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Articles by A. Onasanya
Total Records ( 21 ) for A. Onasanya
  A. Onasanya , Y. Sere , F. Nwilene , M.E. Abo and K. Akator
  High yielding rice genotypes with good levels of resistance to RYMV were identified at Africa Rice Center-WARDA in Cote d‘Ivoire. The yields and resistance stability of these genotypes, however, remain uncertain. The performance of 13 genotypes over 10 different RYMV isolates from 7 localities in Cote d’Ivoire was tested in the screenhouse. Chlorophyll (SPAD) and yield reductions due to RYMV disease were evaluated. Considerable diversity was observed in the reactions of these genotypes to all the RYMV isolates. Percentage yields and SPAD reduction were between 2.3-90.3 and 5.3-40%, respectively. Of 13 rice genotypes studied, IR 47686-15-1-1(P) had the lowest mean SPAD and yield reductions. The levels of resistance shown by japonicas were better than those of indicas. Six genotypes (FARO 11; GIGANTE (tete); H 232-44-1-1; IR 47686-15-1-1(P); IR 47686-15-1-1; ITA 235) could be described as possessing both stable and acceptable levels of resistance to RYMV. The high genotype by environment interactions in the reactions of the rice genotypes to RYMV suggests the possible existence of different strains of RYMV in Cote d’Ivoire. This information could be useful in rice breeding programs aiming at deployment of RYMV resistant genotypes to different rice ecologies and localities in Cote d’Ivoire.
  A. Onasanya , M.M. Ekperigin , Y. Sere , F.E. Nwilene , J.O. Ajele and G. Oboh
  Isozyme fingerprinting and differentiation of Xanthomonas oryzae pv. oryzae (Xoo) isolates, causing rice Bacterial Leaf Blight (BLB) disease in West Africa, was carried out. Of 13 enzyme systems screened, Glucose 6-phosphate dehydrogenase (G6PH) showed adequate resolution and enzyme activity. Thus total proteins from all the 30 isolates were then analyzed using G6PH. This enzyme system was potentially useful as they differentiate all the 30 Xoo isolates studied. The study revealed 40-96.7% polymorphism in G6PH loci within the Xoo enzyme profile. These polymorphic isozyme loci were used to construct phylogenetic relationship cluster dendrogram among the 30 Xoo isolates. All the 30 Xoo isolates were classified into two major genetic groups (Xoo-A and Xoo-B) with five subgroups. Xoo-A possibly covers 46% and Xoo-B 54% of BLB population across West Africa. This study suggests the emergence of subgroup genotypes possibly the result of mutations and interactions among isolates and strains that originally made up Xoo-A and Xoo-B genotypes. The isozyme fingerprint defined for each race of Xoo could be useful for epidemiological surveys, disease diagnoses and in the identification of new virulent strains, isolates and their origin. This information could be useful in rice breeding programs aiming at development of durable Xoo resistant rice cultivars to different rice ecologies and localities in West Africa.
  B.O. Akanji , J.O. Ajele , A. Onasanya and O. Oyelakin
  Genetic fingerprinting of 30 Pseudomonas aeruginosa (Pa) isolates from three types of nosocomial infection cases from two Osun State Teaching Hospitals was compared using RAPD-PCR markers. Ten out of 50 operon primers tested showed polymorphism with reproducible results among the isolates and produced 131 bands of which 74 were polymorphic with sizes ranging between 200 and 3,000 bp. Cluster analysis using the 74 polymorphic markers classified the 30 Pseudomonas aeruginosa isolates into two (PgA and PgB) genetic groups. Comparing isolates proportion in each genotype based on their site of infection, antibiotics resistance pattern and geographical location, it was revealed that the proportion of urinary tract infection isolates in PgA genotype was significantly less than those in PgB genotype (z = -1.195, p<0.05) while the proportion of septicaemia isolates in PgA genotype was significantly higher than its proportion in PgB genotype (z = 1.348, p<0.05). However the proportion of wound infection isolates of PgA and PgB genotypes were significantly the same (z = -0.278, p>0.05). The PgA genotype contained few isolates with increased virulence and resistance to new antimicrobial modules and could possibly be new emerging P. aeruginosa strains from PgB genotype population. The study has critically revealed the genetic diversity and distribution among P. aeruginosa isolates in Osun State.
