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Cucumber plants (Cucumis sativus) displaying symptoms of phyllody, sterility, and flower virescence were observed in fields located in the Dianbai district of Guangdong province, China. Total DNA was extracted from the symptomatic plants; this was followed by molecular detection using a set of universal phytoplasma primer pairs, R16mF2/mR1, P1/P7, and SecYF1(II)/SecYR1(II). This resulted in the PCR amplification of products corresponding to expected sizes of 1.4 kb, 1.8 kb and 1.7 kb, respectively. The 16S rDNA sequence obtained exhibited 100% similarity with the eggplant phyllody phytoplasma, the 'Cleome rutidosperma' witches' broom phytoplasma, and the 'Desmodium ovalifolium' witches' broom phytoplasma strain DeOWB, all of which belong to the 16SrII group. Phylogenetic analysis, based on the 16S rDNA gene and SecY gene sequences, confirmed the close affiliation of the detected phytoplasma isolate, tentatively designated as cucumber phyllody phytoplasma (CuPh) China isolate, with the 16SrII-A subgroup. Additionally, virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA sequence revealed a pattern that was identical to that of the 16SrII-A subgroup. This is the first report of cucumber phyllody phytoplasma in China. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial wilt, caused by Ralstonia solanacearum species complex is a key yield‐limiting factor on crops in Guangdong province, China. The genetic diversity of 110 R. solanacearum strains collected from 16 host plants in different areas of Guangdong province was analysed using biovar and phylotype classification schemes. Of 110 strains, fifty‐five strains belong to biovar 3, fifty‐two strains belong to biovar 4, two strains belong to biovar 2 and one strain belonged to biovar 1. Phylotype‐specific multiplex PCR showed that 108 strains belonged to phylotype I (biovars 1, 3, 4) and two strains belonged to phylotype II (biovar 2). The result of phylogenetic relationships analysis based on egl gene sequences demonstrated that 108 strains of phylotype I were grouped into nine previously described sequevars and a new sequevar 57, and two strains of phylotype II were grouped into sequevar 1. Sequevars 15, 34 and 44 widely distributed in Guangdong were predominant sequevars. Sequevar 45 was first reported on potato and pumpkin in China. These results revealed the genetic structure and phylogenetic relationships of R. solanacearum population in Guangdong and will be helpful in bacterial wilt‐resistance breeding. [ABSTRACT FROM AUTHOR]

The complete nucleotide sequence of a satellite molecule associated with Malvastrum leaf curl Guangdong virus ( MLCuGdV) infecting M. coromandelianum plants exhibiting leaf curl symptoms in a suburb of Guangzhou, Guangdong Province of China, is described and analysed. The molecule has typical features of betasatellites, containing a single ORF in the complementary-sense strand, an A-rich region, the satellite-conserved region and a stem-loop structure. Compared with the geminivirus betasatellites in GenBank database, this molecule shows the highest nucleotide sequence identity of 71.9% with Tomato leaf curl Philippine betasatellite isolate Laguna1 (To LCPB, AB307732). Phylogenetic analysis indicates that it is more related to isolate Laguna 1 and Laguna 2 of To LCPB. According to the proposed species demarcation threshold of betasatellites (78% nucleotide identity), it is a novel betasatellite species, for which we propose the name Malvastrum leaf curl Guangdong betasatellite ( MLCuGdB). [ABSTRACT FROM AUTHOR]

From Synedrella nodiflora plants with leaf curling, vein swelling and enation symptoms on Samal Island, the Philippines, a begomoviral DNA-A and its associated alphasatellite molecule were cloned and sequenced. The begomovirus was identified as an isolate of Ageratum yellow vein China virus (AYVCNV) with 91% nucleotide sequence identity to AYVCNV-[P157] (EU487045), while the alphasatellite molecule was most closely related to tobacco curly shoot alphasatellite-Y99 (TbCSA-Y99, AJ579347) with 74.5% nucleotide sequence identity. The satellite molecule has the typical features of alphasatellites, with a single gene in the virion sense, an A-rich region and a 33-bp predicted stem-loop structure. According to the proposed species demarcation threshold of alphasatellites (83% nucleotide sequence identity), the alphasatellite molecule represents a new species, herein named 'Ageratum yellow vein China alphasatellite' (KF785752). [ABSTRACT FROM AUTHOR]

