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Cucurbit-infecting tobamoviruses known so far belong to six acknowledged or tentative species. Except for cucumber green mottle mosaic virus (CGMMV), which is present worldwide, they are geographically restricted, mostly to Asia, and have not been observed in Africa so far. A tobamovirus isolate infecting a wild Coccinia grandis plant was collected in central Sudan in 2012. Its host range appeared to be mostly limited to cucurbits. Its full-length genome sequence was determined and found to be 85% identical to those of isolates of cucumber fruit mottle mosaic virus (CFMMV) described in Israel and Korea, whereas the aa sequence identity to CFMMV isolates was 92 to 95%, depending on the protein. Based on its biological and molecular properties, we suggest that the Sudanese isolate should be considered a divergent isolate of CFMMV. This is the first description of CFMMV in Africa. Its high divergence from isolates from Israel and Korea suggests a lack of recent exchanges between CFMMV from Sudan and the other known populations.

The "Papaya ringspot virus (PRSV) cluster" of cucurbit-infecting potyviruses contains five acknowledged species that have similar biological, serological and molecular properties. Additional data suggest there are other uncharacterized species from various locations in the world that likely belong to the PRSV cluster including a new PRSV-like virus reported from Sudan in 2003. Molecular and biological data indicated that the virus from Sudan belongs to a new species, tentatively named wild melon vein banding virus (WMVBV). The complete nucleotide sequence of a second virus from Sudan revealed it was a divergent relative of Moroccan watermelon mosaic virus (MWMV). Based on sequence similarity this virus was determined to be a distinct species and tentatively named Sudan watermelon mosaic virus (SuWMV). Molecular analyses indicate that SuWMV is a recombinant between WMVBV- and MWMV-related viruses. Based on surveys performed in Sudan between 1992 and 2012, SuWMV appeared 10 times more frequent than WMVBV in that country (14.6% vs. 1.5% of the samples tested). The geographic structure and molecular diversity patterns of the putative and acknowledged species suggest that the PRSV-like cluster originated in the Old World about 3600 years ago, with an important diversification in Africa., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Two members of the genus Ipomovirus (family Potyviridae) are known to infect cucurbits: cucumber vein yellowing virus (CVYV), which is emerging throughout the Mediterranean Basin, and squash vein yellowing virus (SqVYV), which has been described in America and the Caribbean Basin, and more recently in Israel. In this work, an ipomovirus different from CVYV and SqVYV, tentatively named coccinia mottle virus (CocMoV), was detected in a sample of the cucurbit Coccinia grandis collected in central Sudan in 2012. Sequence identity in nt was 68 % with CVYV, 59-60 % with SqVYV, cassava brown streak virus and Ugandan cassava brown streak virus, and less than 50 % with other members of the family Potyviridae. Preliminary biological and epidemiological studies indicate that CocMoV has a narrow natural host range and a low prevalence.

During a survey conducted in Sudan in 2012, a virus with spherical particles was isolated from a squash plant showing chlorotic leaf spots. The virus was transmitted mechanically and by two whitefly species, but not by aphids. RT-PCR with generic torradovirus primers yielded a band of expected size from total RNA of a symptomatic plant. Next-generation sequencing confirmed that this is tentatively a new torradovirus, for which we propose the name 'squash chlorotic leaf spot virus'. Using specific RT-PCR primers, the virus was detected in cucurbit samples collected since 1992 at different locations in Sudan.

