Detection of Rice Yellow Mottle at the Asymptomatic Stage by Hyperspectral Fluorescence and Reflectance Spectroscopies

Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.

Yield, Growth and Vegetative Development Parameters Response of Dry Beans to Organic and Inorganic Fertilizers and Biofertilizer

As part of the promotion of common bean cultivation, fertilization methods will have to be proposed to growers. The aim of this study is therefore to develop a technical itinerary for dry bean fertilization. To this end, different types of chemical and organic fertilizers were evaluated on three dry bean varieties (HARI25/GHA19, HARI35/GHA19 and HARI36/GUI21). Seven (7) doses of chemical and organic fertilizers were used, including two controls (D0 with no fertilizer and D1, the reference dose using NPK base and cover fertilizers in the form of urea). The fertilization trial was set up as a Split-Plot design, with variety as the primary factor and dose as the secondary factor. The experiment was repeated three (3) times. The results showed that vegetative development parameters and fruit set rate varied according to the variety studied. For yield and its components, the treatments had a significant effect. Indeed, the response of varieties to fertilizers was specific. For each variety used, the optimum yield was obtained with a different treatment, thus highlighting the genotype effect of the dry bean varieties studied. Among the treatments tested, D4 (5 t organic fertilizer/ha) performed best in all three varieties, generating yield increases of 20%, 46% and 91% respectively.

Water Stress Early Detection of Eggplant Plants by Hyperspectral Fluorescence Spectroscopy

Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T100), intermediate irrigation (T50) and no irrigation (T0). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.

Evaluation of the Productivity of Intercropping Plantain Cultivar (PITA 3) Fertilized with Two Types of Manure, under Coconut Tree Based (Cocos nucifera L.), on the Tertiary Sands of Côte d’Ivoire

Pressure on land tenure is having a negative impact on the coconut sector, reducing farmers’ incomes. Intercropping cultivars plantain under coconut based has been considered as a solution to this problem. The aim of this work is to diversify the sources of income for coconut growers. The plantain variety PITA 3, popularised by the CNRA, was grown in coconut inter-rows (PB113+), with two types of manure (chemical, organic). Six (06) treatments D1, D2, D3, D4, D5 and D6 were studied. In the tenth month after planting, treatment D3, which included banana plants fertilised with 9 kg of manure/plant, got the best agromorphological performance: height (264.08 cm), neck circumference (57.68 cm) and 12 leaves. In terms of production parameters, D3 banana plants had a shorter production cycle (347 days) and the highest diet mass (9.3 kg). However, the plants that received no fertiliser (D6) showed stunted growth and were unable to produce brunch. The fertilization of plantain with 10 t/ha of laying hen droppings permitted good development and production of plantains on tertiary sands.

Former Botanical Garden of ORSTOM(Côte d’Ivoire):What Remain after Thirty Years of Abandonment and Forest Restoration

Botanical gardens represent important places for ex situ conservation.One of these botanical gardens has been abandoned in Côte d’Ivoire for 30 years.This is the former botanical garden of ORSTOM.This study was conducted to determine the level of diversity of this former garden in order to assess the opportunity for its rehabilitation.The authors carried out inventories in 18 quadrats of 500 m2 through the vegetation to collect woody species.Dendrometric measurements(height,diameter)were also recorded to assess the structure of the site.A total of 190 species have been identified.They belong to 141 genera and 47 families.This former botanical garden contains important species because of their origin,status or particularity(threatened,endemic,rarity,etc.).A total of 19 threatened species including 2 endangered and west African endemic(Chrysophyllum azaguieanum J.Miège,Placodiscus pseudostipularis)were found at the site.Also,Chrysophyllum azaguieanum is declared extinct from Côte d’Ivoire.Four species are rare in the flora of Côte d’Ivoire:Balanites wilsoniana,Chrysophyllum azaguieanum,Gilletiodendron kisantuense and Loesenera kalantha.The most abundant species is Hopea odorata.Although this introduced species is considered globally vulnerable,it presents a risk of invasion in the forest of Côte d’Ivoire.The diameter and height structures show that all the stages of development are presented indicating a good regeneration on the site.Ultimately,this botanical garden deserves to be rehabilitated and especially urgent management of Hopea odorata is needed to prevent an invasion of this species.

