Section 6
Chapter 5,083

Cyto genetic studies of oryza officinalis complex part 6 karyotype chromosome pairing in a ha ploid oryza minuta and its possible role in auto tetra ploid speciation

H.C H.

Botanical Bulletin of Academia Sinica (Taipei) 20(1): 39-49


Accession: 005082006

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A shrunken seed obtained from a cross of Q. minuta .times. O. eichingeri was germinated in White's medium and found to be haploid (2n = 24). The plant morphology was similar to O. minuta except for smaller size. Length of chromosomes in root tip cells varied from 2.6 .mu.-1.1.mu. Eight pairs had median and 1 pair submedian or subterminal constrictions. The other 3 pairs were heteromorphic with either median, submedian or subterminal constrictions. There were 4 satellite chromosomes, and 2 with secondary constrictions. In meiosis, one completely paired pachytene cell was detected among many incomplete or disordered pachytene cells. The mean pairing of bivalents found in meta-anaphase I was 1.09. A gene which suppressed pairing between 2 sub-genomes apparently arose at the time of spontaneous doubling of chromosomes in the diploid O. officinalis strain of the Philippines. This doubled form later differentiated into the tetraploid species O. minuta. Cytogenetic evidence from recent studies supports this conclusion.

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