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Articles by F.E. Nwilene
Total Records ( 21 ) for F.E. Nwilene
  S.A. Ogunbayo , D.K. Ojo , A.R. Popoola , O.J. Ariyo , M. Sie , K.A. Sanni , F.E. Nwilene , E.A. Somado , R.G. Guei , D.D. Tia , O.O. Oyelakin and A. Shittu
  Morphological and molecular characterization of ninety-six landrace rice (Oryza sativa L.) accessions including six checks collected from four regions (North-West, North, West and Central-West) of Cote d’Ivoire were assessed using 14 agro-botanical traits and 10 Randomly Amplified DNA Polymorphisms (RAPDs) primers, respectively. Accessions were evaluated in a field experiment in an augmented experimental design with three replicates. The aim of the research was to study variations and to select lines that could be used as potential parents in future breeding programs. A principal components plot and a dendrogram based on distance between genotype cluster groups for mean values of the morphological variables were used to group the accessions. Genetic relatedness among accessions based on RAPD molecular marker was also presented in form of a dendrogram generated by clustering analysis using the Unweighted Pair Group Method with Arithmetic mean (UPGMA). The relative effectiveness of the RAPD markers compared to botanical descriptors in assessing diversity among the accessions was investigated. Clustering analysis technique using NTSYS classified the 96 landrace accessions into 8 morphological groups whereas PCA re-ordered the accessions into three broad groups that had within cluster similarities and inter-cluster differences in morphological variations. Reaction products (bands) of the RAPD analysis were highly polymorphic, more discriminatory and informative as they were able to differentiate more pairs of accessions than the botanical descriptors. Apart from checks, highest grain yield (2316 g/plot) was observed for accessions 46 (DNN 184) with an average of 12 filled tillers, plant height of 136 cm and medium maturity date of 136 days. It was observed that number of total and filled tillers per se was not a function of yield but rather, these traits were significantly associated with plant height and maturity date. Although, landrace rice accessions in Côte d’Ivoire is associated with relatively narrow genetic base, positive heterosis could be promoted if any of the Gagnoa (GGA) accessions from Central West of the country is used in a future hybridization program with Danane (DNN) accessions from west because of genetic distance between members of the two groups.
  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.
  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.
  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.
  A. Togola , F.E. Nwilene , A. Agbaka , F. Degila , A. Tolulope and D. Chougourou
  The stalk-eyed fly or Diopsid, Diopsis sp. (Diptera, Diopsidae) is an economically significant insect pest of rice in Tropical Africa. The objective of this study is to develop a fast screening method of rice varieties for resistance to Diopsis sp. in a view to advice breeders on resistance sources and to guide producers in the use of resistant varieties to reduce or avoid insecticidal treatments of the fields. The study was conducted in 2008 at the AfricaRice/IITA Station, Cotonou where, 18 upland NERICA varieties and their parents (Oryza glaberrima and O. sativa) were twice screened under artificial infestation of Diopsid’s eggs and adults. The screening method was based on Brown Plant Hopper screening techniques using small cages. As results, only NERICA16 and NERICA18 showed good resistance to Diopsid attack at 20 Days after Infestation (DAI) under egg infestation. The remaining 18 entries were more or less susceptible. Under adult infestation, 16 NERICA varieties showed very good resistance to the stalk-eyed fly attack at 20 DAI. Of these, NERICA18, NERICA11, NERICA6 and NERICA15 were highly resistant (% deadhearts <7%). Only NERICA9 and NERICA17 were moderately susceptible. The African O. glaberrima parent CG14 was the most resistant entry. The Asian parent line WAB56-104 also suffered less damage from Diopsis sp. than most of the NERICAs. In this experiment, the adult infestation appeared to be more realistic than infestation with eggs because it is a free choice method in which pest pressure is weak and where varieties can demonstrate their real behaviour.
  A. Togola , F.E. Nwilene , E.A. Kotoklo , K. Amevoin , I.A. Glitho , O.E. Oyetunji and A. Niang
  In tropical Africa, termite damage to rice crops leads to important losses of farmers’ income. The present study aimed to evaluate the effect of rice varieties and cultural practices on termite populations and damage in the field. For this purpose, 10 rice varieties (seven NERICA, one Oryza glaberrima and two O. sativa) were cultivated in rainfed upland at Niaouli (Benin) under four cultivation practices. Termite populations and damage were evaluated during tillering, heading and maturation stages. NERICA 6, CG14 (the African O. glaberrima, parent of the NERICA), NERICA 10, NERICA 2 and NERICA 3 were the least infested and suffered least damage, while NERICA 4 and LA23 were the most susceptible. Among the cultural practices, use of Metarhizium anisopliae and regular weeding resulted in lower termite populations and less damage than other practices. Rice was most susceptible to termite attack in the period from heading to maturation. Results of this study should help rice farmers in their choice of tolerant varieties and adapted cultural practices as effective alternative measures to control termites and save rice production in the rainfed upland ecology.
