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Experimentations to evaluate spatial strategies at the scale of a production basin to control Black leaf streak disease (BLSD) is difficult to implement. Modelling is a key approach to identify innovative scenarios to reduce the use of pesticides while efficiently and sustainably controlling the disease. To achieve this aim, we assess the efficacy of strategies directly based on fungicide applications or based on the deployment of resistant cultivars. For that, we adapted a published spatially-explicit model to simulate BLSD epidemics in a real 300-ha agricultural landscape of Costa-Rica. More than 11,000 simulations of strategies are undergoing and the best scenarios will be identified to be further tested in the field.

Black Leaf Streak Disease (BLSD), caused by the fungus Pseudocercospora fijiensis, is a recent pandemic and the most economically and environmentally important leaf disease of banana. To assist breeding of varieties with durable resistance to the rapidly evolving P. fijiensis, we used a diploid genitor 'IDN 110' with partial resistance to BLSD to search for QTLs. We assessed diploid progeny of 73 hybrids between 'IDN 110' and the diploid cultivar 'Khai Nai On', which is susceptible to BLSD. Hybrids were phenotyped with artificial inoculation under controlled conditions. This method allowed us to focus on resistance in the early stages of the interaction already identified as strongly influencing BLSD epidemiology. Progeny were genotyped by sequencing. As both parents are heterozygous for large reciprocal translocations, the distribution of recombination was assessed and revealed regions with low recombination rates. Fourteen non-overlapping QTLs of resistance to BLSD were identified of which four main QTLs from the 'IDN110' parent, located on chromosomes 06, 07, 08, and 09, were shown to be of interest for marker-assisted selection. Genes that underline those four QTLs are discussed in the light of previous literature.

BLSD is the main challenge in the banana industry since the control of this fungal disease is crucial for banana exportation. In most countries, BLSD control relies on weekly applications of contact fungicides as mancozeb. Regulatory limitations of dithiocarbamates in the EU might soon block the use of this fungicide. Here we have evaluated new strategies excluding mancozeb in humid areas of Ivory Coast where fungicide resistance to most systemic fungicides is established. This strategy relies on weekly observations of biological disease parameters to inform decisions and on a wider use of mineral oil and fungicides from the SBI group 2. This strategy is better in terms of environmental performance and as performant for disease control as the conventional strategy based on mancozeb.

La production de biopesticides pour l'agriculture est une innovation agroécologique qui répond à la nécessité de réduire, d'une part, les externalités négatives de l'utilisation des pesticides chimiques sur la santé et l'environnement, et d'autre part, la dépendance aux aléas du commerce international, surtout dans les pays en développement. Dans ce contexte, elle dépend des objectifs des politiques de développement agricole et des normes internationales qui influencent ces pays. Le développement de la production de biopesticides est ainsi lié à la gouvernance de son processus dans le contexte où elle s'implémente. Nous posons la question de la gouvernance des mécanismes de développement du processus de production des biopesticides au Cameroun. Les données proviennent d'entretiens semi-directifs et de sources secondaires. Nous mobilisons l'Innovation History pour retracer l'historique du processus et l'Event History Analysis pour identifier les fonctions et les boucles fonctionnelles en présence au cours des différentes phases. Nos résultats montrent que la production de biopesticides se structure en trois phases, caractérisées par des boucles fonctionnelles différentes de celles de la littérature. Nous enrichissons ainsi la littérature sur l'analyse fonctionnelle. Nous suggérons aux politiques d'activer les fonctions de réseautage et de conception de normes pour accélérer le processus.

L'approche par les Systèmes d'Innovation (S.I) a été largement mobilisée depuis la fin des années 1980 et a connu pléthores terminologies appropriées aux terrains visités. Cette approche a, à la fois permis de saisir la nature des interactions inter-institutionnelles entre parties prenantes d'un système et a influencé les politiques publiques d'innovation en termes d'instruments pertinents. L'approche en termes de S.I est dupliquée sur de nombreuses échelles territoriales (régionales, locales, nationales) ou encore sectorielles. Néanmoins, aucune proposition intersectorielle n'a été réalisée au sein de cette approche. Nous interpellons ainsi le concept d'une Seule Santé pour pouvoir proposer un Système Intersectoriel d'Innovation dans le cadre du Cameroun. Une Seule Santé représente un cadre d'analyse intégrée connectant les animaux, les plantes et leur environnement. Une Seule Santé peut ainsi représenter un axe potentiel de construction d'un nouveau Système Intersectoriel d'Innovation par une meilleure coordination interministérielle et intersectorielle. En cela, nous verrons comment il peut être intégré comme outil de politique publique intersectorielle, tout comme inséré dans ce nouveau système d'innovation au Cameroun.

