Advances in and Prospects for Actinidia Viruses

Rapid and Visual Detection of Actinidia Chlorotic Ringspot-Associated Virus Using One-Step Reverse-Transcription Recombinase Polymerase Amplification Combined with Lateral Flow Dipstick Assay

Actinidia chlorotic ringspot-associated virus (AcCRaV) occurs widely in major kiwifruit producing areas of China and is often accompanied by coinfecting viruses, affecting the growth, yield, and quality of kiwifruit. Therefore, a rapid and sensitive detection method is crucial for diagnosing and developing effective AcCRaV management strategies. In this study, a one-step reverse-transcription recombinase polymerase amplification combined with a lateral flow dipstick (RT-RPA-LFD) assay was developed for rapid detection of AcCRaV. Specific primers and a probe were designed based on the conserved region of the coat protein gene sequence of AcCRaV. The one-step RT-RPA reaction can be performed at 35 and 40°C within 10 to 30 min, and the amplification results can be read directly on the LFD within 5 min. The detection limit of the one-step RT-RPA-LFD assay was 10-8 ng (about 20 viral copies), which was equal with one-step RT-qPCR and 100 times more sensitive than one-step RT-PCR. Moreover, the one-step RT-RPA-LFD assay was successfully applied to detect AcCRaV from crude extracts, and the entire detection process can be completed within 40 min. These results indicate that the RT-RPA-LFD assay is a simple, rapid, and sensitive strategy that can be used for accurate diagnosis of AcCRaV-infected kiwifruit plants in the field. To our knowledge, this is the first study applying the one-step RT-RPA-LFD assay to detect a kiwifruit virus.

Efficient Elimination of Actinidia Chlorotic Ringspot-Associated Virus from Infected Kiwifruit Shoots Cultured In Vitro

In this study, methods of Actinidia chlorotic ringspot-associated virus (AcCRaV) elimination by shoot tip culture, thermotherapy followed by shoot tip culture, and chemotherapy followed by shoot tip culture were explored. The results showed that the AcCRaV elimination rate was 23.3% when the secondary shoot tip culture method was used and when the shoot tip length was less than 0.5 mm. The AcCRaV elimination rate was 100% when thermotherapy (36°C [day] and 32°C [night]) was applied for 20 days followed by shoot tip culture (shoot tip length less than 1.0 mm). When shoot segments were treated with ribavirin at 15 µg/ml for 2 months followed by shoot tip culture, the elimination rate of AcCRaV was 100% (shoot tip length less than 1.0 mm). When shoot segments were treated with ribavirin at 25 µg/ml for 2 months followed by shoot tip culture, the elimination rate of AcCRaV was 100% (shoot tip length less than 1.5 mm). This is the first report on kiwifruit virus elimination methods.