  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.

  A. Onasanya , M.M. Ekperigin , Y. Sere and J.O. Ajele
  Genetic diversityof 30 Xanthomonas oryzae pv. oryzae (Xoo) isolates, causing rice bacterial leaf blight disease in West Africa, was carried out using isozyme PAGE analysis. Of 13 enzyme systems evaluated, SKDH, EST and G6PH showed adequate resolution, enzyme activity and polymorphism and were used to analyze the total proteins from all the 30 isolates. The study revealed 23 isozyme loci in which SKDH produced 33.3-93.3% polymorphism, EST and G6PH equally gave 40-96.7% polymorphism within the Xoo isolates enzyme profile. These 23 isozyme loci were used to construct phylogenetic relationship cluster among 30 Xoo isolates, of which the Xoo isolates were classified into two major genetic groups (Xoo-A and Xoo-B) with two subgroups each (Xoo-A1 and Xoo-A2) and (Xoo-B1 and Xoo-B2). The 23 isozyme markers obtained clustered into 3 major groups (Gp-1, Gp-2 and Gp-3). Genetic study revealed that Gp-1 is genetically linked to the identification of Xoo-A1 genotype, Gp-2 to Xoo-A2 and Gp-3 characterized Xoo-B1 and Xoo-B2 genotypes. The distinct pattern of each isolate obtained suggests high level of genetic variation and frequent occurrence of mutants in Xoo isolates in different host cells. This information could be useful in rice breeding programs aiming at development of durable Xoo resistant rice cultivars to different rice ecologies and localities in West Africa.
  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.
  Y. Sere , A. Onasanya , F.E. Nwilene , M.E. Abo and K. Akator
  The study aimed to investigate the potential of insect vector Rice yellow mottle virus (RYMV) cultivar screening method. Screening rice cultivars against RYMV under artificial conditions is usually carried out inside the screen house by mechanical inoculation of RYMV isolates. Such an approach may be highly criticized as not fully representative of how RYMV disease is spread or transmitted under field conditions. Consequently, the potential of three RYMV insect vectors, Oxya hyla, Locris rubra and Chnootriba similes, was evaluated in comparing the cultivar screening method with mechanical transmission using eight differential rice genotypes against a highly virulent RYMV Nigerian isolate. The study revealed that each of the three insect vector methods is different from the mechanical transmission method and all methods screened rice cultivars in the same way. This study revealed the potential of the insect vector screening method to provide a basis not only for the development of durable resistant cultivars to RYMV disease but also for further investigation on vectors, virus and rice plants interaction.
  T.A. Agunbiade , F.E. Nwilene , A. Onasanya , M. Semon , A. Togola , M. Tamo and O.O. Falola
  Upland rice is mostly at risk from soil insect pests, including termites which cause significant yield losses. Studies were conducted at Kasua-Mangani, Kaduna State, Northcentral Nigeria, to evaluate the resistance status of 18 upland NERICA rice varieties to termite attack. The percent plant attacked by termites on the 18 NERICA varieties at 60 and 90 Days after Sowing (DAS) was between 2.47 to 12.45% and 3.82 to 20.89%, respectively. There was no significant difference in the response of NERICA rice varieties to termite attack at 60 and 90 DAS. The resistance status of NERICA rice varieties to termite attack was classified into 4 groups as follows: Moderately Resistant (MR), Moderately Susceptible with recessive resistance (MSr), Moderately Susceptible (MS) and Highly Susceptible (HS) according to cluster analysis. Of the 18 NERICA rice varieties studied, only NERICA 5, 14 and 18 were classified as MR and could be recommended as the most adapted rice varieties in termite prone areas of Northcentral Nigeria.
  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.
