Detection and distribution of seed-borne viruses on commercial cowpea (Vigna unguiculata (L.) Walp) cultivars in Ado-odo Ota, Ogun Sate, Nigeria

Cowpea is a major source of dietary protein in the nutrition of people in sub-Saharan Africa. Many viruses have been reported to cause economic reduction in cowpea productivity in Nigeria. However, their current distribution is not well documented while most farmers source their seeds from local markets. This study investigated the detection and distribution of seed-transmitted viruses on commercial cowpea cultivars in Ado-odo Ota Local Government area (LGA) of Ogun State. Cowpea seed samples were collected from eleven markets in the LGA. Coordinates of the locations were recorded with Geographical Positioning System (GPS). Thirty cowpea seeds from each market were sowed in planting pots under screenhouse conditions and seedlings were observed weekly for visible virus symptoms. Four-week old seedlings were tested for viruses using Antigen Coated Plate-Enzyme-Linked Immunosorbent Assay (ACP-ELISA) and Reverse Transcription Polymerase Chain Reaction (RT-PCR). Samples were tested for seven seed-transmitted viruses namely Blackeye cowpea mosaic virus (BlCMV), Cowpea aphidborne mosaic virus (CABMV), Cucumber mosaic virus (CMV), Southern bean mosaic virus (SBMV), Cowpea mottle virus (CMeV), Cowpea yellow mosaic virus (CYMV) and Cowpea mild mottle virus (CPMMV). Seed germination rates ranged from 63.3±15.3% of seeds from Joju to 96.7 ±5.8% for Atan and Iju markets. All samples tested negative to ELISA and were confirmed negative by RT-PCR. These findings suggest absence of seedtransmitted cowpea viruses in the study area as at the time of sampling. Periodic detection survey is recommended to assure the virus-free status of the area.Keywords: ACP-ELISA, Cowpea viruses, Diagnostics, RT-PCR, Seed transmissio

Incidence of leaf blight disease of Egusi melon in South-west Nigeria

Egusi melon ( Citrullus lanatus (Thumb) Mansf.) is an important vegetable crop grown for edible seeds and oil in West Africa. Leaf Blight Disease (LBD) is one of the major constraints to its production, with potential to cause economic damage. The objective of this study was to investigate the incidence and distribution of leaf blight on Egusi melon in Southwestern Nigeria. A survey of LBD of Egusi melon was conducted in 2015 and 2016, in five southwestern States of Nigeria (Ogun, Oyo, Osun, Ekiti and Ondo States). Twenty plants each, were randomly sampled from 150 farms comprising 30 farms each, from each State. The distribution of different Egusi melon varieties planted was recorded. \u201cBara\u201d cv. was the most cultivated variety (51.6%); followed by \u201cBojuri\u201d (30.4%) and \u201cSerewe\u201d (18%). Leaf blight was observed in most farms in the five States, from 73% in Osun and Oyo states to 83% in Ondo State. Disease incidence and severity varied with locations and cultivars, and ranged from 0.0-87.5\ub118% and 1.0\ub10-4.5\ub10.8 in Osun State to 20.0\ub119 - 95.0\ub14.5% and 2.3\ub11.5 - 5.0\ub10 in Ondo State. Out of the twelve fungal pathogens from ten genera isolated from infected plants, only Colletotrichum truncatum , C. gloeosporioides and Lasiodiplodia theobromae caused Leaf blight on Egusi melon.Le melon Egusi ( Citrullus lanatus (Thumb) Mansf.) Est une importante culture l\ue9gumi\ue8re cultiv\ue9e pour les graines et l\u2019huile comestibles en Afrique de l\u2019Ouest. La maladie de br\ufblure foliaire (LBD) est l\u2019une des principales contraintes \ue0 sa production, avec le potentiel de causer des dommages \ue9conomiques. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9tudier l\u2019incidence et la distribution de la br\ufblure foliaire du melon Egusi dans le Sud-ouest du Nig\ue9ria. Une enqu\ueate sur la LBD du melon Egusi a \ue9t\ue9 faite en 2015 et 2016, dans cinq \uc9tats du sud-ouest du Nig\ue9ria (\uc9tats d\u2019Ogun, Oyo, Osun, Ekiti et Ondo). Vingt plantes dans chaque \uc9tat ont \ue9t\ue9 \ue9chantillonn\ue9es au hasard dans 150 fermes comprenant 30 fermes chacune, de chaque \uc9tat. La distribution des diff\ue9rentes vari\ue9t\ue9s de melons Egusi plant\ue9es a \ue9t\ue9 enregistr\ue9e. \uabBara\ubb cv. \ue9tait la vari\ue9t\ue9 la plus cultiv\ue9e (51,6%); suivi de \uabBojuri\ubb (30,4%) et \uabSerewe\ubb (18%). La br\ufblure foliaire a \ue9t\ue9 observ\ue9e dans la plupart des exploitations agricoles des cinq \uc9tats, passant de 73% dans les \uc9tats d\u2019Osun et d\u2019Oyo \ue0 83% dans l\u2019\uc9tat d\u2019Ondo. L\u2019incidence et la gravit\ue9 de la maladie variaient selon les emplacements et les cultivars, et allaient de 0,0-87,5 \ub1 18% et 1,0 \ub1 0-4,5 \ub1 0,8 dans l\u2019\uc9tat d\u2019Osun \ue0 20,0 \ub1 19 - 95,0 \ub1 4,5% et 2,3 \ub1 1,5 - 5,0 \ub1 0 dans l\u2019\uc9tat d\u2019Ondo . Sur les douze agents pathog\ue8nes fongiques de dix genres isol\ue9s de plantes infect\ue9es, seuls Colletotrichum truncatum , C. gloeosporioides et Lasiodiplodia theobromae ont caus\ue9 la br\ufblure foliaire du melon Egusi

