Newly discovered tetraploid Fagopyrum homotropicum in Tibet, China

A cryptic species of Fagopyrum (Polygonaceae), F. homotropicum, is described and illustrated from Mangkang county, Tibet, China. F. homotropicum was firstly discovered in the 90’s, being to be diploid and characterized being a self-pollinating taxon. Detailed information of F. homotropiucm was rarely reported. In this paper, we summarized the morphological and karyological characters of tetraploid form F. homotropiucm (2n=4x=32), it is self-pollinating, and morphology indistinguishable in comparison from the diploid form.

Morphological markers with a triploid set of chromosomes by breeding of apple tree at the polyploid level

The results many years of research in the conditions of the Altai low mountains are given the assessment of hybrid apple populations from heterploid crosses according to the characteristics: resistance to scab, degree of culture, growth strength, stem thickness, leaf thickness, leaf index, morphometry of the graft and stipules, ploidy. The correlation was established by the studied indications with the triploid set of chromosomes of hybrids from heteroploidy’s crosses. It is shown that the cytological assessment of karyotypes selected for a complex of morphological features is required in a significantly smaller volume, and varieties of siberian selection are capable for partial formation of germ sacs with a diploid set of chromosomes. Morphological markers for apple tree selection at the polyploid level were determined by identifying seedlings in the juvenile stage with a triploid set of chromosomes inside a hybrid population. The application of morphological markers makes it possible to identify from 14 to 100% of seedlings with a triploid set of chromosomes in dependence on the original tetraploid form.

Circumnutation in the growth of Chara rhizoids

The chromosome numbers of 24 species of <em>Achillea L. </em>were determined, among them 4 for the first time <em>(A. chamaemelifolia, A. sulphurea, A. teretifolia, A. vermicularis). </em>A tetraploid form of <em>A. lingulata </em>was found for the first time. The occurrence of di- and tetraploid forms <em>of A. crithmifolia </em>and <em>A. setacea </em>is confirmed as are tetraploid forms of <em>A. asiatica </em>and <em>A. sibirica. </em>Attention is drawn to 7 species of <em>Achillea L. </em>occurring in two forms, di- and tetraploid, and the significance of this fact is discussed.

Calendrier des sporogénèses et gamétogénèses femelles chez le diploïde et le tétraploïde induit de Brachiaria ruziziensis (Graminée)

The processes leading to the formation of the gametes are described in two sexual forms of Brachiaria ruziziensis Germain et Evrard: the natural diploid and an induced autotetraploid. This description comes within the framework of an interspecific hybridization program in the genus Brachiaria aiming at the transfer of the genes responsible for apomixis from polyploid apomictic to diploid sexual species. A "reproductive calendar" is established where microsporogenesis and microgametogenesis are used as reference scales for the concomitant events of megasporogenesis and megagametogenesis of the two forms. This calendar will be compared with similar ones which have to be established for B. decumbens Stapf. and B. brizantha (Hochst) Stapf., natural tetraploid apomicts. Differences were noticed between the original diploid and the induced tetraploid form.

Biosystematic studies in the Stylidium crassifolium species complex (Stylidiaceae)

Stylidium elongatum Benth. (n = 13, 26) and Stylidium crassifolium R. Br. (n = 14, 28) have been restored to specific status and a morphologically intermediate species, Stylidium confluens sp. nov. (n = 14), is described. Polyploid entities in the complex have not been given taxonomic ranks although the tetraploid form of elongatum may be considered worthy of subspecific rank, as it is ecologically distinct and contiguously allopatric to its progenitor and to confluens, forming a buffer between these two diploid entities. Tetraploid populations in crassifolium occur within the distributional range of the diploid. All three species carry recessive lethal gene arrays which eliminate the products of self-pollination with great efficiency and result in crosses between close populations yielding seed more effectively than crosses within populations. There is evidence that interpopulational coadaptation may break down with increasing distance between populations. Polyploidy in crassifolium is probably a conservative response in the genetic system of a species where concentrations of lethal genes in small diploid populations became disadvantageous.

Cytogenetics of Hybrids Among Perennial Species of Glycine Subgenus Glycine

A cytogenetic analysis based on F1 hybrids of some of the perennial species of Glycine subgenus Glycine Verdc. shows that G. clandestina and G. canescens are closely related and further, that either one of these diploid species could have provided one genome for the tetraploid form of G. tomentella. On the other hand, it appears that G. falcata and G. tabacina are distinctive species which are not closely related to the other three species. The tetraploid form of G. tomentella is genetically heterogeneous and crosses between certain types yield F1s with low pollen stainability which fail to set seed under conditions of self-fertilization.

CHARACTERIZATION OF MICROSPOROGENESIS IN THE TETRAPLOID FORM WHICH INITIAL FOR APPLE TREE SELECTION

One of the priority directions in apple breeding at VNIISPK is breeding with polyploidy using for the development of triploid apple cultivars with high commercially valuable traits. Tetraploid forms are an intermediate in the creation of apple varieties with a triple set of chromosomes, so the study of the state of the generative sphere is important in assessing them as donors of diploid gametes in breeding with polyploidy using. Data on the study of meiosis in microsporogenesis in tetraploid apple form 34-21-36 [30-47-88 (Liberty×13-6-106 (s.s. Suvorovetz)) (4x) × Krasa Sverdlovska (2x)] obtained in the laboratory of apple breeding, are presented in the article. The disorders at all successive stages of meiosis were observed. At different stages of division there were run-ins and emissions of chromosomes in the cytoplasm of microsporocyte, lags and emissions, presence of micro-nuclei and nuclei in excess of the number. In the metaphase-1, the microspocyte was observed at the same time with two types of disorders in the same cell (run-ins +emissions). At the stage of tetrads, polyads were formed (pentads, hexads, heptads, octads, nanads). The amount of disorder types varied at different stages of microsporogenesis from 1 to 5. Despite the presence of disorders during meiosis, the most part of microsporocytes in the tetraploid apple form had correct pictures of division and in 36.1% of cases the process of microspogenesis ended with the formation of normal tetrads, decaying after maturation into normal microspores containing a diploid set of chromosomes. On the basis of the reduction division it was concluded that tetraploid apple form 34-21-36 (4x) was suitable as a pollinator in intervalent crosses.