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This study is based on the observation that many digital tools and services for agriculture do not put farmers' expectations and interests first, resulting in top-down research and development. On-Farm Experimentation (OFE) contributes to overcoming these limitations because it places farmers at the center of innovation processes, while ensuring rich interactions with various value chain actors. The richness of OFE is in part explained by the diversity of stakeholders involved and the co-learning that results from their interactions. Studies in management and social sciences show that such open innovation processes can be difficult to manage. Aligning the visions and interests of the different stakeholders, fostering the sharing of resources and knowledge to produce value, and sharing the value created in an equitable manner remain a real challenge. Although these issues can refine the understanding of the mechanisms that condition the success of OFE, they have yet to be sufficiently analyzed. Recent publications underline the need to explore the organizational and managerial aspects of OFE to facilitate its implementation in various contexts. This work proposes to fill this gap by providing ten key lessons for conducting OFE with the aim of creating shared value, i.e., developing innovative technologies and practices that benefit all parties but, first and foremost, farmers. These ten key lessons stem from the reflexive monitoring of an OFE process aimed at developing the SoYield® decision support system for helping mango value chain actors to estimate fruit production in Africa. This reflexive monitoring was conducted by the main actors involved in this process, namely, farmers, a private firm and research centers. These key lessons lay the foundations for strengthening a community of practice on OFE implementation and for facilitating its development worldwide. This study also provides insights into the contributions and limitations of digital tools for conducting OFE.

Nutrient management is critical for the development and growth of rubber trees during the immature phase. We present the results of a fertilizer trial during the immature phase of a rubber plantation setup in Cambodia. The main objective of this study was to analyze the response of a specific clone, PB330, in the specific conditions of one of the most important rubber-growing areas of Cambodia. The experiment was arranged in a randomized complete block design with 4 treatments and 4 replications. The four treatments consisted of 3 fertilization treatments with an increasing dose of fertilizers (respectively T1, T2 and T3) compared to a non-fertilized control (T0). The girth of trees was measured every six months from the end of the first year after planting (YAP) to the end of the 6th YAP. Results showed that fertilization had a significant effect on tree girth. At the end of the 6th YAP, fertilization had a significant effect on the number of tappable trees, and stand basal area but not on average tree girth. The most pronounced effect of fertilization was observed from annual increments in girth and stand basal area during the 3rd and 4th YAP. The effect of fertilization on tree growth was evident from all three treatments, although T3 gave the most significant increase compared to T0, increasing doses of fertilizer did not significantly improve the growth parameters. Hence, this study confirmed the importance of mineral nutrition on rubber tree growth during the immature phase even at T1, the lowest level of nutrient inputs. These results can be used to improve the standard fertilizer recommendations for immature rubber trees in Cambodia. We recommend setting up similar trials in different edaphic conditions of the country with the aim to establish nutrient management practices tailored to local biophysical constraints.

The abandonment of insecticide treatments to achieve sustainable crop production calls for a combination of methods to obtain satisfactory pest control. To this end, net houses and biological control are two promising methods, though we suspected that most natural enemies are blocked outside the net houses. In Kenya, tomato crops are particularly threatened by Trialeurodes vaporariorum (Westwood 1856) and Tuta absoluta (Meyrick, 1917) that are targets of most insecticide treatments in this country. We investigated in an on-farm experiment (i) the abundances of T. vaporariorum and T. absoluta in open fields and in net houses, (ii) the diversity of arthropod natural enemies of these pests, and (iii) the effect of net houses on the natural regulation. To complete, in the laboratory, we checked the capacity of natural enemies to pass through different net types. We identified several natural enemies, mainly the mirid bug Nesidiocoris tenuis (Reuter 1895) that was the most abundant predator for both pests. One parasitoid species was also identified for each pest, i.e. Encarsia formosa Gahan (1924) and Copidosoma sp. for T. vaporariorum and T. absoluta respectively. Net houses reduced drastically the pest populations. Predators were less abundant under net houses, while parasitoids did not seem to be affected by the nets. Encarsia formosa was shown to be able to pass through the different net types, while N. tenuis adults were not. These results raise the potential for augmentative biological control under net houses. Using kairomones to attract natural enemies, or introducing natural enemies under the net houses through inoculative releases, are two approaches to increase the abundance of natural enemies under net houses.

