BACKGROUND: B and Q biotypes of the whitefly, Bemisia tabaci (Gennadius), are generally regarded as the most significant given their global distribution and strong resistance to insecticides. Since these biotypes can coexist and differ markedly in their insecticide resistance profiles, a rapid but reliable means of discriminating between them would be a valuable complement to resistance monitoring and management programmes. Recently, PCR-based methods have been developed to determine the biotype status of B. tabaci populations. However, these require post-amplification procedures, which increase time and labour. RESULTS: The authors have developed an allelic discrimination real-time PCR assay using fluorescent dye-labelled probes to distinguish the B and Q biotypes. The assay targets a single nucleotide polymorphism (SNP) in the mitochondrial cytochrome oxidase I (mtCOI) gene. To evaluate the assay, DNA was extracted from individual whiteflies of six known biotype strains, and all scored correctly as either a B or Q biotype. As further validation, 72 individuals from field samples collected in different parts of the world were also tested by the assay. No failed reactions were observed, with all 72 samples scoring clearly as either the B or Q biotype. CONCLUSION: The development of this rapid and high-throughput assay has important potential for routine monitoring of B and Q biotypes on ornamental plants and for the screening of B. tabaci populations in countries where these biotypes are not yet established.
BACKGROUND: B and Q biotypes of the whitefly, Bemisia tabaci (Gennadius), are generally regarded as the most significant given their global distribution and strong resistance to insecticides. Since these biotypes can coexist and differ markedly in their insecticide resistance profiles, a rapid but reliable means of discriminating between them would be a valuable complement to resistance monitoring and management programmes. Recently, PCR-based methods have been developed to determine the biotype status of B. tabaci populations. However, these require post-amplification procedures, which increase time and labour. RESULTS: The authors have developed an allelic discrimination real-time PCR assay using fluorescent dye-labelled probes to distinguish the B and Q biotypes. The assay targets a single nucleotide polymorphism (SNP) in the mitochondrial cytochrome oxidase I (mtCOI) gene. To evaluate the assay, DNA was extracted from individual whiteflies of six known biotype strains, and all scored correctly as either a B or Q biotype. As further validation, 72 individuals from field samples collected in different parts of the world were also tested by the assay. No failed reactions were observed, with all 72 samples scoring clearly as either the B or Q biotype. CONCLUSION: The development of this rapid and high-throughput assay has important potential for routine monitoring of B and Q biotypes on ornamental plants and for the screening of B. tabaci populations in countries where these biotypes are not yet established.