Determination of Leafy Vegetables Need in Water andNitrogen Use Efficiency by Using the Diviner 2000 andthe Isotopes Techniques: Case of Amaranth(Amaranthus cruentus)

A study was conducted to determine how the nitrogen(N)in the fertilisers can be quantified and what amounts of fertilizers should be given to leafy vegetables to achieve their requirements.This study also aimed to determine the efficient use of water by the plant.The experiment was laid out in a randomized complete block with three replicates and three levels of urea(T0=0 kg/ha,T1=43.5 kg/ha,T2=65 kg/ha).Estimation of growth parameters and biomass yield revealed that the treatments produced statistically identical values.But numerically,T1(43.5 kg of urea/ha)gave the highest yields and T2(65 kg of urea/ha)produced the lowest.It was the same for the determination of the water use efficiency(WUE)by the plant where T1 produced the highest values compared to T2.The yield curve as a function of the applied urea dose allowed the identification of the urea dose that corresponds to optimal yield in amaranth.From the dose of 65 kg of urea/ha,any increase becomes harmful to the plant.This results in a decrease in yield in the amaranth plant.

High-Yielding and Carotenoid-Rich Clones Identification among Thirty-One Cassava Clones with Colored Flesh

Cassava is the second most important food crop produced and consumed in Côte d’Ivoire, after yam. White-fleshed varieties, which are low in total carotenoids, are widespread, while coloured-fleshed varieties (yellow to orange), carotenoid-rich, are rare. However, the consumption of carotenoid-rich cassava varieties could help to alleviate health problems related to vitamin A deficiency. This study aims to identify high agronomic performance, carotenoid-rich and versatile cassava varieties among 31 clones introduced from IITA. They were compared to three controls, Bocou2, Yacé and Bonou2, according to agronomic and technological parameters. Results found that out of the 31 clones, six (I082425, I084157, I084563, I085894, I083774 and I070520) were more productive than the control Bocou2 (46.01 ± 14.88 t·ha-1);the clone I083774 had the highest yield (55.88 ± 6.16 t·ha-1). Twenty-one clones had dry matter contents, ranging from 37% to 41%, significantly similar to Yacé control (42.70%). Thirteen clones had highest total carotenoid contents than the control Bocou2. Clones I084157 and I082425 recorded the highest total carotenoid contents with 17.57 ± 1.92 and 18.39 ± 1.19 μg·g-1 respectively. Overall 31 tested clones were fibrous to varying degrees while 27 clones had mild or neutral post-cooking flavours and 17 clones had poor cooking. The clone I084157 is the best compromise of agronomic and technological desired traits.

Biometric Analysis on Genetic Divergence between Parental and Regenerated Accessions in Tall Coconut Palms (Cocos nucifera L.) from International Genebank for Africa and the Indian Ocean

This study endeavour assesses agromorphological likeness between initial introductions and regenerated accessions at the International Coconut Genebank for Africa and the Indian Ocean (ICG-AIO) based in C?te d’Ivoire. Ten couples of parental (G0) and regenerated (G1) accessions of Tall coconut palms were analyzed using Principal Component Analysis (PCA) and Multiple Analysis of Variance (MANOVA) from 26 agromorphological characters. The main results showed a relative decrease in the expression of the phenotypical traits concerning the component of the fruit, height and vigor of the stem and yield of bunches and fruits after one regeneration cycle. But, a high proportion (69%) of studied characters from leaf, inflorescence and nut components showed likeness between G0 and G1 accessions. After one regeneration cycle, the controlled pollination method guarantees significant conservation of the expression of the majority of agromorphological traits. Consequently, regenerated accessions of Tall coconut palms can be used to pursue research and development programs in C?te d’Ivoire.

Effect of Water Stress Induced by Polyethylene Glycol 6000 on Somatic Embryogenesis in Cocoa (<i>Theobroma cacao</i>L.)

Climate change, coupled with insufficient and irregular rains, led to a decline in the productivity of Ivorian cocoa production. The present study aimed to screen three cocoa (Theobroma cacao L.) genotypes in order to evaluate their response to water stress at callus and somatic embryos induction and proliferation stages. Staminode and petal explants of the genotypes C1, C14 and C16 from the collection of National Center of Agronomic Research (CNRA) of Ivory Coast, were placed on medium DKW (Driver & Kuniyuki Walnut) in the presence of different concentrations of Polyethylene glycol (PEG) 6000 (0, 25, 50, 75, 100 and 125 g/l). This polymer was used as osmoticum to stimulate water stress. Data were recorded for callus induction frequency, callus fresh weight, embryogenic callus percentage and average number of somatic embryos. The results obtained showed that intensity of callus proliferation decreased with increasing concentration of PEG 6000. In all genotypes tested, only the petal explants underwent somatic embryogenesis. The induction rates and average number of somatic embryos per explant were reduced with the increase in the concentration of PEG 6000. Among the tested genotypes, C1 produced somatic embryos with all concentrations of PEG 6000 and expressed highest frequencies of induction (62%) and average number of somatic embryos per explant (6.22). This genotype would be the most tolerant to water stress. Somatic embryos obtained with high concentrations of PEG 6000 in this study provide an important basis for the selection and further production of water stress-tolerant varieties of cocoa.