Alternative farming systems have developed since the beginning of industrial agriculture. Organic, biodynamic, conservation farming, agroecology and permaculture, all share a grounding in ecological concepts and a belief that farmers should work with nature rather than damage it. As ecology-based agricultures rely greatly on soil organisms to perform the functions necessary for agricultural production, it is thus important to evaluate the performance of these systems through the lens of soil organisms, especially soil microbes. They provide numerous services to plants, including growth promotion, nutrient supply, tolerance to environmental stresses and protection against pathogens. An overwhelming majority of studies confirm that ecology-based agricultures are beneficial for soil microorganisms. However, three practices were identified as posing potential ecotoxicological risks: the recycling of organic waste products, plastic mulching, and pest and disease management with biopesticides. The first two because they can be a source of contaminants; the third because of potential impacts on non-target microorganisms. Consequently, developing strategies to allow a safe recycling of the increasingly growing organic matter stocks produced in cities and factories, and the assessment of the ecotoxicological impact of biopesticides on non-target soil microorganisms, represent two challenges that ecology-based agricultural systems will have to face in the future.

Phytophagous and beneficial arthropods were inventoried on three traditional aromatic plants, lemongrass (Cymbopogon citratus), basil (Ocimum basilicum), and chives (Allium fistulosum), cropped in separate plots in a field experiment in the Caribbean island of Martinique. The same inventory was made on tomato plots, as a culture of association. Arthropods were collected using D-vac suction and Pitfall traps. Our results showed that hemipterans and dipterans dominated in D-vac suction samples with a high abundance of hemipterans on basil and of dipterans on tomato. Pitfall trap sampling revealed a high abundance of ants (mainly of the genus Pheidole) on all four crops. Aromatic plants had a significant positive effect on the abundance of both phytophagous and beneficial arthropods, while arthropod composition varied almost not at all between plant species. The Shannon index of basil and lemongrass were the highest. Aromatic plants may be used to increase population of beneficials in horticultural crops.

The sterile insect technique (SIT) can be an efficient solution for reducing or eliminating certain insect pest populations. It is widely used in agriculture against fruit flies, including the Mediterranean fruit fly (medfly), Ceratitis capitata. The re-mating tendency of medfly females and the fact that the released sterile males may have some residual fertility could be a challenge for the successful implementation of the SIT. Obtaining the right balance between sterility level and sterile male quality (competitiveness, longevity, etc) is the key to a cost-efficient program. Since field experimental approaches can be impacted by many environmental variables, it is difficult to get a clear understanding on how specific parameters, alone or in combination, may affect the SIT efficiency. The use of models not only helps to gather knowledge, but it allows the simulation of a wide range of scenarios and can be easily adapted to local populations and sterile male production. In this study, we consider single- and double-mated females. We first show that SIT can be successful only if the residual fertility is less than a threshold value that depends on the basic offspring number of the targeted pest population, the re-mating rates, and the parameters of double-mated females. Then, we show how the sterile male release rate is affected by the parameters of double-mated females and the male residual fertility. Different scenarios are explored with continuous and periodic sterile male releases, with and without ginger aromatherapy, which is known to enhance sterile male competitiveness, and also taking into account some biological parameters related to females that have been mated twice, either first by a wild (sterile) male and then a sterile (wild) male, or by two wild males only. Parameter values were chosen for peach as host fruit to reflect what could be expected in the Corsican context, where SIT against the medfly is under consideration. Our results suggest that ginge

Dans un contexte de changement climatique et d'intensification des échanges internationaux, les situations sanitaires des végétaux peuvent évoluer rapidement, avec un risque sanitaire accru. Afin d'informer au mieux les gestionnaires des risques sanitaires, la Plateforme d'Épidémiosurveillance en Santé Végétale (ESV) a mis en place une Veille Sanitaire Internationale (VSI) qui condense les éléments d'intérêt dans des bulletins publics. Cette veille relaie des informations médiatiques et scientifiques permettant d'identifier et/ou de suivre les évolutions de foyers épidémiques dans une zone géographique donnée, ainsi que des avancées scientifiques qui présentent un intérêt opérationnel. Pour répondre à ces objectifs, la Plateforme ESV a développé sa propre méthode de veille, pour laquelle la collecte d'informations est basée notamment sur le Web scraping. La chaîne de traitement des articles est semi-automatique, hybridant codes informatiques, système d'information et apports humains, permettant la diffusion de ces derniers à travers des bulletins. À ce jour, les articles diffusés par la VSI de la Plateforme ESV représentent environ 1 % de la totalité des articles collectés. Ce taux de pertinence est en lien avec les méthodes utilisées. Dans le futur, un des enjeux de l'évolution de la chaîne de traitement sera d'améliorer les processus de collecte et de tri des articles sans dénaturer la qualité des informations récupérées puis diffusées. Pour ce faire, la VSI souhaite s'appuyer sur le développement d'outils informatiques opérationnels, notamment issus de travaux de recherche.

Les invasions par des insectes exotiques ayant des impacts économiques, sanitaires et environnementaux sont de plus en plus fréquentes. C'est le cas notamment à La Réunion avec le psylle, un insecte originaire d'Australie qui menace le tamarin des Hauts, arbre endémique de l'île. Des recherches sont en cours pour étudier la préfaisabilité d'une lutte biologique.

