Cross Protection Between Strains of Yellows-type Viruses

Abstract

Publisher Summary Plants invaded by one virus are generally protected against other closely related viruses, but are not protected against distantly related viruses. There is a considerable variation in the degree of cross protection afforded by plant viruses that are believed to be closely related. Cross protection reactions between closely related viruses of plants and original experiments on cross protection between yellows-type viruses are discussed in this chapter. California aster yellows produces symptoms in several different plants that distinguish it from aster yellows, but is cured by heat treatments similar to those that cure aster yellows. The California strain of aster yellows virus and ordinary aster yellows virus protect against each other in asters and other plants. They also protect against each other in the aster leafhopper that, when infective for one, apparently becomes immune from infection by the other. How protection is afforded is not presently known, but several theories have been advanced to account for it. One that fits the known facts rather satisfactorily assumes that closely related viruses require the same host cell materials for multiplication. A strain of a virus that invades a plant cell first uses up these materials and without them a second strain of the same virus cannot multiply. It also assumes that distantly related viruses use different host cell materials for multiplication.