Co-composting of sewage sludge and Echinochloa pyramidalis (Lam.) Hitchc. & Chase plant material from a constructed wetland system treating domestic wastewater in Cameroon

Trials were conducted at the Cité-Verte domestic wastewater treatment station (Yaoundé-Cameroon) in order to assess the effect of three sewage sludge: Macrophyte ratios on the co-composting process and compost quality. The ratios were T1: 25 kg of plant material (Echinochloa pyramidalis) and 75 kg sludge; T2: 50 kg of plant material and 50 kg sludge, and T3: 75 kg of plant material and 25 kg of sludge. The assessment parameters of the co-composting process included the daily evolution of temperature, the pH and water content for each month. The quality of the mature compost obtained was analysed based on their C/N ratio, Ca, Mg, P, K, trace elements and helminth eggs content. During cocomposting, maximum temperatures ranged from 45.3 ± 4.7°C (T1) to 70.77 ± 2.76°C (T3). Mature cocompost was obtained after 3 months (T1), 4 months (T2) and 5 months (T3). Mean pH and C/N ratio of co-composts respectively ranged from 7.26 to 7.62 and from 10 to 15. In mature compost, the average values of organic matter, N and P respectively were 3323 ± 405 mg/kg, 165 ± 32 mg/kg and 36 ± 5 mg/kg for T1; 2945 ± 128 mg/kg, 152 ± 30 mg/kg and 27 ± 6 mg/kg for T2; and 228 ± 103 mg/kg, 105 ± 48 mg/kg and 7 ± 1 mg/kg for T3. K content was 1 mg/kg in all three co-composts. Heavy metals were found at trace levels. Helminth eggs concentration in compost was 0.2 ± 0.03 egg/g (T1), 0.1 ± 0.02 egg/g (T2) and 0.007 ± 0.01 egg/g (T3). All these co-composts did not present a significant hygienic risk with regards to WHO guidelines (2006) for safe reuse of faecal matter or faecal sewage in agriculture (less than 1 egg/g TS). For a given amount of plant harvested, it was concluded that the quickest way to produce a compost safe of parasites will be to mix them with 3/4 of sludge from the digestion tank.Key words: Co-composting, Cameroon, compost quality, Echinochloa pyramidalis, hygienic risk, sewage sludge

Evaluation of maize (Zea mays L.) accessions using line x tester analysis for aluminum and manganese tolerance

Soil acidity is a limiting factor severely affecting the growth and yield of maize. The present study aimed at estimating the breeding value of inbred lines and to assess the test-cross performance of the hybrid maize under acid soil conditions. A line x tester analysis involving 63 test-crosses generated by crossing 20 maize inbred lines with 3 testers and between testers themselves, and 1 standard check was investigated during the cropping season 2012 in two contrasted regions with aluminum and manganese toxicity in Cameroon. Both treatments, acid soil and non-acid soil, using dolomitic lime were conducted in a randomized complete block design with 3 replications. Seven hybrids producing high grain yield (4.27 to 9.88t/ha), with high specific combining ability (SCA) and slow rate of yield loss were discovered such as tolerant for both types of acidic soils. Likewise, four inbred lines (ATP-46, 87036, and Cam Inb gp117, C4SRRA7) with high general combining ability (GCA) were retained as good progenitors. The GCA and SCA effects showed that the tolerance to aluminum toxicity was controlled by additive effects of genes while on acid soil with manganese toxicity, the contribution of non-additive effects of genes was dominant.Keywords: Inbred lines, hybrids, acid soil, GCA, SCA, humid forest zone

Phytoremédiation de sols pollués par les hydrocarbures – évaluation des potentialités de six espèces végétales tropicales