  D.C. Chougourou , A. Togola , F.E. Nwilene , J. Adeliossi , F. Bachabi and O.E. Oyetunji
  The lesser grain borer, Rhyzopertha dominica, is a major primary insect of stored cereals worldwide. In Benin, it causes serious damages on paddy rice stored in rural zones. Nowadays, there is a big interest in developing alternative measures included the use of resistant varieties for controlling this key pest. For this purpose, a study was conducted at Africa Rice Center in 2008 to establish the resistance of 17 improved rice varieties included 13 NERICA, 2 Oryza sativa and 2 Oryza glaberrima to this pest. The varieties were artificially infested under laboratory conditions. The results showed that CG14, WAB56-50, WAB56-104 and NERICA4 had good resistance against the attack of Rhyzopertha dominica while NERICA10 and NERICA8 were highly susceptible. The most tolerant cultivars investigated from this study could be recommended for safe storage to reduce pest and economic losses in all endemic zones where R. dominica represents a major threat.
  A. Togola , P.A. Seck , I.A. Glitho , A. Diagne , C. Adda , A. Toure and F.E. Nwilene
  In Benin, on-farm storage of paddy rice is increasingly exposed to pest damage. Insect infestation causes a loss of income to farmers and other post-harvest stakeholders. The objective of this study is to assess the magnitude of damage caused to rice stored on-farm and evaluate the potential economic risk. In this study, 65 stocks of paddy rice were inspected and sampled in order to assess the economic losses. In addition, an agronomic survey was carried out to determine producer perceptions about the economic impact of stored rice pests in a farming environment. The findings show that weight loss amounts to 5.47% after 6 months of storage in the southern region, 4.07% in the central region and 1.64% in the northern region. From an economic perspective, 6 months duration of storage is likely to cause an estimated loss of 21,315 FCFA (Franc of the African Financial Community) per ton of paddy in the South region, compared to losses of 8,088 FCFA in the North. Furthermore, 36.92% of farmer respondents consider that these insects cause considerable economic damage to stored rice. This study made it possible not only to assess current losses attributable to insect pests in the country but also to obtain future projections about trends in high-risk regions. These findings will undoubtedly pave the way for future research in improved stored rice protection and income safeguards for various stakeholders intervening in the post-harvest sector.
  O.E. Oyetunji , C.O. Peluola , F.E. Nwilene and A. Togola
  Termites are serious biotic threat to rainfed upland rice ecology. The objective of this study was to evaluate the root and stem damage caused by the effect of termite-fungi (Botryodiplodia theobromae and Trichoderma sp.) interaction on three upland rice varieties (OS 6, LAC 23 and NERICA 1) planted on ultisol soil under screenhouse condition. It was laid on Randomized Complete Block Design (RCBD) with three replications. The results showed that rice variety OS 6 was found to be most susceptible to termite infestation and the termite- fungi interaction as the damage caused on root was high. The root weight was low indicating the level of susceptibility of rice varieties (OS 6>NERICA 1>LAC 23) to termite infestation and damage. NERICA 1 treated with termite, termite+Botryodiplodia and Botryodiplodia only had significant low root weight, OS 6 treated with Trichoderma only, termite+Botryodiplodia and Termites+Trichoderma had significant root weight reduction. The stem girth taken was significantly low in some treatments with termite and fungi. LAC 23 treated with termite+ Botryodiplodia had low stem girth even at three weeks after treatment. NERICA 1 treated with termites had significant low stem girth while OS 6 treated with termite+Trichoderma had low stem girth. The nutrient uptake by the roots of rice plant treated with the two fungi was significantly low. The studies harness the economic importance of Botryodiplodia theobromae and Trichoderma spp., which penetrate into rice plant via termite attack.
  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.
  A. Togola , E.A. Kotoklo , F.E. Nwilene , K. Amevoin , I.A. Glitho , O.E. Oyetunji and P. Kiepe
  Termites are considered useful insects in natural savannah because of their role in soil fertility regulation, soil aeration and soil porosity. However, they are perceived as a serious threat for tropical agriculture. Due to the complexity of their populations and habitats, they cause high losses on dryland crops, especially upland rice. The present study aimed to analyze the specific diversity of termites on rice (Oryza) in rainfed upland conditions in Benin and to assess the damage they cause. Sampling was carried out in natural savannah and rice fields with 10 upland varieties to evaluate the population of termites. Specific damage was located on the susceptible organs of rice plants. The study allowed the identification of four termite species in the shrub savannah and six species in rice field. The commonest species on rice were Microcerotermes parvus, Microtermes sp., Pseudacanthotermes militaris and Amitermes evuncifer. Termite attack was diverse, but mainly affected roots and stems. The results of this study contributed to the identification of the diversity of termite species on rainfed upland rice and also to the identification of the damage they cause in order to undertake targeted measures against the key species.
