Detection, identification and assessment of variation of whitefly-transmitted geminiviruses
1994
Harrison, B.D.
Whitefly-transmitted geminiviruses (WTGs) characteristically have serologically related particles. Thus although several of the viruses have been detected in plant sap by ELISA or immunosorbent electron microscopy with polyclonal antibodies, these tests do not identify them. Monoclonal antibodies (MAbs) raised against particles of three of the viruses, and used in triple-antibody-sandwich ELISA, have provided a sensitive detection test for 30 WTGs from 20 crop and weed species in 50 countries. Moreover, most of the viruses can be identified by their relative reactivities with sub-sets of 30 of the MAbs. Some crops such as cassava and tomato were shown by these tests, supported by nucleotide sequence data, to be infected with different WTGs in different geographical regions. WTG genomes consist of two DNA molecules, or in some viruses only one. The molecule always present has a well conserved sequence except for the large intergenic region; the other molecule, where it occurs, is not well conserved in different WTGs. WTGs can therefore be detected by hybridization with DNA probes for conserved sequences or by a polymerase chain reaction (PCR) with primers based on these sequences. Many of the viruses can be differentiated by analysis of the fragments produced by restriction endonuclease digestion of the PCR products, or by using probes or primers specific for sequences of one virus. WTGs can be detected and identified by PCR in extracts of single whiteflies (Bemisia tabaci)
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