The Genetic Basis of High Resistance to Rice Yellow Mottle Virus (RYMV) in Cultivars of Two Cultivated Rice Species

Three cultivars of Oryza sativa (IR64, Azucena, and Gigante) and four cultivars of O. glaberrima (Tog5681, Tog5673, CG14, and SG329) were evaluated for their resistance to two isolates of rice yellow mottle virus (RYMV) by enzyme-linked immunosorbent assay (ELISA) and symptomatology. Cultivars Tog5681 and Gigante were highly resistant, and no symptoms were observed when either virus isolate was inoculated at 10 or 20 days postgermination and assayed by ELISA at 7, 14, 22, 35, 50, or 64 days postinoculation. Azucena showed a partial resistance, whereas the other cultivars were susceptible. Symptom appearance was associated with increase in ELISA absorbance in the systemically infected leaves. The best discrimination among the cultivars occurred when the plants were inoculated at 10 days postgermination. Crosses were made between the highly resistant (Gigante and Tog5681) and the susceptible (IR64) cultivars to determine the genetic basis of resistance to RYMV. Evaluation of F1 hybrids and interspecific progenies, as well as the segregation of resistance in F2 and F3 lines of the IR64 × Gigante cross, provided results consistent with the presence of a single recessive resistance gene common to Tog5681 and Gigante.

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First Report of Rice yellow mottle virus in Rice in Uganda

Plant Disease ◽

10.1094/pd-90-0683b ◽

2006 ◽

Vol 90 (5) ◽

pp. 683-683 ◽

Cited By ~ 6

Author(s):

A. Pinel-Galzi ◽

D. Fargette ◽

R. Hull

Keyword(s):

Lake Victoria ◽

Sister Group ◽

Rice Cultivation ◽

Eastern Africa ◽

Mottle Virus ◽

Enzyme Linked Immunosorbent Assay ◽

Rice Yellow Mottle Virus ◽

Cultivated Rice ◽

Northern Tanzania ◽

Yellow Mottle

Rice yellow mottle virus (RYMV) of the genus Sobemovirus is a major biotic constraint to rice production in Africa. First reported in Kenya in 1966, RYMV was later found in most countries in Africa where rice (Oryza sativa) is grown (2). During July 2000, plants with leaf yellowing and mottling symptoms were observed in Uganda in a subsistence rice field northeast of Lake Victoria, close to the Nile River. RYMV was detected by using enzyme-linked immunosorbent assay with polyclonal RYMV antisera (1) in the four samples collected. Discriminant monoclonal antibodies revealed that the samples contained RYMV serotype 4, a serotype found in eastern Africa (Madagascar, Kenya, and Tanzania) (2). The 720-nt long coat protein gene of two isolates was amplified by reverse transcriptase-polymerase chain reaction and sequenced (1). The two Ugandan isolates had 99% nt sequence identity (EMBL Accession Nos. AM114523 and AM114524). They belonged to a monophyletic group (97% nt identity) containing isolates from eastern Kenya and northern Tanzania (close to the Lake Victoria). These form a sister group (93% identity) of isolates from Lake Malawi Region in western Tanzania and are more distantly related (88% identity) to the basal strains from eastern Tanzania (2). Isolation of the Lake Victoria Region from the rest of the Tanzania by distance, physical barriers, and patchy rice cultivation explains the specificity of the strain. Year-round growth of wild and cultivated rice around the lake ensures host continuity in time and space that facilitates spread that accounts for the homogeneity of the isolates of this area. Knowledge of the presence of RYMV in Uganda is important since rice cultivation is intensified in this country and is planned in neighboring southern Sudan. References: (1) A. Pinel et al. Arch. Virol. 145:1621, 2000. (2) O. Traoré et al. Mol. Ecol. 14:2097, 2005.

