Timing imbalance in the meiosis of the F1hybridOryza sativa×O. australiensis

The meiosis in theF1hybridOryza saliva×O. australiensiswas studied. Contrary to the observations of Gopalakrishnan (1959), true allosyndetic bivalents were not found at metaphase I. The most frequent associations were non-chiasmatic, end-to-end pseudobivalents. Autosyndetic bivalents were recorded mostly in the complement belonging toO. sativa, which are distinguishable by their smallness and lighter staining. The meiotic cycle exhibits timing imbalance with earlier condensation, and possibly migration, of the univalents belonging toO. australiensis. The data on meiotic pairing in the F1hybrid and the comparative morphology ofO. sativa, O. officinalisandO. australiensisinicate that the last species is the most primitive member, having originated from the pre-Sativa and pre-Officinalis complex.