Characterization of a Virus from Pigeonpea with Affinities to Species in the Genus Aureusvirus, Family Tombusviridae

Abstract

In attempts to identify the causal agent of pigeonpea sterility mosaic disease (PSMD), which is transmitted by eriophyid mites, a virus was isolated with great difficulty from some PSMD-affected pigeonpea (Cajanus cajan) plants from different locations in India. Once isolated from pigeonpea, the virus was transmitted readily by mechanical inoculation to several herbaceous species, reaching very high concentrations in some species. The virus was transmitted experimentally through soil to herbaceous test plants but not to pigeonpea. When virus particles were purified and inoculated mechanically to healthy pigeonpea, the virus induced necrosis in inoculated leaves only and did not spread systemically. Therefore, the virus is not the causal agent of PSMD. The virus has isometric particles approximately 30 nm in diameter that sediment as a single component and had a buoyant density in CsCl and Cs2SO4 of 1.34 and 1.27 g·cc-1, respectively. Purified virus particle preparations contained a single major protein of approximately 44 kDa and three RNA species of approximately 4,300, 2,700, and 1,500 nucleotides. Only the largest RNA species was infective to plants; the two smaller species were encapsidated subgenomic species of the 3′ end of the larger genomic RNA. The viral genome was sequenced and showed 93% homology to that of Pothos latent virus (PoLV), a recently described virus in the genus Aureusvirus, family Tombusviridae, and was indistinguishable from PoLV in gel double-diffusion serological tests. This virus, therefore, is regarded as a pigeonpea isolate of PoLV (PoLV-PP). In field studies in different locations in India, enzyme-linked immunosorbent assay and reverse-transcriptase polymerase chain reaction detected PoLV-PP in 10.7% of PSMD-affected and 8.1% of asymptomatic pigeonpea plants. The significance of these findings is discussed.

Molecular characterization of emaraviruses associated with Pigeonpea sterility mosaic disease

“…Leaf samples were plucked in labelled separate Ziploc bags placed in ice chest with dry ice and transported to the lab. SMD infected pigeonpea samples from the field may be infected by other viruses as low and rare incidences of other viral infections 67 , 68 have been reported. In addition, Tobacco streak virus (TSV) has been reported affecting pigeonpea plants in the fields 69 .…”

A Novel Mite-Transmitted Virus with a Divided RNA Genome Closely Associated with Pigeonpea Sterility Mosaic Disease

“…Purified viral RNA (2 µg) was mixed with 4.5 µg of random hexamers (Promega) and the mixture was denatured with 20 mM methyl mercuric hydroxide for 30 min at room temperature and quenched on ice for 10 min. The mixture then was used for cDNA synthesis using the Universal Riboclone Synthesis kit (Promega) and cloned into the pCR4-Blunt TOPO vector (Invitrogen) as described previously (27). Recombinant clones were screened for inserts and clones containing inserts of >400 bp were isolated using the QIAminiprep kit (Qiagen) and sequenced by dideoxy sequencing using the Universal M13 forward and reverse primers as described previously (25).…”

“…A purification procedure to minimize the influence of such components before inoculation onto herbaceous test plants led to the isolation of an Aureusvirus from pigeonpea (27), but this virus was present in only some SMD-infected plants and also in healthy plants (27). Simultaneously, attempts were made to isolate and purify the SMD causal agent directly from SMD-affected pigeonpea using methods for isolating viruses from woody plants or for unstable viruses.…”

Identification and Characterization of Pothos latent virus Causing Necrotic Ringspots and Line Patterns on Lisianthus (Eustoma grandiflorum) in Taiwan

“…; Kumar et al. ). Among 18 plant species tested, symptom development after challenging with PoLV‐Lis was very similar to that caused by PoLV‐pothos isolate.…”

“…) and pigeonpea ( Cajanus cajan ) (Kumar et al. ). PoLV has biological and ecological properties similar to those of members of the family Tombusviridae; however, PoLV has very different physiochemical properties from those of genera Tombusvirus and Carmovirus (Martelli et al.…”