Location: Crop Diseases, Pests and Genetics
Title: Molecular Analysis Among MCA13-reactive Isolates Reveals a Strategy for Rapid Assessment of Citrus tristeza Virus Severity Authors
|Saponari, Maria -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2009
Publication Date: N/A
Technical Abstract: Citrus tristeza virus (CTV) genotypes vary in disease severity ranging from symptomless to virulent (stem pitting) in commercial citrus plantings. Because CTV is spread by propagation and by aphid vectors, rapid identification and virulence typing are critical for control and interdiction activities. The monoclonal antibody MCA 13 has been widely used for screening of severe CTV isolates since it reacts with nearly all virulent isolates in field trees. MCA13 generally fails to react with mild isolates, however, low level reactivity has been reported for some mild isolates. Thus, a wide range of severity and genetic diversity are associated with MCA13 reactive isolates. We have developed a strategy for large-scale assessment of severe CTV strains which is useful when CTV is endemic but not causing significant economic damage in a region. Field samples are first collected and tested serologically for CTV universal and MCA13 reactivity. Positive samples are tested in a multiplex quantitative reverse transcription (qRT-) PCR reaction using three strain-specific TaqMan® probes. This allows differentiation of MCA13-reactive isolates into at least three distinct CTV genotype groups associated with mild reaction on experimental indicators, severe stem-pitting and seedling yellows reactions, as decline. These results provide an indication of genetic diversity within CTV populations and allows identification of genotypes. If genotype(s) associated with virulent strains of CTV are found, delimiting surveys as well as biological indexing can begin immediately. This, coupled with a hierarchical sampling strategy, provides an estimate of CTV disease incidence and virulence in the sampled area.