Tomato leaf curl New Delhi virus (ToLCNDV) poses a significant threat to cucurbit crops, causing severe yield losses. While being well documented in southern China, it has been found on melon, cucumber, and smooth luffa crops in Shandong Province of northern China for the past 2 years. Field surveys on symptomatic plants further confirmed its widespread occurrence and significant impact on these economically important crops. Whole-genome sequencing of the DNA-A and DNA-B components revealed over 99% sequence homology among the strains isolated from all three hosts. The phylogenetic analysis of sequencing data further confirmed that cucumber and smooth luffa strains clustered most closely with other Chinese ones, whereas the strain isolated from melons exhibited a closer evolutionary relationship to Indian isolates. A set of loop-mediated isothermal amplification (LAMP) primers targeting the conserved regions of DNA-A was designed, and an assay integrating the heat-labile uracil-DNA glycosylase (UDG) and lateral flow dipstick (LFD) was developed for rapid and visualized ToLCNDV detection. The optimal reaction conditions consisted of a 5-min incubation at 30°C, followed by an incubation at 62°C for 50 min. The assay was 10-fold more sensitive than conventional PCR with no cross-reactions detected among other cucurbit viruses. Therefore, the UDG-LAMP-LFD assay developed in this study provides a dependable diagnostic tool for the surveillance of ToLCNDV and the early detection of the virus on cucurbit seedlings.

Two phylogenetically unrelated viruses transmitted by different insect vectors, tomato spotted wilt virus (TSWV) and tomato yellow leaf curl virus (TYLCV), are major threats to tomato and other vegetable production. Although co‐infections of TSWV and TYLCV on the same host plant have been reported on numerous occasions, there is still lack of research attempting to elucidate the mechanisms underlying the relationship between two viruses when they coexist in the same tomato or other plants. After assessing the effect of four TSWV‐coded proteins on suppressing TYLCV in TSWV N transgenic Nicotiana benthamiana seedlings, the TSWV N protein proved to be effective in reducing TYLCV quantity and viral symptoms. Western blot analysis indicated that TSWV N was involved in down‐regulating the expression level of the V1, C3, and C4 proteins of TYLCV, among which V1 was the most significantly suppressed one. Moreover, TSWV N was confirmed to reduce TYLCV V1 within both nucleus and cytoplasm, but a greater suppression was observed in cytoplasm. The co‐immunoprecipitation and mass spectrometry identified 244 differential proteins from the TYLCV‐infected TSWV N transgenic N. benthamiana seedling. These proteins pertaining to energy metabolism pathways were enriched, suggesting that TSWV N could inhibit TYLCV through competing for energy or regulating energy‐related metabolism. The evidence presented here offers a novel perspective that will facilitate a comprehensive understanding of virus–virus and virus–host interactions, as well as a potential strategy for plant virus control through using TSWV N in the near future.

Watermelon silver mottle virus (WSMoV), a potentially invasive virus, is known to reduce the yield and degrade the quality of infected crops in Cucurbitaceae and Solanaceae families, resulting in significant economic losses in limited areas of several Asian countries. WSMoV, previously detected on various crops in southern China, has now become more prevalent on watermelon and sweet pepper in the northern cities of China for the first time. A sequencing-based phylogenetic analysis has confirmed that the viral strains infecting cucumber, watermelon, and sweet pepper plants in Shandong Province are most closely related to those isolated from Guangdong, Guangxi, and Taiwan, suggesting a farther and continuous spread of WSMoV throughout China. To develop a fast, accurate, and practical protocol for WSMoV detection, we designed a set of primers from the conserved sequence of the WSMoV nucleocapsid protein (N) gene for a one-step assay based on reverse transcription loop-mediated isothermal amplification (RT-LAMP). The RT-LAMP assay was performed successfully for 50 min at 61°C and exhibited a highly specific result without cross-reactions with other similar viruses and a sensitivity that is 100-fold higher than that of the traditional RT-PCR. The confirmation of 26 WSMoV suspect samples collected from various regions in Shandong through the RT-LAMP testing has demonstrated that the assay is suitable and practical for detection of WSMoV in both laboratory and field settings.

Stemphylium lycopersici is the causal pathogen of the devastating tomato gray leaf spot with a wide range of alternative plant hosts. To mitigate its potential endemic in facility-cultivated tomatoes, novel disease control strategies should be attempted to minimize the use of chemical fungicides. In this study, we identified a metalloprotease from S. lycopersici genome and designated it as SlMEP1, as it appears to be a typical zinc metalloproteinase containing a WLM (WSS1-like metalloprotease) domain and a characteristic HEXXH motif, which we determined by analyzing its transcriptional profile and enzymatic functions. The transcription level of SlMEP1 increased greatly during the fungal invasion of tomato leaves. The deletion of the SlMEP1 gene from S. lycopersici hindered its mycelial growth and reduced its pathogenicity. An assessment of the functional dissection indicated that SlMEP1 induced cell collapse and inhibited the expression of the host chitinases, which consequently made tomato cells more susceptible to S. lycopersici and other pathogenic fungi.