to Cuba) has 2n = 16, identical chromosome numbers occur in X. emarginata (Central Brazil), X. ferruginea (Asia) and African members of the genus. A comparison between X. aromatica and D. furfuracea in regard to chromosomes, ecology, distribution areas, growth forms and systematics leads to the conclusion that the two Annonaceous species exhibit dissimilar differentiation patterns (disruptive in the D. furfuracea complex, more clinal in X. aromatica and allied taxa).

A new triploid race ofPennisetum orientale Rich exhibiting chromosomal numerical mosaicism and neo-centric activity

An allotriploid ofP. orientale Rich with 2n=27 chromosomes was located. Cytomorphological studies revealed that it is a new chromosomal race exhibiting chromosomal numerical mosaicism and neo-centric activity. Heterochromatic knobs present on the chromosomes are considered as sites of neo-centromeres. The possible causes of chromosomal mosaicism and neo-centric activity are discussed. Polyploidy coupled with hybridization seems to play a major role in the evolution of this taxon and the aberrant meiotic behaviour is not a barrier for the survival of the species since it is an apomict.

Studies on the cytotypes ofAtrichum undulatum(Hedw.) P. Beauv. II. Chromosome length and relative DNA content

Abstract Evidence is presented showing that the chromosomes of diploid and triploid races of Atrichum undulatum are significantly shorter than those of haploid plants. Relative DNA contents of the three cytotypes have been estimated and they differ significantly from an expected 1:2:3 ratio in haploid, diploid and triploid races.

Cytogenetics of ticks (Acari: Ixodoidea). 12. Chromosome and hybridization studies of bisexual and parthenogenetic Haemaphysalis longicornis races from Japan and Korea.

Haemaphysalis longicornis consists of diploid bisexual races (20+ XX♀; 20+X♂), triploid obligatory parthenogenetic races (30–35 chromosomes) and an aneuploid race capable of bisexual and parthenogenetic reproduction (22–28 chromosomes). Karyotypes were analyzed for each race. Hybridization failed between diploid and triploid races, but succeeded between bisexual diploid males and parthenogenetic aneuploid females. F1 and F2 progeny were produced and their chromosomes studied. Crossing of F1 progeny to a bisexual race was successful. Parthenogenetic ability was almost completely lost in F1 and F2 females. Several possible modes of evolution from diploid bisexual individuals to triploid parthenogenetic ones are discussed as is species characterization in taxa with races reproducing bisexually, parthenogenetically and by a combination of both methods.

Cytological studies in some aquatic angiosperms

The paper deals with the cytological investigation of eight taxa,viz., Hydrolea zeylanica Vahl (2n=24),Ipomoea aquatica Forsk. (2n=30, 2n=30+1),Ottelia alismoides Pers. (2n=22 and 33),Monochoria vaginalis Presl ex Kunth (2n=52),Eichhornia crassipes Solms (2n=32),Pistia stratiotes L. (2n=28),Limnophyton obtusifolium Miq. (2n=22) andAmmannia salicifolia Monti (2n=28) which were collected from the suburbs of Mysore. Of these, the chromosome numbers forHydrolea zeylanica andAmmannia salicifolia are newly reported. Karyomorphological studies have been made inHydrolea zeylanica, Ammannia salicifolia, Ipomoea aquatica, Ottelia alismoides, Eichhornia crassipes andLymnophyton obtusifolium. Mitotc studies ofOttelia alismoides reveal the occurrence of both diploid and triploid races. Of these, triploid number of 2n=33 is the first report. An extra small chromosome from somatic nuclei is also the first record inIpomoea aquatica. Further,Ottelia alismoides shows the occurrence of univalents, tetravalents and hexavalents, whileLimnophyton obtusifolium reveals the presence of chromatin bridge, fragment chromosome and micronuclei.

CHROMOSOME SURVEY IN THIRTY-FOUR SPECIES OF BISEXUAL AND PARTHENOGENETIC WEEVILS OF CANADA

Introduction Since the pioneer chromosonle studies of parthenogenetic Curculionidae by Suornalainen (1940), a comparatively large number of cytological papers on the family have been published (Suomalainen, 1915, 1917, -1949, 1951, 1955, 1958; Seiler, 1917; A/Iiltulslta, 1919, 1950, 1951, 1960; AlIanna and Smith, 1959; Smith, 1952, 1953, 1956a, b, 1960; Smith and Taltenouchi, 1962; Taltenouchi, 1953, 1951, 1955, 1957a-c, 1958a, b, 1961, 1963; Sanderson, 1953). Weevil species and races with parthenogenetic reproduction show geographical parthenogenesis connected with polyploidy (Suornalainen, 1910, 1919). So far the chron~osome data on 37 parthenogenetic species from the Austrian and Eastern ,41ps, Central Europe, Finland, Switzerland, Germany, Poland, Australia, and Japan have been accumulated. Of these, 13 are triploid, with a chromosome number of 33 or thereabouts; four are tetraploid, with 41 chromosomes; two are pentaploid, having 55 chromosomes; five have both a diploid bisexual race and a triploid parthenogenetic race; one has a tetraploid parthenogenetic race besides the diploid bisexual race; two have triploid and tetraploid parthenogenetic races; one has triploid and pentaploid parthenogenetic races. In Otiorrhys7chz~s scaber L., triploid and tetraploid parthenogenetic races exist as well as a diploid bisexual race. A diploid parthenogenetic race is found in two species, namely, Polydros~~s 7?;roLLis Stroin. and Listroderes costirostris Schon., each of which also has a triploid race. The diploid chomoson~e number of the former is 22, but according to Sanderson (1956) the latter species has 2n = 30 chromoson~es. The cl~romoson~e number of the triploid race of both species is 3 3, as usual (Suomalainen, 1951; A4iltulslta, 1919; Taltenouchi, 1957a). On the other hand, in the course of a chromosome survey in search of parthenogenetic species, a total of over 130 diploid bisexual species has been studied. This paper deals with the chromoson~es of 31 species of Canadian weevils, including four parthenogenetic species. The results of the investigation are described with some remarks on the chron~osoines of the insects already reported by other cytologists.

STUDIES ON THE BIOTYPES OF CYNODON DACTYLON (L.) PERS.

Summary. Studies on clones of cynodon dactylon (L.) Pers. have revealed the existence of four biotypes of this species. The sole use of morphological characters to classify them was found unsatisfactory and other definite diagnostic characters have been introduced comprising hair group characteristics and leaf and stolon epidermal structures. Cytotogical studies showed that the biotypes differ in their chromosome number; tetraploid and triploid races have been distinguished. Phasic growth investigations have pointed out that thr biotypes have a similar growth behaviour but that the tetraploids are more vigorous plants than the triploids. Studies on the seasonal variation in available carbohydrates in rhizomes and roots have established that the seasonal trend of this reserve substance in these organs is related to rhizome growth. Recherches sur des biotypes de Cynodon dactylon (L.) Pers.