Simple serological assays for detecting rice tungro viruses

An attempt was made to produce sensitive and specific polyclonal antisera a gainst the viruses causing rice tungro disease, and to assess their potenti al for use in simple diagnostic tests. Using a multiple. sequential injecti on procedure, seven batches of polyclonal antisera against rice tungro baci lliform virus (RTBV) and rice tungro spherical virus (RTSV) were produced. These were characterized for their sensitivity and specificity using ring-i nterface precipitin test and double antibody sandwich (DAS) ELISA. Thirty-o ne weeks after the first immunization, antiserum batch B6b for RTBV showed the highest ring interface titer (DEP = 1:1920). For RTSV, batches S3, S4b and S5b all had similar titres (DEP = 1:640). In DAS-ELISA, however, signif icant differences among purified antisera (IgG) batches were observed only at IgG dilution of 10(-3). At that dilution, IgGB4b showed the greatest sen sitivity, while IgGS3 showed greatest sensitivity for RTSV. When all IgG ba tches were tested against 11 tungro field isolates (dual RTBV-RTSV infectio ns) at sample dilution of 1:10, IgGB4b and IgGB6b for RTBV and IgGS3 and Ig GS6b for RTSV performed equally well. However, after cross adsorption with healthy plant extracts in a specially prepared healthy plant-Sepharose affi nity column, only IgGB6b could be used specifically to detect RTBV in a sim ple tissue-print assay.