Controlling pest populations in cotton fields is crucial to reduce yield losses due to plant damage. However, knowing the economic, environmental and agronomical issues related to the systematic use of chemical insecticides, it is urgently needed to better assist spraying decisions based on the development of an Early Warning System. In Benin, one of the major cotton producers in West Africa, a comprehensive annual monitoring of the incidence of key pests has been implemented for more than ten years. Here, we propose to use these long-term and multilocal observational data to (1) better understand the relationships between environmental variables, including climate, landscape context, but also crop management, and intra- or inter-annual pest population dynamics within the cotton-growing area, and to (2) better predict the risk of yield loss due to key pests as to better target interventions. As a perspective, we suggest developing standardized data collection and management throughout the West-African cotton-growing area for areawide pest management.

Natural pest regulation is a key ecosystem service to achieve agroecological intensification. However, its routine integration to pest management strategies is pending because of its unpredictability, hampering the trust of producers to rely on this service. To reduce this knowledge gap and increase foresight of natural pest regulation in production systems, we studied its drivers in vegetable crop fields in La Réunion, a tropical island in the Indian Ocean. We selected and characterized 20 fields representing the diversity of the grown crops, surrounding habitats, management practices and seasonality of the island. We then assessed the plant and arthropod communities associated with the crop and its margins using quadrats and non-selective interception and pitfall traps. We also observed the presence of pests and their natural enemies on the crop, whilst measuring crop damages and yield. Finally, the surrounding landscape was described at the short scale (within 500m) through GIS. Results demonstrated the strong relation between plant diversity and arthropod diversity, with subsequent consequences on pest abundance and pressure. Effects of the management practices and the landscape on these interactions were highlighted and discussed. Aside increased knowledge concerning systemic pest regulation mechanisms, this study opens the discussion on the utility of the development of bioindicators of these services. Such tools are expected to help stakeholders to further mobilize and integrate these services in their management strategies.

Tuta absoluta and Bemisia tabaci are two key worldwide tomato pests. In response to chemical control limits, the use of zoophytophagous mirid predators as biocontrol agents is being increasingly studied and proposed for the management of these pests. However, the use of some mirid species and in particular Nesidiocoris tenuis, which naturally occurs in European tomato crops, is controversial due to its ability to inflict significant damage on tomato plants (necrotic rings) in parallel of its high predation capacity. Combining other mirid species such as Macrolophus pygmaeus and Dicyphus errans with N. tenuis could reduce the population growth of T. absoluta and of B. tabaci, while maintaining N. tenuis populations below a critical crop damage threshold. In this study, we tested the effect of combining N. tenuis with M. pygmaeus (at two densities: 10 and 15 individuals per plant) and with or without D. errans (five individuals per plant) on the abundance of all insects (predators and pests) for 8 weeks. We also measured leaf damage by T. absoluta and plant and flower damage (necrotic rings, flower abortion rate) by N. tenuis. We found that the combined presence of D. errans, M. pygmaeus and N. tenuis rapidly and significantly reduced the densities of B. tabaci adults, and T. absoluta larvae and damage compared to when M. pygmaeus (with both densities) was only present with N. tenuis. The presence of D. errans was critical to reduce N. tenuis population growth and necrotic rings on tomato plants, while higher densities of M. pygmaeus density reduced the rate of aborted flowers by N. tenuis. The manipulation of M. pygmaeus densities added to the presence of D. errans could provide a sustainable solution to control multiple pests simultaneously while reducing the damaging phytophagous activity of N. tenuis in tomato crops.

The increase in the populations of root-knot nematode Meloidogyne enterolobii in various vegetables such as tomatoes grown under greenhouse conditions as well as increasing restrictions on the use of certain chemical nematicides have led to the search for new, effective management strategies, preferably ones that are sustainable biological alternatives. In this work, two formulations of the nematophagous fungus Metarhizium carneum, one concentrated suspension and one wettable powder, were evaluated under greenhouse conditions to reduce the M. enterolobii infestation in tomato plants. In addition, the effectiveness of the liquid formulation of M. carneum was compared with two biological and three chemical commercial nematicides. The results show that the two M. carneum formulations reduced the M. enterolobii population density by 78 and 66% in relation to the control treatment. In comparison, the liquid formulation of M. carneum and Purpureocillium lilacinum treatments reduced nematode population density by 72 and 43%, respectively, while for metam sodium preplanting applications followed by M. carneum applications during the tomato growth stage, the reduction was 96%. The alternate use of some chemical compounds plus the application of M. carneum as a biocontrol is a good starting strategy for managing M. enterolobii populations. These results confirm that M. carneum is a serious candidate for the short-term commercialization of an environmentally friendly biological nematicide.

