Chromosome structure rearrangements and genome relationship in Maydeae

Abstract

SummaryThis review attempts to lay stress on topics of current importance in addition to providing a comprehensive idea of pure and evolutionary aspects of cytogenetics of Maydeae.The classical concepts have been confirmed by experimentation in areas such as cytogenetics of heterochromatin. New insight has been obtained through analysis of genetic fine structure, regarding wx and other loci. Several gross duplications have been well analyzed within the genome of maize. Banding studies have provided an understanding of the structure of chromosomes at mitotic as well as meiotic stages. Mapping of loci for the specific genetic phenomena, utilizing B‐chromosome, is in progress using appropriate B‐A translocation complements. Monosomic studies have been much facilitated with the discovery of r‐xl deficiency. Ultrastructural patterns have revealed the mode of initiation and progress of synapsis. Studies involving hemizygosity have given a new dimension to cytogenetic mapping. Advanced analytical techniques have been employed to study the activity of several enzyme loci. Controlling element which itself should form a review by itself has not been dealt with in the present review.Recent discovery of diploperennial teosinte and intergenomic mapping studies within the American Maydeae, coupled with earlier studies on crossability relationships and pairing in hybrids, are contrary to the tripartite hypothesis Maize as a possible mutant derivative of teosinte is strongly advocated, A new theory — Cataclysmic sexual transmutation theory — has been advanced to explain the origin of maize ear from teosinte tassel.