Aphid transmission of nonpersistent plant viruses with special reference to theBrassica nigravirus

does not appear. First page follows. Introduction During the past few decades the study of transmission of plant viruses by insects has become increasingly important. Of the various groups of insects which act as vectors, aphids are probably the most important, both in number of species which are vectors and in number of different viruses transmissible by them. It is the intention of this paper to report on details of some recent experimental work on transmission of the Brassica nigra virus (Takahashi, 1949), and to review the knowledge to date concerning aphid transmission of nonpersistent viruses in order to present a hypothesis on the mode of transmission of this group of viruses by aphids. The first portion is concerned with unreported experimental work. Materials and Methods The Brassica nigra virus was originally obtained from Dr. W. N. Takahashi, and has been maintained in Brassica juncea Coss. in this laboratory for experimental purposes. Test plants were B. juncea seedlings, unless otherwise noted. The vector principally used was the green peach aphid, Myzus persicae (Sulzer), with some trials also including the turnip aphid (= the false cabbage aphid), Rhopalosiphum pseudobrassicae (Davis). Noninfective colonies were maintained on healthy B. juncea plants. Insects were transferred with a camel’s hair brush, and the acquisition feedings, unless otherwise noted, were watched and timed with a stop watch. The plants were fumigated after the test-feeding period before being placed in the greenhouse for incubation. The greenhouses were routinely sprayed to prevent aphid buildup. More detailed descriptions of methods are given in connection with specific experiments.