  A. Koudamiloro , F.E. Nwilene , D. Silue , A. Togola , O. Oyetunji , Y. Sere and M. Akogbeto
  Insects represent a major group of vectors of Rice yellow mottle virus (RYMV). This study aimed at identifying the main entomofauna transmitting RYMV to rice crop in Benin. Therefore, the transmission ability of 13 insect species was tested during the rice vegetative stages. These species belong to the Orthoptera order (Oxya hyla, Conocephalus longipennis, Paracinema tricolor, Acrida bicolor and Stenohippus aequus), the Coleoptera order (Chnootriba similis, Aulacophora foveicollis and Xanthadalia effusa), the Homoptera order (Cofana spectra, Nephotettix modulatus, Cofana unimaculata and Poophilis costalis) and the Diptera order (Diopsis thoracica). Among them, four species including P. tricolor, S. aequus, N. modulatus and P. costalis were identified for the first time as RYMV vectors. The species belonging to the Homoptera order appeared to be the most virulent, with higher values of viral titer. Virus distribution in the vector body parts was specific to each order. Basically, virus was more important in the Orthopteran, Coleopteran and Homopteran insects head part. It was also evident in the abdomen part of the Homopteran and the Orthopteran especially for P. tricolor, C. spectra and P. costalis. Disease severity was only observed in C. similis after inoculation and persisted until rice maturity with a score of 5 compared to the control which was 1 from a 1 to 9 scale. This study allowed identifying the presence of RYMV insect vectors in Benin among which, four are reported for the first time in Africa.
  E.O. Ogah and F.E. Nwilene
  Rice is an important cereal crop and is cultivated virtually in all agro-ecological zones in Nigeria. However, production capacity is far below national requirement. One of the major reasons for the low yields of rice in Nigeria is depredation by pests, particularly the insect pests. The rice plant is an ideal host for a large number of insect pests-root feeders, stems borers, leaf feeders and grain feeders. High yield losses associated with these insect pest categories portray the role of the insects in low rice yield in Nigeria and sub-Saharan Africa as a whole. Unfortunately, the potential for proper management of rice insect pests to enhance yield has not been fully realized in Africa. Proper management of rice pests therefore is a pre-requisite for enhanced and sustainable rice production amidst smallholder farmers that typify the rice production industry in Nigeria. In this review, major insect pests of rice were identified with emphasis on their pest status, distribution and control methods. Cultural, biological, host plant resistance and chemical controls and the development of integrated pest management programmes were reviewed. The long-term and wide adoption of integrated insect pest management of rice in Nigeria was advocated, emphasizing the use of host plant resistance and biological control but the current cultural practices should be evaluated from time to time for enhanced efficiency.
  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.
  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. 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.
  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.
  O.E. Oyetunji , F.E. Nwilene , A. Togola and K.A. Adebayo
  African Rice Gall Midge (AfRGM) Orseolia oryzivora Harris and Gagné (Diptera: Cecidomyiidae), is a major insect pest mainly of rainfed and irrigated lowland rice in Africa. Of the management options identified for controlling AfRGM, host plant resistance is the most compatible and farmer-friendly manner. Rice varieties have morphological and/or biochemical traits associated with resistance which induces diverse resistance to pests. Two resistance mechanisms (antixenosis and antibiosis) were evaluated on ten rice genotypes under artificial infestation. Level of infestation was assessed while morphological traits were observed physically; leaf samples were collected for biochemical analysis in the laboratory. The results showed that the three O. glaberrima varieties were resistant to AfRGM (little or no pest infestation) and all the interspecific genotypes were susceptible to AFRGM. In Oryza sativa varieties, long leaf and leaf sheath have been identified to confer antixenotic resistance to AfRGM. But in Oryza glaberrima varieties, secondary metabolites-Phenol, Terpenoids, Salicylic acids and Monotepernoid have been identified as the key antibiotic traits associated with resistance to AfRGM. The result of the Principal Component Analysis (PCA) of the traits produced four major clusters accounting for 79% of the total variation of the traits which had negative correlation with percentage tiller infestation thereby conferring resistance to AfRGM. Understanding the mechanisms and traits/factors contributing to resistance of host plant is useful in deciding appropriate breeding methodologies for varietal improvement. This work facilitates the effort of plant breeders and entomologists in developing and deploying insect-resistant cultivars to overcome new insect biotypes.
 
 
 
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