Plant Virus-Vector Relationships

Abstract

Publisher Summary The chapter discusses a fairly comprehensive account of the main factors in relationships between plant viruses and their vectors. The vectors occur among almost every kind of organism that feeds upon plants and that the relationships consist of all grades from a purely mechanical contamination to a close biological relationship between virus and vector. Mechanical transmission of plant viruses in this context refers to a mode of transfer, in which there is no evidence of any biological relationship between virus and vector. The question as to whether some aphid borne viruses are mechanically transmitted is discussed in the chapter dealing with aphid-virus relationships, and with one exception, this chapter is concerned with virus transmission by insects with biting mouthparts. The methods of mechanical transmission dealt with, so far, have been concerned only with external contamination; there are, however, other examples of mechanical transmission in which more than this is involved. Biological transmission indicates a definite relationship between plant virus and insect vector. It has been seen something of this in the discussion of the viruses of potato leaf roll and Sonchus yellow vein and their aphid vectors, but it is in regard to some of the leafhopper-borne viruses that ones knowledge of this phenomenon is the greatest. It could be that in considering the vector transmission of plant viruses, observing the gradual extension of the host range of the viruses by long-continued association of insect and plant, with transmission an incidental factor arising out of this long-continued association.