Browsing by Author "Nyaku, S.T."
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Item 18S and ITS1 genomic sequence variations in Rotylenchulus reniformis isolates from Alabama(Journal of Cotton Science, 2013-01) Nyaku, S.T.; Kantety, R.V.; Tilahun, Y.; Lawrence, K.S.; Soliman, K.M.; Cebert, E.; Sharma, G.C.Upland cotton, Gossypium hirsutum L., is highly susceptible to infection by reniform nematode (Rotylenchulus reniformis), which can cause over 10% reduction of cotton yields in Alabama. Detection of reniform nematode (RN) and analysis for molecular variation within its population is important for understanding its interactions with cotton and other host plant species. Restriction analysis of PCR products of ITS1 regions was achieved using four restriction enzymes, HaeIII, HhaI, MspI, and RsaI. These showed similar banding patterns for both male and female populations. However, MspI digestion of ITS1 amplification products showed variants within the combined sex and location effects primarily attributed to a 500 bp fragment that was absent in other restriction digestions. Intra-nematodal variations in 18S and ITS1 rDNA were studied in detail by sequencing a minimum of ten clones in each individual male and female RN isolates in both directions. Multiple sequence alignment of the 18S rDNA sequences showed two major types of sequences within this gene for both male and female RN clones, which could be distinguished at 27 specific sites. Two distinct ITS1 fragments of lengths (550 bp and 720 bp) were observed; referred to as ITS1S and ITS1L respectively. Neighbor-joining analysis was used in revealing the relationships and grouping characteristics between male and female RN clones, with clones grouping together irrespective of sex and isolate. Sequencing of one-third of the 18S and ITS1 rDNA regions provided clear evidence of intra-and inter-nematode variability, in addition to gene conversion events in the 18S rDNA of individual male and female RN clones. © The Cotton Foundation 2013.Item Canonical discriminant analysis of Rotylenchulus reniformis in Alabama(Nematropica, 2013-01) Nyaku, S.T.; Kantety, R.V.; Lawrence, K.S.; Van Santen, E.; Sharma, G.C.The reniform nematode, Rotylenchulus reniformis, infests over 300 plant species worldwide and over the last two decades it has emerged as a major cotton pest in the southeastern United States. Nine locations in Alabama and one location in Mississippi were selected for study of R. reniformis. Thirteen morphometric measurements were made on 20 male and 20 female nematodes from each population. The sex and location interaction was significant (P < 0.005) for all traits except total body length (P = 0.29) and the derived ratio trait a (body length / maximum body width, P = 0.06). Canonical discriminant analysis effectively separated the 10 sampling locations into three distinct groups; among them, Group 1 and 3 were distinct with an intermediate group (Group 2) differentiating in the middle. Furthermore, both female and male R. reniformis based on the morphometrics measured here adhered to this metrics-based grouping. Belle Mina (Limestone County, AL), Huxford (Escambia County, AL), and Mississippi State University, MSU (Oktibbeha County, MS) locations were separated from the remaining seven locations based on the large positive CAN1 centroid means. Eight out of 13 traits had high phenotypic correlations (r > 0.80) with CAN 1 for both sexes. Anal width and length of the hyaline portion of the tail measurement accounted for a significant amount (r > 80%) of the variation in total and sex-based canonical structure. Occurrence of the three non-overlapping morphometric groups in cotton-growing fields in close proximity (250 mile radius) suggests a greater biological variation in this species than expected. Cotton cultivars with differential resistance and soil types are among the major factors to be tested for further delineating the causes of morphometric variation in R. reniformis.Item Characterization of the reniform nematode genome by shotgun sequencing(Genome, 2014-06) Nyaku, S.T.; Sripathi, V.R.; Kantety, R.V.; Cseke, S.B.; Buyyarapu, R.; Mc Ewan, R.; Gu, Y.Q.; Lawrence, K.; Senwo, Z.; Sripathi, P.; George, P.; Sharma, G.C.The reniform nematode (RN), a major agricultural pest particularly on cotton in the United States, is among the major plant-parasitic nematodes for which limited genomic information exists. In