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The Resistance of Farmers' rice Varieties to Rice Yellow Mottle Virus (RYMV) at Badeggi, Nigeria
Abo, ME.,Gana, AS.,Maji, AT.,Ukwungwu, MN.
Tropicultura , 2005,
Abstract: Forty-eight farmers' rice varieties and 12 improved and released varieties were screened in the screenhouse at the National Cereals Research Institute (NCRI) Badeggi, Nigeria by mechanical sap inoculation for their resistance to Rice Yellow Mottle Virus (RYMV). The rice varieties were categorized into 4 groups: highly susceptible, moderately susceptible, moderately resistant and resistant, based on standard evaluation scale (SES) for rice. Back-inoculation tests to a highly susceptible variety, Bouake 189 and enzyme linked immunosorbent assay (ELISA) showed that none of the varieties was immune to RYMV. The highly susceptible varieties displayed conspicuous yellow, mottle and stunting symptoms of RYMV. Many varieties were highly susceptible to RYMV and elicited high virus titre. Most of these farmers' varieties are either highly susceptible or moderately susceptible to RYMV.
Pathogenecity of two strains of rice yellow mottle virus on aromatic rice cultivars
ZL Kanyeka
Tanzania Journal of Science , 2006,
Abstract: Development of rice cultivars with resistance to rice yellow mottle virus (RYMV) requires characterization of pathogenecity of existing strains against susceptible cultivars. The pathogenecity of two RYMV strains; S4 and S“New” identified in Tanzania were assessed against seven local and introduced rice genotypes including cultivars Zambia, ITA173 and TXD 88. The two virus strains showed similar effects on the rice cultivar Zambia killing all the plants at 25d after inoculation. The strains significantly reduced the plant height, panicle length, and number of tillers per pot and total dry matter of all the two cultivars. In another trial, the pathogenecity of the two strains was assessed against four aromatic rice cultivars M-69-9, Loya, Shingo ya mwali and Motisoro. The analysis of variance revealed significant differences only among cultivars for all plant parameters except for the disease severity, which showed significant statistical differences for cultivars, strains and their interactions. The strain S“New” caused more severe disease incidences on inoculated plants than S-4 strain indicating its appropriateness to use in screening for RYMV resistance due to its aggressiveness on susceptible rice genotypes. Tanzania Journal of Science Vol. 32 (1) 2006: pp. 53-60
Potential for biological control of rice yellow mottle virus vectors
N Woin, N Djomaila, S Ismael, S Bourou, T Bebom
African Crop Science Journal , 2007,
Abstract: Insect pests and disease infestations are the primary constraints in rice (Oryza sativa) production systems in Africa and Asia. For Cameroon in particular, the rice yellow mottle virus (RYMV) is increasingly a serious problem to rice production. During the poulations of the various insect vectors of RMYV are not known, and hence the need for this study. Unfortunately, 2002 - 2004, two sampling methods were combined to assess the population of insects vectors of rice yellow mottle virus (RYMV) in the three major irrigated rice ecosystems in northern Cameroon (Lagdo, Maga and Yagoua), and in low land rice fields. Sampling was conducted using sweep net and D-Vac (sucking trap) fortnightly in 2002 and 2003 until mid October in low land rice fields, while in the irrigated fields, samplings occurred between December and April. Rearing using dead insects was conducted simultaneously in the laboratory to identify the parasitoid insect species. From samples obtained at different sites: (i) the dominant structure of the RYMV insect vectors was analysed according to the rice phenology; and (ii) the diversity and the occurrence of potential major groups of predators and parasitoids were assessed. Among the RYMV insect vectors sampled: Chaetocnema pulla Chapuis (Coleoptera: Chrysomelidae), Chnootriba similis Mulsant (Coleoptera: Coccinellidae), Trichispa sericea Guerin-Meneville (Coleoptera: Chrysomelidae), Locris rubra Fabricius (Hemiptera: Cicadellidae), Oxya hyla St l (Orthoptera: Acrididae), and Conocephalus longipennis (de Haan) (Orthoptera: Tettigoniidae) were the most encountered insect species during the rice growing seasons. With regard to predator populations, spiders (Araneae) were the most abundant, with high concurrency of Pardosa spp (> 42 %) in all sites. In Maga and Yagoua sites, the carabid beetle species, Abacetus crenulatus Dejean and Abacetus foveolatus Chaudoir, were the most numerous whereas the Lagdo site was highly colonised by Clivina. erythropyga Putzeys. Paederus sabaeus Erichson, and Stenus ravus Puthz were the most abundant Staphylinid beetles. From reared dead RYMV insect vectors, Eurytoma spp., Pediobius spp., Tetrastichus spp. and Telenomus spp. emerged as parasitoids. Results of this study reveal a great potential of biological control against rice yellow mottle virus vectors using predators and parastoids. This potential should be developed to manage the yield losses caused by the virus infection in rice cropping systems.