Vascular wilt caused by the ascomycete fungal pathogen Fusarium oxysporum f. sp. cubense (Foc) is a major constraint of banana production around the world. The virulent race, namely Tropical Race 4, can infect all Cavendish-type banana plants and is now widespread across the globe, causing devastating losses to global banana production. In this study, we characterized Foc Subtropical Race 4 (STR4) resistance in a wild banana relative which, through estimated genome size and ancestry analysis, was confirmed to be Musa acuminata ssp. malaccensis. Using a self-derived F2 population segregating for STR4 resistance, quantitative trait loci sequencing (QTL-seq) was performed on bulks consisting of resistant and susceptible individuals. Changes in SNP index between the bulks revealed a major QTL located on the distal end of the long arm of chromosome 3. Multiple resistance genes are present in this region. Identification of chromosome regions conferring resistance to Foc can facilitate marker assisted selection in breeding programs and paves the way towards identifying genes underpinning resistance.

We review interactions between crop protection practices (developed to control plant pathogens and invertebrate pests) and human fungal infectious diseases. Unlike viral, bacterial and parasitic infections, fungal infections in humans are usually only superficial in healthy individuals, but can become invasive and pose serious risks to immunosuppressed individuals. Although their global impact is less than that of other infectious diseases, human fungal infections still pose serious public health issues. For instance, the use of synthetic agricultural fungicides, particularly the azole class, under conventional intensive, or efficiency improvement-based crop protection practices, is at risk as far as antimicrobial resistance is concerned, due to cases of cross-resistance to clinical azoles used to treat pulmonary aspergillosis, candidiasis and cryptococcocis. In this respect, the One Health approach, originally designed for other types of human pathogens, looks relevant for human pathogenic fungi. Additionally, some entomopathogenic fungi used as biocontrol products against crop pests in a substitution-based approach, may be potentially pathogenic to humans. Very few examples of redesign-based practices (i.e. Agroecological Crop Protection) emerged from our analysis on human fungal diseases. However, discontinuing agricultural azole fungicides (as practiced on organic farms, and which may to some extent be related to the redesign strategy) appears to be the best way to reduce selection pressure and hence the level of azole-resistant human pathogenic fungal strains in the environment.

La lutte biologique et le biocontrôle sont des concepts de protection des cultures qui ont des points communs mais qui ont également leurs spécificités. La première est connue depuis les années 1880, alors que le second est apparu dans les années 2010 dans le paysage français. Depuis quelques années, on constate régulièrement une confusion dans les termes et dans les interprétations de ces concepts qui ne sont pas de même nature : la lutte biologique est définie par des stratégies et le biocontrôle par des produits. Ce papier vise donc à répondre à un besoin de clarification : il contribue à distinguer les périmètres et les contenus de ces concepts, à pointer certains rapprochements abusifs et à proposer des clarifications sémantiques. Il passe en revue les termes anglophones et francophones relatifs à la lutte biologique et au biocontrôle à l'échelle européenne. Le papier discute enfin du rôle et de la pertinence des deux concepts dans la protection agroécologique des cultures. La lutte biologique par conservation y occupe une place centrale, car elle relève d'une approche systémique et préventive des risques liés aux bioagresseurs des cultures. Si certains produits de biocontrôle sont prometteurs pour la prévention des risques liés aux bioagresseurs, beaucoup d'autres s'inscrivent dans une démarche curative, similaire à celle de l'utilisation des pesticides chimiques de synthèse, avec les mêmes types de retombées commerciales pour l'agro-industrie.

While integrating trees into agricultural systems (i.e., agroforestry systems) provides many valuable ecosystem services, they can also interact with plant diseases. We demonstrate that a detailed understanding of how plant diseases interact with trees in agroforestry systems is necessary to identify key tree canopy characteristics, leaf traits, spatial arrangements, and management options that can help control plant diseases at different spatial scales. We focus our analysis on how trees affect coffee leaf rust, a major disease impacting one of the world's most significant crop commodities. We show that trees can both promote and discourage the development of coffee leaf rust at the plot scale via microclimate modifications in the understory. Based on our understanding of the role of tree characteristics in shaping the microclimate, we identify several canopy characteristics and leaf traits that can help manage coffee leaf rust at the plot scale: namely, thin canopies with high openness, short base height, horizontal branching, and small, dentate leaves. In contrast, at the edge of coffee farms, having large trees with high canopy volume and small, thick, waxy leaves is more useful to reduce throughflow wind speeds and intercept the airborne dispersal of urediniospores, an important consideration to control disease at the landscape scale. Seasonal pruning can help shape trees into the desired form, and trees can be spatially arranged to optimize desired effects. This case study demonstrates the added value of combining process-based epidemiology studies with functional trait ecology to improve disease management in agroforestry systems.

