ABSTRACT
A new virus species, belonging to the family Potyviridae and capable of infecting most of the soybean cultivars grown in Brazil, was collected in Lavras, Minas Gerais, Brazil, and named Soybean yellow shoot virus (SoyYSV). In this study, the complete 9,052-nucleotide genome of SoyYSV was determined and the structural, biological, and molecular properties of the virus were investigated. The SoyYSV genome encoded a single polyprotein that could be subsequently cleaved, generating 11 proteins. The SoyYSV genome shared 49% nucleotide and 36% amino acid sequence identity with Blackberry virus Y. However, the P1 protein of SoyYSV was much smaller and lacked the ALK1 domain characteristic of the genus Brambyvirus. Electron microscopy revealed flexuous filamentous virus particles, 760 to 780 nm in length, and cytoplasmic inclusions typical of those found in plant cells infected with Potyviridae species. In addition to soybean, SoyYSV infected species in the Amaranthaceae, Caricaceae, Fabaceae, and Solanaceae families. Among the most common potyviruses present in Brazil, only SoyYSV induced local necrotic lesions in Carica papaya L. SoyYSV was transmissible by Myzus persicae and Aphis gossypii but lacked the HC-Pro domain required for aphid transmission in other potyviruses. No seed transmission in soybean was observed.
Subject(s)
Genome, Viral , Glycine max , Potyviridae , Brazil , Genome, Viral/genetics , Phylogeny , Potyviridae/classification , Potyviridae/genetics , Glycine max/virology , Viral Proteins/chemistry , Viral Proteins/geneticsABSTRACT
In Brazil, Potato virus Y (PVY) currently presents a significant problem for potato production, reducing tuber yield and quality. Recombinant tuber necrotic isolates of PVY had been reported to occur in the country but no systematic study of the PVY isolate diversity was conducted thus far. Here, a panel of 36 PVY isolates, randomly collected in Brazil from potato between 1985 and 2009, was subjected to a systematic molecular and serological typing using reverse-transcription polymerase chain reaction and a series of PVYO- and PVYN-specific monoclonal antibodies. The data collected were combined with biological characterization of the same isolates in tobacco. Of the 36 isolates tested, 3 were typed as PVYO, 10 as PVYN:O/N-Wi, 21 as PVYNTN, and 2 as "unusual" or inconclusive. Of the 10 isolates from the recombinant PVYN:O/N-Wi strain group, 1 isolate, MAF-VOY, was found to have an unusual serological profile identical to the nonrecombinant PVYO-O5 strain group. The 21 tested PVYNTN isolates included 1 isolate that did not induce vein necrosis in tobacco and 2 isolates with an unusual serological profile (i.e., displaying negative reactivity to one commercial PVYN-specific monoclonal antibody). Whole genome sequences were determined for four PVY isolates from Brazil, representing PVYO, PVYNTN, and PVYN-Wi strains. The genome of the MAF-VOY isolate was found to be recombinant, having characteristic N-Wi structure with two recombinant junctions and carrying a single mutation in the capsid protein at position 98, which led to an unusual O5 serological reactivity. Taken together, the data obtained suggest that the two recombinant strains, PVYNTN and PVYN:O/N-Wi, now are apparently dominant in the Brazilian potato crop. The data also suggest that recombinant isolates in Brazil often have unusual serological reactivity which may hamper their correct identification by conventional typing based on enzyme-linked immunosorbent assay.
