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Papaya sticky disease, caused by Papaya meleira virus (PMeV), results in complete crop loss in papaya orchards, because infected fruits are unacceptable for consumption. Little is known about sticky disease epidemiology, and the best available strategy for disease management is to rogue infected plants. Identification of alternative hosts for this virus is important for developing control strategies. In Mexico, papayas and watermelons are often cultivated in close proximity or overlapping cycles, which may favor virus interspecies transmission by putative insect vectors of PMeV. Watermelon seedlings (Citrullus lanatus Thunb.) were inoculated with latex from papayas infected with a Mexican variant of PMeV (PMeV-Mx), and infection was confirmed by reverse transcription-PCR (RT-PCR) and quantitative RT-PCR (RT-qPCR). Amplicons (491 bp) of the RNA-dependent RNA polymerase (RdRp) gene of PMeV-Mx were detected in axillary leaves of all inoculated seedlings seven days post-inoculation (dpi). Circa 10 to 12 dpi, necrotic lesions were observed on the edges of the leaves. Absolute quantification of PMeV-Mx-RNA by RT-qPCR showed an increase in viral load over time (from 0.51 to 586.15 pg/μL), three to 14 dpi. Molecular and experimental evidence demonstrate is also a host for PMeV-Mx and may be an alternative host. [ABSTRACT FROM AUTHOR]

Aims: To determine the seasonal occurrence and diversity of norovirus (NoV) and human adenovirus (HAdV) in groundwater from sinkholes, and brackish water used for recreational activities in the karst aquifer of the Yucatan Peninsula, Mexico., Methods and Results: Hollow fibre ultrafiltration was used to concentrate viruses and standard plaque assay methods were used to enumerate somatic and F+ specific coliphages as viral indicators. Real-time quantitative polymerase chain reaction assays were used to estimate the number of genome copies for NoV strains GI, and GII, and HAdVs. The predominant NoV genotypes and HAdV serotypes were identified by comparative sequence analysis. Somatic and male F+ specific coliphages were detected at concentrations up to 94 and 60 plaque-forming units per 100 ml respectively. The NoV genogroup I (GI) was associated with 50% of the sampled sites during the rainy season only, at concentrations ranging from 120 to 1600 genome copies per litre (GC l -1 ). The NoV genogroup II (GII) was detected in 30 and 40% of the sampled sites during the rainy and dry seasons, respectively, at concentrations ranging from 10 to 290 GC l -1 . During the rainy and dry seasons, HAdVs were detected in 20% of the sites, at concentrations ranging from 24 to 690 GC l -1 . Identification of viral types revealed the presence of NoV GI.2, GII.Pe, GII.P16 and GII.P17, and HAdV F serotypes 40 and 41., Conclusions: These findings demonstrate that NoVs and HAdVs are prevalent as virus contaminants in the karst aquifer, representing potential health risks particularly during the rainy season, in one of the most important areas used for tourism in Mexico., Significance and Impact of the Study: This is one of the few studies conducted in karst aquifers that provide a foundational baseline of the distribution, concentrations and diversity of NoVs and HadVs in these particular environments., (© 2019 The Society for Applied Microbiology.)

Papaya meleira disease was identified in Brazil in the 1980s. The disease is caused by a double-stranded RNA virus known as Papaya meleira virus (PMeV), which has also been recently reported in Mexico. However, previously reported PMeV primers failed to diagnose the Mexican form of the disease. A genomic approach was used to identify sequences of the Mexican virus isolate, referred here to as PMeV-Mx, to develop a diagnostic method. A mini cDNA library was generated using total RNA from the latex of fruits; this RNA was also sequenced using the Illumina platform. Sequences corresponding to the previously reported 669-base pair sequence for PMeV from Brazil (PMeV-Br) were identified within the PMeV-Mx genome, exhibiting 79-92% identity with PMeV-Br. In addition, a new sequence of 1154-base pairs encoding a putative RNA-dependent RNA polymerase was identified in PMeV-Mx. Primers designed against this sequence detected both virus isolates, 2 amplicons of 173 and 491 base pairs from PMeV-Br and PMeV-Mx, and shared 100 and 98% identity, respectively. PMeV-Mx was found in the latex of fruits, in seedlings, and in the leaves, flowers, petioles, and seeds of mature plants. PMeV-Mx was more abundant in the latex of fruits than in the leaves. The limit of detection of the CB38/CB39 primer pair was 1 fg and 1 pg using total RNA extracted from the latex of fruits and from seedlings, respectively. A sensitive and early diagnosis protocol was developed; this method will enable the certification of seeds and seedlings prior to transplantation to the field.