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Articles by J.K. Okoro
Total Records ( 2 ) for J.K. Okoro
  J.T. Onwughalu , M.E. Abo , J.K. Okoro , A. Onasanya and Y. Sere
  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.
  J.T. Onwughalu , M.E. Abo , J.K. Okoro , A. Onasanya and Y. Sere
  The study on Rice yellow mottle virus (RYMV) infection and reproductive losses in rice was carried out under screenhouse condition in Nigeria. Thirty-five rice varieties were evaluated for RYMV resistance. Percent productive tillers, date to 50% flowering and percent spikelets fertility per plant were between 43.2-96.7%, 57.67-112 days and 0-71.8%, respectively. Number of panicles per plant, number of grains per panicle and 1000 grain weight per plant were between 8.33-45.67, 0-77 and 0-27.57 g, respectively. Yield losses of between 17-100% were obtained from all the rice varieties evaluated. Out of the 35 rice varieties studied, only Gigante (18%), Moroberekan (19%) and NERICA-L 42 (32%), have the least yield losses and RYMV resistance characteristics. The three varieties (Gigante, Moroberekan and NERICA-L 42) are known to possess stable resistance characteristic to RYMV disease and will comparatively be suitable for cultivation in areas where RYMV incidence is endemic and on a long term be used by rice breeders as sources for breeding for durable resistance to RYMV disease in Nigeria.
 
 
 
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