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Plant pathogens can adapt to quantitative resistance, eroding its effectiveness. The aim of this work was to reveal the genomic basis of adaptation to such a resistance in populations of the fungus Pseudocercospora fijiensis, a major devastating pathogen of banana, by studying convergent adaptation on different cultivars. Samples from P. fijiensis populations showing a local adaptation pattern on new banana hybrids with quantitative resistance were compared, based on a genome scan approach, with samples from traditional and more susceptible cultivars in Cuba and the Dominican Republic. Whole-genome sequencing of pools of P. fijiensis isolates (pool-seq) sampled from three locations per country was conducted according to a paired population design. The findings of different combined analyses highly supported the existence of convergent adaptation on the study cultivars between locations within but not between countries. Five to six genomic regions involved in this adaptation were detected in each country. An annotation analysis and available biological data supported the hypothesis that some genes within the detected genomic regions may play a role in quantitative pathogenicity, including gene regulation. The results suggested that the genetic basis of fungal adaptation to quantitative plant resistance is at least oligogenic, while highlighting the existence of specific host-pathogen interactions for this kind of resistance.

Cowpea (Vigna unguiculata(L. Walp) is an important grain legume for human and livestock nutrition, especially in sub-Saharan Africa. Aphid,Aphis craccivoraKoch (Homoptera: Aphididae), is one of the most widespread and destructive insect pests of cowpea and host-plant resistance is an effective approach to minimize the pest damage at seedling stage. This study was aimed at identifying resistant sources toA. craccivorawithin the cowpea mini core collection, a set of accessions from the largest world cowpea germplasm collection maintained at the International Institute of Tropical Agriculture (IITA). A total of 375 lines including 373 from IITA mini core collection, one resistant (TVu-801) and one susceptible (TVx-3236) checks were evaluated through artificial infestation in screening cages during the seedling stage. In cages, genotypes were planted in single rows containing four plants. They were arranged in an augmented design in which the two checks were sown in individual cages. Scoring for aphid population and damage levels were carried out on individual plants at 7, 14, and 21 days after planting. Advanced bioassays and biochemical analyses were conducted to investigate the mechanism of resistance toA. craccivora. Overall, three genotypes TVu-6464, TVu-1583, and TVu-15445 showed good levels of resistance comparable to the resistant check TVu-801. The HPLC analyses proved that both low sucrose levels in the plant, as well as high levels of kaempferol and quercetin, aglycones of phenolic compounds, were related with high resistance to aphids. The above genotypes with promising levels of resistance toA. craccivorawill be used in cowpea breeding programs to develop improved resistant lines against this pest.

The productivity of Arabica coffee trees in the Toba Highlands (North Sumatra) suffers from inadequate agricultural practices and virtually non-existent protection against the coffee berry borer (CBB), Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae). While awaiting the development of a CBB control programme, this study proposed to achieve a rapid gain in productivity through coffee tree pruning. A comparison between the average production of ripe berries on pruned and unpruned coffee trees showed that pruning resulted in significantly higher yields over a two-year period. Within this increased production, the quantity of infested berries remained similar in the two treatments, due to the inherent dispersion behaviour of CBB, which seemed to occur throughout the fruiting period. Proper coffee tree pruning did not lead to any harvest losses in the first year, but affected the dynamics of production with a significant increase in the second year. As that improvement did not cause any increase in the number of infested berries in the pruned coffee trees, infestation rates fell. However, towards the end of the second harvest in year two, infestation levels of those coffee trees tended to reach those of unpruned coffee trees. In the Toba Highlands, pruning is probably the first step needed to improve yields and help to reduce CBB infestations, by bolstering the generally recommended sanitation harvesting.