International audience; Organic waste (OW) reuse in agriculture is a common practice fostered by benefits in terms of waste recycling and crop production. However, OW amendments potentially affect the fate of pesticide spread on fields to protect the crops from pests and weeds. The influence of OW on the sorption, degradation, and leaching of pesticides is generally studied for each mechanism separately under artificial laboratory conditions. Our study aims at evaluating the balance of these mechanisms under more realistic conditions to clarify the influence of three common OW amendments on the fate, in soil, of the widely used herbicide S-Metolachlor. We performed leaching experiments in large undisturbed soil cores amended with raw sewage sludge, composted sludge, and digested pig slurry (digestate), respectively. We monitored S-Metolachlor and its two main metabolites MET-OA and MET-ESA in the leachates during a succession of 10 rainfall events over 126 days. We also quantified the remaining S-Metolachlor and metabolites in the soil at the end of the experiments. S-Metolachlor leaching didn't exceed 0.1% of the applied dose with or without OW amendment. Despite a soil organic carbon increase of 3 to 32%, OW amendments did not significantly affect the amount of S-Metolachlor that leached through the soil (0.01 to 0.1%) nor its transformation rate (6.0 to 8.6%). However, it affected the degradation pathways with an increase of MET-OA relative to MET-ESA formed after OW amendment (28 to 54%) compared to the controls (8%). Concentration of S- Metolachlor and metabolites in the leachates of all treatments greatly exceeded the regulatory limit for groundwater intended for human consumption in Europe. These high concentrations were probably the consequence of preferential macropore flow. Colloids had comparable levels in the leachates after S-Metolachlor application. Dissolved organic carbon was also comparable in the controls, digestate, and sludge treatments but was 65% higher in the compost-amended cores. These results, along with a great variability among replicates inherent to experiments performed under realistic conditions, partly explain the limited impact of OW on the transport of S-Metolachlor.

Mirids (Sahbergella singularis and/or Distantiella theobroma) are the major pests of cacao farms in Africa. Cocoa production losses due to these species have been widely documented in West Africa. However, their impact on cocoa production is unknown in Central Africa, especially in Cameroon. Moreover, no data are available on the threshold level of fruits tolerance to mirid attacks. For these reasons, we assessed the effect of S. singularis on the productivity of ten cacao genotypes as well as the threshold number of the lethal feeding punctures to fruits under a randomized experimental design. Observations were made on three categories of fruits (cherelle, immature and mature/ripe). A control trial was also set up per batch. The overall results showed that 68.0% and 0.4% of fruits aborted, respectively, in mirid and control trials. The percentages of aborted fruits were significantly (p

International audience; Aedes albopictus and Aedes aegypti are invasive mosquito species that impose a substantial risk to human health. To control the abundance and spread of these arboviral pathogen vectors, the sterile insect technique (SIT) is emerging as a powerful complement to most commonly-used approaches, in part, because this technique is ecologically benign, specific, and non-persistent in the environment if releases are stopped. Because SIT and other similar vector control strategies are becoming of increasing interest to many countries, we offer here a pragmatic and accessible ‘roadmap’ for the pre-pilot and pilot phases to guide any interested party. This will support stakeholders, non-specialist scientists, implementers, and decision-makers. Applying these concepts will ensure, given adequate resources, a sound basis for local field trialing and for developing experience with the technique in readiness for potential operational deployment. This synthesis is based on the available literature, in addition to the experience and current knowledge of the expert contributing authors in this field. We describe a typical path to successful pilot testing, with the four concurrent development streams of Laboratory, Field, Stakeholder Relations, and the Business and Compliance Case. We provide a graphic framework with criteria that must be met in order to proceed.

