The years of translocations in the onion fly, Delia(=Hylemya) antiqua

Over a period of ten years more than 70 chromosomal rearrangements have been isolated for genetic insect control purposes. No significant difference was observed between X-rays and fast neutrons in the efficiency of translocation induction. Low doses around 2 Gy, mainly on 7-day-old males, were applied. On the basis of F1-semi-sterility and cytological analysis, translocations and inversions were scored. Mostly only asymmetrical translocations were kept for further inbreeding. From 30 of such stocks finally two gave homozygous translocation lines. Re-irradiation of a Y-linked stock with normal fertility was carried out to induce complex Y-linked translocations for the development of a genetic sexing mechanism. Several combinations were observed, except the Y-2-4 translocation in which the dieldrin locus should be present. Following re-irradiation of viable homozygous translocations, in later studies multiple translocations were induced and some again were made homozygous. Further basic cytogenetic studies provided more insight into the behaviour of the chromosomes, which was used in these studies of structural rearrangements. (author)