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N’Guessan, P.; Pinel, Alexandre; Caruana, Marie-Line; Frutos, Roger; Sy, A. A.; Ghesquière, Alain; Fargette, Denis

doi:10.1023/a:1008792109954

Cited by 54 publications

(12 citation statements)

References 17 publications

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“…Scores for the susceptible varieties ranged from 3.7 for Sahelika to 5.3 for FKR 28, indicating The results indicate that visual rating of period for symptom expression, reduction in plant height and grain yield per plant can be useful symptomatology studies for differentiating RYMV isolates and evaluating rice varieties for RYMV resistance. This is in accordance with the findings of Fomba et al (2001), N'Guessan et al (2001) and Sow et al (2015). Resistance of the NILs to RYMV have been reported elsewhere in the West African subregion (Sereme, 2016).…”

Section: Resultssupporting

confidence: 93%

“…The virus induces chlorosis in leaves, stunting and yield reduction in susceptible hosts. N'Guessan et al (2001) reported a significant relationship between symptom severity and yield loss. However, yield losses allowed better discrimination among isolates and varietal responses to RYMV infection than did symptom expression or plant height.…”

Section: Introductionmentioning

confidence: 97%

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Evaluation of a set of near isogenic lines (NILS) for rice yellow mottle virus (RYMV) resistance and farmers participatory varietal evaluation in Sierra Leone

Taylor¹,

Jalloh²

2017

Afr. J. Agric. Res.

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Rice yellow mottle virus (RYMV) is the most important rice -infecting virus in Africa.Isolates of the virus were collected from Eastern, Southern and Northern Provinces of Sierra Leone and evaluated for pathogenicity on rice, using visual symptom rating and other disease-related traits such as plant height and yield depression. Near Iso-lines NIL 2, NIL 16, NIL 54 and NIL 130, developed by AfricaRice and conferring RYMV resistance were evaluated for resistance to the disease under natural infection. The accessions, together with popularly grown released and local rice varieties, were evaluated by farmers in demonstration plots in the Eastern, Southern and Northern Provinces of Sierra Leone. Results show that the isolates varied in pathogenicity but all developed symptoms of the disease following inoculation of rice plants all the NIL accessions were resistant to the disease. NIL 2 was identified as the best variety by 5, 2.5 and 42.5% farmers in Kenema, Bo and Kambia, respectively. NIL 130 was also identified as the best variety by 7.5, 17.5 and 5% farmers in Kenema, Bo and Kambia, respectively. High tillering and panicles with many spikelets were the main selection criteria by farmers. NIL 16 and NIL 54 were location-specific and selected as the best variety by 20 and 12.5% farmers in Kenema and Kambia, respectively. The NILS, particularly NIL 2 and NIL 130 with multi-locational acceptance, show promise for rice varietal improvement in Sierra Leone.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 97%

Evaluation of a set of near isogenic lines (NILS) for rice yellow mottle virus (RYMV) resistance and farmers participatory varietal evaluation in Sierra Leone

Taylor¹,

Jalloh²

2017

Afr. J. Agric. Res.

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“…Samples from the last emerged leaf were collected 4 weeks after inoculation for all isolates and 6 weeks after inoculation for 12 isolates (BF1, CI4, CI8, Ni1, Ng106, Ng109, Ng113, Tg274, Mg1, Tz5, Tz211). Direct double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was performed as described by Ndjiondjop et al (1999) with a polyclonal antiserum prepared against a RYMV isolate from Madagascar (N’Guessan et al, 2000). About 1 mg of fresh leaves in 1 ml buffer was used.…”

Section: Methodsmentioning

confidence: 99%

Mutations in Rice yellow mottle virus Polyprotein P2a Involved in RYMV2 Gene Resistance Breakdown

