Unexpected segregation ratios from male-linked translocations in the Mediterranean fruitfly, Ceratitis capitata (Diptera: Tephritidae)

Abstract

Three male-linked translocations were isolated in the Mediterranean fruitfly, Ceratitis capitata (Wiedemann) which showed sex linkage foran autosomal pupal colour marker, white pupa (wp). The wild type allele (wp-) was translocated to the male-determining chromosome. Males emerge from wild type pupae (brown) and females from white pupae. These lines will be used to develop an automatic sexing system.During maintenance of these lines in large populations it was noted that in two of them there was a significant distortion in the expected 1: I segregation ratio for pupal colour and excess white pupae were produced. However, adults did not emerge from a large proportion of these pupae. Using known numbers of Ist instar larvae from the three lines, the distortion was further studied and the effect confirmed. To account for this pupal colour segregation distortion it was assumed that certain duplication;' deficiency zygotes survive to the late pupal stage. These zygotes have a deficiency for the wild type allele, therefore the normally recessive mutant allele wp could be expressed ('pseudo-dominance').The overall fitness of the three lines was calculated; and their suitability for the genetic sexing of large populations is discussed.

Field cage studies with a genetic sexing strain in the Mediterranean fruit fly, Ceratitis capitata

“…(i) T101 genetic sexing line, males emerge from brown pupae and females from white pupae (details see Robinson, 1984). (i) T101 genetic sexing line, males emerge from brown pupae and females from white pupae (details see Robinson, 1984).…”

“…Strains. (i) T101 genetic sexing line, males emerge from brown pupae and females from white pupae (details see Robinson, 1984). The line was induced in Seibersdorf genetic background; (ii) S Seibersdorf colony; (iii) W Wild population.…”

“…Several approaches are being considered to produce genetic sexing systems, the most advanced being pupal colour sexual dimorphism (R6ssler, 1979, 1980Robinson, 1984;Robinson & Van Heemert, 1982;Robinson & Riva, 1983). One of the available lines, T101 (Robinson, 1984) was chosen for a series of field trials on Procida Island, Italy as it has shown good stability during many generations of small scale laboratory rearing at the Research Institute ITAL. The line was transferred to the IAEA laboratory at Seibersdorf where it was mass reared and the pupae were air freighted to Procida for the field trials.…”