In this study, 58 endophytic bacterial strains were isolated from pods of two hybrid vanilla plants from Madagascar, Manitra ampotony and Tsy taitra. They were genetically characterized and divided into four distinct phylotypes. Three were associated to genus Bacillus species, and the fourth to the genus Curtobacterium. A selection of twelve strains corresponding to the identified genetic diversity were tested in vitro for four phytobeneficial capacities: phosphate solubilisation, free nitrogen fixation, and phytohormone and siderophore production. They were also evaluated in vitro for their ability to biocontrol the growth of the vanilla pathogenic fungi, Fusarium oxysporum f. sp. radicis vanillae and Cholletotrichum orchidophilum. Three bacteria of phylotype 4, m62a, m64 and m65, showed a high nitrogen fixation capacity in vitro, similar to the Pseudomonas florescens F113 bacterium used as a control (phospate solubilizing efficiency respectively 0.50 ± 0.07, 0.43 ± 0.07 and 0.40 ± 0.06 against 0.48 ± 0.03). Strain t2 related to B. subtilis showed a higher siderophore production than F113 (respectively 1.40 ± 0.1 AU and 1.2 ± 0.1 AU). The strain m72, associated with phylotype 2, showed the highest rate of production of Indole-3-acetic acid (IAA) in vitro. Bacteria belonging to the pylotype 4 showed the best capacity to inhibit fungal growth, especially the strains m62b m64 and t24, which also induced a significant zone of inhibition, suggesting that they may be good candidates for controlling fungal diseases of vanilla. This competence was highlighted with spectral imaging showing the production of lipopeptides (Iturin A2 and A3, C16 and C15-Fengycin A and C14 and C15-Surfactin) by the bacterial strains m65 confronted with the pathogenic fungi of vanilla.

Banana bunchy top virus is a multicomponent circular ssDNA virus (family Nanoviridae) that causes one of the most devastating diseases of cultivated bananas and plantains (family Musaceae). It is transmitted by the aphids Pentalonia nigronervosa and P. caladii among host plants of Musaceae and some other families of monocots. Our Illumina sequencing reconstruction of virome components of BBTV-infected banana plants and their neighbor non-banana plants sampled in Vietnam and Laos revealed the monocot Commelina sp. (Commelinaceae) and the dicots Bidens pilosa and Chromolaena odorata (both Asteraceae) as hosts of BBTV and circular ssDNA alphasatellites (family Alphasatellitidae). Counting the proportions and relative abundances of Illumina reads representing BBTV genome components and alphasatellites suggested that Chromolaena and Commelina are poor hosts for BBTV and one to three alphasatellite species, whereas Bidens is a permissive host for BBTV and four alphasatellite species representing two genera of Alphasatellitidae. Our findings provide evidence for the dicot plants of family Asteraceae as alternative hosts of BBTV and its alphasatellites, which warrants further investigation of these and other dicots as a potential refuge and source of BBTV and multiple alphasatellites that become associated with this virus and likely affect its replication, transmission, and host range.

Cupuassu (Theobroma grandiflorum [Willd. ex Sprengel] Schumann) seeds constitute the raw material for oil extraction and fabrication of cupulate (product similar to chocolate). However, fungal diseases such as witches' broom caused by Moniliophthora perniciosa have interfered with the large-scale development of cupuassu plantations. Cupuassu genetic breeding programmes focus on a variety of biotechnological tools or approaches to select genes related to quality or resistance mechanisms. In this study, we used expression and interactomics analyses of preselected genes involved in fruit quality and/or resistance to better understand the molecular and physiological mechanisms associated with these plant processes. It was found that (i) resistant and susceptible cupuassu genotypes showed different pulp characteristics as well as gene expression patterns; (ii) monosaccharide and carbohydrate transport pathways were enhanced during fruit maturation; (iii) sugar accumulation participated in signal transduction associated with fruit development and stress response in maturing fruits; and (iv) maturing pulp and seeds showed increased phospholipid metabolism and translocation, as well as immune system activation. The TgSTP1, TgWRKY33, TgCZF1, and TgUBA1 genes in cupuassu and the orthologues of DIN10, CNI1, and TET8 identified by the interactomics approach may be good candidates for marker-assisted selection in breeding programmes focusing on both fruit quality and resistance/tolerance to biotic/abiotic stress.

The phototaxis of insects is closely related to light source factors, such as spectrum and light intensity. The cane grub, Exolontha castanea Chang (Coleoptera: Melolonthidae), is an important underground pest of sugarcane in Guangxi province of China. To clarify the effect of spectral sensitivity and light intensity response on the phototactic behavior of E. castanea, the phototactic behavior responses of male and female adults to 13 monochromatic lights in the wavelength range of 365–630 nm and different light intensities were measured. We found that both male and female adults had positive phototaxis to 13 monochromatic lights. The phototactic response rate of males and females at ultraviolet and violet light was the highest in the wavelength range of 365–420 nm. Among them, the most sensitive spectrum of females and males was at 365 nm and 420 nm, respectively. From the intensity response of phototactic behavior to different spectrum, the G1 (strong phototaxis) response rates of females at 365 nm and males at 420 nm were the highest. In addition, the phototactic response rate of females and males increased with the light intensity, showing a significant positive correlation. This study showed that the spectrum and light intensity were the key factors affecting the phototactic behavior of E. castanea. The sensitive spectrum of males and females were different, with a similar trend in phototaxis.

