RESUMO
Crapemyrtle bark scale (CMBS, Acanthococcus lagerstroemiae), an invasive polyphagous sap-sucking hemipteran, has spread across 14 states of the United States since 2004. The infestation of CMBS has negatively impacted the flowering of ornamental plants and even the fruiting of some crops. Host identification is critical for determining potential risks in ecosystems and industries and helps develop strategic management. A host confirmation test was performed over 25 weeks using six Lagerstroemia species (L. caudata, L. fauriei 'Kiowa', L. indica 'Dynamite', L. limii, L. speciosa, and L. subcostata) and California loosestrife (Lythrum californicum). The 25-week observations confirmed all tested plants as the hosts. The repeated measures of analysis of variance (ANOVA; Tukey's HSD, α = 0.05) indicated that the average number of CMBS females differed significantly between L. limii and L. speciosa. The highest number of the females observed on L. limii was 576 ± 25 (mean ± SE) at 17 weeks after inoculation (WAI), while the highest number was 57 ± 15 on L. speciosa at 19 WAI. In addition, L. subcostata and L. speciosa had significantly high and low numbers of males, respectively, among the Lagerstroemia species. Our results suggest that L. speciosa could be incorporated in developing new cultivars with low CMBS suitability.
RESUMO
Rose rosette disease, caused by Rose rosette virus (RRV; genus Emaravirus) is a major threat to the rose industry in the U.S. The only strategy currently available for disease management is early detection and eradication of the infected plants, thereby limiting its potential spread. Current RT-PCR based diagnostic methods for RRV are time consuming and are inconsistent in detecting the virus from symptomatic plants. Real-time RT-qPCR assay is highly sensitive for detection of RRV, but it is expensive and requires well-equipped laboratories. Both the RT-PCR and RT-qPCR cannot be used in a field-based testing for RRV. Hence a novel probe based, isothermal reverse transcription-recombinase polymerase amplification (RT-exoRPA) assay, using primer/probe designed based on the nucleocapsid gene of the RRV has been developed. The assay is highly specific and did not give a positive reaction to other viruses infecting roses belonging to both inclusive and exclusive genus. Dilution assays using the in vitro transcript showed that the primer/probe set is highly sensitive, with a detection limit of 1 fg/µl. In addition, a rapid technique for the extraction of viral RNA (<5min) has been standardized from RRV infected tissue sources, using PBS-T buffer (pH 7.4), which facilitates the virus adsorption onto the PCR tubes at 4°C for 2min, followed by denaturation to release the RNA. RT-exoRPA analysis of the infected plants using the primer/probe indicated that the virus could be detected from leaves, stems, petals, pollen, primary roots and secondary roots. In addition, the assay was efficiently used in the diagnosis of RRV from different rose varieties, collected from different states in the U.S. The entire process, including the extraction can be completed in 25min, with less sophisticated equipments. The developed assay can be used with high efficiency in large scale field testing for rapid detection of RRV in commercial nurseries and landscapes.