Occurrence and population distribution of plant parasitic nematodes associated with roselle (Hibiscus sabdariffa L.) in northern Nigeria

Pests including nematodes have been reported as a limiting factor to the production of roselle worldwide. A survey of rosellefarmsinsix Northern Sates of Nigeria was conductedin 2013 to identify the diverse nematode species associated with the soils and roots of the plant and determine their population densities on farmers’ fields. Eightsoil and ten plant samples were randomly collected from each of twenty farms from which nematodes were extracted and identified. Four genera of plantparasitic nematodes (Meloidogyne spp., Helicotylenchus spp., Rotylenchulus spp.and Tylenchus spp.) were found in association with roots and rhizosphere of roselle plants. Meloidogyne were most populous (62.29%) on the roots while Tylenchuswas least (1.68%). Helicotylenchus spp appeared in highest density (50.05%) in plant rhizosphere, but not identified from the roots. The highest percentage of nematode population (22.7 %) wasfrom Katsina, followed by Sokoto (21.6%), Jigawa (17.4%), Zamfara (16.5%), Kano (15.1%) and Kaduna states (6.7%).The generally low nematode density observed might be due to low precipitation and high soil temperature of the six states. Occurrence of varied species of nematodes demands effective control measures for improved roselle productivity. Kano, Zamfara and Jigawawith low nematode population densities can be considered for further research towards the establishment of pest-free areas or area of low pest prevalence for roselle nematodes in Nigeria, useful in the agricultural export trade. Further studies are required on the determination of density economic threshold and the definitive roles of nematodes in causing low productivity of roselle.Keywords: Export value, Hibiscus sabdariffa, nematodes, population densities, pest-free are

Effects of phosphorus and sulphur on dry matter yield of maize (Zea mays) in some soils at Abeokuta, Ogun State, Nigeria

Phosphorus and Sulphur fertilizers are important for increasing the productivity of maize in most parts of Nigeria. A screen-house experiment was conducted to investigate the effects of phosphorus (P) and sulphur (S) on maize dry-matter yield (MDY) in soils of five locations (Obantoko I, II, Alabata I, II, and III) in Abeokuta, Ogun State of Nigeria. Three levels of sulphur (0, 10 and 20 kg S ha–1) and phosphorus (0, 30 and 45 kg P ha–1) were evaluated in a 3 × 3 × 5 factorial experiment laid in Completely Randomised Design with three replications. Pre-planting analyses were performed to determine soil pH, particle size, organic matter, K, Na, P and S. Eight weeks after planting, maize parts above the soil level were harvested, oven-dried and dry-matter yield were computed and recorded. Application of S fertilizer appears not to be critical to maize production in the study areas since singly added S did not produce significant increase in biomass yield. In contrast, applied P significantly increased MDY in all the soils except Obantoko II, which already contained high amount of P sufficient for maize yield. Both synergism (Alabata II and III) and antagonistic (Alabata I) interactions were observed between P and S on MDY without any interactive effect in Obantoko I soil. Application rate of 30-45 kg P ha–1 with or without 10 or 20 kg S ha–1 resulted in significant effects on the MDY in the study areas. Field studies on effects of P and S on maize grain yield are recommended.Keywords: available P and S, maize productivity, Nigeria soils, biomass, fertilizer