Rootstocks are an important component for citrus adaptation to increasing biotic and abiotic stresses resulting from global climate change. There is a strong complementarity between Citrus species, which adapt to abiotic stresses, and Poncirus trifoliata and its intergeneric hybrids, which exhibit resistances or tolerances to major diseases and pests. Thus, symmetrical somatic hybridization between complementary diploid rootstocks of these two genera appears to be an efficient way to develop new tetraploid rootstocks in order to address the new challenges of the citrus industry. New intergeneric somatic hybrids were obtained by electrofusion between protoplasts of Citrus and P. trifoliata hybrids. Extensive characterization of the nuclear and cytoplasmic genomes was performed by genotyping-by-sequencing (GBS) analysis. This revealed diploid cybrids and nuclear somatic hybrids. Mitochondrial genomes were mostly inherited from the callus parent, but homologous recombination events were observed for one parental combination. Chloroplasts exhibited random uniparental inheritance. GBS revealed local chromosomal instabilities for all nuclear somatic hybrids and whole chromosome eliminations for two hybrids. However, at the whole genome level, symmetrical addition of the nuclear genomes of both parents was predominant and all somatic hybrids displayed at least one trifoliate orange haplotype throughout the genome.

The role of agroforest systems in pathogen regulation through structural characteristics such as shade and tree diversity is recognized. However, few studies have examined the importance of these factors on the spread of diseases of associated fruit trees in agroforestry systems, especially cocoa-based agroforestry systems (CBAS). The aim of this study was to evaluate the effect of associated tree diversity and shade rate into CBAS on citrus Phytophthora foot rot disease (PFRD) intensity. The study was carried out in five citrus production basins of Cameroon, contrasted by ecology and rainfall regimes. A set of 33 CBAS plots was mapped and their species composition and vertical structure were determined. Field data were used to reconstruct CBAS in 3D with Shademotion 5.1.47 software. Using static simulations with shadow overlays, shade rate received by each citrus tree was calculated. Subsequently, citrus trees were grouped into three categories according to the shade rate they received: (i) full sun, with shade rate <30%; (ii) light shade with shade rate 30–70% and, (iii) dense shade, with shade rate >70%. PFRD intensity was determined by measuring the canker extent relatively to the citrus crown circumference. A significant difference in PFRD intensity was observed between the different shade rates. Citrus trees receiving no shade were significantly more attacked by PFRD than those receiving little shade or dense shade. The antagonistic effect of shade was demonstrated. At the expense of factors related to the specific composition of the CBAS, shade, temperature, relative humidity and rainfall were found to be the main factors explaining PFRD intensity in CBAS. This study shows that microclimatic alterations due to the biodiversity in tropical agroforestry systems contribute to sustainable pest management.

Huanglongbing (HLB), the most destructive citrus disease, is associated with unculturable, phloem-limited Candidatus Liberibacter species, mainly Ca. L. asiaticus (Las). Las is transmitted naturally by the insect Diaphorina citri. In a previous study, we determined that the Oceanian citrus relatives Eremocitrus glauca, Microcitrus warburgiana, Microcitrus papuana, and Microcitrus australis and three hybrids among them and Citrus were full-resistant to Las. After 2 years of evaluations, leaves of those seven genotypes remained Las-free even with their susceptible rootstock being infected. However, Las was detected in their stem bark above the scion-rootstock graft union. Aiming to gain an understanding of the full-resistance phenotype, new experiments were carried out with the challenge-inoculated Oceanian citrus genotypes through which we evaluated: (1) Las acquisition by D. citri fed onto them; (2) Las infection in sweet orange plants grafted with bark or budwood from them; (3) Las infection in sweet orange plants top-grafted onto them; (4) Las infection in new shoots from rooted plants of them; and (5) Las infection in new shoots of them after drastic back-pruning. Overall, results showed that insects that fed on plants from the Oceanian citrus genotypes, their canopies, new flushes, and leaves from rooted cuttings evaluated remained quantitative real-time polymerase chain reaction (qPCR)-negative. Moreover, their budwood pieces were unable to infect sweet orange through grafting. Furthermore, sweet orange control leaves resulted infected when insects fed onto them and graft-receptor susceptible plants. Genomic and morphological analysis of the Oceanian genotypes corroborated that E. glauca and M. warburgiana are pure species while our M. australis accession is an M. australis × M. inodora hybrid and M. papuana is probably a M. papuana × M. warburgiana hybrid. E. glauca × C. sinensis hybrid was found coming from a cross between E. glauca and mandarin or tangor. Er

The vascular disease Verticillium wilt of cacao (Theobroma cacao), caused by the soilborne fungus Verticillium dahliae, is often qualified as a “minor” disease. However, it can cause severe losses locally, for example, in western Uganda and northeast of the Democratic Republic of Congo. This disease is difficult to control, notably due to an extended host range and prolonged survival in the soil. Therefore, Verticillium wilt must be addressed through an integrated disease management strategy as employed for other tree crops such as olive. Few studies, nonetheless, have focused on how to confront this disease in cacao. This paper aims to provide an overview of our knowledge on Verticillium wilt on cacao and the integrated disease management strategies for preventing and controlling it. Promising avenues based on findings in other crops that could be adapted to cacao are also explored. Good agricultural practices, genetic resistance, biological control, induced resistance, and the use of organic amendments with or without biocontrol agents are discussed. Moreover, the potential benefits of some of these solutions toward the resistance to other cacao diseases, abiotic stress, and nutrition improvement are presented.

