Figure 1.

Progress of plant chromosome research over 50 years. A, A timeline showing when significant technologies were first adopted by frontrunners in the plant science community. The arrows underneath each indicate that use of the technologies continues forward to the present. B, The timing of some significant landmarks in research progress. C, Symbolization of the major developments in chromosome research over the 50 years. In the early years studies were focused mainly on metaphase chromosomes because little could be discerned in interphase chromosomes, except heterochromatin. Now, details of interphase chromatin are being described at the subgene level as a result of full analyses of genes and genomes and application of HiC and related technologies. Left hand picture: The 21 wheat meiotic bivalents photographed in the group of cytogeneticists that I joined in 1969 (Bayliss and Riley, 1972). Right hand picture: Model of wheat interphase chromosome organization in which segments are brought together into transcription factories, taken from Concia et al. (2020) (see the “Chromosomes have 3-D order and links to one another in nuclei” section).