Les écoulements et les transferts de matières à travers les sols et sous-sols sont des processus qui impactent les ressources en eau. Ainsi, la restauration des milieux dégradés participe à la préservation de la qualité de la ressource. Afin de contribuer à la décontamination des sols pollués par phytoremédiation - technique de dépollution basée sur l’action des plantes en association avec les micro-organismes du sol - des inventaires floristiques de sites potentiellement pollués et non pollués (témoins) par les hydrocarbures ont été réalisés dans quatre villes du Cameroun. Sur la base d'indicateurs floristiques, six espèces ont été sélectionnées, et leurs capacités phytoremédiatrices testées dans un sol pollué par du fioul à 82,5 mL∙kg‑1 de sol pendant 150 jours en présence de trois modalités : Tn - sols non pollués plantés (6), To - sols pollués non plantés (3) et Tp - sols pollués plantés (18). La biodiversité des sites pollués (106 espèces, 76 genres et 30 familles) est moins élevée que celle des témoins (166 espèces, 125 genres et 50 familles). Les espèces les plus fréquentes (Fri > 10 %) et abondantes (7 % < A < 10 %) sur les sites potentiellement pollués sont dominées par 15 espèces tropicales; parmi lesquelles, Eleusine indica (L.) Gaertn., Cynodon dactylon (L.) Pers., Alternanthera sessilis (L.) R. Br. ex DC†, Commelinpa benghalensis L., Cleome ciliata Schum. et Thonn., et Asystasia gangetica (L.) T. Anderson, sont utilisées dans des essais de phytoremédiation des sols contaminés au fioul domestique. Seules trois de ces espèces, notamment E. indica, C. dactylon et A. sessilis ont pu survivre et se développer. Contrairement à A. sessilis, E. indica et C. dactylon ne présentent pas de différence significative pour les paramètres de croissance considérés entre les modalités Tn et Tp. Les espèces E. indica et C. dactylon seraient donc plus tolérantes au fioul domestique que l’espèce A. sessilis.Flows and transfers of materials through soils and subsoils are processes that impact water resources. Thus the restoration of degraded areas contributes to the preservation of the quality of the resource. In order to contribute to the decontamination of polluted soil, phytoremediation (a clean-up technique based on the action of plants in association with soil microorganisms), floristic surveys of potentially polluted and unpolluted (control) sites by hydrocarbons were carried out in four cities of Cameroon. On the basis of floristic indicators, six species were selected and their phytoremediation capacities tested in a soil polluted by fuel oil at 82.5 mL∙kg‑1 of soil for 150 d in the presence of three modalities: Tn - unpolluted soil planted (6), To - unplanted polluted soils (3) and Tp - polluted soil planted (18). The biodiversity of polluted sites (106 species, 76 genera and 30 families) was lower than the controls (166 species, 125 genera and 50 families). The most frequent species (Fri > 10%) and most abundant (7% < A < 10%) on potentially polluted sites were dominated by 15 tropical species; among these, Eleusine indica (L.) Gaertn., Cynodon dactylon (L.) Pers., Alternanthera sessilis (L.) R. Br. ex DC†, Commelinpa benghalensis L., Cleome ciliata Schum. & Thonn. and Asystasia gangetica (L.) T. Anderson were used in phytoremediation trials on soil polluted with domestic oil. Only three of these species, including E. indica, C. dactylon and A. sessilis, were able to survive and develop. Unlike A. sessilis, E. indica and C. dactylon showed no significant difference for the growth parameters considered between the Tn and Tp modalities. E. indica and C. dactylon are therefore more tolerant to domestic oil than A. sessilis

Micropropagation of Dioscorea alata L. from microtubers induced in vitro

A new method made up of different steps was established for micropropagation of Dioscorea alata. First plantlets were regenerated from shoots proliferating on nodal cuttings cultured on half strength Murashige and Skoog salt medium (MS/2) (basal medium) supplemented with 0.5 mg l-1 BAP and 1 mg l-1 NAA. These plantlets were used to induce microtubers on the basal medium supplemented with 1 to 5 mg l-1 6-benzylaminopurine (BAP), kinetin (Kin) or α-naphthalene acetic acid (NAA) and 10 to 60 g l-1 sucrose. BAP at 2 to 3 mg l-1 combined with 20 to 30 g l-1 sucrose was more effective than Kin and NAA. It gave rise to 92% plantlets producing microtubers and the highest numbers of microtubers per plantlet varied between five and six. Microtubers, when sectioned and cultured on the basal medium supplemented with different BAP/NAA or Kin/NAA ratios, differentiated into shoots that, when isolated and subcultured in the same media, gave rise to rooted plantlets. The highest percentage of microtubers that differentiated into shoots was 98.8%, the highest number of shoots per microtuber was 7.5 and hence the highest number of rooted plantlets regenerated from those shoots was induced with BAP/NAA ratio (3/2 mg l-1) compared to that of BAP/NAA and Kin/NAA ratios. When the plantlets were acclimatized in different substrates, 97% survived in the mixture black soil/sand at equal volume (V/V) and this was the best result for the final step of the micropropagation of D. alata in this study. The different steps here described, allowed the regeneration of 45 and 16 plantlets from microtubers in about 251 days using BAP and NAA, respectively, and constituted a new and rapid method for the production of healthy seeds of this species.Keywords: Growth regulators, micropropagation, microtubers, yamAfrican Journal of Biotechnology Vol. 12(10), pp. 1057-106

