To facilitate the introgression of desirable traits of Allium fistulosum into the genome of A . cepa, several accessions of the hybrid between these species were pollinated with A . cepa as the recurrent parent, and in vitro ovary and ovule culture were performed to obtain an increase in the recovery of backcross progeny . Compared to the results obtained from seed development in planta, the increase in the number of backcross progeny was generally very limited, and in some cases even a decrease was found . Raising the sucrose concentration in the ovary culture medium resulted in a higher frequency of ovules developing back seed coats but this was not followed by an increase in the number of backcross progeny obtained . Pollen tube growth of A . cepa was disturbed in the styles of the interspecific hybrids . Per ovule, frequencies of micropylar penetration exceeded frequencies of backcross progeny only to a limited extent . Hence, it was concluded that in the tested interspecific hybrid accessions the attainable gain in viable backcross progeny by the application of in vitro culture techniques is limited by strong pre-fertilization barriers acting at the level of stylar incongruity.

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