Meiotic mutations and crop improvement.

Meiosis is a complex multistep process characterized by highly defined events which include chromosome pairing, synaptonemal complex formation, crossing over and recombination, disjunction of homologous chromosomes, and cytokinesis. Together with DNA replication combined with two successive nuclear divisions, meiosis leads to chromosome reduction, accurate chromosome transmission and genetic recombination. The complexity of such events is tightly regulated by several specific genes to ensure each successful meiotic step. The normal pattern of meiosis can be drastically modified by meiotic mutations which may operate at each stage, starting from meiotic commitment and initiation of premeiotic DNA synthesis. These meiotic defects can strongly affect gamete viability and plant fertility. However, some deviations from normal meiosis have been crucial for plant evolution and represent important tools for plant breeding.