DIFFERENCES IN THE LIFE PARAMETERS RELATED TO POPULATION INCREASE OF SOME MAJOR GENOTYPES OF SCOTTISH Myzus persicae, THE MAIN VECTOR OF Potato leafroll virus

Different clones of Myzus persicae, the main vector of Potato leafroll virus (PLRV),vary in reproductive performance, host-plant adaptation, insecticide resistance and vector efficiency. In this study some important life parameters related to population increase of five major genotypes of Scottish M. persicae, characterized by the ribosomal DNA intergenic spacer fingerprinting technique, denoted type A, B, C, J, and I along with clone 4010 of M. antirrhinii were analyzed. The life parameters measured were average daily offspring production, reproduction time, total offspring production and longevity. These were measured by putting fourth instar nymphs from each genotype on detached leaves of oilseed rape and potato, recording the number of offspring produced by each individual and removing them from the leaves daily until each individual died. The developmental time of the genotypes was also determined by putting one day old offspring of each genotype on detached leaves of the same plants and recording the period from birth to maturity. Significant differences in life parameters of the genotypes were observed. Genotype A was one of the most reproductive genotypes on both hosts and genotype B was so, on potato. It has already been shown that these two genotypes were resistant to insecticides and more efficient vectors of PLRV. Taking these matters into account, it is clear that the existence of such genotypes that are very reproductive, resistant to insecticides and efficient in transmitting PLRV, can potentially increase the spread of the virus if they become established as the predominant genotypes in each area. This in turn, further reinforces the necessity of monitoring M. persicae genotypes with regard to resistance to insecticides, virus transmission efficiency and reproduction capacity in each specific region.