Studies of Meiosis in Oryza Species, with Special Reference to Secondary Association

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Abstract
Secondary pairing of the chromosomes at meiosis was compared in 7 diploid (n = 12) and 1 allotetraploid (n = 24) species of Oryza. The species investigated were: diploid - O. sativa L., O. sativa f. spontanea Ros., O. glaberrima Steud., O. breviligulata A. Chev. et Roehr., O. officinalis Wall., O. australiensis Dom., O. brachyantha A. Chev. et Roehr., O. subulata Nees; tetraploid - O. ridleyi Hook. All the diploid species showed the same type of maximum secondary association, 2(3) + 3(2). Also, the mean number of secondary associations per cell was the same in all diploids. The pattern of secondary association in the allotetraploid species, O. ridleyi was the same as in the diploids. The evidence suggests there is secondary polyploidy in Oryza, and perhaps a doubling of the genetic materials in the remote ancestry of the genus.