Résumé : L'hévéa (Hevea brasiliensis) est la seule source de caoutchouc naturel commercialisé à travers le monde. En Afrique et en Asie, la maladie 'Corynespora Leaf Fall' (CLF), causée par le champignon nécrotrophe Corynespora cassiicola, affecte les plantations hévéicoles en provoquant des défoliations massives sur les clones les plus sensibles. L’évaluation précoce de la sensibilité des clones dans les programmes de sélection est un enjeu majeur pour écarter les individus les plus sensibles des programmes de développement et ainsi réduire la pression de la maladie. Une des méthodes d’évaluation envisagée consiste à tester indirectement la sensibilité des clones aux effecteurs fongiques responsables de la virulence (test toxinique). Parmi tous les effecteurs potentiels du champignon identifiés in silico, seule la cassiicoline Cas1 a été purifiée et caractérisée à ce jour. Il s’agit d’une petite glycoprotéine sécrétée qui jouerait un rôle dans les phases précoces de l’infection en induisant la nécrose des tissus. Les souches porteuses du gène Cas1 sont parmi les plus agressives sur les clones d'hévéa testés. Néanmoins, certaines souches de C. cassiicola ne produisant pas de cassiicoline présentent tout de même une agressivité modérée, suggérant l'implication d'autres effecteurs dans l'établissement de la maladie CLF. Les objectifs de cette thèse sont (i) de déterminer si la sensibilité à la cassiicoline Cas1 est un critère de sélection pertinent pour identifier les clones d’hévéa les plus sensibles à la maladie CLF, et (ii) d’identifier chez l’hévéa des facteurs de sensibilité à la cassiicoline Cas1. Nous avons d'abord analysé l’inoculum naturel et montré que les souches porteuses du gène Cas1 représentent un quart de la population de C. cassiicola dans les plantations d’hévéa d’Afrique de l’Ouest, le reste étant majoritairement constitué de souches dépourvues du gène codant la cassiicoline (Type A/Cas0). Nous avons ensuite créé un mutant de délétion du gène Cas1 pour la souche de référence CCP et comparé sa virulence à celle de la souche sauvage. Nous avons ainsi pu montrer que la cassiicoline Cas1 est bien un effecteur de nécrotrophie déterminant pour la virulence de C. cassiicola chez l’hévéa puisque la souche délétée perd toute virulence sur les clones testés. Enfin, nous avons recherché chez l'hévéa des facteurs de sensibilité à la cassiicoline Cas1 à travers deux approches. La technique de "double hybride en levures" nous a permis d'identifier une trentaine de protéines candidates qui pourraient interagir physiquement avec la toxine. Une approche transcriptomique, nous a permis d’identifier les gènes d’hévéa dont l’expression est modifiée suite à l’application de la cassiicoline purifiée, en comparant un clone sensible (PB260) et un clone tolérant (RRIM600). En conclusion, ces travaux ont permis de mieux comprendre les mécanismes impliqués dans l'interaction compatible entre C. cassiicola et l'hévéa et ouvrent la voie de la sélection assistée par effecteur

International audience; South Africa is a large country of approximately 1.22 million km(2), made up of nine provinces with three climatic zones. Farming in the country is mostly defined by regional differences. Of the different organisms isolated from milk samples of dairy cows, Staphylococcus aureus poses a challenge to maintain udder health and wholesome dairy products for human consumption. Antibiotic resistant bacteria are therefore a potential health hazard. The objective of this study was to investigate the seasonal and regional relationships of antibiotic resistance of S. aureus, of which little is known. This study was undertaken to evaluate a data set of 3410 S. aureus isolates, taken from milk samples with a somatic cell count of > 400 000 cells/mL from commercial dairy herds. These isolates were tested for antimicrobial susceptibility using the Kirby Bauer method for ampicillin, cloxacillin, penicillin G, clindamycin, oxy-tetracycline, cephalexin, cefuroxime and tylosin. The samples were from 830 dairy herds, out of the estimated 2000 commercial dairy herds in South Africa. All the antibiotics tested, except for cephalosporins, showed a predicted prevalence of resistance of above 50% in most provinces, which is a concern. The lowest prevalence of resistance to the majority of the categories of antibiotics tested was present in KwaZulu-Natal during spring. The cephalosporins had the lowest levels of prevalence of bacterial resistance in Gauteng during winter. Resistance patterns of S. aureus to the eight antibiotics varied in the different seasons and provinces, possibly because of different weather conditions, and the action and spectrum of antibiotics.

International audience; Exotic pathogens cause severe damage in natural populations in the absence of coevolutionary dynamics with their hosts. However, some resistance to such pathogens may occur in naive populations. The objective of this study was to investigate the genetics of this so-called 'exapted' resistance to two pathogens of Asian origin (Erysiphe alphitoides and Phytophthora cinnamomi) in European oak. Host-pathogen compatibility was assessed by recording infection success and pathogen growth in a full-sib family of Quercus robur under controlled and natural conditions. Two high-resolution genetic maps anchored on the reference genome were used to study the genetic architecture of resistance and to identify positional candidate genes. Two genomic regions, each containing six strong and stable quantitative trait loci (QTLs) accounting for 12-19% of the phenotypic variation, were mainly associated with E. alphitoides infection. Candidate genes, especially genes encoding receptor-like-kinases and galactinol synthases, were identified in these regions. The three QTLs associated with P. cinnamomi infection did not colocate with QTLs found for E. alphitoides. These findings provide evidence that exapted resistance to E. alphitoides and P. cinnamomi is present in Q. robur and suggest that the underlying molecular mechanisms involve genes encoding proteins with extracellular signaling functions.

