Some Variables Affecting the Use of Cowpea as an Assay Host for Cucumber Mosaic Virus

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Abstract
A study was made of the factors affecting the production of local lesions by cucumber mosaic virus (CMV) on cowpea (Vigna sinensis). Cowpea is a satisfactory host for quantitative work with CMV at dilutions of inoculum from 1/20 to 1/200. The half-leaf technique can be used to advantage. CMV inoculum is most infectious at pH 8, has greatest longevity at pH 7, and will tolerate a pH range from 4 to 10. Alauxite and carborundum (both 500-mesh) were superior to all other abrasives tested. Washing of inoculated leaves did not increase the no. of lesions developed. More lesions developed on cowpea plants placed under fluorescent lights at 200 f.c. than on plants placed either in the glasshouse or under higher light intensities. Rapid drying of inoculated leaves increased the no. of lesions developed. The use of leaf-culture techniques has not made possible a reduction in the variation between plants.