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

Relationship between yield and some yield components in cowpea varieties infected with two cowpea potyviruses

Bean common mosaic virus–blackeye cowpea strain (BCMV-BlC) and cowpea aphid-borne mosaic virus (CABMV) belonging to the genus potyvirus are cosmopolitan and economically important pathogens of cowpea. This study analysed the linear relationship between yield and some yield related characters (numbers of pods per plant, number of seeds per pod, pod growth rate, etc) in 15 cowpea lines infected with BCMV-BlC and CABMV. Isolates of the viruses were mechanically inoculated into the cowpea lines; as a result of the effect of viruses, the cowpea lines were categorized as highly resistant, tolerant, susceptible and highly susceptible. The linear associations between yield and other characters in resistant and tolerant varieties were similar to the associations in susceptible and highly susceptible varieties. The similarity in the correlation coefficient regardless of the susceptibility status was caused by systemic spread of infections in susceptible cowpea varieties such that organs were uniformly reduced while there was minimal reduction in tolerant and no reduction in highly resistant varieties. Pod growth rate correlated (p > 0.05) positively and highly with the yield in seven susceptible varieties and in 5 of the 8 resistant varieties infected by CABMV and BCMV-BlC and the relationship between disease severity and yield showed that as disease severity increased cowpea yield decreased. BCMV-BlC reduced the seed yield between 62 to 87% and CABMV between 54 to 87% in some cowpea varieties. Keywords: cowpea, potyvirus, virus infection, correlation, plant disease Global Journal of Pure and Applied Sciences Vol. 12(1) 2006: 11-1

SCREENING COWPEA (Vigna unguiculata (L.) Walpers) LINES FOR RESISTANCE TO SOME VIRUSES IN NIGERIA

Thirty-three Cowpea lines were screened in a greenhouse at Ibadan, southwest Nigeria for response to four cowpea viruses, namely the bean common mosaic Potyvirus-blackeye Cowpea strain (BCMV-BIC), Cowpea aphid-borne mosaic Potyvirus (CABMV), Cowpea Mottle Carmovirus (CMeV) and southern bean mosaic Sobevirus (SBMV). Disease severity was scored from; 1=no infection, to 5=very severe infection. Symptomless lines were serologically tested with protein-A sandwich enzyme- linked immunosorbent assay (PAS-ELISA) to distinguish lines with latent infection from the non-infected lines. Nine Cowpea lines were severely or very severely infected by the four viruses. Three viruses namely BCMV-BIC, CABMV and SBMV-BIC did not infect two lines (IT90K-284-2 and IT82D-889). In addition, CABMV and BCMV-BIC did not infect the cowpea varieties IT85F-2687 and Futo Coiled. SBMV and BCMV-BIC did not cause infection on CP-VAR8. No infection in some Cowpea lines indicated resistance to the virus and such lines are potential breeding materials for elite varieties. The incidence of BCMV-BIC infection was 100% in 13 lines, CABMV infection in 9, CMeV in 15 and SBMV in 3

Ecological Characteristics of Para Rubber (Hevea brasiliensis Muell. Arg) Productivity in the Niger Delta Region of Nigeria

The Niger Delta region is the rubber belt of Nigeria, and rubber production in the area which is dominated by smallholder plantations, is characterized by low latex yield, due mainly to ageing plantations, unsuitable agronomic practices and high cost of labour. Differences in soil and weather attributes of the area require that farmers adopt location-specific management practices in order to increase yield. Consequently, the relationship between medium-term latex yield of rubber and soil and weather attributes were studied in three rubber growing areas of the Niger Delta, with a view to assessing the fertility status of soils supporting rubber and determining the critical weather factors so as to make recommendations on best management practices. Weather data for estate plantations located in Calabar (latitude 5º 7’N and 8º 18’ E), Nko (latitude 5º 5’ N; 8o 11’ E), and Uyo ((latitude 5º 0’ N; 7º 10’E), spanning a period of 20 years (1993-2012), were obtained from the Nigerian Meteorological Service (NIMET) and subjected to multiple linear correlation and regression analysis with archival latex yield data from the various estates covering the same period. The minimum amount of rainfall received was 2148.7 mm/annum spread over a period of 135 days at Nko, while a maximum of 3968.7 mm/annum of rainfall spread over 143 days was received in Calabar. Rainfall intensity varied widely across the three locations, while the relative humidity was high, but similar across the locations and the highest ambient temperature of about 32ºC was at the Nko plantation. There was high correlation between weather variables and latex yield. The high negative correlation of latex yield with rainfall in Calabar and Uyo suggest that these areas experience excessive rainfall which might result in the prevalence of fungal diseases and frequent disruption of tapping operations. Maximum temperature correlated negatively with yield at Nko implying that measures to reduce evapo-transpiration such as mulching the base of trees and cover cropping should be adopted in this area. The soil texture was sandy loam in Calabar and Uyo, and sandy clay loam at Nko, and although the pH across the estates was within the recommended range of 4.0 - 6.5, the soils at Calabar and Uyo requires liming for sustained high productivity

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