  Y. Sere , A. Onasanya , K. Akator , A. Afolabi and M.E. Abo
  Serological diversity of 178 RYMV isolates was determined by phylogenetic analysis of Serological Differentiation Indices (SDI) data generated from antigen coated-plate enzyme-linked immunosorbent assay (ACP-ELISA) using 26 RYMV Polyclonal antisera. These RYMV isolates were obtained from northern, southern, eastern and western Cote d`Ivoire. All the RYMV isolates was classified into three main serogroups (Sg1, Sg2 and Sg3) and six subgroups (Sg1a, Sg1b, Sg2a, Sg2b, Sg3a and Sg3a). This indicates the existence and levels of serodiversity among RYMV isolates in Cote d`Ivoire. These results provide evidence of a possible relationship between serological property, host plant and ecological origin of RYMV isolates. Phylogenetic classification of each RYMV isolate defined by SDI data in ACP-ELISA is potentially useful in epidemiological studies to assess isolate identity and interaction as well as to assist breeding programs aiming at the development of cultivars with durable resistant to RYMV in Cote d`Ivoire.
  F.E. Nwilene , A.K. Traore , A.N. Asidi , Y. Sere , A. Onasanya and M.E. Abo
  The study aimed to investigate the vectorial capacity of twelve insect species to transmit Rice Yellow Mottle Virus (RYMV) from diseased seedlings of a susceptible rice variety (Bouaké 189) and a perennial wild rice (Oryza longistaminata) to seven alternative host plants. Results indicated that Trichispa sericea, Chaetocnema pulla, Chnootriba similis, Conocephalus longipennis, Oxya hyla, Paratettix sp., Zonocerus variegatus, Euscyrtus sp., Cofana spectra, Cofana unimaculata, Locris rubra and Locris maculata were capable of transmitting RYMV from infected Bouaké 189 and Oryza longistaminata to alternative weed hosts Leersia hexandra, Imperata cylindrica, Digitaria horizontalis, Echinochloa colona, Echinocloa crus-pavonis, Eleusine indica and Brachiaria lata. Only Chaetocnema pulla, Trichispa sericea, Chnootriba similis, Oxya hyla, Zonocerus variegatus, Euscyrtus sp., Parattetix sp., Cofana spectra, Cofana unimaculata and Locris rubra played an important role in transmitting the disease from rice to O. longistaminata, Leersia hexandra and Imperata cylindrica. The present study confirmed the vectorial capacity of these vectors out of which eight were reported for the first time in West Africa.
  F. E. Nwilene , A. Onasanya , A. Togola , O. Oyetunji , M. Semon , M. Tamo , E.O. Bright and S. Ofodile
  Rice and maize intercrop is a common feature of traditional upland rice cultivation in Nigeria. Stemborer larvae cause significant yield loss in rice. The study aimed at identifying stemborer resistant status of upland NERICA rice varieties and evaluating the effectiveness of maize as a trap crop to protect upland NERICA rice varieties against stemborers. The resistance status of 7 NERICA rice and 2 other rice varieties to stemborer was evaluated in 2006 and 2007 under natural infestation maize and cassava intercropping systems in the humid forest zone of Nigeria. In 2006 study, NERICA1, NERICA2 and NERICA5 together with the resistant check LAC23 were classified as stemborer resistant (SBR) and NERICA3, NERICA4, NERICA6 and NERICA7 together with susceptible check OS6 were classified as stemborer susceptible (SBS). The SBR varieties (NERICA1 and NERICA2) from the 2006 study intercropped with maize and cassava in 2007 revealed the effectiveness of maize as a trap crop and cassava as a refuge for generalist predators against stemborer damage on upland rice. Maize appeared an effective trap crop for rice stemborers because there was a marked and significant reduction in the stemborer attack on rice in the NERICA rice/maize intercrops (GrB cluster) as compared to the NERICA rice monocrops (GrA cluster) and NERICA rice/cassava intercrops (GrA cluster). Maliarpha separatella Ragonot was the predominant stemborer species on rice followed by Sesamia calamistis Hampson. It was concluded that NERICA1 and NERICA2 could be recommended to farmers in stemborer prone areas and that maize was a suitable trap crop for managing rice stemborers.