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Emergence of a resistance-breaking isolate of Rice yellow mottle virus during serial inoculations is due to a single substitution in the genome-linked viral protein VPg

Journal of General Virology ◽

10.1099/vir.0.81659-0 ◽

2006 ◽

Vol 87 (5) ◽

pp. 1369-1373 ◽

Cited By ~ 39

Author(s):

Eugénie Hébrard ◽

Agnès Pinel-Galzi ◽

Anne Bersoult ◽

Christelle Siré ◽

Denis Fargette

Keyword(s):

Infectious Clone ◽

Recessive Gene ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Recessive Resistance ◽

Nucleotide Polymorphism ◽

Single Nucleotide ◽

Resistance Breaking ◽

The Family ◽

Yellow Mottle

The recessive gene rymv-1, responsible for the high resistance of Oryza sativa ‘Gigante’ to Rice yellow mottle virus (genus Sobemovirus), was overcome by the variant CI4*, which emerged after serial inoculations of the non-resistance-breaking (nRB) isolate CI4. By comparison of the full-length sequences of CI4 and CI4*, a non-synonymous mutation was identified at position 1729, localized in the putative VPg domain, and an assay was developed based on this single-nucleotide polymorphism. The mutation G1729T was detected as early as the first passage in resistant plants and was found in all subsequent passages. Neither reversion nor any additional mutation was observed. The substitution G1729T, introduced by mutagenesis into the VPg of an nRB infectious clone, was sufficient to induce symptoms in uninoculated leaves of O. sativa ‘Gigante’. This is the first evidence that VPg is a virulence factor in plants with recessive resistance against viruses outside the family Potyviridae.

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Direct Interaction Between the Rice yellow mottle virus (RYMV) VPg and the Central Domain of the Rice eIF(iso)4G1 Factor Correlates with Rice Susceptibility and RYMV Virulence

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-03-10-0073 ◽

2010 ◽

Vol 23 (11) ◽

pp. 1506-1513 ◽

Cited By ~ 38

Author(s):

Eugénie Hébrard ◽

Nils Poulicard ◽

Clément Gérard ◽

Oumar Traoré ◽

Hui-Chen Wu ◽

...

Keyword(s):

Molecular Mechanisms ◽

Direct Interaction ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Recessive Resistance ◽

In Planta ◽

Central Domain ◽

Yellow Mottle

The adaptation of Rice yellow mottle virus (RYMV) to recessive resistance mediated by the rymv1-2 allele has been reported as a model to study the emergence and evolution of virulent variants. The resistance and virulence factors have been identified as eukaryotic translation initiation factor eIF(iso)4G1 and viral genome–linked protein (VPg), respectively, but the molecular mechanisms involved in their interaction are still unknown. In this study, we demonstrated a direct interaction between RYMV VPg and the central domain of rice eIF(iso)4G1 both in vitro, using recombinant proteins, and in vivo, using a yeast two-hybrid assay. Insertion of the E309K mutation in eIF(iso)4G1, conferring resistance in planta, strongly diminished the interaction with avirulent VPg. The efficiency of the major virulence mutations at restoring the interaction with the resistance protein was assessed. Our results explain the prevalence of virulence mutations fixed during experimental evolution studies and are consistent with the respective viral RNA accumulation levels of avirulent and virulent isolates. Our results also explain the origin of the residual multiplication of wild-type isolates in rymv1-2–resistant plants and the role of genetic context in the poor adaptability of the S2/S3 strain. Finally, the strategies of RYMV and members of family Potyviridae to overcome recessive resistance were compared.

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Genetic basis and mapping of the resistance to Rice yellow mottle virus. III. Analysis of QTL efficiency in introgressed progenies confirmed the hypothesis of complementary epistasis between two resistance QTLs

Theoretical and Applied Genetics ◽

10.1007/s001220100642 ◽

2001 ◽

Vol 103 (6-7) ◽

pp. 1084-1092 ◽

Cited By ~ 44

Author(s):

N. Ahmadi ◽

L. Albar ◽

G. Pressoir ◽

A. Pinel ◽

D. Fargette ◽

...

Keyword(s):

Genetic Basis ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Resistance Qtls ◽

Yellow Mottle

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Identification of a second major resistance gene to Rice yellow mottle virus, RYMV2, in the African cultivated rice species, O. glaberrima

Theoretical and Applied Genetics ◽

10.1007/s00122-010-1300-2 ◽

2010 ◽

Vol 121 (1) ◽

pp. 169-179 ◽

Cited By ~ 39

Author(s):

Deless Thiémélé ◽

Arnaud Boisnard ◽

Marie-Noëlle Ndjiondjop ◽

Sophie Chéron ◽

Yacouba Séré ◽

...