Evidence for Non-Transmission of Rice Yellow Mottle Virus (RYMV) through Rice Seed
Abo, ME.,Alegbejo, MD.,Sy, AA.,Afolabi, A.
Tropicultura , 2004,
Abstract: An indexing of the organs (radicle and plumule) and components (husk, endosperm and embryo) of rice seeds using Enzyme Linked Immunosorbent Assay (ELISA) was carried out to detect Rice yellow mottle virus (RYMV) and establish the exact location of the virus in the rice seed. RYMV was detected only in the husk (seed coat) but not in the endosperm, plumule, radicle, nor embryo. None of the seedlings raised from the seeds expressed RYMV symptoms. No virus particle was detected by the ELISA test in the leaves of the screenhouse-reared plants obtained from seeds of infected plants. The results indicate that RYMV is apparently not transmitted through rice seed probably because the virus is seed-borne in the husk (seed coat) of mature rice seeds.
Diagnostic sérologique des isolats soudano-sahéliens du virus de la panachure jaune du riz (Rice Yellow Mottle Virus, RYMV)
Traoré, O.,Traoré, EVS.,Gumedzoé, MYD.,Konaté, G.
Tropicultura , 2008,
Abstract: Serological Diagnosis of Sudano-Sahelian Isolates of Rice Yellow Mottle Virus (RYMV). Rice Yellow Mottle Virus (RYMV) is the most damaging virus infecting rice in Africa. Serology is a suitable detection method for RYMV but most available anti-RYMV polyclonal antibodies react poorly with some isolates of the virus, which undermine the reliability of the method. A broad-spectrum polyclonal antibody was raised against Rice Yellow Mottle Virus (RYMV) in order to improve the serological detection of the virus. This antibody was used to diagnose the virus in field samples collected from both irrigated and upland rice and wild host plants in five West and Central African countries (Burkina Faso, Cameroon, Chad, Mali and Togo). RYMV was readily detected in about 500 samples whereas a new natural host species (Eragrostis atrovirens) collected from Mali was identified. The viral isolates gathered in this study constitute the starting point for a reference collection of plant viruses in the Sudano-Sahelian region. This collection will be particularly useful for the assessment of RYMV variability which is a key factor in developing rice varieties with stable resistance to the virus.
Detection and Serological Characterization of Rice Yellow Mottle Virus in Central African Republic  [PDF]
Régis Dimitri Sokpé Longué, Innocent Zinga, Silla Semballa, Nicolas Barro, Oumar Traoré
Agricultural Sciences (AS) , 2016, DOI: 10.4236/as.2016.712082
Abstract:
Serological and biological detection of Rice Yellow Mottle Virus (RYMV) in leaf samples belonging from cultivated rice species and wild grasses revealed 201 positive detections. All these isolates occurred exclusively on cultivated rice species (Oryza sativa L. and O. glaberrima Steud). A relationship was found between cultural practices and presence of RYMV in fields (X2 = 108.83, df = 1, P < 0.001). The serological characterization using Monoclonal antibodies (Mabs A and D), showed homogenous reaction with Mabs A alone. These results indicated that Ser1 serotype is present in the south of Central African Republic.
Abiotic Transmission of Rice yellow mottle virus Through Soil and Contact Between Plants  [PDF]
M.D. Traore,V.S.E. Traore,A. Galzi-Pinel,D. Fargette
Pakistan Journal of Biological Sciences , 2008,
Abstract: The roles of guttation fluid, irrigation water, contact between plants and transplantation into contaminated soil in the transmission of Rice yellow mottle virus (RYMV) were assessed. RYMV presence and infectivity were tested by Enzyme-Linked Immunosorbent Assay (ELISA) and by inoculation to susceptible rice cultivar BG90-2. The virus was readily detected in guttation fluid collected from infected rice plants. Transmission tests from this fluid led to high disease incidence (86.6%). Irrigation water collected at the base of infected plants growing in pots was less infectious, as inoculations led to disease incidences below 40%. No virus was detected and could be transmitted from field-irrigation water. Up to 44% healthy rice plants whose leaves were in contact with those of infected plants became infected but, no transmission occurred through intertwined roots. Transplantation of rice seedling into virus-contaminated soil also led to plant infection. However, virus survival in the soil decrease rapidly and infectivity was completely lost 14 days after soil contamination. Altogether, these results indicated that high planting densities of rice are likely to favour secondary spread of rice yellow mottle disease. Transplantation of rice seedlings not earlier than 2 weeks after soil preparation should prevent soil transmission of the virus. Although guttation fluid is highly infectious its contribution to virus infectivity in irrigation water is negligible as field-irrigation water was not found to be an infectious source for RYMV.
