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Epidemiology, Molecular Characterization and Yield Loss Assessment of Rice Due To Rice Yellow Mottle Sobemovirus in Northern Nigeria

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Epidemiology, Molecular Characterization and Yield Loss Assessment of Rice Due To Rice Yellow Mottle Sobemovirus in Northern Nigeria.

ABSTRACT

Screenhouse and  field experiments were conducted between 2008 and 2010 to quantify yield loss due to Rice yellow mottle virus (RYMV) in some selected rice cultivars.

determine  the epidemiology of RYMV in relation to weather factors on the incidence of RYMV and insect vector population composition and identification studies; identify its alternative hosts.

determine serotypes  of the pathogen; and molecular characterization of the strains and their distribution in the northern states of Nigeria.

The screenhouse experiment was arranged in a strip plot design with three replicates. Significant interaction between the effects of inoculation regimes and rice cultivars were found between the disease, growth and yield parameters.

The critical periods of RYMV  infection for most of the rice cultivars used were within 4 – 8  Weeks after sowing (WAS). Paddy yield losses of 6.59 – 79.11 % and 3.65 – 81.67 % were recorded on the test cultivars in rainy and dry seasons, respectively.

Keeping the plants RYMV- free for up to 10 WAS resulted in  grain  yield  almost similar to control. The epidemiology experiment was laid out in a  randomized  complete  block design (RCBD) with three replicates.

Significant positive and negative correlations were recorded between RYMV incidence and severity index, some insect vectors and weather  factors.

INTRODUCTION

Rice (Oryza sativa L.) Is a staple food for about one half of people in the world and is mainly harvested  and  consumed  in Asia and Africa (Anonymous, 2005; Sun et al., 2006). In many regions, it is eaten with every meal and provides more calories than any other single food (Hynes, 2007).

It is not only consumed by humans and fed to livestock as it is also useful industrially for processing into acetic acid, glucose, and starch. Rice straw and stems are used by local farmers as bedding for animals and for weaving roofs, hats, baskets and sandals. The inedible rice hull is used as fuel, fertilizer, and insulation (Schalbroeck, 2001; Gao et al., 2004; Hynes, 2007).

Rice is produced in about 10% of all cropland (144 million hectares) in over 110 countries (Luth, 1980). It has the ability to adapt to diverse environmental conditions and is, therefore,  grown in varied climatic conditions ranging from the Sahel to the Rainforest ecological zones (Luth, 1980) in every country in West Africa (WARDA, 1995).

The main production ecologies are rainfed lowland, rainfed upland, irrigated lowland, deep water/flooding and mangrove swamp (Onyishi et al., 2010). Nigeria cultivated 2.191 million hectares of land with rice paddy production of 3.28 million metric tonnes in 1999 while land area under rice production increased by 0.4 % with 3.30 metric tonnes in 2000 (Anonymous, 2001).

The potential land  area  for  rice production in Nigeria is between 4.6 and 4.9 million hectares (Nwilene et al., 2009a). Despite the continuous increase in the land area that is cultivated with rice, Nigeria still imports rice annually (FAO, 2010). It was reported in order to meet local demand, Nigeria imported 1.7 and 1.8, million tonnes of rice in 2008/ 2009 and 2009/ 2010,  respectively (FAO,  2010).

REFERENCES

Abo, M.E. (1998). Studies on the mode of transmission of rice yellow mottle virus Sobemovirus. Unpublished Ph.D Thesis, Ahmadu Bello University, Zaria, Nigeria, pp. 148.

Abo, M.E. and Alegbejo, M. D. (1997). Strategies for sustainable control of viral disease of some crops in Nigeria. Journal of sustainable Agriculture, 10 (2/3): 57-80.

Abo, M. E. and Sy, A. A. (1998). Rice Virus Diseases: Epidemiology and Management Strategies. Journal of Sustainable Agriculture, 10 (2/3): 113-134.

Abo, M.E., Okusanya, B. A. and Imolehin, E. D.  (1995). The status of rice  yellow mottle virus (RYMV) in Nigeria.paper presented at the 1st International  symposium on RYMV from 18-22 September, 1995, Mbe, WARDA/ADRAQ, Bouake, Cote d’Ivoire.

Abo, M.E., Sy, A. A. and Alegbejo, M. D. (1998). Rice yellow mottle virus (RYMV) in Africa. Evolution, distribution and economic significance on sustainable rice production and management strategies.  Journal  of Sustainable Agriculture.  11 (2/3): 85-111.

Abo, M. E., Ukwangwu, M. N., Hughes, J.d’ A.  and  Misari, S.M. (2001).  Possible sources  of resistance to Rice yellow mottle virus (RYMV), genus Sobemovirus  in some rice genotypes in Nigeria. Journal of Agriculture and Environmen,, 2  (2): 263 – 270.

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