F all groups of plants, none can match the cereal grains in importance to O m a n . Their origins in cultivation have been traced back some 9,000 years to the beginnings of agriculture ( HELBAEK 1960). Extensive cytogenetic studies have been undertaken with this group of plants from which their taxonomic and supposed evolutionary relationships may be deduced (BELL 1965; RILEY 1965). Some of the...

A large fraction of the genomes of grasses, members of the family Graminae, is composed of retrotransposons. These elements resemble animal retroviruses in their structure and possess a life cycle similar to theirs that includes transcription, translation, and integration of daughter copies. We have investigated if retrotransposons are generally transcribed in the grasses and other plants, and ...