ABSTRACT
A quantitative real-time reverse transcription-polymerase chain reaction (RT-qPCR) procedure using a general primer set and three TaqMan(®)MGB probes was developed for general and genotype-specific detection and quantitation of the genomic M segment of Tomato spotted wilt virus (TSWV). Standard curves using RNA transcripts homologous to the three probes allowed reproducible quantitative assays with a wide dynamic range (10(3)-10(10) TSWV M segment RNA copies/ng of total RNA) and high sensitivity. This protocol was assayed with a battery of TSWV isolates, covering the range of the present known genetic variation, in single and/or mix infections in three plant hosts, as well as in the thrips vector Frankliniella occidentalis. This quantitative detection assay will be a valuable tool for molecular biology and epidemiology studies, diagnosis and disease control.
Subject(s)
Insect Vectors/virology , Insecta/virology , Plant Diseases/virology , RNA, Viral/analysis , Reverse Transcriptase Polymerase Chain Reaction/methods , Tospovirus/isolation & purification , Animals , Capsicum/virology , DNA Probes , Datura/virology , Genotype , Solanum lycopersicum/virology , RNA, Viral/genetics , RNA, Viral/isolation & purification , Sensitivity and Specificity , Taq Polymerase , Tospovirus/classification , Tospovirus/geneticsABSTRACT
The production of clementine fruit was affected by varying densities of Aphis spiraecola Patch (Hemiptera: Aphididae) maintained on four groups of clementine, Citrus clementina Hort. ex Tan., trees individually isolated in mesh cages. A formula relating the number of aphids per square meter of canopy per group of trees to yield loss in that group of trees was obtained, permitting us to calculate the economic injury levels (EILs) and economic thresholds (ETs) for treatment against A. spiraecola, i.e., EIL, ET, environmental economic injury level (EEIL), and environmental economic threshold (EET). In an example case with current values, EIL = 370, ET = 322, EEIL = 614, and EET = 533 aphids per m2 of canopy. Formulae designed for easier use in the field were obtained to express each of these thresholds. The formulae are compared with those obtained for Aphis gossypii Glover in a previous study; the intervention thresholds for A. spiraecola are slightly higher than those found for A. gossypii.
Subject(s)
Aphids/physiology , Citrus/parasitology , Animals , Costs and Cost Analysis , Host-Parasite InteractionsABSTRACT
Different levels of Aphis gossypii Glover were maintained on clementine trees by means of isolation inside mesh cages. Clementine yield loss was correlated with the number of aphids per square meter of canopy, obtaining the corresponding formula. Starting from this formula, the economic injury level (EIL) was calculated as follows: [218,333C + 11,130.6 VP0K]/[57.08 VP0K - 100C] = EIL (aphids/m2), where C = total insecticide cost per hectare, V = fruit price per kilogram, P0 = yield per hectare of a minimum pest level orchard, and K = reduction of injury due to treatment. Starting from the EIL, the economic threshold, the environmental EIL, and the environmental economic threshold were obtained. Formulae relating the number of aphids per square meter with other simpler indices expressing these thresholds (percentage of infested shoots, infested shoots per 0.25 m2 ring, index of infestation, percentage of occupied rings, and number of weekly captured aphids in a yellow trap) also were calculated.