  A. Onasanya , Y. Sere , M. Sie , K. Akator , M.M. Coulibaly and A. Hamadoun
  Screenhouse studies were conducted using 10 RYMV isolates from 6 different localities in Mali against 8 WARDA differential rice genotypes to investigate the possible existence and classification of different pathotypes of RYMV in Mali. The reaction of 8 rice genotypes to the 10 RYMV isolates was different in terms of SPAD and yield reductions. The interaction between isolates and rice cultivar was also significant. AMMI cluster analysis revealed the existence of two pathotypes (HPI and MPI) of RYMV isolates in Mali. Of 8 rice genotypes studied, only Bouake 189 was highly susceptible to the two pathotypes. This information could be useful in the rice breeding programs aiming at deployment of RYMV resistant genotypes to different rice ecologies and localities in Mali.
  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.
  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.
  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.
  S. Issaka , A. Onasanya , A. Basso , F. Sorho , A. Haougui , A.Y. Sido , S. Ake , D. Fargette and Y. Sere
  This study has been conducted in screen house with an aim to asses the Rice yellow mottle virus pathogenic diversity and the level of resistance of released varieties in Niger republic. Sixty RYMV isolates from 23 Niger rice perimeters were inoculated mechanically to nine rice cultivars. The disease symptoms were scored at 42 days after inoculation. Analysis of Variance (ANOVA) and Additive Main effect and Multiplicative Interaction (AMMI) analysis were performed on the percentage of severity. The reaction of the rice cultivars to the virus isolates was significantly different. The interaction between isolates and rice cultivars was also significant. AMMI cluster analysis revealed the existence of four major pathotypes (Path 1 to 4) of Rice Yellow Mottle Virus (RYMV) in Niger republic. Path 4 pathotype included 12 resistance breaking isolates (20%). Path 3 and Path 2 pathotypes consist of 15 and 26 isolates respectively and were typical of wild type isolates with moderate level of pathogeny, including none aggressive (path 3 = MP) and aggressive isolates (Path 2 = MPA). The fourth pathotype Path 1 was made of 7 isolates and typical of particular isolates which have a moderate pathogenic level (FP). Resistance Breaking (RB) isolates occupied 30% of Niger rice ecologies in variable proportion. The rice varieties (Bassiroumo, IR15-29-690-3-1 and Kassoumo) released in Niger were highly susceptible to RYMV and therefore constituted a favorable condition for the rice yellow mottle disease propagation. This information is useful in rice breeding programs in the development and deployment of RYMV resistant cultivars to different rice perimeters in Niger Republic.
  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.
  A. Banito , E.A. Kadai , A. Onasanya and Y. Sere
  The present study aimed at determining Xanthomonas oryzae pv. oryzae pathogenic diversity. Therefore, the disease survey was conducted in three ecozones of Togo-Forest savanna transition, Forest and dry savanna zones and the diseased samples were collected, the bacteria isolated and characterized by testing their virulence on 21 rice genotypes. The results revealed the occurrence of the bacterial leaf blight in the three ecozones. High bacterial leaf blight incidence of 50-65% was observed in Forest savanna transition and Forest zones, while it was up to 70% in the dry savanna zone. The highest incidence (70%) was recorded in dry savanna zone and the lowest (25%) was frequently observed in Forest zone. Pathotyping analysis of 13 bacterial isolates from samples collected from the infected fields against 21 rice genotypes to isolate and characterize bacteria virulence was carried out. Thus, AMMI cluster analysis revealed the existence of 3 Pathotypes (Pt) among these isolates: PtA highly virulent has 1 isolate, PtB virulent was made up of 3 isolates and PtC moderately virulent was made up of 9 isolates. At ecozone the analysis revealed the presence of PtB and PtC in the Forest savanna transition zone, PtA and PtC in Forest zone and PtB and PtC in the dry savanna zone. The present results provided knowledge on the bacteria virulence and its structure across ecozones of Togo and provided useful information for selection of genotypes for durable resistance to the disease.
 
 
 
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