Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Plant Pathology


It has long been known that plants infected with certain virus strain develop no further symptoms when inoculated with another strain of the same virus. The phenomenon became known as premunity, antagonism, interference or cress protection workers have differentiated the terms cross protection and interference. A situation in which virus infection with one strain confers protection against a related strain was termed cross protection. Hypothesis were formulated to explain the existence of cross protection and interference. Workers have confirmed, however, that when two viruses, related or otherwise, were introduced at the same time into a plant, simultaneous infections by both viruses resulted. A similar situation seems to exist in insect vectors of plant viruses. Evidences were presented that cross protection between viruses. Strains existed in the vectors. Very little is known, at present, about the ability of insects to transmit more than one stylet-borne virus or virus strain at a time. Since stylet-borne viruses are acquired and held at the mouthparts of the insects, multiplication is less likely to occur than with persistent viruses which accumulate within the insect body. In the e present work, the term interference is used to designate any effects a virus strain, carried by an aphid, will have on the acquisition or transmission of another strain. The present investigations were designed to determine if two strains of cucumber mosaic virus (CMV) and alfalfa mosaic virus (AMV) can be acquired and transmitted simultaneously by single Myzus Persicae aphids.

Library of Congress Subject Headings

Virus diseases of plants
Mosaic diseases
Green peach aphid


Includes bibliographical references



Number of Pages



South Dakota State University