Genomic In Situ Hybridization to Understand Hybrid Genomes

Fluorescent in situ hybridization (FISH) has revolutionized our ability to identify the origins of chromosomes in polyploids and examine chromosome and chromosome segment introgression. Amphipolyploidy involving genomes of more than one species coming together in a hybrid, with subsequent doubling of chromosome number, is widespread in plants, and the exploitation of synthetic hybrids is critical to diversifying the genetic basis of crop species. In this talk I will be reviewing our work over the past 20 years on the development and use of total genomic DNA as a probes (genomic in situ hybridization - GISH) to analyse hybrid genomes. We have used the method to identify parental species and alien chromosomes in a variety of plant species groups including Triticeae, Aveneae, Brassicas, Nicotiana and Crocus, with both natural and man-made hybrids and their derivatives. A particular interest of ours is understanding the interaction of the genomes in the hybrid and how chromosomes behave during interphase and meiosis. Lately we have investigated the nature of chromosome pairing in hybrid species to understand the evolution and control of chromosome recombination events. GISH is allowing recombinants to be identified and focuses studies with molecular markers for fine mapping on regions of interest while assessing the value for recombination. Examples of the importance of molecular cytogenetic analysis in wheat-alien lines used to introduce variation for characters not present in wheat, from wild alien relatives, will be given.  We also investigated the progression and failure of meiotic chromosome pairing in the sterile triploid Crocus sativus (saffron crocus), comparing its behaviour with diploid species and garden hybrids. We acknowledge EU-Crocusbank and IAEA/FAO for financial support. For references see: www.molcyt.com.