Background: Bacterial wilt (BW), caused by Ralstonia solanacearum species complex (RSSC), is considered as one of the most destructive plant diseases worldwide. In this study, two strains of Bacillus siamensis, BB605-1 and BB653, were screened and identified from endophytes in healthy tomato and mangrove plants, respectively., Results: Both strains demonstrated antagonistic activities against all 16 RSSC strains, representing eight sequevars from various hosts. The growth of RSSC was suppressed by the crude antimicrobial extracts produced by two strains. The pot inoculation experiment revealed the control efficiencies of two strains against tomato bacterial wilt as 59.63% and 63.98%, respectively. After imparting rifampicin resistance to the strains and applying them to tomato plants, both strains successfully established stable colonization in the rhizosphere, roots, stems, and leaves of tomato plants. Additionally, our study demonstrated that both strains exhibited significant plant growth-promoting properties. Complete genome sequencing revealed genome size of 3.868 M bp with 3594 protein-coding genes for BB605-1, and 3.857 M bp with 3600 protein-coding genes for BB653. Genome analysis of both strains identified seven secondary metabolite clusters with known antimicrobial properties and predicted three unknown compounds with potentially novel properties. Genome mining revealed several key genes associated with plant growth regulation, colonization, and biofilm formation, and we also detected these corresponding substances., Conclusions: These findings provide a compelling case for the application of B. siamensis in agricultural practices. The isolates' multiple capacities to colonize, enhance plant growth, and exert antagonistic effects against BW positions them as highly promising candidates for an integrated biological solution. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Tomato yellow leaf curl Guangdong virus (TYLCGdV), a monopartite begomovirus first identified in 2004, remains poorly characterised. In this study, we demonstrate that TYLCGdV associates with a betasatellite, TYLCGdB, and the βC1 protein encoded by TYLCGdB is essential for symptom development. We also explore the role of TYLCGdV C4 protein by generating a C4-deficient infectious clone (TYLCGdV mC4 ), revealing a dynamic role for TYLCGdV C4. Specifically, viral accumulation in TYLCGdV mC4 /TYLCGdB-inoculated plants was significantly lower than that in TYLCGdV/TYLCGdB-inoculated plants at 7 and 14 days post-inoculation (dpi), but surpassed that of TYLCGdV/TYLCGdB-inoculated plants by 25 dpi. Furthermore, although C4 proteins in other begomoviruses typically exhibit one or more of the following properties: (i) suppression of post-transcriptional gene silencing (PTGS), (ii) suppression of transcriptional gene silencing (TGS), (iii) enhancement of pathogenicity in potato virus X (PVX) and (iv) symptom induction when transgenically expressed, TYLCGdV C4 did not exhibit any of these properties. However, the dynamic role of TYLCGdV C4 in viral infection appears to result from its effects on viral DNA methylation. At 7 dpi, the cytosine methylation level in the TYLCGdVmC4 genome was notably elevated compared to that of the wild-type virus. However, this trend reversed by 14 dpi, with the wild-type virus exhibiting a higher methylation level. By 25 dpi, the cytosine methylation levels of both TYLCGdVmC4 and TYLCGdV were comparable. These results indicate that TYLCGdV C4 modulates viral infection via an unconventional mechanism. This novel observation highlights the need for further investigation into the diverse roles of C4 proteins in begomoviruses., (© 2025 The Author(s). Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

