Some properties of a previously undescribed virus from cassava: Cassava American Latent Virus

Abstract

A virus with spherical particles c. 28 nm in diameter was sap-transmitted from different cassava (Manihot esculenta) cultivars to a limited range of species in the families Chenopodiaceae and Solanaceae. Cassava seedlings infected by inoculation with sap or with purified virus preparations did not show any symptom, although the virus was readily detected by ELISA or by further inoculations. Leaf extracts from infected Nicotiana benthamiana were infective after dilution of but not 10-4, and after heating for 10 min at 70°C, but not at 72°C. The virus was purified from N . benthamiana, N. clevelandii or from cassava. On sucrose gradients, the virus particles sediment as three components all containing a protein of mol. wt c. 57 OOO. The genome of the virus is composed of two RNAs of mol. wt c. 2.54 x lo6 (RNA-1) and 1.44 x 106 (RNA-2). RNA-2 was detected in the middle and the bottom nucleoprotein components, and RNA-1 only in the bottom component. An antiserum prepared to purified virus particles was used to readily detect the virus in cassava and other host plants by ELISA and by ISEM. No serological relationship was shown between this virus and eight nepoviruses, including the recently described cassava green mottle nepovirus infecting cassava in the Solomon Islands (Lennon, Aiton & Harrison, 1987). The virus described here is the first nepovirus isolated from cassava in South America, and is named cassava American latent virus.

Unraveling complex viral infections in cassava (Manihot esculenta Crantz) from Colombia

“…5A). Similar experiments could not be performed with CsALV due to the lack of inoculum, however unlike CsALV (Walter et al, 1989), CsTLV caused LS in 'Secundina' in the absence of the other viruses as determined in two independent assays (Fig. 4A).…”

“…Cassava virus studies in the Americas have focused on the properties of isolated viruses and have given little attention to virus interactions in mixed infections in terms of variety of symptoms, disease severity and effect on yield (Lennon et al, 1987;Aiton et al, 1988;Walter et al, 1989;Calvert et al, 1995). Some of these viruses have been associated with distinct LS (e.g., CsCMV, CsVMV) and at least one of them to severe RS (CsFSaV).…”

“…Some of these viruses have been associated with distinct LS (e.g., CsCMV, CsVMV) and at least one of them to severe RS (CsFSaV). The potexviruses CsCSLV, CsALV, 'Cassava symptomless virus' (CsSLV) and CsVX (Table 3) are not associated with LS or RS (Kitajima and Costa, 1979;Lennon et al, 1986;Walter et al, 1989). However, the result of their mixed infections with heterologous viruses has not yet been investigated.…”

“…Other virus particles reported in cassava are the isometric members of the family Secoviridae, CsGMV and Cassava American latent virus (CsALV; Genus Nepovirus), which have been previously characterized but not at sequence level (Lennon et al, 1987;Walter et al, 1989). We have preliminarily completed a region of 1980 nt of the RNA1 segment (GenBank: KC 505250) and 2992 nt of the RNA2 segment (GenBank: KC 505251) of a member of the Secoviridae family.…”

Cassava

“…The casual agent of frogskin disease is not known, but a virus is suspected because the disease is graft-transmissible. There is only one report of Cassava American latent virus from Brazil and Guyana, and little is known of its distribution (Walter et al 1989). They have been detected only in Colombia.…”