Inheritance of resistance to three endemic viral diseases of cowpea in Nigeria

Mosaic diseases, caused by bean common mosaic virus-blackeye cowpea mosaic strain (BCMV-BlCM), southern bean mosaic virus (SBMV), and cucumber mosaic virus (CMV), hamper the productivity of cowpea (Vigna unguiculata (L.) Walp.). Under single or mixed infections, these endemic viruses significantly reduce cowpea yield in sub-Saharan Africa. Planting resistant varieties is the most effective control method. Knowledge of the mode of inheritance of viral resistance is crucial in developing resistant varieties. Inheritance of resistance to BCMV-BlCM, SBMV, and CMV was investigated in two improved cowpea breeding lines. For BCMV-BICM, crosses were made between resistant IT97K-1042-3 (female) and susceptible IT99K-1060 (male); for SBMV, between resistant IT98K-1092-1 (male) and susceptible IT99K-1060 (female); and for CMV, between tolerant IT98K-1092-1 (female) and susceptible IT99K-573-1-1 (male). The F1 progenies were advanced to F2, and some F1 plants were backcrossed to the two parental lines. Reciprocal crosses were made and the 7-day-old seedlings of P1, P2, F1, F2, BCP1, and BCP2 were phenotyped by mechanical inoculation with BCMV-BlCM, SBMV, and CMV under screenhouse conditions. Data on disease incidence and severity were taken at weekly intervals for 5-week post-inoculation. Virus infections were confirmed via antigen-coated plate enzyme-linked immunosorbent assay or reverse transcription-polymerase chain reaction. Chi-square analysis of the genetic segregation indicated that a recessive gene pair in IT97K-1042-3 controlled the inheritance of resistance to BCMV-BlCM. Duplicate dominant genes conditioned the resistance to SBMV and tolerance to CMV in IT98K-1092-1. The backcrosses confirmed the monogenic and digenic inheritance patterns, whereas reciprocal crosses indicated absence of cytoplasmic effects

Disease incidence and severity in cowpea lines evaluated for resistance to single and multiple infections of endemic viruses in Nigeria

Published online: 05 Oct 2020Cowpea (Vigna unguiculata (L.) Walp) is susceptible to several viruses in West Africa. Cowpea viral diseases are mainly controlled through the use of resistant cultivars. Co-infection with more than one virus is frequent in the fields and the resultant synergistic effect often compromises host resistance identified by screening against individual viruses under field or controlled conditions. In this study, eight improved cowpea breeding lines, identified as resistant to single infections and a susceptible cultivar (Ife Brown), were evaluated for their reactions to single and multiple infections of three viruses endemic in West Africa; viz., bean common mosaic virus-blackeye cowpea mosaic strain (BCMV-BlCM), southern bean mosaic virus (SBMV), and cucumber mosaic virus (CMV). Cowpea seedlings were inoculated with these viruses singly or in combination. Disease incidence and severity were recorded at weekly intervals for eight weeks. Virus infection was confirmed by enzyme-linked immunosorbent assay or reverse transcription-polymerase chain reaction. Systemic mosaic, vein-banding, and stunting were observed on inoculated plants. Mixed infection increased symptom severity and the highest severity was found in plants co-infected with CMV. Phenotyping against mixed-infections was more promising for estimating host resistance response in cowpea than single infections. Based on virus incidence and severity, lines IT97K-1069-6 and IT04K-405-5 were found to be resistant to SBMV, whereas IT99K-1060 and IT98K-503-1 were susceptible to the three viruses. IT-98 K-1092-1 was found to be resistant to BCMV and SBMV and tolerant to CMV under mixed inoculation scenario. Cowpea line IT-98 K-1092-1 is, thus, the best resistance source for use in virus resistance-breeding programs