Keyword(s):

Resistance Gene ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Cultivated Rice ◽

Major Resistance Gene ◽

Yellow Mottle

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First Report and Characterization of Rice yellow mottle virus in Central Africa

Plant Disease ◽

10.1094/pdis.2001.85.8.920a ◽

2001 ◽

Vol 85 (8) ◽

pp. 920-920 ◽

Cited By ~ 12

Author(s):

O. Traoré ◽

A. Pinel ◽

D. Fargette ◽

G. Konaté

Keyword(s):

West Africa ◽

Phylogenetic Analyses ◽

Central Africa ◽

Sister Group ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Cultivated Rice ◽

Wild Rice Species ◽

Field Samples ◽

Yellow Mottle

Rice yellow mottle virus (RYMV) of the genus Sobemovirus is the main virus infecting rice (Oryza sativa) in Africa. First reported in Kenya (East Africa), RYMV was later found in most countries of East and West Africa where rice is grown, and in Madagascar in the Indian Ocean. In Central Africa however, the disease had never been reported in rice fields. Ninety-eight field samples with typical yellow mottle symptoms from cultivated rice and two wild rice species (Oryza longistaminata and O. barthii) were collected in the Soudano-Sahelian zones, in the north of Cameroon and the south of Chad (Central Africa) in September 2000. RYMV was detected by ELISA with polyclonal antisera (1) in all samples. All virus isolates were also mechanically transmitted to rice cv. BG 90-2, which is highly susceptible to RYMV. Tests with monoclonal antibodies showed that most isolates from Central Africa were of the SI serotype, which is widespread in the Soudano-Sahelian zones of West Africa (1). The coat protein gene of 7 isolates was amplified by RT-PCR and the expected 720 bp fragment was obtained. Resulting sequences (AJ306735, AJ317949, AJ317950, AJ317951, AJ317952, AJ317953, AJ317954) shared over 95% sequence identity. They were compared to a set of sequences of RYMV isolates from cultivated rice of different geographical origins (2). Phylogenetic analyses by maximum parsimony (PAUP 4) showed that isolates from Central Africa belonged to a monophyletic group, a sister group of West African isolates from the Soudano-Sahelian zones, further supporting the geographic basis of RYMV diversity (2). RYMV incidence was generally less than 10% but reached 20% in some irrigated plots in the two countries. References: (1) G. Konaté et al. Arch Virol. 142:1117, 1997. (2) A. Pinel et al. Arch. Virol. 145:1621, 2000.

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A Recessive Resistance to Rice yellow mottle virus Is Associated with a Rice Homolog of the CPR5 Gene, a Regulator of Active Defense Mechanisms

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-13-0127-r ◽

2013 ◽

Vol 26 (12) ◽

pp. 1455-1463 ◽

Cited By ~ 31

Author(s):

Julie Orjuela ◽

E. F. Thiémélé Deless ◽

Olufisayo Kolade ◽

Sophie Chéron ◽

Alain Ghesquière ◽

...

Keyword(s):

Defense Mechanisms ◽

Defense Mechanism ◽

Mottle Virus ◽

Reference Sequence ◽

Oryza Glaberrima ◽

Resistance Quantitative Trait Locus ◽

Rice Yellow Mottle Virus ◽

Single Mutation ◽

Recessive Resistance ◽

Yellow Mottle

RYMV2 is a major recessive resistance gene identified in cultivated African rice (Oryza glaberrima) which confers high resistance to the Rice yellow mottle virus (RYMV). We mapped RYMV2 in an approximately 30-kb interval in which four genes have been annotated. Sequencing of the candidate region in the resistant Tog7291 accession revealed a single mutation affecting a predicted gene, as compared with the RYMV-susceptible O. glaberrima CG14 reference sequence. This mutation was found to be a one-base deletion leading to a truncated and probably nonfunctional protein. It affected a gene homologous to the Arabidopsis thaliana CPR5 gene, known to be a defense mechanism regulator. Only seven O. glaberrima accessions showing this deletion were identified in a collection consisting of 417 accessions from three rice species. All seven accessions were resistant to RYMV, which is an additional argument in favor of the involvement of the deletion in resistance. In addition, fine mapping of a resistance quantitative trait locus in O. sativa advanced backcrossed lines pinpointed a 151-kb interval containing RYMV2, suggesting that allelic variants of the same gene may control both high and partial resistance.

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