Sex chromatin body as a marker of radiation-induced sex chromosome aberrations in the potato tuber moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

Genetic sexing technique based on the construction of a balanced lethal strain (BLS) has been proposed for Phthorimaea operculella (Zeller). The isolation of female with T(W;Z) translocation is a fundamental step to develop such a strain. Gamma irradiation was used to induce the requested translocations. The availability of sex-linked morphological marker is required to facilitate the detection of such mutations. Since a visible sex-linked marker has not been found in P. operculella, the main objective of our study was therefore to determine the possibility of using sex heterochromatin body as a marker to identify the required translocated females. The appearance of sex heterochromatin body and the analysis of sex chromosomes in F-1 females of irradiated P. operculella females were investigated. The percentage of abnormality in sex heterochromatin body in highly polyploid Malpighian tubule nuclei was positively correlated with the applied dose. Based on the appearance of this body, three mutant lines were isolated: elongated, small and fragmented lines. W chromosome was easily distinguished from Z chromosome when the analysis of pachytene sex chromosome bivalents of P. operculella females was carried out. The aberrations involved in W chromosome directly influenced the appearance of sex heterochromatin body in highly polyploid somatic cells of the isolated mutant lines. The results showed that sex heterochromatin could be used as sex determination and cytogenetic marker in P. operculella.