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Articles by R.O. Onasanya
Total Records ( 7 ) for R.O. Onasanya
  A. Onasanya , A. Basso , E. Somado , E.R. Gasore , F.E. Nwilene , I. Ingelbrecht , J. Lamo , K. Wydra , M.M. Ekperigin , M. Langa , O. Oyelakin , Y. Sere , S. Winter and R.O. Onasanya
 

Case No: 26082013

This article has been withdrawn due to technical issue.

  R.O. Onasanya , O.P. Aiyelari , A. Onasanya , F.E. Nwilene and O.O. Oyelakin
  An experiment to determine the effects of different levels of nitrogen and phosphorus fertilizers on the growth and yield of maize was conducted between June and October, 2007 at the Teaching and Research Farm of the Federal University of Technology, Akure. The experiment was laid out in a Randomized Complete Block Design (RCBD) consisting of twelve treatments with three replicates. The treatments were, 0 kg N ha-1 + 0 kg P ha-1 (T1), 60 kg N ha-1 + 0 kg P ha-1 (T2), 120 kg N ha-1 + 0 kg P ha-1 (T3), 0 kg N ha-1 + 20 kg P ha-1 (T4), 0 kg N ha-1 + 40 kg P ha-1 (T5), 0 kg N ha-1 + 60 kg P ha-1 (T6), 60 kg N ha-1 + 20 kg P ha-1 (T7), 60 kg N ha-1 + 40 kg P ha-1 (T8), 60 kg N ha-1 + 60 kg P ha-1 (T9), 120 kg N ha-1 + 20 kg P ha-1 (T10), 120 kg N ha-1 + 40 kg P ha-1 (T11) and 120 kg N ha-1 + 60 kg P ha-1 (T12). The result of the study showed that application of 120 kg N ha-1 + 0 kg P ha-1 and 60 kg N ha-1 + 40 kg P ha-1 significantly increased the growth of maize than other treatments. The application rate of 120 kg N ha-1 +40 kg P ha-1 significantly (p = 0.05) enhanced grain yield. The study therefore suggests that, for optimum grain yield, 120 kg N ha-1 + 40 kg P ha-1 should be applied particularly in the study area and its environment.
  A. Joseph , D.B. Olufolaji , F.E. Nwilene , A. Onasanya , M.M. Omole , R.O. Onasanya and Y. Sere
  Chlorophyll reduction in rice leaves is a prominent feature of rice yellow mottle virus-infected plants. This research work was carried out to investigate the effect of rice yellow mottle disease on the chlorophyll content of eight differential rice cultivars screened for resistance to rice yellow mottle virus (RYMV) with vector transmission technique. Border row rice seedlings mechanically inoculated with RYMV isolate at 21 days after sowing metamorphosed into infected rows, following which the rice cultivars were sown 15 days after. Two days after sowing the test cultivars, life adults of three vectors (Oxya hyla, Locris rubra and Chnootriba similis) of rice yellow mottle virus were released onto the infected rows inside separate insect-proof screen house to acquire and transmit the virus to the test cultivars. The chlorophyll contents of the leaves were then measured at 42, 56 and 70 days after sowing. The result of the genotype by environment interaction showed that environment exerted the most profound effect on chlorophyll reduction (36.26%) in the rice cultivars screened with O. hyla while the least effect (5.87%) was recorded when the screening was carried out with C. similis. Findings from this research work showed that chlorophyll reduction varied among the rice cultivars at different stages of rice plant. Though, the photosynthetic rate of the rice leaves were not investigated, it could be deduced that this physiological function would invariably reduce in the rice cultivars.
  A. Onasanya , P. Kiepe , A. Basso , G. Nkima , F.E. Nwilene , I. Ingelbrecht , J. Lamo , M.M. Ekperigin , R.O. Onasanya , O. Oyelakin , S. Winter and Y. Sere
  Genomic DNA fingerprinting is a useful tool for effective and reliable identification and differentiation of Xanthomonas oryzae pv. oryzae (Xoo) pathogen from rice. The study aimed to conduct molecular characterization and DNA fingerprinting of 23 Xoo isolates from East Africa and two Xoo isolates from IRRI (Philippines) as control. PCR analysis was carryout on genomic DNA of 25 Xoo isolates using 6 Xoo specific primer pairs. Cluster analyses of genetic data obtained from 25 Xoo DNA fingerprints revealed two major genotypes (GrpA and GrpB) among the 25 Xoo isolates. GrpA has three subgroups (GrpA1; GrpA2; GrpA3) and GrpB (GrpB1; GrpB2; GrpB3). GrpA genotype consists of 20 Xoo isolates from Uganda, Rwanda and Philippines while GrpB genotype has 5 Xoo isolates from Rwanda. Some Xoo isolates were identical (PX-1, PX-2; UX621, RX2101; RX554, UX623, RX4113; UX211, UX213, UX214, RX4112, UX215). The emergence of subgroup genotypes could possibly be due to mutations and interactions among isolates and strains in host cells. Some Xoo isolates from Rwanda and Uganda were identical suggesting possible pathogen migration between these countries and long-term survival. Durable resistance rice cultivars would need to overcome both GrpA and GrpB Xoo genotypes in order to survive after their deployment into different rice ecologies in East Africa.