Quinoa may be a promising alternative solution for arid regions, and it is necessary to test yield and mineral accumulation in grains under different soil types. Field experiments with Chenopodium quinoa (cv. CICA-17) were performed in Egypt in non-saline (electrical conductivity, 1.9 dS m−1) and saline (20 dS m−1) soils. Thirty-four chemical elements were studied in these crops. Results show different yields and mineral accumulations in the grains. Potassium (K), P, Mg, Ca, Na, Mn, and Fe are the main elements occurring in the quinoa grains, but their concentrations change between both soil types. Besides, soil salinity induced changes in the mineral pattern distribution among the different grain organs. Sodium was detected in the pericarp but not in other tissues. Pericarp structure may be a shield to prevent sodium entry to the underlying tissues but not for chloride, increasing its content in saline conditions. Under saline conditions, yield decreased to near 47%, and grain sizes greater than 1.68 mm were unfavored. Quinoa may serve as a complementary crop in the marginal lands of Egypt. It has an excellent nutrition perspective due to its mineral content and has a high potential to adapt to semi-arid and arid environments., The Ministry of Foreign Affairs, International Trade and Worship, Buenos Aires, Argentina, partially supported this research through the South-South cooperation project “Development of quinoa crop in marginal areas of Egypt”, FO.AR-6429, and Fundación Miguel Lillo (Miguel Lillo 251, T4000, Tucumán, Argentina) under the Project B-0004-1 (“Ecophysiology of selected varieties of quinoa and others species with nutritional values in lab and field”).

Population breeding through recurrent selection is based on the repetition of evaluation and recombination among best-selected individuals. In this type of breeding strategy, early evaluation of selection candidates combined with genomic prediction could substantially shorten the breeding cycle length, thus increasing the rate of genetic gain. The objective of this study was to optimize early genomic prediction in an upland rice (Oryza sativa L.) synthetic population improved through recurrent selection via shuttle breeding in two sites. To this end, we used genomic prediction on 334 S0 genotypes evaluated with early generation progeny testing (S0:2 and S0:3) across two sites. Four traits were measured (plant height, days to flowering, grain yield, and grain zinc concentration) and the predictive ability was assessed for the target site. For days to flowering and plant height, which correlate well among sites (0.51–0.62), an increase of up to 0.4 in predictive ability was observed when the model was trained using the two sites. For grain zinc concentration, adding the phenotype of the predicted lines in the nontarget site to the model improved the predictive ability (0.51 with two-site and 0.31 with single-site model), whereas for grain yield the gain was less (0.42 with two-site and 0.35 with single-site calibration). Through these results, we found a good opportunity to optimize the genomic recurrent selection scheme and maximize the use of resources by performing early progeny testing in two sites for traits with best expression and/or relevance in each specific environment.

The outbreak of frosty (Moniliophthora roreri) and black pod (Phytophthora palmivora) in Central American cacao agroforests throughout the 1980s led to the breeding of Theobroma cacao clones resistant to these diseases. However, while clonal disease resistance has been well-documented, clonal adaptability to contrasting pedoclimates remains less understood. Plant functional responses to environmental constraints can be assessed by evaluating intraspecific trait variation (ITV), but trait-based approaches have rarely been implemented in genotype assessments. The objective of our study was to determine cacao clone ITV in contrasting environments. Here, we used bivariate, multivariate, and functional trait space analyses to quantify ITV in nine leaf functional traits, among six disease-resistant cacao clones, growing in two clonal gardens with distinct environmental characteristics (a “mild dry season” with near-optimal cacao growing conditions and a “harsh dry season” site with sub-optimal conditions). All leaf traits varied among the six clones, though trait differences among clones differed depending on the site: physiological trait differences among clones were larger at the “mild dry season” site, chemical trait differences were wider at the “harsh dry season” site, and morphological trait differences among clones were similar at both sites. Multivariate and hypervolume trait space analyses revealed greater site influence on trait values of the least productive clones, while the most productive clones were characterized by higher specific leaf area, independent of the site. To our knowledge, our paper is among the first to show evidence that functional traits provide new insights into genotype × environment interactions and clonal selection in agroforestry systems and support in favor of applying functional trait-based research to plant breeding paradigms.

