Incidence of Rice yellow mottle virus (RYMV) on rice plants (ofada) grown in two local government areas (LGAs) of Ogun State had been evaluated during a two year field survey. Six month old rice plants were observed for symptom expression and leaf samples collected for serological indexing. Of the 60 leaf samples collected for both years, 96.7 % were presented with symptoms and severity ranged from 1 to 5 in 2012. Symptoms of brown blotches, chlorosis, leaf yellowing and necrosis were observed on rice plants from which samples were collected at Ewekoro LGA. Similar symptoms were also seen on rice plants at Obafemi Owode. Disease incidence due to RYMV was 7.7 % at Ewekoro in 2012 while it was 13.3 % for plants surveyed at Obafemi owode in the same year. In 2013, incidence varied from 30.0 to 90.0 % and the higher incidence was observed on samples at Obafemi owode. Serodiagnosis of Grasshopper (Zonocerus variegatus) and Locust (Locusta migratoides) trapped at the rice fields during the survey revealed that they were not implicated in virus transmission as their absorbance values at spectrophotometric wavelength of 405 nm were not up to one and half times the values of the healthy controls.Keywords: rice, ELISA, incidence, virus symptom, survey Correspondence: sdara@hotmail.com IntroductionWith increase in world population, there is emphasis on increasing level of food production, among which is rice. Rice (Oryza spp.) is grown widely in many parts of the world. It is the major food source for about 40 % of the world's human population (Ortiz, 2011) Production of rice in Nigeria is being threatened by infections from various pathogens such as Rice yellow mottle virus (RYMV) and others such as Maize streak virus (MSV) (Alegbejo, 2013). The virus, Rice yellow mottle virus (RYMV) is a non-enveloped isometric virus belonging to the genus Sobemovirus. Its particle size is 25 nm in diameter with conspicuous capsomere arrangement. The biochemical properties of RYMV include its virions containing 23 % nucleic acid, 77 % protein and 0 % lipid. It is a RNA virus, single stranded and its total genome size is 4.2 kb (kilobase).
A field survey was conducted in eight local government areas (LGA) of Ogun state, Nigeria to assess the incidence of viral diseases of yams in the areas. Leaf samples were collected from 90 yam plants which were either symptomatic or asymptomatic. These were bulked into 45 during serological tests and the viruses indexed include yam mosaic virus (YMV); Dioscorea alata bacilliform virus (DaBV) and cucumber mosaic virus (CMV). DaBV was the most prevalent virus on the field with incidence of 48.9% (22/45) followed by YMV which occurred in 42.2% (19/45). CMV had the lowest percentage of incidence; 2.2% (1/45). Of all the LGAs visited, Abeokuta north and Abeokuta south had the highest incidence of YMV and DaBV, respectively. Mixed virus infections were also detected.
A survey in Southern Nigeria reveals the presence of Cucumber mosaic virus subgroup I in Musa crops. Abstract-Introduction. Cucumber mosaic virus (CMV), genus Cucumovirus, is distributed worldwide; it is a common pathogen of Musa spp. and it is present in all banana-producing areas. Materials and methods. Banana and plantain (Musa) leaf tissues were collected from six major Musa-growing states of Southern Nigeria in August 2000. A broad-spectrum CMV polyclonal antibody was used in Protein A Sandwich (PAS) ELISA to detect CMV isolates, while a CMV subgroup I-specific polyclonal antibody was used in DAS-ELISA to separate subgroup I isolates. Results. Of 108 Musa leaf samples collected, 76 samples (70.4%) reacted positively with the CMV polyclonal antibodies used, in which 32 samples (42.1%) belonged to CMV subgroup I. Edo and Ondo states had low CMV subgroup I incidence of 13.6% and 17.2%, even though both states had high CMV incidence of 63.6% and 62.1% in infected samples, respectively. Imo state had the highest CMV incidence of 72.4% and subgroup I incidence of 55.2%. Of the 32 leaf samples infected with CMV subgroup I, 18 samples expressed one type of viral symptom such as interveinal chlorosis, chlorotic streaks, leaf puckering and crisp deformed leaf. Thirteen other samples expressed two or three viral symptoms, showing either vein thickening or general leaf chlorosis and any of the former symptoms. One asymptomatic leaf tissue was also infected with the virus. Discussion. Our results confirm that subgroup I and other subgroups are responsible for CMV infection in Musa species in Nigeria. The detection of CMV over a large geographical area underscores the importance of virus control measures. CMV can be controlled by use of virus-free suckers. Nigeria / Musa / viruses / bromoviruses / ELISA / identification Une prospection dans le sud du Nigéria indique la présence en bananeraie du sous-groupe I du virus de la mosaïque du concombre. Résumé-Introduction. Le virus de la mosaïque du concombre (CMV), genre Cucumovirus, est distribué dans le monde entier ; c'est un pathogène commun du genre Musa et il est présent dans toutes les zones de production du bananier. Matériel et méthodes. Des tissus de feuille de bananiers et plantains (Musa) ont été collectés en août 2000 dans six États du Sud nigérian importants pour la culture du bananier. Un anticorps polyclonal du CMV à large spectre a été utilisé dans un test ELISA Sandwich (PAS-ELISA) pour détecter les isolats de CMV, alors qu'un anticorps polyclonal spécifique du sous-groupe I du CMV était utilisé dans un test double sandwich ELISA (DAS-ELISA) pour séparer des isolats du sous-groupe I. Résultats. Sur 108 échantillons de feuilles de bananier collectés, 76 échantillons (70,4 %) ont réagi positivement avec les anticorps polyclonaux du CMV utilisés, parmi lesquels 32 échantillons (42,1 %) ont été rattachés au sous-groupe I du CMV. Les États d'Edo et d'Ondo ont été peu concernés par le sous-groupe I du CMV (13,6 % et 17,2 %, respectivement) bien que le CMV ait eu une...
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