Molecular evidence of Cacao swollen shoot virus acquisition and retention by Planococcus citri (Risso) and Pseudococcus longispinus (Targioni-Tozzetti) and Pseudococcus viburni (Signoret) Mealybugs (Hemiptera: Pseudococcidae)

Cacao swollen shoot virus (CSSV) remains a significant viral pathogen endemic in West African cacao-growing countries. Eradication of affected trees (complete removal) and resistance breeding in existing cacao (Theobroma cacao L.) germplasm have not yielded the expected results in terms of controlling the spread of CSSV. CSSV is reported to be vectored by at least 16 species of mealybugs (Hemiptera: Pseudococcidae), but there have been no molecular evidences to validate these reports. Inconsistent reports exit on CSSV transmission which were based on visual assessments of CSSV infection which are highly subjective, especially on asymptomatic cacao. The validation of the transmission efficiency of CSSV by mealybugs are arguable. In this study, the presence of CSSV in three mealybug species, Planococcus citri (Risso), Pseudococcus longispinus (Targioni Tozzetti) and Pseudococcus viburni (Signoret), was monitored via PCR after a 72-h virus acquisition access period (AAP) on symptomatic T. cacao (var. Amelonado) seedlings ‘infected’ with New Juaben, a severe strain of CSSV. Solanum tuberosum sprouts were then fed to the mealybugs over a sixday period. Sequenced PCR products of the destructively sampled and CSSV-screened individual mealybug species provided a molecular evidence of CSSV acquisition. qPCR results gave another evidence that CSSV retention is highly variable between and within mealybug species. This is the first molecular evidence highlighting a non-West African mealybug species, Ps. viburni, as a capable CSSV vector. Apparently, these results could validate the efficacy of non-malvaceous species as barrier crops and in screening for resistance to CSSV vectors in T. cacao

Electropenetrography application and molecular-based virus detection in mealybug (Hemiptera: Pseudococcidae) vectors of Cacao swollen shoot virus on Theobroma cacao L.

© 2018 Cacao swollen shoot virus (CSSV) is a peril exclusive to the West African cacao-growing countries; causing the Cacao swollen shoot virus disease. This study was set out (1) to analyse the feeding behaviour of two West African and one non-West African mealybug species, Planococcus citri (Risso) and Pseudococcus longispinus (Targioni Tozzetti) and Ps. viburni (Signoret) respectively on CSSV-free cacao. and (2) to provide molecular-based information on the ability of these mealybugs to acquire and transmit the ‘New Juaben’ CSSV strain from CSSV-infected cacao. Electrical penetration graph (EPG) analysis established that these three mealybug species performed both extracellular (C, E1e, F, G and Np waveforms) and intracellular (E1 and E2 waveforms) feeding activities on cacao which were typical of stylet-possessing, phloem-feeding, virus transmitting hemipterans. Waveform F reported in this study is the first for Pl. citri, Ps. longispinus and Ps. viburni feeding on cacao. The competitive feeding efficiency of Ps. viburni on cacao highlights its potential as a ‘new’ vector of CSSV. PCR-based results show that Pl. citri, Ps. longispinus and Ps. viburni can acquire CSSV after a 72-h access acquisition period (AAP). DNA sequences of CSSV were detected in leaf tissues of the test plants after a 30-day post 72-h inoculation access period (IAP) by the viruliferous mealybug individuals. It is the first report, with molecular evidence, of T. cacao serving as an acceptable host to Ps. viburni

Variations in agromorphological characteristics of IPGRI Cowpea (Vigna unguiculata (L.) Walp.) accessions

Cowpea (Vigna unguiculata (L.) Walp.) remains an important crop in the tropics. One of its challenges remains the selection and improvement of genotypes to meet location–specific needs. We studied ten cowpea accessions in Akamkpa and Ikom, Cross River State, Nigeria. Principal component and biplot analyses associated high yield with growth, flowering, pod and seed traits. Seed weight per plot and number of seeds per plot were phenotypically correlated (rp = 0.99, p ≤ 0.01). Number of seeds per plot and number of seeds per pod were genotypically correlated (rg = 1.00, p ≤ 0.01). TVu–980 did not flower at Akamkpa and TVu–1019 did not grow at Ikom. TVu–992, TVu–53, TVu11, TVu–3629 and TVu–980 (only at Ikom) cowpea accessions showed promising agromorphological attributes for possible crop improvement programmes in Ikom and Akamkpa

Canary melon (Cucumis melo L. var. Inodorus) response to lime-amended acid soil in the humid tropical rainforest of Nigeria

Preliminary field experiments were conducted to examine the influences of lime (CaCO3) rate (0, 1, 2, 3, 4, and 5 t ha-1 ) on the production of canary melon (Cucumis melo L. var. Inodorus) on acidic soil of Calabar, Nigeria. Canary melon production is presently limited to the northern part of Nigeria. The southern part of Nigeria has the potential to support its production, but for low soil pH. The experiment was laid out in a randomised complete block design with three replicates. The initial soil pH (1:2.5 H2O), 4.13, was improved to 4.69 (1 t ha-1 ) – 5.93 (5 t ha-1 ). There was no significant difference (p > 0.05) in soil pH increase after 2 t ha-1 of CaCO3. Liming significantly (p ≤ 0.05) increased available P, total N, Ca2+ , Mg2+ , K+ , effective cation exchange capacity, and base saturation of the soil, but reduced exchangeable acidity. Increased lime rates increased (p ≤ 0.05) seedling emergence, leaf (area, area index), vine (length and thickness), and fruit and seed yields. However, fruits sweetness was inconsistent. CaCO3 had significant (p ≤ 0.001) linear relationships and correlations with growth and yield traits of canary melon. Canary melon can be cultivated in Calabar with an application of 2 – 5 t ha-1 of CaCO3