this study, over 380 Mb of sequence data were generated from pooled DNA of four adult female RNs and assembled into 67 317 contigs, including 25 904 (38.5%) predicted coding contigs and 41 413 (61.5%) noncoding contigs. Most of the characterized repeats were of low complexity (88.9%), and 0.9% of the contigs matched with 53.2% of GenBank ESTs. The most frequent Gene Ontology (GO) terms for molecular function and biological process were protein binding (32%) and embryonic development (20%). Further analysis showed that 741 (1.1%), 94 (0.1%), and 169 (0.25%) RN genomic contigs matched with 1328 (13.9%), 1480 (5.4%), and 1330 (7.4%) supercontigs of Meloidogyne incognita, Brugia malayi, and Pristionchus pacificus, respectively. Chromosome 5 of Caenorhabditis elegans had the highest number of hits to the RN contigs. Seven putative detoxification genes and three carbohydrate-active enzymes (CAZymes) involved in cell wall degradation were studied in more detail. Additionally, kinases, G protein-coupled receptors, and neuropeptides functioning in physiological, developmental, and regulatory processes were identified in the RN genome. © 2014 Published by NRC Research Press.Item Characterizing Repeats in Two Whole-Genome Amplification Methods in the Reniform Nematode Genome(Hindawi, 2021) Nyaku, S.T.; Sripathi, V.R.; Lawrence, K.; Sharma, G.One of the major problems in the U.S. and global cotton production is the damage caused by the reniform nematode, Rotylenchulus reniformis. Amplification of DNA from single nematodes for further molecular analysis can be challenging sometimes. In this research, two whole-genome amplification (WGA) methods were evaluated for their efficiencies in DNA amplification from a single reniform nematode. The WGA was carried out using both REPLI-g Mini and Midi kits, and the GenomePlex single cell whole-genome amplification kit. Sequence analysis produced 4 Mb and 12 Mb of genomic sequences for the reniform nematode using REPLI-g and SIGMA libraries. These sequences were assembled into 28,784 and 24,508 contigs, respectively, for REPLI-g and SIGMA libraries. The highest repeats in both libraries were of low complexity, and the lowest for the REPLI-g library were for satellites and for the SIGMA library, RTE/BOV-B. The same kind of repeats were observed for both libraries; however, the SIGMA library had four other repeat elements (Penelope (long interspersed nucleotide element (LINE)), RTE/BOV-B (LINE), PiggyBac, and Mirage/P-element/Transib), which were not seen in the REPLI-g library. DNA transposons were also found in both libraries. Both reniform nematode 18S rRNA variants (RN_VAR1 and RN_VAR2) could easily be identified in both libraries. This research has therefore demonstrated the ability of using both WGA methods, in amplification of gDNA isolated from single reniform nematodes.Item Grafting for sustainable management of Fusarium wilt disease in tomato production in Ghana(Journal of Agriculture and Food Research, 2023) Awu, J.E.; Nyaku, S.T.; Amissah, J.N.; Okorley, B.A.; Agyapong, P.J.A.; Doku, F.E.; Nkansah, G.O.Fusarium wilt disease limits tomato production, especially in Ghana. In managing the Fusarium wilt disease, two rootstocks (Solanum torvum and Solanum macrocarpon) were used in grafting experiments. Plant growth, yield, disease severity and incidence of both grafted plants, and non-grafted plants were evaluated in a pot experiment and also under a naturally infected open field condition at Berekum. During the early stage (14 days after inoculation) under artificial inoculation conditions, grafted plants exhibited higher photosynthetic rates (10.41 μmol− 2 s − 1 ) compared to the non-grafted plants (8.36 μmol− 2 s − 1 ). Under naturally infested field conditions, chlorophyll content and photosynthetic rate of non-grafted plants decreased. Solanum lycopersicum grafted onto S. macrocarpon and S. torvum were moderately susceptible (20%–40%) to Fusarium oxysporum. However, the non grafted plants were highly susceptible (50%–100%). Yield from the pot experiment for S. lycopersicum grafted onto S. macrocarpon was significantly higher (453.1 g/plant), compared to S. lycopersicum grafted onto S. torvum (350.3 g/plant) and the non-grafted plant (205 g/plant). However, in naturally infected field, the grafted plants increased in fruit yield compared to the non-grafted tomato plants. Solanum macrocarpon and S. torvum as rootstocks offered