What is new on plant cytogenetics?

Abstract

Plant chromosomes have traditionally been a fruitful material for almost every kind of cytogenetic research. However, in the last two decades, with the development of cytomolecular techniques, mainly FISH (Fluorescent In Situ Hybridization) and its numerous variants, plant cytogenetics research has greatly advanced, revealing unexpected details of chromosome behavior and evolution. The book, Plant Cytogenetics, edited by the Spanish cytogeneticists Maria Puertas and Tomas Naranjo and carefully published by Karger as a reprint of Cytogenetic and Genome Research, v. 109, number 1-3, offers us a wide variety of themes on this subject. The hardbound volume consists of 51 peer-reviewed articles on 408 glossy pages, 182 figures (81 in colour) and 54 tables. As a single topic issue it constitutes a well-done review of the current research on plant cytogenetics. Two important themes were apparently intentionally not emphasized: B chromosomes and DNA content, both recently thoroughly reviewed (the former in another special volume of this same journal and the latter in a special issue of Biological Journal of the Linnean Society, August/2004, and in Annals of Botany, January/2005). The book is divided in five sections (Cytogenetics and Genomics, Physical Mapping; Nuclear and Chromosome Organization; Cell Division, Mitosis and Meiosis; Chromosome Evolution and Plant Breeding, and Cytogenetics and Plant Breeding), but this division is not always so clear. Although general cytogenetics is well treated, the cytogenetics of cultivated grasses is the subject of most of the articles, with about 20 of them dealing specifically with the tribe Triticeae (wheat, rye, barley, etc) and several others dealing with maize, oat, sugarcane, the Lolium-Festuca complex, rice, etc. Indeed, the cytogenetics of grasses has always been the most advanced area in plant cytogenetics and when combined with FISH and GISH (Genomic In Situ Hybridization) it furnishes a flexible model to study the behavior of individual genomes, individual chromosomes, or chromosomal fragments in natural and artificial hybrids. Since most plants, notoriously the cultivated ones, originated from one or two hybridization events followed by polyploidization, this technique has become the most common way to analyze allopolyploids, and again grasses. Furthermore, the many chapters discuss very well the gene and chromatin introgression of wild species into cultivated ones not only concerning Triticeae but also other genera, such as Solanum and Beta. In several aspects, the cytogenetics of hybrids has also received special attention in this volume, mainly concerning plant breeding. Since hybrid derivatives may contain a variable number of alien chromosomes or chromosome arms, the use of GISH opens the doors to a clear genome distinction where before there was a lot of speculations. It also offers the possibility of analysing “painted chromosomes” through the whole cell cycle, elegantly demonstrated in colourful photographs.