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MORENO-PEREZ, Esaú del Carmen; GARCIA-VELAZQUEZ, Armando  e  AVENDANO-ARRAZATE, Carlos Hugo. CYTOLOGICAL STUDY IN DIPLOID AND POLIPOID POPULATIONS OF THE Tripsacum GENUS. INCI [online]. 2009, vol.34, n.11, pp. 791-795. ISSN 0378-1844.

The Tripsacum (Poaceae) genus has phylogenetic affinity with maize and is widely distributed in America. The basic number of chromosomes is x=18, and there are natural populations ranging from diploids (2n=2x=36) to hexaploids (2n=6x=108). The plants of this genus reproduce sexually and asexually and, in polyploids, apomixis occurs. A cytological study was conducted in plants with different ploidy level. Analysis of meiosis was made in tassels, and seedlings were obtained whose chromosomal number was determined in root tips and by DNA quantification using flow cytometry. Populations made up only of triploids or tetraploids were found, and others containing a mixture from diploids to hexaploids. During diakinesis, diploid chromosomes associate in bivalents; in triploids, univalents, bivalents, and trivalents are formed; and in tetraploids, univalents, bivalents, trivalents, and quadrivalents are formed. In prophase II, the diploids form with high frequencies segregating chromosomal groups of 18; the triploids, groups from 21 to 33; and tetraploids, from 32 to 38. The chromosomal number in progenies of diploid plants was 2x=36 and 3x=54; of triploids 3x=54, 4x=72, 5x=90, and 6x=108; and from tetraploids, 4x=72, 5x=90, and 6x=108. Results indicate that the diploid individuals have sexual origin and the triploids and tetraploids may be apomictic.

Palavras-chave : Apomixis ; Citología ; Gametogénesis ; Ploidía ; Polen ; Tripsacum .

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