resistance against F. oxysporum and showed significantly lower disease progression, than the non-grafted plants (P < 0.05). This study revealed that grafting is an effective tool for the management of Fusarium wilt disease and for tomato growth and yield improvement.Item Molecular characterization, pathogenicity and copper sensitivity of Xanthomonas citri pv mangiferaeindicae, the causal agent of mango bacterial black spot disease in Ghana(Taylor & Francis Group, 2021) Honger, J.O.; Osabutey, S.; Nyaku, S.T.; Lambon, J.B.Recent outbreak of the mango bacterial black spot disease has resulted in massive damages to the Ghanaian mango industry. Research was carried out to confirm the etiology of the disease. Diseased mango fruits and leaves were collected from Greater Accra (Asutuare and Dodowa), Eastern (Akuse, Somanya) and Volta (Juapong) regions, and the sus pected causal bacterium was isolated. The pathogen was identified as Xanthomonas citri pv mangiferaeindicae based on cultural and morphological characteristics and sequence analysis of the cpn60 gene. The pathogenicity of the bacterial pathogen on mango and cashew was determined and its sensitivity to some selected copper based fungicides available in Ghana was evaluated by the agar diffusion bio-assay. All strains of the pathogen were able to cause disease symptoms on artificially inoculated mango and cashew leaves. The pathogen was highly sensitive to Copper oxychloride, Copper hydroxide and Coprous oxide at very low concentrations.Item Morphometric Characterisation of Root-Knot Nematode Populations from Three Regions in Ghana(Plant Pathology Journal, 2018-12) Nyaku, S.T.; Lutuf, H.; Cornelius, E.Tomato (Solanum lycopersicum) production in Ghana is limited by the root-knot nematode (Meloidogyne incognita, and yield losses over 70% have been experienced in farmer fields. Major management strategies of the root-knot nematode (RKN), such as rotation and nematicide application, and crop rotation are either little efficient and harmful to environments, with high control cost, respectively. Therefore, this study aims to examine morphometric variations of RKN populations in Ghana, using principal component analysis (PCA), of which the information can be utilized for the development of tomato cultivars resistant to RKN. Ninety (90) second-stage juveniles (J2) and 16 adult males of M. incognita were morphometrically characterized. Six and five morphometric variables were measured for adult males and second-stage juveniles (J2) respectively. Morphological measurements showed differences among the adult males and second-stage juveniles (J2). A plot of PC1 and PC2 for M. incognita male populations showed clustering into three main groups. Populations from Asuosu and Afrancho (Group I) were more closely related compared to populations from Tuobo-dom and Vea (Group II). There was however a single nematode from Afrancho (AF4) that fell into Group III. Biplots for male populations indicate, body length, DEGO, greatest body width, and gubernaculum length serving as variables distinguishing Group 1 and Group 2 populations. These same groupings from the PCA were reflected in the dendogram generated using Ag-glomerative Hierarchical Clustering (AHC). This study provides the first report on morphometric characteri-sation of M. incognita male and juvenile populations in Ghana showing significant morphological variation.Item Morphometric characterisation of Scutellonema bradys populations from the Guinea Savanna and Transitional Rain Forest ecological zones of Ghana(Taylor and Francis Ltd., 2017-07) Nyaku, S.T.; Jamani, Y.S.; Cornelius, E.; Lutuf, H.Yam (Dioscorea spp.) forms a large portion of Ghanaian diets and is cultivated in most regions. However, yam is highly susceptible to parasitism by the yam nematode, Scutellonema bradys. Ten major yam communities from 10 districts (Yendi, Karaga, East Gonja, Kumbungu, Savelugu/Nanton, Kintampo North, Techiman, Wenchi, Atebubu/Amanten and Ejura/Sekyeredumase) were selected for soil and yam tuber sampling. Body lengths ranged from 624.6 to 858.5 µm, and 609.5 to 854.1 µm for female and male S. bradys populations, respectively. Tail lengths ranged from 5.3 to 9.6 µm, and 5.2 to 8.6 µm for female and male S. bradys populations, respectively. Principal component analysis did not reveal distinct groups among the female and male populations. This was further confirmed through agglomerative