PARTIAL-PURIFICATION OF A VIRUS-ASSOCIATED WITH A SPANISH ISOLATE OF CITRUS RINGSPOT

A citrus ringspot isolate from Star Ruby grapefruit (RS-SR) was mechan ically transmitted to Chenopodium quinoa. RS-SR was partially purified by differential centrifugation, fractionation in a sucrose gradient, and agarose gel electrophoresis of selected fractions. Infectivity of concentrated extracts on C. quinoa was lost in individual fractions of the gradient, but it was recovered by combining a top and a bottom co mponent. Both components contained a 48-kDa protein not found in simil ar preparations from healthy plants. After further purification the 48 kDa protein was detected at the top edge of the agarose gel. In the i nitial experiments a 38-kDa protein was found in the same fractions th at later contained the 48-kDa protein. An antiserum obtained to the 38 kDa protein reacted in Western blots with both the 38- and the 48-kDa proteins, whereas another antiserum raised to the Florida isolate CRS V-4 (also containing a 48-kDa protein) did not react with the 38-kDa p rotein, indicating that the latter was probably a degradation product of the 48-kDa protein. Filamentous flexous particles were observed by serologically specific electron microscopy in crude extracts from RS-S R-infected C. quinoa plants. These results indicate that RS-SR is asso ciated with a two-component virus similar to those associated with sev eral psorosis and ringspot isolates, and serologically related to CRSV -4.