INHERITANCE TO TOP COMPONENT FORMATION IN COWPEA MOSAIC VIRUS

Two local lesion isolates of cowpea mosaic virus (CPMV) were fractionated first by velocity sucrose gradient centrifugation and then by equilibrium cesium chloride centrifugation. The isolate Sb24 yielded four principal components distinguishable by their buoyant densities: T, M, BU, and BL. The last two components have the same sedimentation coefficient and cannot be separated by sucrose gradient centrifugation. The isolate Sb2 yielded only M, BU, and BL. Some component combination of the form M + BU or M + BL appears to be necessary to initiate an infection. Inocula were prepared containing these pairs of components, either with both from one isolate or with one from isolate Sb2 and the other from Sb24. Inocula containing component M from isolate Sb24 caused T to be formed while progeny from inocula containing M from Sb2 tended to be free of T, regardless of the isolate which was the origin of the component BU or BL in the inoculum. Thus the inheritance of top component production seems to be through M, and the total genome of cowpea mosaic virus is apparently associated with two kinds of RNA molecules, one in the M particle and one in a BU or a BL particle. © 1969.