No abstract

Aphids tend to show karyotype variations because of the presence of holocentric chromo somes and thelytokous mode of reproduction . Structural heterozygosity and variation in chromosome number within species have been reported in some aphid species (Blackman 1971, Chattopadhay et al. 1982, Brown and Blackman 1988 , Blackman et al. 1990). These studies indicate that there is association between karyotypes and host plant in aphids . In this paper, karyotype variation in the aphid Sitobion rosaeiformis (Das) collected from Rosa sp. and Rubus ellipticus is reported. Materials and methodsThe populations of aphid Sitobion rosaeiformis (Das) (Subfamily-Aphidinae; Tribe -Macrosiphini) were collected from two different hosts Rosa sp. and Rubus ellipticus belonging to the family Rosaceae (Table 1). The collections were sent to CAB International Institute of Entomology, London for authentication and will be deposited in the Natural History Museum (BMNH) collection. Apterous, viviparous female aphids were taken and chromosome squash preparations were made from young embryos dissected from these aphids. Fresh material was used in this study . Embryos were given pretreatment in 0.7% sodium citrate solution for 30min and then fixed in a fresh mixture of 1:3 acetic ethanol. After 25min embryos were transferred to a drop of 50% acetic acid on a glass slide. A coverslip was gently put on the material and it was then squashed, first by tapping and then by applying thumb pressure. Coverslips were dislodged off the slides with a sudden jerk. The slides and coverslips were dried and stained with 2% Giemsa stain at pH 6.8.