The susceptibility of cocoa to harsh climatic conditions is evident in cocoa growing areas in Ghana, and climate distribution models show reduced cocoa suitability to climate change. We assessed how cocoa health and productivity were affected by varying climate conditions for 4 years in 23 cocoa farms along a gradient of low rainfall/high temperature in the north to high rainfall/low temperature in the south of Ghana's cocoa belts. Twenty cocoa trees per farm (in total 460) were observed and scored for their canopy condition, flower intensity, and damaged pods due to mirids, cocoa shield bugs, and black pod disease (BPD). Harvested pods and extracted dried cocoa beans were evaluated to ascertain yield/productivity. Insect pest damages to pods were on average 2.3 ± 0.8, 2.2 ± 1.0, and 3.0 ± 0.7 pods tree−1 year−1 in the south, middle and north, respectively. The healthiest and highest yielding trees were in the rainy south at 0.99 ± 0.02 kg dry beans tree−1 followed by the middle (0.84 ± 0.02 kg) and the north (0.60 ± 0.01 kg). BPD infection was highest in the south at 1.1 ± 1.1 pods tree−1 year−1, followed by the middle (0.7 ± 0.8), and the north (0.4 ± 0.6). Within sites variability in rainfall and temperature was not found to affect yields significantly. The variability in cocoa performance and occurrence of pests and diseases observed within sites may thus be caused by farm management practices that are key to the enhancement of productivity at site level. We recommend regular pruning of cocoa and shade trees to increase aeration and prevent BPD in high rainfall areas, and an increase in shade tree components in dry regions for insect pest management in cocoa systems.

Non-crop habitats, depending on their composition, can enhance the abundance and diversity of natural enemies of crop pests, but also at the same time provide resources to pests, thereby reducing the effect on pest incidence and resulting yield losses. The objective of the present study was to test (1) the effect of semi-natural habitats in the landscape on crop colonization by pests and natural regulation, and (2) the relationship between natural regulation and pest incidence. The pearl millet head miner (MHM) was selected as a case study because it is a key pest of millet cultivated in traditional pesticide-free tree-crop agroforestry systems in which its control mostly relies on the action of natural enemies. A set of 24 millet fields were selected in a 20×20 km area in Senegal, from the analysis of high-resolution satellite images (Pléiades), and hypotheses on the relative abundance of semi-natural habitats (here trees and rangelands) in the agricultural landscape. Millet fields were monitored for pest infestation of panicles and pest natural regulation. We used partial least squares structural equation modelling (PLS-PM) to evaluate the relationships between the abundance and diversity of semi-natural habitats at the landscape scale, crop colonization, natural pest regulation, and pest incidence. Panicle colonization by the MHM was generally high (14–92%) and increased with the abundance of trees and to a lesser extent with the rangeland area at a 1000 m-radius around millet fields. However, regulation provided by natural enemies was amplified by the abundance of trees at a local scale (250 m-radius around millet fields). This was particularly true at early crop colonization of the MHM with parasitism and direct predation on eggs and young larvae. This multi-scale effect of semi-natural habitats on crop colonization and natural regulation could explain why no clear relationship between crop colonization and pest incidence, nor natural regulation and pest incide

Leaf scald caused by Xanthomonas albilineans is one of the major bacterial diseases of sugarcane that threaten the sugar industry worldwide. Pathogenic divergence among strains of X. albilineans and interactions with the sugarcane host remain largely unexplored. In this study, 40 strains of X. albilineans from China were distributed into three distinct evolutionary groups based on multilocus sequence analysis and simple sequence repeats loci markers. In pathogenicity assays, the 40 strains of X. albilineans from China were divided into three pathogenicity groups (low, medium, and high). Twenty-four hours post inoculation (hpi) of leaf scald susceptible variety GT58, leaf populations of X. albilineans strain XaCN51 (high pathogenicity group) determined by qPCR were 3-fold higher than those of strain XaCN24 (low pathogenicity group). Inoculated sugarcane plants modulated the reactive oxygen species (ROS) homoeostasis by enhancing respiratory burst oxidase homolog (ScRBOH) expression and superoxide dismutase (SOD) activity and by decreasing catalase (CAT) activity, especially after infection by X. albilineans XaCN51. Furthermore, at 24 hpi, plants infected with XaCN51 maintained a lower content of endogenous salicylic acid (SA) and a lower expression level of SA-mediated genes (ScNPR3, ScTGA4, ScPR1, and ScPR5) as compared to plants infected with XaCN24. Altogether, these data revealed that the ROS production-scavenging system and activation of the SA pathway were involved in the sugarcane defense response to an attack by X. albilineans.