  A. Joseph , D.B. Olufolaji , F.E. Nwilene , A. Onasanya , M.M. Omole , R.O. Onasanya and Y. Sere
  The physiological age of rice plant plays a significant role in Rice Yellow Mottle Virus (RYMV) infection. Both flag and old leaves of rice plant differ in their susceptibility to RYMV infection. The present study was, therefore, carried out to examine the effect of leaf age on RYMV severity and chlorophyll content in Moroberekan cultivar with mechanical inoculation and vector transmission method. Border row rice seedlings mechanically inoculated with RYMV isolate at 21 days after sowing metamorphosed into infected rows, following which seeds of Moroberekan were sown 15 days after. Eighty adults each of Locris rubra and Oxya hyla were released onto the infected rows inside separate screenhouse to acquire and transmit the virus to the rice plant. In another trial, three-week old seedlings of Moroberekan were mechanically inoculated with the RYMV isolate. In both experiments, RYMV severity and chlorophyll content of flag and old leaves were assessed at 42, 56 and 70 days after sowing. The highest disease severity (61.65%) was observed in the old leaves of mechanically inoculated plants at 42 DAS while the least disease severity (22.97%) was recorded in the flag leaves of O. hyla inoculated plants at 70 DAS. The highest chlorophyll content (49.29%) was observed at 70 DAS while the least (12.71%) was recorded at 56 DAS. Findings of this study showed that flag leaves of Moroberekan rice cultivar are more susceptible to RYMV infection than older leaves.
  R.O. Onasanya , D.B. Olufolaji , A. Onasanya , Y. Sere , F.E. Nwilene , M. Wopereis and P. Kiepe
  Rice Yellow Mottle Virus (RYMV) genus Sobemovirus is a highly variable pathogen that is very infectious to rice plant. This variability hinders rice breeding for durable resistance to the virus and effective deployment of improved cultivars in Southwest Nigeria. Disease surveys in 5 Southwest states (Lagos, Oyo, Ogun, Ekiti and Ondo) revealed RYMV disease incidence of between 15-70% in farmers’ fields and serological indexing confirmed 92% of collected leaf samples positive to RYMV with 24% from rice and 76% from weeds. The weed with 76% RYMV positive suggests being the main reservoir of RYMV in Southwest Nigeria. Biological test on collected fields leaf samples identified 3 groups (GroupA, GroupD and GroupE) of Resistance Breaking (RB) RYMV isolates and 2 groups (GroupB and GroupC) of normal isolates. Pathotyping 20 RYMV isolates against 10 differential varieties identified 17 isolates as Highly Pathogenic Isolates (HPI) and 3 as Mildly Pathogenic Isolates (MPI) while 4 rice varieties were Highly Resistant (HR), 2 were Moderately Resistant (MR) and 4 were susceptible. HPI isolates present in five states and MPI isolates in two states. Serological study using the same 20 RYMV isolates revealed two major Nigeria serogroup (NSg1 and NSg2) and four subgroups (NSg1a, NSg1b, NSg2a and NSg2b). NSg1a and NSg1b comprised both normal and RB isolates while NSg2a and NSg2b were typical of RB isolates only. This information would assist rice breeding programs to develop durable resistant cultivars to RYMV disease in Southwest Nigeria.
  A. Onasanya , A. Joseph , D.B. Olufolaji , M.M. Ekperigin , Y. Sere , F.E. Nwilene , P. Kiepe and R.O. Onasanya
  RYMV transmission by insect vectors is considered to fully represent how RYMV disease is spread under natural field conditions. The present study aimed to use Oxya hyla, Locris rubra and Chnootriba similes vectors after acquisition of the virus to determine RYMV movement and distribution in insect body and transmission to rice cultivars. RYMV susceptible BG 90-2 was sown in 5 L plastic pots each at 0.5, 1 and 1.5 m distance from test entries and seedlings were mechanically inoculated with a highly virulent RYMV Nigerian isolate 14 days after sowing. Seven days after inoculation of BG 90-2, test entries were sown in 5-litre plastic pots and same day Oxya hyla, Locris rubra and Chnootriba similes vectors were introduced into the screen house to feed on RYMV infected BG 90-2. RYMV content in Oxya hyla, Locris rubra and Chnootriba similes whole body was 71.8, 44.1 and 50 and head part was 42, 44.6 and 10.1%. RYMV incidence at 0.5, 1.0 and 1.5 m vector migration distance was 14.6, 16.0 and 19.0% for Oxya hyla, 31.3, 35.2 and 39.6% for Locris rubra and 13.7, 16.2 and 19.9% for Chnootriba similes. Cluster dendrogram revealed three groups (GrpA, GrpB, GrpC) of RYMV cultivar screening methods. GrpA was typical of Locris rubra, GrpB has mechanical and Oxya hyla while Chnootriba similes formed GrpC. The information reported in this study would help to better understand RYMV disease epidemic in farmers’ fields and to develop durable resistant rice varieties against the disease.
 
 
 
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