Dans les élevages laitiers de l'ouest du Burkina Faso, la production de lait est limitée par un déficit fourrager en saison sèche. Cette étude visait à évaluer la faisabilité et la potentialité des banques fourragères arbustives (BFA) pour complémenter l'alimentation des vaches laitières en saison sèche avec un fourrage de bonne valeur nutritionnelle. Un travail de coconception, d'installation et d'exploitation de BFA, composées de Leucaena leucocephala et de Morus alba, a été réalisé dans trois élevages de bovins laitiers de l'ouest du Burkina Faso. Les trois BFA ont été plantées à haute densité, avec 20 000 plants.ha-1, en juillet 2016. La croissance a été rapide durant les sept premiers mois (saison des pluies et début de saison sèche). Au jour de plantation (jp) plus sept mois, L. leucocephala mesurait 145 ± 11 cm et M. alba 143 ± 72 cm. Puis, durant la saison sèche, la croissance s'est ralentie. Les caractéristiques du sol, le manque de pluies et la faible profondeur des lits de plantation expliquaient les différences de croissance observées selon les sites expérimentaux. Les attaques de termites (BFA3) et le passage du feu (BFA1) ont affecté le développement des BFA concernées sans les anéantir. La production de biomasse sur BFA2 et BFA3, cumulée sur les trois coupes d'exploitation (jp+13, jp+15 et jp+17-18 mois), a été plus élevée avec L. leucocephala (8,2 ± 2,6 t MS.ha-1) qu'avec M. alba (1,8 ± 2,3 t MS.ha-1). Le coût d'installation et d'exploitation de 625 m² de BFA a été de 896 188 FCFA (environ 1350 €). Des solutions sont à trouver pour les rendre financièrement plus accessibles aux éleveurs.

Background Rice blast, caused by the fungus Pyricularia oryzae, represents the most damaging fungal disease of rice worldwide. Utilization of rice resistant cultivars represents a practical way to control the disease. Most of the rice varieties cultivated in Europe and several other temperate regions are severely depleted of blast resistance genes, making the identification of resistant sources in genetic background adapted to temperate environments a priority. Given these assumptions, a Genome Wide Association Study (GWAS) for rice blast resistance was undertaken using a panel of 311 temperate/tropical japonica and indica accessions adapted to temperate conditions and genotyped with 37,423 SNP markers. The panel was evaluated for blast resistance in field, under the pressure of the natural blast population, and in growth chamber, using a mixture of three different fungal strains. Results The parallel screening identified 11 accessions showing high levels of resistance in the two conditions, representing potential donors of resistance sources harbored in rice genotypes adapted to temperate conditions. A general higher resistance level was observed in tropical japonica and indica with respect to temperate japonica varieties. The GWAS identified 14 Marker-Traits Associations (MTAs), 8 of which discovered under field conditions and 6 under growth chamber screening. Three MTAs were identified in both conditions; five MTAs were specifically detected under field conditions while three for the growth chamber inoculation. Comparative analysis of physical/genetic positions of the MTAs showed that most of them were positionally-related with cloned or mapped blast resistance genes or with candidate genes whose functions were compatible for conferring pathogen resistance. However, for three MTAs, indicated as BRF10, BRF11–2 and BRGC11–3, no obvious candidate genes or positional relationships with blast resistance QTLs were identified, raising the possibility that they represent new sources of blast resistance. Conclusions We identified 14 MTAs for blast resistance using both field and growth chamber screenings. A total of 11 accessions showing high levels of resistance in both conditions were discovered. Combinations of loci conferring blast resistance were identified in rice accessions adapted to temperate conditions, thus allowing the genetic dissection of affordable resistances present in the panel. The obtained information will provide useful bases for both resistance breeding and further characterization of the highlighted resistance loci.

Sugarcane yellow mite, Oligonychus sacchari (Prostigmata: Tetranychidae), is one of the main detrimental pests in sugarcane growing areas in Iran. The early populations of mites colonize on the lower surfaces of sugarcane leaves. Because of high reproductive potential, multi-generation are produced per year under warm and humid temperature during sugarcane growing season. This pest imposes economic damage to sugar industries. Field trials were conducted on evaluation of varietal resistance of five sugarcane varieties against yellow mite during two successive seasons 2014–2015 and 2015–2016 in sugarcane fields at Salman Farsi Agro-industry unit in Ahwaz, Iran. After initiation of O. sacchari activity in fields, in each plot, fifteen leaves were selected at random and number of living mites was recorded. The results showed that there were significant differences among tested varieties. The variety IRC99-02 was the most susceptible in tested years by CP57-614 in the total number of living mites and dry-leaf even though CP69-1062 was the most resistant variety.