IMPLICATIONS OF CRUDE OIL EXTRACTION ON AGRICULTURE AND LIVELIHOOD IN OIL PRODUCING RURAL COMMUNITIES IN NIGERIA

Activities of the oil and gas (O&G) industry directly influence the natural potentials of the ecosystem and human livelihood. In particular, the impacts of crude oil extraction grossly interfere with the daily economic life of man and the natural environment. This study evaluates people’s perception of the implications of crude oil extraction on agriculture and people’s livelihood in oil producing rural communities in Nigeria with particular focus on the Niger Delta region, an area where most onshore and offshore crude oil extractions are carried out. The bias in this study came from the fact that crude oil is mainly either extracted or transported across rural communities in the region through water routes and/or arable lands, the population here almost solely depends on natural resources – water and land – for their daily livelihood. Findings suggest that livelihood sources in the region are under evident direct threat of pollution and other impacts of the O&G industry. Results obtained from the descriptive analysis of 446 respondents indicate a perception of high impact of crude oil extraction on food prices (74.7%), food safety (60.5%), crop yield (48.2%) and animal production (28.3%). The results of the Ordered Probit regression analysis suggest that farmers and fishermen are more vulnerable or mostly affected by impacts of crude oil extraction in the region. The study thus opined that adequate mitigation of negative impacts of crude oil extraction would promote improved food safety, affordable food supply and improved household income in oil producing rural communities. Therefore, the O&G industry should intensify its commitments towards mitigating undesirable implications of exploration and extraction activities by O&G companies in the oil producing areas. In a bit to mitigate prevailing livelihood problems in the Niger Delta region, there is a need for O&G companies and government to provide necessary compensations, trainings and other support to help the rural people sustain their livelihood. In addition, all stakeholders in the O&G industry should collaborate with academic and research institutions to promote research in agriculture towards achieving improved food production and food safety in areas affected by impacts of crude oil extraction

GGE Analysis of Multi-Location Yield Trial of Ginger (Zingiber officianale Rosc.) Genotypes in South-Eastern, Nigeria

Multi-location trials were conducted in 2016 and 2017 at Calabar, Ikom and Ogoja in Cross River State, Nigeria, to determine the yield stability of 17 ginger genotypes (G1–G17) using genotype and genotype by environment (GGE) biplot model. The location and year combination gave six environments (E1–E6). The experiment was laid out in split plots using a randomized complete block design with three replications. Yield related traits like rhizome fingers, rhizome length, and rhizome yield were determined. E3 (i.e. Ikom in 2016) was ranked as the ideal environment for ginger production in Cross River State. While G5 (UGI-5-04) was classified as the ideal genotype for rhizome yield in Calabar, Ikom and Ogoja. Ikom in 2016 (E3) and 2017 (E4) were identified as mega-environments for UG1-13-02, UG1-5-04, UG1-5-18, UG1-5-35, UG1-5-38, UG2-11-03 and UG2-9-01 while Ogoja in 2016 (E5) and 2017 (E6) were identified as mega-environments for UG1-2-35, UG1-5-48, UG1-5-52 and UG1-7-24 ginger mutants. Ikom is recommended as a suitable environment for the cultivation of generally adapted ginger genotypes namely, UG1-5-04, UG1-5-38, UG1-13-02 and UG2-9-01). Ogoja was suitable for specific adaptation of UG1-7-24 and UG1-5-48 ginger mutants. These mutants are recommended for consideration in subsequent ginger breeding and improvement programmes

GGE Analysis of Multi-Location Yield Trial of Ginger (Zingiber officianale Rosc.) Genotypes in South-Eastern, Nigeria

Multi-location trials were conducted in 2016 and 2017 at Calabar, Ikom and Ogoja in Cross River State, Nigeria, to determine the yield stability of 17 ginger genotypes (G1–G17) using genotype and genotype by environment (GGE) biplot model. The location and year combination gave six environments (E1–E6). The experiment was laid out in split plots using a randomized complete block design with three replications. Yield related traits like rhizome fingers, rhizome length, and rhizome yield were determined. E3 (i.e. Ikom in 2016) was ranked as the ideal environment for ginger production in Cross River State. While G5 (UGI-5-04) was classified as the ideal genotype for rhizome yield in Calabar, Ikom and Ogoja. Ikom in 2016 (E3) and 2017 (E4) were identified as mega-environments for UG1-13-02, UG1-5-04, UG1-5-18, UG1-5-35, UG1-5-38, UG2-11-03 and UG2-9-01 while Ogoja in 2016 (E5) and 2017 (E6) were identified as mega-environments for UG1-2-35, UG1-5-48, UG1-5-52 and UG1-7-24 ginger mutants. Ikom is recommended as a suitable environment for the cultivation of generally adapted ginger genotypes namely, UG1-5-04, UG1-5-38, UG1-13-02 and UG2-9-01). Ogoja was suitable for specific adaptation of UG1-7-24 and UG1-5-48 ginger mutants. These mutants are recommended for consideration in subsequent ginger breeding and improvement programmes