Activated Carbon Based on Acacia Wood (<i>Auriculeaformis</i>, Côte d’Ivoire) and Application to the Environment through the Elimination of Pb²⁺Ions in Industrial Effluents

The objective of this study is to develop carbon, that of Acacia auriculeaformis through its activation in order to eliminate lead in an aqueous medium. A series of activated carbon has been prepared by chemical activation with phosphoric acid, sodium hydroxide and sodium chloride. The determination of the physico-chemical properties of the prepared carbon guided the choice of phosphoric acid activated carbon as the best adsorbent for the elimination of lead(II) in an aqueous solution. Pb2+ adsorption tests in batch mode have shown that the adsorption capacity is influenced by various parameters such as mass, pH, concentration of Pb2+ ions and contact time linked to the medium and the adsorbent. Adsorption isotherms, kinetic models and thermodynamics have been used to describe the adsorption process. The equilibrium data for activated charcoal correspond well to the model of Freundlich, Langmuir, Temkin and Kiselev. The kinetic adsorption data proved to be better described by the pseudo-second order model with external and intraparticle diffusion which are two decisive steps in the adsorption process of Pb2+ ions. Thermodynamics and adsorption isotherms predict a spontaneous exothermic surface reaction, of the chemisorption type, with ion retention in orderly monolayers on the heterogeneous surface of the adsorbent. Tests carried out with this adsorbent material have contributed to the elimination of the Pb2+ ions contained in an industrial effluent with a reduction rate reaching 42.52% against 85.90% in a synthetic solution.

Stand Structure,Allometric Equations,Biomass and Carbon Sequestration Capacity of Acacia mangium Wild.(Mimosaceae)in Cote d’Ivoire

In addition to bioenergy production, Acacia magium, a fast growing species, plays a major role in climate change mitigation through carbon sequestration from the atmosphere. The objective of this study was to improve estimates of aboveground biomass of 3, 7 and 11 years old stands of Acacia mangium set up through natural regeneration at Anguédédou in C?te d’Ivoire. Tree measurements were done in circular plots of 615 m2 located at the center of each stand. 24 trees of circumference at breast height (cbh) between 31 and 116 cm were felled, weighed and measured. Multiple linear regressions were used to develop allometric equations linking aboveground biomass of trees to cbh and/or height. The carbon stock and sequestration capacity of each stand was assessed using these predictive models. The average cbh was 39.4 cm, 73.5 cm and 91.4 cm respectively for 3, 7 and 11 years old stands with a density ranging between 845 trees·ha-1 and 553 trees·ha-1. The allometric equations for biomass estimation were Btotal aboveground = exp(-3.455 + 2.081 × ln(C)), Btrunk = exp (-5.153 + 1.681 × ln(C) + 1.056 × ln(H)), Bbranches = exp(-2.005 + 0.498 × ln(C2 × H)), Bleaves = exp(-2.415 + 1.339 × ln(C)). Total height had no influence on total and leaf biomass but increased precision of trunk and branch biomass. The carbon sequestration capacity of aboveground biomass was highest in Acacia mangium stand of 7 years old with 45.14 teqCO2·ha-1·year-1 and lowest in the 3-year stand with 33.90 teqCO2·ha-1·year-1.

Water quality and water-use conflicts in Lake Taabo(Ivory Coast)

The Lake Taabo (Ivory Coast, Africa) results of the construction of the Taabo dam on the Bandama River. The changes in the water level of the 69-km2 lake depend on 1) the rainfall linked to alternating dry/wet seasons;2) the extraction of water for human uses;3) the discharge of water from the upstream dam and the volumes turbined by the Kossou dam;4) the various anthropic effects (discharge of untreated waste water from towns and industries, and leaching from agricultural land). The average concentrations of nutrients (NH4-N: 1.1 mg/L, NO3-N: 1.62 mg/L, PO4-P: 10 mg/L, SiO2: 15 mg/L) and chlo- rophyll a (from 4.8 to 16.5 μg/L, average 11.4 μg/L) indicates some degree of eutrophication. The cumulated effects that threaten the ecosystem (degradation of water quality and eutrophication) are such that they are likely to interfere with various water uses. In a context of growing health and environmental concerns in Africa, this study demonstrates conflicts between different uses of this water resource and the urgent need for an appropriate policy including specific monitoring of lake water quality, wastewater control, and a programme to reduce agricultural fertilizers.