Effects of varying PAHs-polluted soils on the morpho-anatomy and physiology of Bermuda grass

This study was conducted to show the effects of high PAH levels on the external and internal structures as well as the functioning of a Poaceae species – Bermuda grass – during phytoremediation process. Two modalities – Tn: unpolluted planted soil and Tp: polluted planted soil – are applied to the monoculture of Bermuda grass for pollution at 10%, 20%, and 30% (weight/weight) with fuel oil, and co-cropping with Goosegrass in soils polluted at 10%. Morphological results revealed that monoculture is better than co-cropping as the sociability of the two species is negatively affected by PAHs. Contrary to monoculture, in the co-cropping the relative growth rate of Bermuda grass morphological parameters is decreasing over time in Tp. For monoculture, the aboveground plant density of Bermuda grass in Tp is not significantly different to Tn, while its specific root length is higher in Tn than Tp. Anatomical and physiological analyses of Bermuda grass show that PAHs impacted the hydromineral nutrition of this species. In fact, the vascular bundles of the stems and roots of Bermuda grass were less numerous in Tp, and the chlorophyll synthesis was 50% inhibited. Despite the slower physiological processes of Bermuda grass in polluted soils, the phytotoxicity of very high PAH levels is not fatal to this species. Its development and evolution on soils highly polluted with PAHs and its phytoremediation potential (more than 95% for total petroleum hydrocarbons and up to 100% for chrysene) therefore recognize it as particularly suitable for hydrocarbon phytoremediation, with wide geographical application thanks to its cosmopolitan nature.</p

Modelling PAHs Transfer from Polluted Soil to Herbaceous Species in Phytoremediation Attempts

To address the soil&ndash;plant transfer modelling of 13 US-EPA Polycyclic Aromatic Hydrocarbons (PAHs), a mechanistic model&mdash;MM_19&mdash;has been developed based on the fugacity concept. For that, the Mackay_97 model has been improved in terms of reconsidering the losses related to the transport and transformation mechanisms taking place in the compartments&mdash;roots and aboveground shoots&mdash;of the three short-life species (Eleusine indica, Cynodon dactylon and Alternanthera sessilis). Model input parameters consist of both experimental and literature data, including the initial soil and air PAHs content, flowrates, PAHs physico-chemical properties, retention times and transport half-lives of PAHs inside plant species. Using in situ weather data and Penman&rsquo;s law, xylem flows were estimated as the evapotranspiration for each plant. Model calibration was performed using a Generalized Reduced Gradient (GRG) nonlinear optimization solver method. Sensitivity analysis showed that the phloem flow was the most sensitive among all tested parameters. According to the Nash&ndash;Sutcliffe efficiency (NSE), the MM_19 model is more efficient than the Mackay_97 model for all three plant species. Finally, the impact of PAHs physico-chemical parameters on their sol-plant transfer was discussed in terms of slight, intermediate and high molecules weight. The NSE values showed that the MM_19 model is more efficient than the Mackay_97 model. Indeed, comparisons between experimental and simulated results in the MM_19 model showed similarities for each compartment of the plant species. Thus, the MM_19 model can be used to predict the soil&ndash;plant transfer of organic pollutants

Phytoremédiation de sols pollués par les hydrocarbures – évaluation des potentialités de six espèces végétales tropicales

