Reverse Transcription‐Polymerase Chain Reaction‐Based Detection of Plant Viruses

Current and emerging trends in techniques for plant pathogen detection

Plant pathogenic microorganisms cause substantial yield losses in several economically important crops, resulting in economic and social adversity. The spread of such plant pathogens and the emergence of new diseases is facilitated by human practices such as monoculture farming and global trade. Therefore, the early detection and identification of pathogens is of utmost importance to reduce the associated agricultural losses. In this review, techniques that are currently available to detect plant pathogens are discussed, including culture-based, PCR-based, sequencing-based, and immunology-based techniques. Their working principles are explained, followed by an overview of the main advantages and disadvantages, and examples of their use in plant pathogen detection. In addition to the more conventional and commonly used techniques, we also point to some recent evolutions in the field of plant pathogen detection. The potential use of point-of-care devices, including biosensors, have gained in popularity. These devices can provide fast analysis, are easy to use, and most importantly can be used for on-site diagnosis, allowing the farmers to take rapid disease management decisions.

Detection and Simultaneous Differentiation of Three Co-infected Viruses in Zanthoxylum armatum

Green Sichuan pepper (Zanthoxylum armatum) is an important economic fruit crop, which is widely planted in the southwest region of China. Recently, a serious disease, namely flower yellowing disease (FYD), broke out, and the virus of green Sichuan pepper nepovirus (GSPNeV) was identified to be highly correlated with the viral symptoms. Meanwhile, green Sichuan pepper idaeovirus (GSPIV) and green Sichuan pepper enamovirus (GSPEV) were also common viruses infecting green pepper. In our research, specific primers were designed according to the reported sequences of the three viruses, and a multiplex reverse transcription-polymerase chain reaction (RT-PCR) method for the simultaneous detection of GSPNeV, GSPIV, and GSPEV was established. The annealing temperature, extension time, and cycle number affecting the multiplex RT-PCR reaction were adjusted and optimized. Sensitivity analysis showed that the system could detect the three viruses simultaneously from the complementary deoxyribonucleic acid (cDNA) samples diluted by 10⁻³. The results of the ten samples detected by the multiplex RT-PCR system were consistent with the results of a single PCR, indicating that the method can be successfully used for rapid detection of field samples.

Current Developments and Challenges in Plant Viral Diagnostics: A Systematic Review

Plant viral diseases are the foremost threat to sustainable agriculture, leading to several billion dollars in losses every year. Many viruses infecting several crops have been described in the literature; however, new infectious viruses are emerging frequently through outbreaks. For the effective treatment and prevention of viral diseases, there is great demand for new techniques that can provide accurate identification on the causative agents. With the advancements in biochemical and molecular biology techniques, several diagnostic methods with improved sensitivity and specificity for the detection of prevalent and/or unknown plant viruses are being continuously developed. Currently, serological and nucleic acid methods are the most widely used for plant viral diagnosis. Nucleic acid-based techniques that amplify target DNA/RNA have been evolved with many variants. However, there is growing interest in developing techniques that can be based in real-time and thus facilitate in-field diagnosis. Next-generation sequencing (NGS)-based innovative methods have shown great potential to detect multiple viruses simultaneously; however, such techniques are in the preliminary stages in plant viral disease diagnostics. This review discusses the recent progress in the use of NGS-based techniques for the detection, diagnosis, and identification of plant viral diseases. New portable devices and technologies that could provide real-time analyses in a relatively short period of time are prime important for in-field diagnostics. Current development and application of such tools and techniques along with their potential limitations in plant virology are likewise discussed in detail.

Detection of plant viruses in mixed infection by a macroarray-assisted method

The protocol for a simple, sensitive, and specific method using a cDNA macroarray to detect multiple viruses is provided. The method can be used even at the production sites for crops, which need a reliable routine diagnosis for mixed infection of plant viruses. The method consists of three steps: RNA extraction, duplex RT-PCR, and "microtube hybridization" (MTH). Biotinylated cDNA probes are prepared using RT-PCR and used to hybridize a nylon membrane containing target viral cDNAs by MTH. Positive signals can be visualized by colorimetric reaction and judged by eyes. We here demonstrate this method to detect asparagus viruses (Asparagus virus 1 and Asparagus virus 2) from latently infected asparagus plants.