CONTENTS INTRODUCTION ... ..... ... .. 54 Cross-Specific Comparisons 55 LOWER EUCARYOTES .... 57 Criteria for Mutant Isolation 57 Fertility 57 Effects on specific meiotic events 58 Mitotic disturbances 58 Yeasts 59 Fertility mutants ........ ... ... 60 Mutants with altered meiotic exchange .. ...... 62 Defective mating-type control of sporulation 63

The genetic control of meiosis.

Publisher Summary This chapter presents the classification of polyploidy The whole subject of polyploidy is too large thus, the chapter confined to those aspects in which the relation between the natural and the artificial polyploidy is of major theoretical and practical importance On the tetraploid level there are autopolyploids, segmental allopolyploids, and true allopolyploids Autopolyploids usually are characterized by the presence of multivalents at meiosis of tetrasomic ratios, and in the examples artificially produced of slower development and reduced fertility They may be descended from the relatively homozygous diploids, or from hybrids between varieties or subspecies of a diploid species The latter are more likely to be successful in nature; therefore, the differences between wild autopolyploids and their nearest diploid relatives may be genetic in nature as well as the result of chromosome doubling per se

Types of polyploids; their classification and significance.

Publisher Summary This chapter discusses chromosome aberrations induced by ionizing radiations. Chromosome aberrations are used as general indices of cellular damage or as cell markers in studying cell-population kinetics in irradiated or tumor tissues. Of primary importance are the mechanisms involved in aberration induction and in the action of modifying agents that alter the overall frequency or relative frequencies of the different aberration types. The types of aberrations that are induced following irradiation or treatment with certain radiomimetic chemicals are classified according to the unit of breakage or exchange that is involved. The types of structural changes that can occur within or between chromosomes and chromatids are of two kinds: the simple deletion and the exchange. The simple deletion appears to be the result of a single break in the chromosome or chromatid and the exchange is a new rearrangement following the joining of breakage ends that result from separate breaks. Comparisons among different types of ionizing radiations and among similar radiation types having different energies for their capacity for producing chromosome aberrations are of considerable fundamental importance in the study of aberration production.

Chromosome Aberrations Induced by Ionizing Radiations

The studies reviewed date from 1925 to 1972 and contain extensive anatomical and cytological information all too often incomplete or vague. The terminology for microsporogenesis used is also often sketchy or inaccurate. An attempt therefore has been made to establish some consistency in microsporogenesis terminology via Fig. 1 and the tables. We have given, in convenient tabular form, CMS taxa, investigators, and the morphological and cytological events reported. By referring to a few keys, the reader can gain further insight into specific CMS taxa and can easily compare studies The work of Laser (1972) is only part of a more extensive investigation of the anatomy, cytology, and histochemistry of N and CMSSorghum bicolor (Laser, unpub.). To date, only a small part is published (Christensen, Horner & Lersten, 1972), but when completed it probably will be the most complete study to date of these aspects of CMS. Hoefert (1969a, 1969b, 1971) has investigated only normal microsporogenesis so far, but her intention also is to make a detailed descriptive comparison of N and CMS development. Such comparative electron microscope studies will be needed to help answer questions raised in the Introduction of this review. Concerning the events within microspores at the beginning of abortion, for example, there is complete ignorance of what organelle shows the first sign of disintegration or whether there is a definite sequence or simply a simultaneous collapse. The answer to this question could yield valuable clues to the direct cause of abortion Looking at the existing published studies and taking into account numerous examples of questionable technique and interpretation, we conclude that abortion has been shown to occur at almost every point in development, and that probably more than one mechanism is involved

Anatomy and cytology of microsporogenesis in cytoplasmic male sterile angiosperms

The first haploid angiosperm, a dwarf form of cotton with half the normal chromosome complement, was discovered in 1920, and in the ninety years since then such plants have been identified in many other species. They can occur either spontaneously or can be induced by modified pollination methods in vivo, or by in vitro culture of immature male or female gametophytes. Haploids represent an immediate, one-stage route to homozygous diploids and thence to F(1) hybrid production. The commercial exploitation of heterosis in such F(1) hybrids leads to the development of hybrid seed companies and subsequently to the GM revolution in agriculture. This review describes the range of techniques available for the isolation or induction of haploids and discusses their value in a range of areas, from fundamental research on mutant isolation and transformation, through to applied aspects of quantitative genetics and plant breeding. It will also focus on how molecular methods have been used recently to explore some of the underlying aspects of this fascinating developmental phenomenon.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-7652.2009.00498.x

Haploids in flowering plants: origins and exploitation.

The phylogenetic relationship of five species of pigs including Guizhou miniature pig, Bama pig, Xisuangbanna inbred pig, Rongchang Pig and Landrance was studied by RAPD analysis. Thirty-nine single polymorphic primers were selected out of 190 primers. The amplified fragments of thirty-nine primers were analysed by the RAPDistance package version 1.04 and the phylogenetic tree was constructed using NJ method. The results indicated as the following: three strains of miniature pigs have close phylogenetic relationship and the phylogenetic relationship between Guizhou miniature pig and Bama miniature pig was much closer. Landrance and Rongchang pig have close phylogenetic relationship too, but their phylogenetic relationship is far from the three strains of miniature pigs.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1936.tb02649.x

Cytological studies on inbred rye

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1945.tb02750.x

Cytogenetic studies in Solanum, sect. Tuberarium.

Notes on a haploid potato hybrid

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1953.tb03404.x

Investigations on some tuberbearing solanum hybrids

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1951.tb02899.x

Robert Lamm

Papers

Cytological studies on inbred rye

Cytogenetic studies in Solanum, sect. Tuberarium.

Notes on a haploid potato hybrid

Investigations on some tuberbearing solanum hybrids

Cytogenetical studies on translocations in pisum