Les écoulements et les transferts de matières à travers les sols et sous-sols sont des processus qui impactent les ressources en eau. Ainsi, la restauration des milieux dégradés participe à la préservation de la qualité de la ressource. Afin de contribuer à la décontamination des sols pollués par phytoremédiation - technique de dépollution basée sur l’action des plantes en association avec les micro-organismes du sol - des inventaires floristiques de sites potentiellement pollués et non pollués (témoins) par les hydrocarbures ont été réalisés dans quatre villes du Cameroun. Sur la base d'indicateurs floristiques, six espèces ont été sélectionnées, et leurs capacités phytoremédiatrices testées dans un sol pollué par du fioul à 82,5 mL∙kg‑1 de sol pendant 150 jours en présence de trois modalités : Tn - sols non pollués plantés (6), To - sols pollués non plantés (3) et Tp - sols pollués plantés (18). La biodiversité des sites pollués (106 espèces, 76 genres et 30 familles) est moins élevée que celle des témoins (166 espèces, 125 genres et 50 familles). Les espèces les plus fréquentes (Fri &gt; 10 %) et abondantes (7 % &lt; A &lt; 10 %) sur les sites potentiellement pollués sont dominées par 15 espèces tropicales; parmi lesquelles, Eleusine indica (L.) Gaertn., Cynodon dactylon (L.) Pers., Alternanthera sessilis (L.) R. Br. ex DC†, Commelinpa benghalensis L., Cleome ciliata Schum. et Thonn., et Asystasia gangetica (L.) T. Anderson, sont utilisées dans des essais de phytoremédiation des sols contaminés au fioul domestique. Seules trois de ces espèces, notamment E. indica, C. dactylon et A. sessilis ont pu survivre et se développer. Contrairement à A. sessilis, E. indica et C. dactylon ne présentent pas de différence significative pour les paramètres de croissance considérés entre les modalités Tn et Tp. Les espèces E. indica et C. dactylon seraient donc plus tolérantes au fioul domestique que l’espèce A. sessilis.Flows and transfers of materials through soils and subsoils are processes that impact water resources. Thus the restoration of degraded areas contributes to the preservation of the quality of the resource. In order to contribute to the decontamination of polluted soil, phytoremediation (a clean-up technique based on the action of plants in association with soil microorganisms), floristic surveys of potentially polluted and unpolluted (control) sites by hydrocarbons were carried out in four cities of Cameroon. On the basis of floristic indicators, six species were selected and their phytoremediation capacities tested in a soil polluted by fuel oil at 82.5 mL∙kg‑1 of soil for 150 d in the presence of three modalities: Tn - unpolluted soil planted (6), To - unplanted polluted soils (3) and Tp - polluted soil planted (18). The biodiversity of polluted sites (106 species, 76 genera and 30 families) was lower than the controls (166 species, 125 genera and 50 families). The most frequent species (Fri &gt; 10%) and most abundant (7% &lt; A &lt; 10%) on potentially polluted sites were dominated by 15 tropical species; among these, Eleusine indica (L.) Gaertn., Cynodon dactylon (L.) Pers., Alternanthera sessilis (L.) R. Br. ex DC†, Commelinpa benghalensis L., Cleome ciliata Schum. & Thonn. and Asystasia gangetica (L.) T. Anderson were used in phytoremediation trials on soil polluted with domestic oil. Only three of these species, including E. indica, C. dactylon and A. sessilis, were able to survive and develop. Unlike A. sessilis, E. indica and C. dactylon showed no significant difference for the growth parameters considered between the Tn and Tp modalities. E. indica and C. dactylon are therefore more tolerant to domestic oil than A. sessilis

Flavan‑3‑ol and favonol analysis in healthy and infected parents and progenies of cocoa leaves (Theobroma cacao L.) with Phytophthora megakarya Bras. and Grif

Flavonoids are phenolic compounds involved in defense mechanisms against black pod disease (BPD). Crossing between Forastero and Trinitario-resistant cocoa genotypes usually produce resistant progenies with high contents of bioactive components. This study aims at analyzing flavan-3-ol and flavonol content in the defense against P. megakarya in T. cacao genotypes for their potential selection as markers of partial resistance to BPD. Assessment of necrosis development and biochemical markers of stress (total polyphenols (TPP), total flavonoids (TF), and condensed tannins (CT)) through spectrophotometric methods of 19 genotypes identified eight hybrids that contained higher amounts (P˂0.05) of bioactive components than the better parent T79/467. The necrosis length revealed to be negatively correlated with metabolite concentrations (P < 0.05). Flavan-3-ols and flavonols were analyzed by normal phase (NP) and reverse phase (RP) HPLC–DAD-ESI (-)-MS/MS. Among the best genotypes, flavan-3-ol monomers (( +)-catechin, (-)-epicatechin), derived procyanidins (especially B2 and four of its isomers, C1, and one pentamer), and flavonols (quercetin, quercetin-3-O-arabinoside, quercetin-3-O-glucoside, quercetin-3-O-rhamnoglucoside, and one isomer) were evidenced both in healthy and infected leaves. Analyzed metabolites increase following infection, but infection does not trigger the synthesis of new compounds. The order of accumulation of biomolecules is as follows: (-)-epicatechin (196%), procyanidin C1 (184%), pentamers (140%), procyanidin B2 (135%), quercetin (80%), quercetin derivatives (57–69%), and ( +)-catechin (57%). Yet their accumulation after infection revealed to be genotype-dependent. This breeding approach is designed to select partial resistant cocoa genotypes against BPD evidenced useful biomarkers in hybrids with high flavonoid content