Fruit flies (Diptera: Tephritidae) are considered to be major pests of mango (Mangifera indica) worldwide. Their management, with an increasing focus on replacing synthetic pesticides with alternative pest control methods, is a challenging issue. A study was carried out from 2015 to 2017 in Reunion Island under field conditions in order to characterize the incidence of fruit flies on mango production and to link fruit fly infestation with fruit maturity and fly pressure. Mango fruits were mainly infested by Bactrocera zonata. Few fruits were infested by Ceratitis quilicii, and even fewer by Ceratitis capitata. Infestation increased as fruits ripened. Less than 4% of the fruits were infested at the green, green-mature and early yellow-point stages. Infestation increased to 10–11% at later yellow-point stages, and reached 14–16% at ripe and overripe stages. Fruit infestation was closely related to changes in the peel texture (firmness, in particular) and chlorophyll fluorescence of the fruit as it ripened. Whereas variability in fruit fly abundance in traps was observed between orchards and years, it did not clearly explain variability in fruit infestations, which was mostly explained by variability in fruit maturity. The study suggests that fruit fly trapping is not adequate to assess infestation risk or to guide management decisions, but instead provides evidence that fruit fly damage could be reduced by adjusting harvest timing, especially by harvesting fruits at the green-mature stage or at the yellow-point onset.

Black beetles (BB: Heteronychus spp.: Coleoptera, Scarabaeidae) are serious constraints to upland rice production in the Madagascar central highlands. From 2002 to 2007 we compared the effects of two soil management and two fertilization modalities in an upland rice-based cropping system on soil macrofauna abundance, diversity and BB damage to rice crops and yield. This cropping system involved a 2-year rotation of upland rice the first year, followed by common bean the second year, with oat as a relay crop under both conventional tillage (CT) and no-tillage soil management (NT), each under both organic (OF) and mineral fertilization (MF). All four modalities (CT-OF; CT-MF; NT-OF and NT-MF) were managed under two plant protection levels (seed dressing with imidacloprid + thiram vs no seed dressing). Herbivorous/detritivorous beetles were the most abundant soil biota, respectively representing more than two-thirds and half of all macrofauna at the outset of the experiment and 4 years later, with the BB Heteronychus arator rugifrons (Fairmaire) being the dominant pest species (herbivore). The Shannon diversity index was reduced significantly between the beginning and the end of the experiment 4 years later, while it was only marginally affected by soil management, fertilization and seed dressing regimes at both sampling dates. Throughout the study period, seed dressing resulted in a significant reduction in BB damage, and in a significantly higher rice grain yield as compared to control. NT management did not enable seed dressing discontinuation based on grain yield and BB damage level after 3 and 4 years of this practice, respectively. In this respect, CT-MF management ranked best in the absence of seed dressing. The reasons for the poor performance of NT management in the studied cropping system as compared to the same strategy used in other systems reported in earlier studies are discussed. (Resume d'auteur)

In the central highlands of Madagascar, blast, a serious fungal disease of rice caused by Magnaporthe oryzae, was shown to be less severe in conservation agriculture (CA) than in conventional tillage (CT) cropping systems. To assess the effects of CA cropping systems on rice susceptibility to blast and to understand the mechanisms involved, an experiment was conducted over three growing seasons in two sites (at high and mid-altitude). Two fertilization treatments, one with mineral nitrogen (N) fertilizer, and one without, were studied in interaction with two different cropping systems (CA/CT) and two rice varieties that differ in their susceptibility to blast. The performances of the two cropping systems were assessed, and results showed that yields were no higher in the CA or were lower than in CT cropping systems. The effects of the treatments on upland rice crop growth were measured by leaf N content as an indicator of N crop status, and leaf area index (LAI) as an indicator of canopy density. In all years at both sites, leaf N content during early growth stages was higher in the CT than in the CA cropping system. The LAI was lower in the CA than in the CT cropping system at the high altitude site in all three years, and in two out of three seasons at the middle altitude site. Overall, when the level of blast was high, blast was less severe in the CA cropping system and with no N fertilizer. Leaf N content and LAI were used as intermediate explanatory variables in the statistical analyses, and one or the other or both always masked the effect of the cropping system or of N fertilization. Our results show that leaf N content during early growth stages masks the effect of the cropping system on leaf blast severity. When the LAI is strongly affected by the cropping system, it also masks the effect of the cropping system on the severity of leaf and panicle blast. Very often both variables masked the effects of the cropping system and of N fertilization. These findings should help improve disease management by modifying fertilization practices and crop nutrition in conservation agriculture cropping systems.

