A previous study has identified two types of recombinant variants of Potato virus Y strain NTN (PVY^NTN) in China and sequenced the complete genome of the variant PVY^NTN-HN2. In this study, the complete genome of isolate PVY^NTN-HN1 was fully sequenced and analyzed. The most striking difference between the two variants was the location of recombinant joint three (RJ3). In PVY^NTN-HN1, like other typical European-PVY^NTN isolates such as PVY^NTN-Hun, the RJ3 was located at nucleotide (nt) 9183, namely the 3' proximal end of the CP gene (nt. 8571-9371), thus leading to most (the first 613 nucleotides from the 5' proximal end) of the CP gene (801 bp) with a PVY^N origin and PVY^N-serotype; whereas in contrast, the RJ3 in PVY^NTN-HN2 was located at nt 8572, consequently leading to a CP gene of PVY^O origin and PVY^O-serotype. The varied genome composition among PVY^O, PVY^N, PVY^N:O, PVY^NTN-HN1 and PVY^NTN-HN2 made them useful for the investigation of possible roles of gene segment(s) in symptom formation on host plants. When Physalis floridana plants were infected with different PVY isolates, two types of symptoms were induced. PVY^N and PVY^NTN-HN1 induced mild symptoms (mainly mild mottling) whereas PVY^O, PVY^N:O and PVY^NTN-HN2 induced serve symptoms including leaf and stem necrosis, leaf-drop and stunting. These results, together with a previous study using artificial PVY chimeras, demonstrate that the CP gene, especially the 5' proximal segment (nt 8572-9183), and/or CP likely determine the pathogenicity of PVY in P. floridana.

Potato tubers exhibiting necrotic rings/arcs were found in a winter potato crop ‘Favorita’ in the subtropical area Huidong county, Guangdong province, China, in 2012. When the symptomatic tubers were cut crosswise, light to dark brown necrotic arcs were observed in the tuber flesh. A mini-survey of the crop found 8% symptomatic tubers in an area of 10 meters². To reveal the causal agent of the disease, reverse transcription–polymerase chain reactions (RT-PCR) targeting 9 common potato viruses including those viruses (e.g, Potato mop-top virus (PMTV), Tobacco rattle virus, Tomato spotted wilt virus, and Potato virus Y tuber necrosis strain) known to be capable of induction of tuber necrosis, were carried out. Except for PMTV, no other viruses were detected. Sequencing of the 460 bp amplicon revealed that the fragment exhibited a 99-100% sequence identify with most PMTV coat protein sequences deposited in GenBank, which was confirmed by a further phylogenetic analysis. Enzyme linked immunosorbent assay with PMTV antibody on the symptomatic tubers was also carried out, and a positive reading was observed. Together, these results demonstrate that PMTV was the causal agent for the spraing disease in potatoes in the winter crop in Guangdong. To our knowledge, this is the first report of PMTV in Guangdong province, China, and the first scientific confirmation of PMTV in China.

A versatile strategy for electrochemical determination of glycoalkaloids (GAs) was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA) modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors.

A preliminary screening for garlic viruses in garlic plants in Hunan, China, using existing monoplex (simplex) reverse transcription-polymerase chain reaction (RT-PCR) procedures detected four viruses/virus groups. These viruses/virus groups were Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV), Shallot latent virus (SLV) and allexiviruses (e.g., garlic viruses A, B, C, D, E, X). Sequence analysis of the projected allexivirus amplicons revealed the allexivirus in the infected garlic plants was Garlic virus D (GarV-D), which shared 92–97% sequence identities with various isolates from the world. A multiplex RT-PCR (mRT-PCR) was therefore developed to simultaneously detect and differentiate the four viruses/virus groups. To achieve this, four primer pairs targeting allexiviruses, OYDV, LYSV and SLV were designed. The anticipated amplicon sizes are 183 bp (allexiviruses), 265 bp (OYDV), 404 bp (LYSV) and 592 bp (SLV), respectively. All primer pairs produced virus-specific fragments in both simplex and multiplex formats, thus confirming the efficacy of the newly developed mRT-PCR for detection of these viruses. The mRT-PCR further was evaluated by applying it to garlic plant samples collected in two geographic locations in Hunan. Allexiviruses, OYDV, LYSV and SLV were detected in 50.9, 40.3, 28.3 and 58.5% of leaf samples, respectively; and mixed infections with two or more viruses accounted for 54% of the garlic samples. The results obtained by mRT-PCR were confirmed by simplex RT-PCR assays. In conclusion, this newly developed mRT-PCR provides a rapid, sensitive and reliable method for the detection and identification of major garlic viruses.