RATES OF GROWTH AND INCREASE OF MYZUS-PERSICAE ON VIRUS-INFECTED POTATOES ACCORDING TO TYPE OF VIRUS-VECTOR RELATIONSHIP

Growth, reproduction and survival ( = performance) of the aphid Myzus persicae Sulzer was measured on virus-free and virus-infected potato p lants. The principle objective was to evaluate if various viral infect ions affected aphid performance differently, and if so, whether any or der in the performance response of the aphid was discernible according to the type of virus-vector relationship. Three viruses varying in th eir dependency on M. persicae as a vector were used. Plants infected w ith potato leafroll virus (PLRV), a circulative virus highly dependent upon M. persicae for dispersal and transmission, were superior hosts as determined by the significantly greater mean relative growth rate ( MRGR) and intrinsic rate of increase (r(m)) of M. persicae compared wi th those of aphids reared on other plants. Plants infected with potato virus Y, a noncirculative virus less dependent upon M. persicae for d ispersal than PLRV, were intermediate in their quality based upon inte rmediate MRGR and r(m) values. Plants infected with potato virus X, a nonvectored virus independent of M. persicae, were least suitable host s along with the group of virus-free plants according to the lower MRG R and r(m) values.