Observations of the vegetative and reproductive biomass produced annually and the mineral element contents have been conducted on diverse oil palm plant materials tested in a genetic test in Indonesia. The results show that the nutrient uptake (for trunk growth, leaf renewal and bunch export) greatly varies (CV = 10% for N uptake and 17% for K uptake) with the origins of the planting materials considered. For equivalent production, the uptake in nutrients of certain plant material may differ very significantly; for the same level of uptake in nutrients, production can vary significantly. This study supports the hypothesis that the optimal nutrient thresholds are intrinsically linked to the plant material. It assumes that some planting materials have different needs and that a fertilizer regime could be adapted to their specific needs without losses in performance. To confirm these assumptions, the need of implementing specific experimental devices with differentiated fertilization regimes is discu...

On the request of decision-makers, the Life Cycle Assessment (LCA) framework is increasingly applied in agri-food value chains in developing countries under particularly demanding constraints. Based on the cradle-to-farm-gate LCA results of the tomato in Rwamagana district in Rwanda commissioned by the European Union, the main objectives of the paper were to validate statistically the differences in environmental impacts among expert-based types for this crop based on location and season and identify the key-drivers of these impacts. The study was developed thanks to two intensive field visits and a survey of 15 plots. The functional unit was one kg of tomato at farm-gate. Combining several statistical analyses allowed identifying three groups of plots with contrasting input profile and eco-efficiency. For most impact categories, the first group with mainly plots in marshland during wet season had the lowest impacts and the third group with plots in hillside showed the highest impacts. The yield of tomato being significantly different between marshland and hillside plots was an important driver of these results. The second group composed of plots in marshland during the dry season generally showed intermediate impacts due to the withdrawing of water for irrigation. The second group obtained a higher freshwater ecotoxicity due to a more intensive use of toxic insecticides. The factorial analysis for mixed data (FAMD) confirmed the importance of the location and the season for the eco-efficiency of tomato plots and the hierarchical clustering on principle components (HCPC) separated the tomato plots into three clusters. The generalized linear models (GLMs) validated the differences in the environmental impacts per kg of tomato between the clusters. The principal component analysis (PCA) combined to GLM revealed that only the use of water was significantly different between the three groups. Compared to existing datasets, all groups showed high freshwater ecotoxicity impacts due to the use of toxic insecticides and the excessive use of mancozeb. The third group also showed a high freshwater eutrophication in relation to P losses due to erosion and low yield. From a methodological point of view, we demonstrated in this paper that using expert-based typologies combined with adapted statistical analyses constituted a relevant approach under such circumstances.

L’effet concurrentiel des communautés d’adventices (CA) est mal connu. De plus, une des priorités de recherche en malherbologie consiste à caractériser les relations entre diversité des adventices et pertes de rendement (PR). Nous avons testé l’hypothèse que (i) toutes les CA ne sont pas responsables de PR et que (ii) les CA plus diversifiées réduisaient les PR grâce à une plus faible probabilité d’espèces dominantes et compétitives. Un essai au champ sur blé tendre a été mené pendant 3 ans sur 2 parcelles différentes chaque année. Sur chaque parcelle, 9 zones (6 non désherbées, 3 désherbées) présentant une flore contrastée ont été installées. Au sein de chaque zone, 5 quadrats ont été disposés (3 stades de la culture plus 1 à maturité couplé à 1 quadrat désherbage manuel). Un relevé initial ainsi que les prélèvements de biomasse aux 4 stades du blé nous ont permis de calculer des indices de biodiversité sur la densité et la biomasse. Sur les 6 CA identifiées, seulement 4 ont engendrées des PR significatives (19 à 56%) dans les zones non désherbées. Le nombre d’épis par pied fut la composante de rendement la plus affectée par la compétition avec les adventices. Nous avons également démontré que les CA diversifiées réduisaient les PR grâce à une production de biomasse moins importante. Les CA diversifiées ont limitées l’effet négatif des espèces dominantes et compétitives tout en potentiellement

With its high biomass yield potential and its adaptability to a large spectrum of crop management schemes (dedicated, double cropping), sorghum is a relevant candidate crop for anaerobic digestion. Moreover, the large genotypic variability of its biochemical composition offers opportunities to cultivate specific varieties that fit the expectations of different end-users. Within this context, the need to evaluate the variability of biomethane potential (BMP) among different genotypes cultivated at various geographical sites has become crucial. In this study, four sorghum genotypes were grown at three different sites and harvested at the same maturity stage (dough grain stage). Consistent BMP obtained from different assays enabled genotype comparisons. The methane potentials observed between genotypes and production sites ranged between 200 ± 5 NmLCH4/gTS and 259 ± 12 NmLCH4/gTS. Evaluation of the genotypic and cultivation site effects produced highly significant results, thus accounting for 36 and 34%, respectively, of the phenotypic variability.