et al. 2016

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Rice yellow mottle virus (RYMV) is one of the major diseases of rice in Africa. The high resistance of the Oryza glaberrima Tog7291 accession involves a null allele of the RYMV2 gene, whose ortholog in Arabidopsis, CPR5, is a transmembrane nucleoporin involved in effector-triggered immunity. To optimize field deployment of the RYMV2 gene and improve its durability, which is often a weak point in varietal resistance, we analyzed its efficiency toward RYMV isolates representing the genetic diversity of the virus and the molecular basis of resistance breakdown. Tog7291 resistance efficiency was highly variable depending on the isolate used, with infection rates ranging from 0 to 98% of plants. Back-inoculation experiments indicated that infection cases were not due to an incomplete resistance phenotype but to the emergence of resistance-breaking (RB) variants. Interestingly, the capacity of the virus to overcome Tog7291 resistance is associated with a polymorphism at amino-acid 49 of the VPg protein which also affects capacity to overcome the previously studied RYMV1 resistance gene. This polymorphism appeared to be a main determinant of the emergence of RB variants. It acts independently of the resistance gene and rather reflects inter-species adaptation with potential consequences for the durability of resistance. RB mutations were identified by full-length or partial sequencing of the RYMV genome in infected Tog7291 plants and were validated by directed mutagenesis of an infectious viral clone. We found that Tog7291 resistance breakdown involved mutations in the putative membrane anchor domain of the polyprotein P2a. Although the precise effect of these mutations on rice/RYMV interaction is still unknown, our results offer a new perspective for the understanding of RYMV2 mediated resistance mechanisms. Interestingly, in the susceptible IR64 variety, RB variants showed low infectivity and frequent reversion to the wild-type genotype, suggesting that Tog7291 resistance breakdown is associated with a major loss of viral fitness in normally susceptible O. sativa varieties. Despite the high frequency of resistance breakdown in controlled conditions, this loss of fitness is an encouraging element with regards to RYMV2 resistance durability.

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“…In the fields where yellow mottle symptoms were observed, we ran specific serological diagnostic test (ELISA) (Ndjiondjop et al, 1999; N'Guessan et al, 2000; Traoré et al, 2008), on sampled symptomatic leaves. Approximately three centimeters of dried leaves were homogenized in 1-mL sterile water in extraction bags (Bioreba, Reinach, Switzerland).…”

Section: Methodsmentioning

confidence: 99%

Virus-Bacteria Rice Co-Infection in Africa: Field Estimation, Reciprocal Effects, Molecular Mechanisms, and Evolutionary Implications

et al. 2017

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Simultaneous infection of a single plant by various pathogen species is increasingly recognized as an important modulator of host resistance and a driver of pathogen evolution. Because plants in agro-ecosystems are the target of a multitude of pathogenic microbes, co-infection could be frequent, and consequently important to consider. This is particularly true for rapidly intensifying crops, such as rice in Africa. This study investigated potential interactions between pathogens causing two of the major rice diseases in Africa: the Rice yellow mottle virus (RYMV) and the bacterium Xanthomonas oryzae pathovar oryzicola (Xoc) in order to: 1/ document virus-bacteria co-infection in rice in the field, 2/ explore experimentally their consequences in terms of symptom development and pathogen multiplication, 3/ test the hypothesis of underlying molecular mechanisms of interactions and 4/ explore potential evolutionary consequences. Field surveys in Burkina Faso revealed that a significant proportion of rice fields were simultaneously affected by the two diseases. Co-infection leads to an increase in bacterial specific symptoms, while a decrease in viral load is observed compared to the mono-infected mock. The lack of effect found when using a bacterial mutant for an effector specifically inducing expression of a small RNA regulatory protein, HEN1, as well as a viral genotype-specific effect, both suggest a role for gene silencing mechanisms mediating the within-plant interaction between RYMV and Xoc. Potential implications for pathogen evolution could not be inferred because genotype-specific effects were found only for pathogens originating from different countries, and consequently not meeting in the agrosystem. We argue that pathogen-pathogen-host interactions certainly deserve more attention, both from a theoretical and applied point of view.

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Cited by 54 publications

References 17 publications

Evaluation of a set of near isogenic lines (NILS) for rice yellow mottle virus (RYMV) resistance and farmers participatory varietal evaluation in Sierra Leone

Evaluation of a set of near isogenic lines (NILS) for rice yellow mottle virus (RYMV) resistance and farmers participatory varietal evaluation in Sierra Leone

Mutations in Rice yellow mottle virus Polyprotein P2a Involved in RYMV2 Gene Resistance Breakdown

Virus-Bacteria Rice Co-Infection in Africa: Field Estimation, Reciprocal Effects, Molecular Mechanisms, and Evolutionary Implications

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