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Sterility barriers in some artificial F₁ orchid hybrids: female sterility

Maria Neysa Silva Stort; Maria Aparecida Marin Morales

Departamento de Biologia, Instituto de Biociências, Campus Universitário de Rio Claro, UNESP, 13500 Rio Claro. SP, Brasil. Send correspondence to M.N.S.S.

ABSTRACT

In an attempt to detect the causes of sterility in some artificial intergeneric and inter-specific F₁ orchid hybrids, we observed megasporogenesis, fertilization and embryo formation after F ₁ sibcrosses. Also, we estimated the degree of sterility of the female gametes of these hybrids from results obtained from backcrosses using the F₁ hybrids as female parents.
The results of these observations showed that female sterility occurs by breakdown of ovule development at different stages of megasporogenesis. In some hybrids the megaspore mother cell degenerates at the beginning of the first meiotic division or after the first or second meiotic division. In most cases megasporogenesis gave rise to apparently normal ovules, but fertilization did not occur in all of them. The embryo sac of unfertilized ovules degenerated and these ovules produced a seed without an embryo.
The results of the backcrosses using the F _i hybrids as female parents suggest that, with some exceptions, female sterility was higher than male sterility.

Keywords: sterility; artificial; F₁; orchid; hybrids; female.

REFERENCES

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