Conservation agriculture (CA) is an effective tool that is used to increase soil C sequestration and enhance soil quality and agronomic productivity. However, rigorous empirical evidence from Southeast Asia, particularly in the Cambodian agro-ecosystem, is still scarce. We hypothesized that high and diversified biomass-C inputs in CA might be the first step toward to increase SOC in the topsoil by creating the C flow to support C storage overtime. Thus, the aim of this study was to quantify the short-term (i.e., five year) impacts of soil management and cropping systems on soil organic C (SOC), soil total N (STN), particulate organic C (POC) and mineral-associated organic C (MAOC). There were three distinct experiments comprised of a combination of cover and main crops including rice-, soybean- and cassava-based cropping systems, hereafter designated as RcCS, SbCS and CsCS, respectively. The experimental plots were laid out in a randomized complete block design with three replicates. Soil management treatments included conventional tillage (CT) and no-till (NT) and a selected adjacent area of reference vegetation (RV). Soil sampling was conducted in 2011 and 2013 at seven depths (0–5, 5–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm). Soil management and crop sequences significantly affected SOC and STN stocks in all three cropping systems. On average, NT SOC stocks at 0–5 cm depth was greater than those of CT by 10%, 20% and 18% and STN stocks by 8%, 25% and 16% for RcCS, SbCS and CsCS, respectively. SOC levels followed the order RV > NT > CT. SOC stocks in the subsoil layers were consistently lower in NT than in CT in all three cropping systems. POC stocks at 0–5 cm depth in NT were on average 22%, 20% and 78% greater than those in CT in RcCS, SbCS and CsCS, respectively. However, significant differences were detected only in RcCS and CsCS. The major POC stocks were found at 0–20 cm depth. NT treatments in SbCS stored 9% greater MAOC stocks at 0–5 cm depth than those in CT, and an increasing trend of NT was observed in RcCS and CsCS. In all three cropping systems, NT systems with diversified crop species significantly increased SOC stocks ranging by 6 to 28% and POC stocks by 56–127% in the surface soils and tended to restore SOC and POC in the subsoil layers after five years. The results leads to accept the hypothesis that short-term CA associated with high biomass-C inputs (particularly bi-annual rotations) promotes SOC recovery in the topsoil layer and creates a potential to increase SOC in the subsoil layers when deep-rooting cover crops are included in crop rotations.

International audience; Impact of host quantitative resistance on pathogen evolution is still poorly documented. In our study, we characterized the adaptation of the pathogenic fungus Colletotrichum gloeosporioides, to the quantitative resistance of its host, the water yam (Dioscorea alata). Genetic and pathogenic diversities of C. gloeosporioides populations were specified at the field scale. We used nuclear markers to describe fungal population structuring within and between six fields of three cultivars differently susceptible to the fungus. Strain aggressiveness was then quantified in the laboratory through cross-inoculation tests. The high level of genetic diversity and significant linkage disequilibrium revealed a significant influence of clonal reproduction in the C. gloeosporioides evolution. The recorded fungal migration between fields was weak (evidence for a dispersion mode via tubers rather than splashing dispersal), which provides the first molecular evidence for limited C. gloeosporioides migration via yam tuber exchanges. C. gloeosporioides's populations are adapted to their host resistance. The aggressiveness of the fungal clones seems to have evolved toward an accumulation of components specific to each host cultivar. Despite the remaining marks of adaptation to the former widely cultivated host, adaptation to current cultivars was clearly depicted.

