Wheat Chromosomal Resources and Their Role in Wheat Research

Abstract

AbstractBread wheat (Triticum aestivum L.) is grown on more area of land than any other crop, and its global significance is challenged only by rice. Despite the socioeconomic importance, the wheat genome research was lagging behind other crops for a long time. It was mainly a high complexity of the genome, polyploidy and a high content of repetitive elements that were laying obstacles to a thorough genome analysis, gene cloning and genome sequencing. Solution to these problems came in the beginning of the new millennium with the emergence of chromosome genomics—a new approach to studying complex genomes after dissecting them into smaller parts—single chromosomes or their arms. This lossless complexity reduction, enabled by flow-cytometric chromosome sorting, reduced the time and cost of the experiment and simplified downstream analyses. Since the approach overcomes difficulties due to sequence redundancy and the presence of homoeologous subgenomes, the chromosomal genomics was adopted by the International Wheat Genome Sequencing Consortium (IWGSC) as the major strategy to sequence bread wheat genome. The dissection of the wheat genome into single chromosomes enabled the generation of chromosome survey sequences and stimulated international collaboration on producing a reference-quality assembly by the clone-by-clone approach. In parallel, the chromosomal resources were used for marker development, targeted mapping and gene cloning. The most comprehensive approaches to gene cloning, such as MutChromSeq and assembly via long-range linkage, found their use even in the post-sequencing era. The chapter provides a two-decade retrospective of chromosome genomics applied in bread wheat and its relatives and reports on the chromosomal resources generated and their applications.