First report of tomato yellow mottle-associated virus infecting Solanum nigrum in China Zhenggang Li, Yafei Tang, Xiaoman She, Guobing Lan, Lin Yu, and Zifu He† Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, P. R. China. Tomato yellow mottle-associated virus (TYMaV) is a newly found cytorhabdovirus associated with epinasty of leaflet blades, yellow spots, puckering, and mottling symptoms in tomato plants in China (Xu et al., 2017). In May 2020, Solanum nigrum plants exhibiting leaf crinkling and mosaic symptoms (eXtra S1) were found in Shantou city, Guangdong, China. To identify the causal pathogens, the leaves of three symptomatic plants were collected and subjected to total RNA extraction with TRIzol Reagent (Takara, Kusatsu, Japan). About 100 μg RNA mixture, which consisted of an equal amount of total RNA extracted from the three samples, was subjected to small RNA deep sequencing and assembly (sRSA) (Kreuze et al., 2009). Small RNA cDNA library was constructed with the method described previously (Mi et al., 2008). Small RNA deep sequencing was performed with Illumina HiSeq X Ten platform. VirusDetect (Zheng et al., 2017) was used to analyze the sequence data. The result showed that the sequence data includes about 11 million reads and generated 194 unique contigs after removal of host-derived contigs. Subsequently, the unique contigs were screened using BLASTn search against the virus database. One hundred and five unique contigs were mapped to TYMaV genome (reference sequence, KY075646), 21 unique contigs were mapped to RNA1 segment of tomato chlorosis virus (ToCV) genome (reference sequence, KY618796), 67 unique contigs were mapped to RNA2 segment of ToCV genome (reference sequence, KY618797), and one unique contig was mapped to pepper veinal mottle virus (PVMV) genome (reference sequence, FJ617225) (eXtra S1). To verify the sRSA result for TYMaV detection, RT-PCR was performed with two primer pairs TYMaV-F1/R1 (5'-TCATTAGACTCAGGCCTAATCCTCA AAGT-3'/5'-GATATGGAGACGTCCAAGTTCAAAGGGATGGA-3'), and TYMaV-F2/R2 (5'-TATGCGGCAGCTTTCATGTCTATAGACCCT-3'/5'-ATGACCTAGCTTCAATAACAGTCGCG-3'), which are designed according to the sRSA result. All the symptomatic samples tested positive for TYMaV (eXtra S2). Western blot with TYMaV N protein-specific antibody further verified the result (eXtra S2). To obtain the nearly full-length sequence of TYMaV identified in Shantou, 13 primer pairs were designed to amplify the viral fragments. The amplified PCR products were then introduced into pMD19T (Takara, Kusatsu, Japan) and sequenced by Sangon Biotech Co. (Shanghai, China). The nearly full-length sequence of TYMaV Shantou isolate (TYMaV-ST) was assembled from the 13 overlapping sequences (reference sequence, MW527091). TYMaV-ST genome comprises of 13401 nt and shares 84.93% nucleotide sequence identity with the reference genome (KY075646). In addition, 37 S. nigrum samples and 20 tomato samples nearby with viral disease symptoms were collected from different sites of Guangdong province, China. Six S. nigrum samples and five tomato plant samples tested positive for TYMaV by RT-PCR, suggesting a wide spread of the virus in the surveyed region. These results together with those of the sRSA assay also suggest that the disease symptoms shown in the original S. nigrum plants may not necessarily be caused by TYMaV or by TYMaV alone. To our knowledge, this is the first report of TYMaV infecting S. nigrum in China. S. nigrum is a common weed which belongs to the family Solanaceae and may serve as a reservoir for TYMaV in the fields. Further research is needed to verify whether this is indeed the case, and to understand the characteristics of this virus including its transmission, pathogenicity, and economic significance. The authors declare no conflict of interest. Funding This work was supported by the Key Research and Development Program of Guangdong Province (2018B020202006), the Agricultural Competitive Industry Discipline Team Building Project of Guangdong Academy of Agricultural Sciences (202103TD and 202105TD), the Science and Technology Program of Guangzhou (202102020504), and Special Fund for Scientific Innovation Strategy-Construction of High-Level Academy of Agriculture Science (R2019PY-QF003). References: Kreuze, J. F., et al. 2009. Virology. 388: 1. Mi, S., et al. 2008. Cell. 133: 116. Xu, C., et al. 2017. J Virol. 91: 11. Zheng, Y., et al. 2017. Virology. 500: 130.