Historical Contingencies Modulate the Adaptability of Rice Yellow Mottle Virus  [PDF]
Nils Poulicard,Agnès Pinel-Galzi,Oumar Traoré,Florence Vignols,Alain Ghesquière,Gnissa Konaté,Eugénie Hébrard,Denis Fargette
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1002482
Abstract: The rymv1-2 and rymv1-3 alleles of the RYMV1 resistance to Rice yellow mottle virus (RYMV), coded by an eIF(iso)4G1 gene, occur in a few cultivars of the Asiatic (Oryza sativa) and African (O. glaberrima) rice species, respectively. The most salient feature of the resistance breaking (RB) process is the converse genetic barrier to rymv1-2 and rymv1-3 resistance breakdown. This specificity is modulated by the amino acid (glutamic acid vs. threonine) at codon 49 of the Viral Protein genome-linked (VPg), a position which is adjacent to the virulence codons 48 and 52. Isolates with a glutamic acid (E) do not overcome rymv1-3 whereas those with a threonine (T) rarely overcome rymv1-2. We found that isolates with T49 had a strong selective advantage over isolates with E49 in O. glaberrima susceptible cultivars. This explains the fixation of the mutation T49 during RYMV evolution and accounts for the diversifying selection estimated at codon 49. Better adapted to O. glaberrima, isolates with T49 are also more prone than isolates with E49 to fix rymv1-3 RB mutations at codon 52 in resistant O. glaberrima cultivars. However, subsequent genetic constraints impaired the ability of isolates with T49 to fix rymv1-2 RB mutations at codons 48 and 52 in resistant O. sativa cultivars. The origin and role of the amino acid at codon 49 of the VPg exemplifies the importance of historical contingencies in the ability of RYMV to overcome RYMV1 resistance.
The Effect of Rice yellow mottle virus Infection on the Performance of Rice (Oryza sativa L.) Relative to Time of Infection under Screenhouse Condition  [PDF]
J.T. Onwughalu,M.E. Abo,J.K. Okoro,A. Onasanya
Journal of Applied Sciences , 2010,
Abstract: The study on the resistance of Gigante, Moroberekan and Bouake 189 rice varieties was investigated against the Rice yellow mottle virus (RYMV) infection relative to time of infection under screenhouse controlled condition. Rice varieties, Moroberekan, Gigante and Bouake 189, were inoculated with RYMV isolate at seedling, tillering, booting and flowering growth stages. Gigante, Moroberekan and Bouake 189 gave mean yield losses of 12.68, 78.06 and 94.4%, respectively at booting and seedling infection stages. The No. of grains plant-1 is mostly affected at booting infection stage in Bouake 189 and at seedling infection stage in Moroberekan. No significant difference in No. of empty spikelets plant-1 due to infection at different growth stages among the three varieties. Plant height was significantly affected by virus infection at seedling stage of the three varieties and other growth stages of Bouake 189. The highest yield loss of 94.4% obtained in Bouake 189 at seedling and booting infection stages establishes the fact that yield losses to RYMV are strongly influenced by host cultivars as well as time of virus infection. The study revealed that the period from seedling and booting represents the most vulnerable phase to RYMV infection in rice growth stages. This information would strongly assist breeding programmes in the development of durable resistant rice cultivars to RYMV disease.
The Distribution, Incidence, Natural Reservoir Hosts and Insect Vectors of Rice Yellow Mottle Virus (RYMV), Genus Sobemovirus in Northern Nigeria
Abo, ME.,Ukwungwu, MN.,Onasanya, A.
Tropicultura , 2002,
Abstract: Field visits and surveys were carried out in Niger, Kano, Bauchi and Gombe states of northern Nigeria at tillering and panicle initiation stages of rice in the years 2000 and 2001 to determine the distribution, host plants and occurrence of insect vectors of Rice Yellow Mottle Virus (RYMV). Farmers' cultural practices and field situations were also assessed. Visual inspection based on the Standard Evaluation Scale (SES) and enzyme linked immunosorbent assay (ELISA) methods were used in detecting RYMV infection. RYMV presence was established in all the four states surveyed. The virus was widely distributed in Kano state. The insect vectors of RYMV, such as Trichispa sericea Guerin, Chaetocnema pulla Chapius, Chnootriba similis Thunberg and Conocephalus longipennis de Haan, were found in the 4 states. Outbreaks of T. sericea occurred in many farmers' fields in Kano state. RYMV was detected more frequently on Oryza sativa L. than on O. longistaminata Chev. & Roehr and Echinochloa pyramidalis Hitche and Chase.Virus infection was not established in any other grass species, sedges and broadleaf plants tested. It is evident therefore, that RYMV has a narrow host range and is found more frequently in the Oryzeae.
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