Studies on the Genetic Variations between Field Strains of Pectinophora gossypiella (SAUNDERS) using Polymerase Chain Reaction (PCR) Technique

Five different strains of the pink bollworm, Pectinophora gossypiella (Saunders) were used in the present study.The laboratory strain was used as a baseline in the molecular biology assays. Four strains were selected from natural popoulations, fields located in Qalubia, Gharbia, Menoufia and Kafr-Elsheikh Governorates. The molecular studies included the analysis of the plod genomic DNA of the tested strains under this study by using Random Amplified Polymorphic DNA (RAPD) method. A battery of five primers was used to evaluate the mutagenic differentiation among the five strains. The primer S4 generated the highest numbers of fragments (32 fragments). Both primers K15 and S8 generated 23 fragments. The lowest number of fragments appeared in primer C15 and primer P8, (18 fragments). The molecular sizes of fragments ranged between 180 and 1182bp. The RAPD patterns resulted from amplification of DNA of the field colony strains and laboratory strain of the pink bollworm P. gossypiella revealed that the lowest value of similarity index  (0.0%), which reflects the highest degree of change in DNA structure and sequences between the genomes of laboratory pink bollworm and those exposed to a wide spread of different insecticides  for controlling the pest in the fields. On the other hand, there is no compilitily similarity index between field strains and laboratory strain of pink bollworm. The highest similarity index between field strains and laboratory strain of the pink bollworm appeared in primer P8, while the lowest similarity index between field strains and laboratory strain of the pink bollworm appeared in primer K15. The primer S4 recorded that is no similarity index between Qalubia strain and each of laboratory and field strains. It is interrest to note that the less damaging effect to pink bollworm DNA could be attributed to a good detoxifying mechanism developed by the insect as a result of wide spread and long term exposure of insect larvae in additional to different thermal degrees in the fields