ABSTRACT
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.
Subject(s)
Cucurbitaceae/virology , Genome, Viral , Potyviridae/genetics , RNA, Viral/genetics , Sequence Analysis, DNA , Cluster Analysis , Host Specificity , Phylogeny , Plant Diseases/virology , Potyviridae/isolation & purification , Potyviridae/physiology , Prevalence , Sequence Homology , SudanABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
