COLCHICINE INDUCED BIVALENT PAIRING OF TETRAPLOID MICROSPOROCYTES INTRITICUM LONGISSIMUMANDT.SPELTOIDES

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Abstract
The low-pairing gene or genes of diploid Triticum longissimum (Schwinf. &Muschl.) Bowden predispose the induced autotetraploid towards bivalent pairing. In this work, bivalentization was phenocopied in intermediate- and low-pairing lines of T. longissimum and in a high-pairing line of T. speltoides (Tausch) Gren. ex Richter, by colchicine treatment during the last premeiotic mitosis. This treatment induced C-mitosis and tetraploid cells which are characterized by almost exclusive bivalent pairing instead of the expected multivalent pairing. Colchicine disrupted the association of homologous chromosomes in the premeiotic metaphase but left the sister chromatids located close to each other. As a result, rather than being all closely associated, the four homologues were arranged in pairs already prior to meiosis. The effect of colchicine in this respect is reminiscent of that of the "diploidizing genes" in many naturally occurring polyploids. This work demonstrates once again the significance which the pattern of premeiotic homologous association has for the manner of meiotic pairing.