hierarchical clustering with subgroupings showing less than 20% dissimilarity for both female and male populations, and nematodes from different locations clustered together. Significant morphological variation therefore exists both within and among female and male S. bradys populations as reflected in the formation of subgroups. © 2018, © 2018 Southern African Plant & Soil Sciences Committee.Item Screening Selected Solanum Plants as Potential Rootstocks for the Management of Root-Knot Nematodes ( Meloidogyne incognita )(International Journal of Agronomy, 2018-09) Okorley, B.A.; Agyeman, C.; Amissah, N.; Nyaku, S.T.Root-knot nematodes (RKNs) ( Meloidogyne spp.) represent agricultural pest of many economic crops, including tomatoes and potatoes. They advance a complex parasitic relationship with roots of tomato plants leading to modification of host structural and physiological functions in addition to significant yield loss. Resistance in solanaceous plants to RKNs has been identified and associated with the possession of Mi gene. The reaction of four Solanum rootstocks ( S. aethiopicum L., S. macrocarpon L., S. lycopersicum L.“Mongal F1,” and S. lycopersicum L. “Samrudhi F1”) was evaluated in pots and in a natural Meloidogyne spp.-infested field in a two-year trial (2015–2016), to identify RKN-resistant rootstock(s), which can be utilized in tomato grafting as a management measure against these nematodes. A rootstock’s reaction to RKNs was assessed using root gall scores (GSs), egg count/g of root, and reproductive factors (Rfs) at the end of 6 and 12 weeks after transplanting (wat) in infested fields, respectively. Solanum macrocarpon , S. aethiopicum , and Mongal F1 showed tolerant responses with reduced root galling and low to high reproductive factors in pot and field experimentation. Although Samrudhi F1 was resistant in both pot and field trials and consistently decreased nematode root galling (<1.00) and reproduction (Rf < 1.00), it failed to significantly increase yield, as compared with the highest yield obtained by the tolerant rootstock, Mongal F1 (870.3 and 1236.6 g/plant, respectively). Evaluation of the four rootstocks against four (0, 500, 1,000, and 5000) RKN inocula levels (Juveniles) showed no significant differences among the growth parameters (fresh and dry shoot and root weights). Root-knot nematode-susceptible tomato varieties, for example, Pectomech F1, a popular tomato variety in Ghana, can be grafted onto the RKN-resistant and RKN-tolerant rootstocks for increased yields.Item Seed-Borne Fungi Associated with Diverse Rice Varieties Cultivated in the Western North Region of Ghana(International Journal of Microbiology, 2023) Ackaah, F.M.; Nyaku, S.T.; Darkwa, E.Rice is a major staple in the Ghanaian diet. However, its production is constrained by fungal diseases. A survey was conducted in 2018 in three selected districts in the Western North Region of Ghana using a structured questionnaire and face-to-face interaction with 230 farmers to assess their knowledge, perceptions of seed-borne fungal diseases, and management practices. Additionally, fungi associated with farmer’s seeds were isolated and identifed through the Agar and Blotter tests. Findings indicate that 72.7% of the farmers in the selected districts relied on their saved seeds for planting. Thirteen fungal genera were associated with the rice seed samples collected from the three districts. The Juaboso district had the majority (13) of seed-borne fungi. The seed samples were categorized into various forms of discolouration, and significant differences (P < 0.05) existed among the seed samples for this parameter. The AGRA rice, a farmer saved seed from Juaboso, had the highest level of seed discolouration (41.96%). Fungi identifed to be associated with the dark brown/ brown discolouration of rice seeds were Bipolaris spp., Fusarium spp., Macrophomina phaseolina and Aspergillus spp. Te only fungus associated with the yellow/pale yellow colour was Bipolaris spp. The fungi Bipolaris spp., Curvularia spp., and Botryodiplodia spp. were associated with the dark spot discolouration. Alternaria spp., and Aspergillusspp. were observed on the greyish white seed discolouration sample. Fungi are associated with rice cultivation and vary according to district and rice variety. A complex of pathogenic and saprophytic fungi therefore infects rice grains both in field and storage conditions.