Whiteflies are one of the major pests of tomato under greenhouses, and their control partly relies on biocontrol strategies. Among those biocontrol agents, parasitoids or predators are widely used. However, the introduction of a biocontrol agent in a new area is not trivial. For that reason, we investigated the use of a tropical native mirid, Nesidiocoris volucer (Hemiptera: Miridae), for the biological control of whiteflies among other insect pests on tomato crops under greenhouses in the subtropical island of La Réunion, France. Nesidiocoris volucer life history traits and plant injury were examined. Nymphs developed and survived between 15 and 30°C and required on average 49.41 days at 15°C and on average 10.50 days at 30°C to develop (nymph survival >94%). At 25°C, each female produced on average 65 eggs. Nesidiocoris volucer was able to feed on several prey species, but performed better on whiteflies than on spider mites or thrips. No N. volucer feeding injury was observed on tomato. Nesidiocoris volucer has also been found in tropical countries of Africa, and we believe that the data presented on this natural enemy could be of great importance for the biocontrol of whiteflies in tropical areas.

L'utilisation des pesticides chimiques de synthèse dans la protection des cultures a aujourd'hui clairement montré ses limites : risques sanitaires, effets négatifs sur l'environnement, déséquilibres écologiques, pertes d'efficacité et coûts élevés. C'est pourquoi la forte réduction de ces pesticides est maintenant un objectif généralement admis par la plupart des acteurs professionnels et politiques. En France, le biocontrôle est un concept de protection des cultures apparu lors de la dernière décennie et présenté comme une solution permettant de réduire l'utilisation de pesticides. La présente synthèse vise à dresser un état des lieux de ce que recouvre le terme de " biocontrôle " en France. Derrière une définition officielle, la revue des définitions du biocontrôle en France montre une instabilité terminologique significative. La diversité des acceptions du terme de " biocontrôle " est à l'origine d'interprétations variables selon les acteurs. Par ailleurs, l'analyse de l'utilisation du terme " biocontrôle " en France au cours de la dernière décennie montre l'intérêt grandissant du biocontrôle auprès du grand public, des professionnels du monde agricole et agropharmaceutique, des politiques et de la communauté scientifique. L'augmentation de l'usage de ce terme a été observée parallèlement à la diminution de l'usage du terme " lutte biologique ", un concept reconnu et stable depuis plus d'un siècle. Enfin, cette diversité des définitions du biocontrôle et cette augmentation de l'utilisation du terme " biocontrôle " induisent des problématiques dans le domaine de la protection des cultures qui sont évoquées dans cette synthèse.

Fire activity is declining globally due to intensifying land management, but trends remain uncertain for the humid tropics, particularly Equatorial Asia. Here, we report that rates of fire events deemed severe (≥75th severity percentile of 2002-2019) and very severe (≥90th percentile) for Indonesia declined 19-27% and 23-34% over 2002-2019, respectively, controlling for precipitation, where fire-event severity is given by total fire radiative power and duration. The severity of seasonal fire activity – a measure of extremeness – declined 16% in Sumatra and moderately elsewhere. Declines concentrated over mosaic croplands and nearby forest, accounting for one-fifth and one-quarter of fire activity, respectively, with each class contracting 11% amongst severe fire events. Declines were limited over mosaic lands with relatively limited cropping, despite accounting for a similar extent and one-fifth share of fire activity. Declines had an uncertain association with agricultural development but seemingly reflect related political and economic forces for economic and environmental security.

Le poivre de Penja produit au Cameroun, est menacé par les ravageurs et les maladies. Cependant peu ou pas d'informations sont disponibles sur les ravageurs et les maladies ainsi que les mesures de lutte efficaces. De manière générale, les fongicides sont utilisés par la majorité des producteurs comme moyen de lutte. L'objectif de ce travail étaient d'identifier les principaux bioagresseurs associés aux principales maladies du poivre de Penja, d'évaluer les traitements chimiques pratiqués par les producteurs et proposer des solutions alternatives qui incluent l'utilisation des extraits de plantes et des antagonistes. Pour atteindre les deux premiers objectifs, une enquête a été menée auprès de 71 producteurs, des observations ont été menées dans 35 plantations de poivre dans trois zones d'études (Njombe-Penja, Loum et Tombel) et une collecte des échantillons de sol et du matériel végétal qui permettra l'identification des principales maladies et des agents pathogènes. Le dépérissement lent du poivrier et la pourriture racinaire blanche ont été identifiés comme principales maladies dans les plantations de poivre de Penja. Elles étaient présentes chez 42 % (dépérissement lent) et 51 % (la pourriture racinaire blanche) des producteurs et causant en moyenne 5 % de perte par année ce qui représente des pertes de revenus énormes pour le producteur. Une analyse moléculaire des régions ITS de l'ADNr des isolats obtenus ont permis d'identifier Armillaria sp. et Phytopythium sp. comme les potentiels agents pathogènes de la pourriture racinaire blanche et du dépérissement lent respectivement. La troisième partie du travail était consacrée aux méthodes de lutte alternatives. Les fongicides les plus utilisés par les producteurs, Trichoderma asperellum et les extraits aqueux et hydroéthanolique de trois plantes (Chromoleana odorata, Phyllantus amarus, Commelina benghalensis) ont été testés afin de contrôler Phytopythium sp. Les deux, T. asperellum et l'extrait hydroéthanolique de