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Number of surviving initial cells and lack of haplontic selection in gamma ray-induced chimerism in the common bean, Phaseolus vulgaris L.

élio M. Barbosa^I; Cláudio Coelho de Paula^II

^IDepartamento de Biologia Geral, Universidade Federal de Viçosa (UFV), 36571-000 Viçosa, MG, Brasil. Send correspondence to H.M.B.
^IIDepartamento de Biologia Vegetal, UFV, 36571-000 Viçosa, MG, Brasil

ABSTRACT

Seeds of Phaseolus oulgaris L., cv. Milionário 1732, were obtained by planting seeds harvested from a single plant. They were treated with 20 krad from a ⁶⁰Co source and planted in the field. Seeds were harvested from each sector (branch or main stem) and grown as single sector M₂ progeny from each of 500 M₁ plants. The M₃ generation was grown from 11 segregating M₂ progenies. Segregation ratios for chlorophyll and seedcoat color mutants were scored in M₂ and M₃. The objectives were a) to obtain additional information on the number of surviving initial cells from which a plant or sector is derived, and b) to determine whether or not the gametes carrying induced mutations are subject to haplontic selection. M₁ plants of Milionário 1732 grown from seeds treated with 20 krad of gamma rays originated from about five to nine cells. Each M₁ sector was derived from three cells. There was no evidence of haplontic selection.

Keywords: haplontic selection; gamma ray-induced; chimerism; bean; Phaseolus vulgaris L.

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