Resistance of Oryza sativa and Oryza glaberrima Genotypes to RBe24 Isolate of Rice Yellow Mottle Virus in Benin and Effects of Silicon on Host Response

Rice yellow mottle virus (RYMV) is the most harmful virus that affects irrigated and lowland rice in Africa. The RBe24 isolate of the virus is the most pathogenic strain in Benin. A total of 79 genotypes including susceptible IR64 (Oryza sativa) and the resistant TOG5681 (O. glaberrima) as checks were screened for their reactions to RBe24 isolate of RYMV and the effects of silicon on the response of host plants to the virus investigated. The experiment was a three-factor factorial consisting of genotypes, inoculation level (inoculated vs. non-inoculated), and silicon dose (0, 5, and 10 g/plant) applied as CaSiO₃ with two replications and carried out twice in the screen house. Significant differences were observed among the rice genotypes. Fifteen highly resistant and eight resistant genotypes were identified, and these were mainly O. glaberrima. Silicon application did not affect disease incidence and severity at 21 and 42 days after inoculation (DAI); it, however, significantly increased plant height of inoculated (3.6% for 5 g CaSiO₃/plant and 6.3% for 10 g CaSiO₃/plant) and non-inoculated (1.9% for 5 g CaSiO₃/plant and 4.9% for 10 g CaSiO₃/plant) plants at 42 DAI, with a reduction in the number of tillers (12.3% for both 5 and 10 g CaSiO₃/plant) and leaves (26.8% for 5 g CaSiO₃/plant and 28% for 10 g CaSiO₃/plant) under both inoculation treatments. Our results confirm O. glaberrima germplasm as an important source of resistance to RYMV, and critical in developing a comprehensive strategy for the control of RYMV in West Africa.     

Concentrations and Health Risk of Polycyclic Aromatic Hydrocarbons in Some Brands of Biscuits in the Nigerian Market

Concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined in 40 brands of biscuits in the Nigerian market. The analyses were performed by gas chromatography-flame ionisation detection (GC-FID) after Soxhlet extraction of the sample with hexane/dichloromethane and clean-up of the extract. The concentrations of Σ16 PAHs in these biscuit samples were in the range of 35.7–645.3 μg kg^?1, 75.9–490.7 μg kg^?1, 91.5–537 μg kg^?1, 18.4–522.2 μg kg^?1, 123.5–393.8 μg kg^?1, 167.2–880 μg kg^?1, 136.5–316 μg kg^?1, and 135.5–241.6 μg kg^?1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The concentrations of Σ8 carcinogenic PAHs in the samples ranged from not detected (nd)–323.3 μg kg^?1, 15.7–138 μg kg^?1, 9.7–312.9 μg kg^?1, nd–331.7 μg kg^?1, nd–220.9 μg kg^?1, nd–53.3 μg kg^?1, 18.4–56.6 μg kg^?1, and 6.6–170.8 μg kg^?1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The margin of exposure (MOE), based on PAH8 as an indicator for the occurrence and effects of PAHs in food, was less than 10,000, the serious health effects value, in 30% and 8% of the brands for the child and adult scenarios, respectively.     

Variability of chloroplast DNA and nuclear ribosomal DNA in cassava (Manihot esculenta Crantz) and its wild relatives

Chloroplast DNA (cp) and nuclear ribosomal DNA (rDNA) variation was investigated in 45 accessions of cultivated and wild Manihot species. Ten independent mutations, 8 point mutations and 2 length mutations were identified, using eight restriction enzymes and 12 heterologous cpDNA probes from mungbean. Restriction fragment length polymorphism analysis defined nine distinct chloroplast types, three of which were found among the cultivated accessions and six among the wild species. Cladistic analysis of the cpDNA data using parsimony yielded a hypothetical phylogeny of lineages among the cpDNAs of cassava and its wild relatives that is congruent with morphological evolutionary differentiation in the genus. The results of our survey of cpDNA, together with rDNA restriction site change at the intergenic spacer region and rDNA repeat unit length variation (using rDNA cloned fragments from taro as probe), suggest that cassava might have arisen from the domestication of wild tuberous accessions of some Manihot species, followed by intensive selection. M. esculenta subspp flabellifolia is probably a wild progenitor. Introgressive hybridization with wild forms and pressures to adapt to the widely varying climates and topography in which cassava is found might have enhanced the crop's present day variability.     

Variability,repeatability, character correlation and path coefficient analyses in yellow yam

Summary Phenotypic variances, genetic coefficients of variation, repeatability, expected genetic advance, correlation coefficients and path coefficients were estimated for seven agronomic traits in yellow yam. Plant leafiness, leaf virus infection, number of tubers per hill and tuber yield showed higher expected genetic advances associated with higher repeatability. Positive and highly significant correlations of tuber yield with plant leafiness, shoot height and vine dry weight were observed. Correlations of time to vine emergence and leaf virus infection with yield were negative. Path analysis showed that leaf virus infection had a large negative direct as well as indirect effect on yield. Based on these studies, it is suggested that resistance to leaf virus infection, as expressed by foliage vigour, is the chief criterion for selecting high yielding plant types in yellow yam.     

Ethnobotany ofTelfairia occidentalis (cucurbitaceae) among Igbos of Nigeria

The fluted pumpkin (Telfairia occidentalis), an important cucurbitaceous leaf and seed vegetable, is indigenous to the west tropical rainforest area from Bendel to Cross Rivers states of Nigeria (c. longitude 7°–8° E and latitude 5°–6° N). Though endemic to southeastern Nigeria, Telfairia is of local ethnobotanical importance in the folklore and the dietary and cropping systems of Igbos and their neighbours. There is no reported definitive ethnobotanical study relating to this cucurbit.Telfairia has long been important in the internal food trade of Igbos. Like other leaf vegetables, it is of low commerical value, but can in some cases provide an appreciable cash income to small farm families. Its leaves, succulent shoots, and seed kernels constitute the usual ingredients that are popular and regularly consumed in Igbo soups. Soups made of leaf vegetables are essential for consumption of starchy pastes of yam, cassava, or cocoyam, which are frequently consumed in the humid areas of Nigeria. Many good attributes account for the increasing importance of this chief vegetable among 30–35 million people in Nigeria.