Cytogenetical studies on the genus Oryza. XIV. Intergeneric hybridizations between tetraploid Oryza species and diploid Leersia species.

Intergeneric hybrids involving Oryza punctata (2n = 48, BBCC) with Leersia tisseranti (2n = 24), O. punctata with L. perrieri (2n = 24), O. latifolia (2n = 48, CCDD) with L. tisseranti and O. latifolia with L. perrieri were produced at frequencies varying from 0.11% to 0.23% of the pollinated spikelets. Plant morphologies of the hybrids strongly resembled the tetraploid Oryza species. Five hybrids obtained from the four cross-combinations had the expected chromosome number of 2n = 36 (trihaploid) in the somatic cells. The average meiotic chromosome pairings per cell were 0.23II + 35.58I + 0.14(1)/2I (dividing univalent) for O. punctata x L. tisseranti; 0.11II + 35.51I + 0.22(1)/2I for O. punctata x L. perrieri; 0.17II + 35.63I + 0.11(1)/2I for O. latifolia x L. tisseranti; and 0.25II + 35.49I + 0.15(1)/2I for O. latifolia x L. perrieri. From these results, it seems that most of the bivalents observed at MI with a low frequency had originated from the autosyndetic association of the chromosomes of O. punctata or O. latifolia. The results described above suggest that there is no genomic relationship between the parental species in each cross combination.