In summer 2009, a survey for virus diseases in cucurbits was conducted in open fields and plastichouses in Khartoum State, the most important growing area for cucurbits in Sudan. Chlorosis and yellowing symptoms on middle and lower leaves were observed on many muskmelon (Cucumis melo L.) plants grown in open fields in the Assilat agricultural scheme and on approximately 80% of the cucumber (Cucumis sativus L.) plants grown in plastichouses in Khartoum North. Large populations of whiteflies (Bemisia tabaci L.) were present in both locations. Leaf symptoms that were observed were similar to those caused by Cucurbit chlorotic yellows virus (CCYV), a recently described new Crinivirus species infecting cucurbits in Japan (4), indicating presence of this virus previously only reported from Japan, Taiwan (2), and China (1). Samples from seven symptomatic muskmelon leaves were collected from individual plants grown in different open fields in Assilat and from a symptomatic cucumber plant grown in a plastichouse. Total RNA was extracted from these samples with the RNeasy Plant Mini Kit (QIAGEN, Hilden, Germany) to amplify putative CCYV sequences with primers (Crini-s2 5'-CATTCCTACCTGTTTAGCCA and Crini-as2 5'-TGCACTTATAATCTGCTGGTAC) designed from CCYV sequences available at GenBank. A 353-bp DNA fragment of the HSP70 gene was amplified by reverse transcription (RT)-PCR for all samples. Further analysis by direct sequencing of two PCR products showed 99 to 100% nt sequence identity to Asian CCYV isolates. Amplification of the coat protein sequence with the primer pair (CCYV-CPs 5'-ATGGAGAAGACTGACAATAAACAA and CCYV-CPas 5'-TTTACTACAACCTCCCGGTG) followed by cloning and sequencing yielded a 760-bp fragment having 99% nucleotide sequence identity to all Asian isolates. For confirmation, dsRNA preparations of symptomatic muskmelon tissue (collected in June 2010) were made, showing dsRNA patterns typical for criniviruses after separation on agarose gels. This dsRNA was used as template for random RT-PCR followed by sequencing of the cloned PCR products (3). Comparison with sequences available at GenBank revealed that cDNA sequences from dsRNA also were 99 to 100% identical to the CCYV genome sequence (AB523788.1). Whitefly transmission of the virus was confirmed by giving a population of B. tabaci an acquisition access period of 24 h and a further 24 h on muskmelon and cucumber seedlings. Symptoms were observed after 5 to 7 days, and the presence of CCYV was confirmed by RT-PCR. In conclusion, symptoms, RT-PCR, and dsRNA sequencing results confirm the presence and establishment of CCYV in cucurbit crops in Sudan. It is remarkable that the sequences obtained from the Sudanese samples show only negligible sequence differences from Asian isolates. Because of the large whitefly vector populations, the spread of CCYV to neighboring countries in Africa and potentially southern Europe, or wherever cucurbits are grown, can be expected. To our knowledge, this is the first report of CCYV in Sudan and outside Eastern Asia. The sequences obtained in this study have been submitted to GenBank under Accession Nos. JF807053 to JF807055. References: (1) Q. S. Gu et al. Plant Dis. 95:73, 2011. (2) L. H. Huang et al. Plant Dis. 94:1168, 2010. (3) W. Menzel et al. Arch. Virol. 154:1343, 2009. (4) M. Okuda et al. Phytopathology 100:560, 2010.

A virus isolate (Su-95-67) was obtained from a snake melon (Cucumis melo var. flexuosus) plant presenting severe chlorotic spots, mosaic, stunting, and leaf deformations collected in Eastern Sudan in 1995. Su-95-67 was easily mechanically transmissible and had a host range limited to a few cucurbit species. Isometric virus particles approximately 30 nm in diameter were observed in leaf dip preparations. A cytopathological study did not reveal alterations specific for a virus genus or family. A polyclonal antiserum was obtained and used in double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Su-95-67 was transmitted by seed at a low rate, by the red melon beetle (Aulacophora foveicollis), but not by the melon aphid (Aphis gossypii). Because Su-95-67 shared several properties with sobemoviruses, generic Sobemovirus reverse-transcription polymerase chain reaction primers were developed. They allowed amplification of a 384-bp fragment from extracts of plants infected by two sobemoviruses or by Su-95-67 but not from healthy plants extracts. Sequence comparison confirmed that Su-95-67 belongs to a new tentative Sobemovirus species for which we propose the name Snake melon asteroid mosaic virus (SMAMV). DAS-ELISA tests conducted on extracts of virus-infected cucurbit plants collected from 1992 to 2003 revealed the presence of SMAMV in 10.2% of 600 samples originating from different regions of Sudan.

A potyvirus (Su-94-54) was isolated from a naturally infected snake cucumber (Cucumis melo var. flexuosus) plant with severe mosaic and leaf deformation symptoms collected in Eastern Sudan. This isolate has a host range limited to cucurbits and is serologically distantly related to Moroccan watermelon mosaic virus (MWMV) and to Papaya ringspot virus (PRSV). Coat protein sequence analysis of Su-94-54 and MWMV and comparison with other potyviruses indicate that Su-94-54 is more closely related to MWMV than to any other potyvirus. Based on the amino acid sequence identity in the core part of the coat protein with MWMV (86%), this isolate could be regarded as a distinct species. However, because of biological, cytological, and serological affinities with MWMV, we propose that this isolate be considered as a strain of MWMV, possibly an evolutionary intermediate between MWMV and PRSV, until more is known on the structure of the PRSV subgroup within the genus Potyvirus.

Melon rugose mosaic virus (MRMV) was isolated from snake cucumber (Cucumis melo var. flexuosus) in the Kassala region of Sudan in 1993. The host range of the virus was mostly limited to cucurbits, where it induced severe mosaic and leaf deformations. Cytopathological studies revealed severe chloroplast alterations, including vesicles at their periphery and the tendency to aggregate, which are typical of tymovirus infections, providing further evidence that MRMV is a tentative member of the genus Tymovirus. In melon and snake cucumber, MRMV was found to be seed transmitted at rates of 0.9 and 3.8%, respectively. Seed dissection experiments revealed that the virus could be detected in the seed coat, papery layer, and embryo. Seed disinfection treatments did not reduce seed transmission rates, which suggests an internal transmission. A preliminary screening for resistance in melon revealed some resistance in two out of 367 accessions tested.