Comparison of Colombian and Costa Rican strains of rice hoja blanca tenuivirus

Association of a Virus with Wheat Displaying Yellow Head Disease Symptoms in the Great Plains

Wheat with yellow head disease (YHD) (yellow heads and mosaic leaf symptoms) has been observed in Kansas since 1997. A pathogen was transmitted from the infected wheat to maize by vascular puncture inoculation and to Nicotiana benthamiana by rub inoculation. The original infected wheat and infected maize and N. benthamiana test plants all produced a unique 32- to 34-kDa protein when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Time-of-flight mass spectrometry analysis of the unique 32- to 34-kDa protein showed that the amino acid sequence was most closely related to the nucleoprotein of Rice hoja blanca virus, indicating that the virus causing YHD symptoms in wheat is a tenuivirus. Antiserum made to this protein failed to react with extracts made from healthy wheat or wheat infected with Wheat streak mosaic virus or the High Plains virus. The antiserum did react to extracts made from symptomatic wheat, maize, and N. benthamiana, shown by SDS-PAGE to contain the unique protein, and to extracts of wheat with YHD symptoms from Kansas, North Dakota, South Dakota, and Oklahoma. The name Wheat yellow head virus is proposed for this virus.

Phylogenetic placement of a novel tenuivirus from the grass Urochloa plantaginea

Evidence is presented that a tenuivirus recovered from the grass Urochloa plantaginea is probably a novel tenuivirus species, to be called Urochloa hoja blanca virus (UHBV). It is related to both Echinochloa hoja blanca virus (EHBV) and Rice hoja blanca virus (RHBV), and these three form a group distinct from Maize stripe virus (MStV) and Rice stripe virus (RStV). Phylogenetic analysis of the sequence data for RNA-3 and RNA-4 of these viruses supports the hypothesis that EHBV and UHBV may have evolved from an ancestral form of RHBV, precipitated by the introduction of Echinochloa colona and Urochloa plantaginea to America.

Comparison of nucleotide sequences between northern and southern philippine isolates of rice grassy stunt virus indicates occurrence of natural genetic reassortment

Rice grassy stunt virus is a member of the genus Tenuivirus, is persistently transmitted by a brown planthopper, and has occurred in rice plants in South, Southeast, and East Asia [corrected]. We determined the complete nucleotide (nt) sequences of RNAs 1 (9760 nt), 2 (4069 nt), 3 (3127 nt), 4 (2909 nt), 5 (2704 nt), and 6 (2590 nt) of a southern Philippine isolate from South Cotabato and compared them with those of a northern Philippine isolate from Laguna (Toriyama et al., 1997, 1998). The numbers of nucleotides in the terminal untranslated regions and open reading frames were identical between the two isolates except for the 5' untranslated region of the complementary strand of RNA 4. Overall nucleotide differences between the two isolates were only 0.08% in RNA 1, 0.58% in RNA 4, and 0.26% in RNA 5, whereas they were 2.19% in RNA 2, 8.38% in RNA 3, and 3.63% in RNA 6. In the intergenic regions, the two isolates differed by 9.12% in RNA 2, 11.6% in RNA 3, and 6.86% in RNA 6 with multiple consecutive nucleotide deletion/insertions, whereas they differed by only 0.78% in RNA 4 and 0.34% in RNA 5. The nucleotide variation in the intergenic region of RNA 6 within the South Cotabato isolate was only 0.33%. These differences in accumulation of mutations among individual RNA segments indicate that there was genetic reassortment in the two geographical isolates; RNAs 1, 4, and 5 of the two isolates came from a common ancestor, whereas RNAs 2, 3, and 6 were from two different ancestors.