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Analise do fenomeno de segregação preferencial envolvendo uma translocação 9^b em milho (Zea mays l.) (Analysis of the phenomenon of preferential segregation involving a 9^b translocation in maize (Zea mays l.)^*

Dário Ahnert^I; Luiz Sérgio Saraiva^II

^ICEPLAC/DEPEA, Departamento Especial da Amazônia
^IIDepartamento de Biologia Geral, Universidade Federal de Viçosa, 36570 Viçosa, MG, Brasil. Enviar correspondência para L.S.S.

ABSTRACT

A new 9^B translocation in maize in which the entire distal heterochromatin of the accessory B chromosome was transferred to the short arm of chromosome 9 was tested to determine whether the B-heterochromatin behaves like a knob on chromosome 9 with regard to its ability to be preferentially segregated in the presence of abnormal chromosome 10.
Colored (C) seeds from a cross between plants of constitution 9^B (Df Yg₂) C/N9 Yg2 C + K_lp/N_io pollinated by tester yg₂ c gave 4,148 seedlings of which 68.8%; were green (carrying the normal knobless chromosome 9) and 31.2%; were yellow-green (with the 9^B translocated chromosome). This unexpected finding demonstrates the occurrence of preferential segregation for the normal knobless chromosome 9 that was favored over the 9^B chromosome, with the translocation being recovered in only about 31%; of seedlings. The results indicate that the distal B hetero-chromatin and the knobs constitute distinct kinds of heterochromatin and that transposition of the B heterochromatin to an A chromosome does not transform it into a knob-like entity.

Keywords: preferential; segregation; 9^b translocation; maize; Zea mays.

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* Parte da tese apresentada por D.A. à Universidade Federal de Viçosa como uma das exigências para obtenção do título de Magister Scientiae