Abstract
Eleven desynaptic mutants of O. sativa L. were cytogenetically investigated. Mutants were induced by the treatment of fertilized egg cells with N-methyl-N-nitrosourea. Normal chromosome pairing occurred at pachytene in all mutants. Various numbers of univalents appeared at diakinesis and metaphase I in the mutants. The reduction of the mean chiasma frequency per bivalent as well as per cell were recognized in all mutants. The lower the mean chiasma frequency, the lower the mean bivalent frequency. Each of the desynaptic mutants is governed by a single recessive gene; at least 10 loci are represented.