Insights Into Natural Genetic Resistance to Rice Yellow Mottle Virus and Implications on Breeding for Durable Resistance

Rice is the main food crop for people in low- and lower-middle-income countries in Asia and sub-Saharan Africa (SSA). Since 1982, there has been a significant increase in the demand for rice in SSA, and its growing importance is reflected in the national strategic food security plans of several countries in the region. However, several abiotic and biotic factors undermine efforts to meet this demand. Rice yellow mottle virus (RYMV) caused by Solemoviridae is a major biotic factor affecting rice production and continues to be an important pathogen in SSA. To date, six pathogenic strains have been reported. RYMV infects rice plants through wounds and rice feeding vectors. Once inside the plant cells, viral genome-linked protein is required to bind to the rice translation initiation factor [eIF(iso)4G1] for a compatible interaction. The development of resistant cultivars that can interrupt this interaction is the most effective method to manage this disease. Three resistance genes are recognized to limit RYMV virulence in rice, some of which have nonsynonymous single mutations or short deletions in the core domain of eIF(iso)4G1 that impair viral host interaction. However, deployment of these resistance genes using conventional methods has proved slow and tedious. Molecular approaches are expected to be an alternative to facilitate gene introgression and/or pyramiding and rapid deployment of these resistance genes into elite cultivars. In this review, we summarize the knowledge on molecular genetics of RYMV-rice interaction, with emphasis on host plant resistance. In addition, we provide strategies for sustainable utilization of the novel resistant sources. This knowledge is expected to guide breeding programs in the development and deployment of RYMV resistant rice varieties.

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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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Mutations in the eIF(iso)4G translation initiation factor confer high resistance of rice toRice yellow mottle virus

The Plant Journal ◽

10.1111/j.1365-313x.2006.02792.x ◽

2006 ◽

Vol 47 (3) ◽

pp. 417-426 ◽

Cited By ~ 128

Author(s):

Laurence Albar ◽

Martine Bangratz-Reyser ◽

Eugénie Hébrard ◽

Marie-Noëlle Ndjiondjop ◽

Monty Jones ◽

...

Keyword(s):

Translation Initiation ◽

High Resistance ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Mottle Virus ◽

Yellow Mottle

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Insect Vectors of Rice Yellow Mottle Virus

Journal of Insects ◽

10.1155/2015/721751 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Augustin Koudamiloro ◽

Francis Eegbara Nwilene ◽

Abou Togola ◽

Martin Akogbeto

Keyword(s):

Host Range ◽

Resistance Genes ◽

Virus Transmission ◽

Rice Production ◽

Insect Species ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Insect Vectors ◽

African Countries ◽

Yellow Mottle

Rice yellow mottle virus (RYMV) is the major viral constraint to rice production in Africa. RYMV was first identified in 1966 in Kenya and then later in most African countries where rice is grown. Several studies have been conducted so far on its evolution, pathogenicity, resistance genes, and especially its dissemination by insects. Many of these studies showed that, among RYMV vectors, insects especially leaf-feeders found in rice fields are the major source of virus transmission. Many studies have shown that the virus is vectored by several insect species in a process of a first ingestion of leaf material and subsequent transmission in following feedings. About forty insect species were identified as vectors of RYMV since 1970 up to now. They were essentially the beetles, grasshoppers, and the leafhoppers. For this review, we presented the chronology of their identification. Also, the biology, ecology, host range, distribution, and caused damage of these insects were briefly summarized.

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Screening rice varieties for resistance to rice yellow mottle virus disease

Tropical Pest Management ◽

10.1080/09670878309370790 ◽

1983 ◽

Vol 29 (2) ◽

pp. 145-147 ◽

Cited By ~ 3

Author(s):

S. N. M. Okioma ◽

S. Sarkarung

Keyword(s):

Virus Disease ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Rice Varieties ◽

Yellow Mottle

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First Report of Rice yellow mottle virus in Rice in The Gambia

Plant Disease ◽

10.1094/pdis-92-2-0316b ◽

2008 ◽

Vol 92 (2) ◽

pp. 316-316 ◽

Cited By ~ 4

Author(s):

Y. Sere ◽

F. Sorho ◽

A. Onasanya ◽

L. Jobe ◽

S. Darboe ◽

...

Keyword(s):

Coat Protein ◽

Phylogenetic Reconstruction ◽

The Gambia ◽

Eastern Africa ◽

Mottle Virus ◽

Rice Yellow Mottle Virus ◽

Leaf Extracts ◽

Rice Varieties ◽

Embl Accession ◽

Yellow Mottle

Rice yellow mottle virus (RYMV) of the genus Sobemovirus is a major biotic constraint to rice (Oryza sativa) production in Africa. First reported in Kenya during 1966, RYMV was later found in most countries in Africa where rice is grown (1). In countries in westernmost Africa (The Gambia, Guinea-Bissau, Mauritania, and Senegal), plants with leaf yellowing and mottling symptoms were observed, but RYMV was never isolated. Rice is the staple food in The Gambia. In 2006, four samples were collected from local rice varieties in the Kuntaur Region in the center of The Gambia. Mechanical inoculation with leaf extracts from all samples caused typical yellow mottle symptoms on the susceptible rice varieties BG90-2, Bouaké 189, and IR64. RYMV was detected in the four samples collected by ELISA with polyclonal antisera (2). The 720-nt coat protein gene was amplified for each isolate by reverse-transcriptase-PCR with primers 5′-CAAAGATGGCCAGGAA-3′ (sense) and 5′-CTCCCCCACCCATCCCGAGAATT-3′ (antisense) (2). The RT-PCR products were directly sequenced (EMBL Accession Nos. AM765810, AM765811, AM765812, and AM765813) and then aligned using ClustalW with a pool of RYMV coat protein sequences from West African isolates (EMBL Accession Nos. AJ279905, AJ279901, AJ885137, AJ885124, and AJ279935). Phylogenetic reconstruction by maximum-likelihood with PAUP indicated that the isolates from The Gambia formed a monophyletic group with over 97% nucleotide identity and are closely related to isolates of other countries in West Africa (Burkina Faso, Côte d'Ivoire, Guinea, Mali, and Sierra-Leone) with 91 to 94% identity. Detection of RYMV in The Gambia indicates that RYMV is present in westernmost Africa, which is referred to as the ‘rice belt’ of Africa, and shows that RYMV is widely distributed from eastern Africa (Tanzania) to the western part of the continent. References: (1) N. K. Kouassi et al. Plant Dis. 89:124, 2005. (2) A. Pinel et al. Arch. Virol. 145:1621, 2000.

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