For control of the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae), the attract-and-kill or attracticide technique is an alternative to the spraying of traditional organophosphate pesticides. In this study, the effectiveness of Ceranock and AAL&K attract-and-kill bait stations was assessed for control of C. capitata in Tunisian peach (Prunus persica) orchards. Our results showed that, in orchards with early-ripening varieties, the numbers of C. capitata males and fruit damage were significantly lower in plots treated with Ceranock and AAL&K bait stations than in plots treated with conventional organophosphate and pyrethroid insecticides. In addition, the abundances of non-target insects in the Chrysopidae, Coccinellidae and Miridae were significantly greater in plots treated with the bait stations than in plots treated with the conventional pesticides; that is, the use of attract-and-kill bait stations had fewer negative effects than the application of conventional pesticides on the biological diversity in Tunisian peach orchards. Overall, the results indicate that Ceranock and AAL&K attract-and-kill bait stations are useful alternatives for the control of C. capitata in Tunisian peach orchards planted with early-ripening varieties.

This study aims to isolate the supplemental irrigation (SI) scenario from permeable rainwater harvesting basins (RWHBs) best suitable to mitigate the long dry spells (DSs) in Burkinabe Sahel (BS). The water flow in the soil was studied on corn crop during 2013 and 2014 depending on the available water in the monitored RWHB. The experimental design was a block Fisher with four treatments (one under rainfed regime and three under supplemental irrigation). Measurements of the soil water content revealed periods of corn water sufficiency in plots under SI. Average corn yields were respectively 4500 and 4600 kg ha-1 for 2013 and 2014 on plots under SI against 3700 and 3800 kg ha-1 for those in rainfed regime. The average contribution of the SI in increasing corn yield was respectively 24 and 26% in 2013 and 2014 for three supplemental irrigations (SIs), against 19 and 17% for two SIs. With these SIs, the water balance in the RWHB gave respectively at the end of 2013 and 2014, an available water of 60 and 81 mm. The suitable strategy of the SI to mitigate DSs effect in BS was applying two SIs with a dose at least 40 mm around the mid-season. Key words: Supplemental irrigation, rainwater harvesting, dry spell mitigation, sustainable development, corn, Sahel.

Intercropping is a practical way to increase plant diversity in agroecosystems and provide alternative food and habitat to arthropods, including generalist predators. In tropical agriculture, ants are important predators and have complex and often strong effects on pests. With the goal of optimizing control of the banana weevil, Cosmopolites sordidus, we studied maize (Zea mays), cocoyam (Xanthosoma sagittifolium), and bottle gourd (Lagenaria siceraria) as intercrops in a plantain field in Cameroon. We analyzed the effects of intercropping on ant abundance (by taxon) and on the damage caused by C. sordidus larvae to plantain corms. We also analyzed the relationship between ant abundance and C. sordidus damage. When added singly, the three intercropped plants significantly affected the abundance of each of the seven ant taxa but the sign of the effect depended on the intercropped plant species and on the ant taxon. Intercropping had clear effects on ant abundance, which was negatively correlated with C. sordidus damage for the Myrmicinae and positively correlated for the Formicinae and Ponerinae. Intercropping in plantain agroecosystems has the potential to alter ant community structure which contributes to C. sordidus control, but the effect of intercropped plant species remain unclear and further investigations are needed.

Afin d'étudier les effets des facteurs date et densité de semis sur la croissance végétative et le rendement du cotonnier en culture pluviale, quatre essais ont été conduits sur deux sites au Bénin en 2002 et 2003. Un dispositif expérimental en splitsplit plot avec trois répétitions a été utilisé pour comparer 1 O variétés différentes, à trois densités de culture (42.000, 125.000, 167.000 plants.ha-1) et deux dates de semis (juin, juillet/août). La hauteur des plants, le nombre de noeuds par tige, la longueur des branches et le rendement au champ ont été évalués. La date de semis a affecté la morphologie uniquement dans les conditions hydriques limitantes (plants plus courts en semis retardé). Le semis retardé a réduit les rendements de 12% pour la variété précoce et compacte Mar 88-214; contre plus de 30% pour les variétés à fort développement végétatif. Aux fortes densités, tous les génotypes étaient plus courts avec des branches également plus courtes. En semis retardé et à forte densité, Mar 88-214 et Guazuncho 2 ont produit au moins 100 kg.ha-1 de plus que les variétés végétatives; les variétés précoces et compactes semées aux fortes densités conviennent mieux lorsque les conditions hydriques sont limitantes. La densité de semis influence plus nettement la croissance végétative et le rendement du cotonnier que la date de semis.