BGPI : équipe 2 / 5; International audience; Efficient strategies for limiting the impact of pathogens on crops require a good understanding of the factors underlying the evolution of compatibility range for the pathogens and host plants, i.e., the set of host genotypes that a particular pathogen genotype can infect and the set of pathogen genotypes that can infect a particular host genotype. Until now, little is known about the evolutionary and ecological factors driving compatibility ranges in systems implicating crop plants. We studied the evolution of host and pathogen compatibility ranges for rice blast disease, which is caused by the ascomycete Magnaporthe oryzae. We challenged 61 rice varieties from three rice subspecies with 31 strains of M. oryzae collected worldwide from all major known genetic groups. We determined the compatibility range of each plant variety and pathogen genotype and the severity of each plant pathogen interaction. Compatibility ranges differed between rice subspecies, with the most resistant subspecies selecting for pathogens with broader compatibility ranges and the least resistant subspecies selecting for pathogens with narrower compatibility ranges. These results are consistent with a nested distribution of R genes between rice subspecies.

International audience; Interspecific competition with native species during biological invasions can sometimes limit alien expansion. We aimed to determine the potential ecological effects of Limatus durhamii Theobald 1901, a native Neotropical mosquito (Diptera: Culicidae) species, on the invasive species Aedes (Stegomyia) aegypti (Linnaeus 1762) that breeds in the same artificial water containers. Development time and adult dry mass were measured in three rearing conditions: control (a single larva), intraspecific competition (two conspecific larvae), and interspecific competition (two heterospecific larvae). Food was provided ad libitum to eliminate exploitative competition. For Ae. aegypti, development time was not affected by interspecific interference competition (non-significant differences with the control) and the adult dry mass was significantly higher, meaning that individual fitness likely increased. Yet, because previous studies showed longer development time and lighter adults during competition with other invasive mosquitoes, it is likely that Ae. aegypti can express a different phenotype depending on the competing species. The similar pattern found for Li. durhamii females and the non-significant difference with the control for males explain in part why this species can compete with Ae. aegypti.

In this study, we investigated the resistance of C. oleifera Abel. fruit shell's probe to fungi and termites. The degree of decay of C. oleifera Abel. fruit shells inoculated with Coriolus versicolor , Pycnoporus sanguineus , Coniophora puteana and Antrodia spp . in temperate or tropical environment was assessed. The resistance of the shells to subterranean termites in a tropical chamber was also assessed. It was found that there is an overall difference between the resistance to fungi decay and to termite attack. It was found that: the degree of degradation of the shell colonized by white-rot fungi is more severe than the fragmentation of the shell by brown-rot fungi. It was also found that the white-rot decay of C. oleifera Abel. fruit shell is greater than to beech wood, and then brown-rot decay of Scots pine sapwood is severer than to C. oleifera Abel. fruit shell. The resistance of C. oleifera Abel. fruit shell to attack by the subterranean termites was found to be high. It was concluded that the fungal species was an important controlling factor to the decomposition of C. oleifera Abel. fruit shell; and that termite infestation of C. oleifera Abel. fruit shell did take place but termite mortality (100%) occurred. Based on these results, further investigations are being made in order to solve the use of massive by-product from edible tea-seed oil industries.

Key Message This article presents the enhancement in boron fixation as well as the improved biological resistance against fungi and termites for wood samples treated with tannin-caprolactam and tannin-PEG formulations. Context Although the recently developed tannin-boron wood preservatives have shown high biological protection, they presented also average resistance against weathering. The tannin-caprolactam formulations have shown improved weathering resistances and dimensional stability. Aims For this reason, more detailed biological tests were performed to evaluate the influence of the caprolactam and PEG on the biological resistance. Methods In this paper, the boron leaching of the tannin-caprolactam and tannin-PEG impregnated Scots pine specimens was observed and the biocidal effect against fungi (Antrodia spp. and Coniophora puteana) and insects (Reticulitermes flavipes and Hylotrupes bajulus) were determined according to the guidelines of EN 113, EN 117, and EN 47. Results The advanced formulations containing PEG have shown interesting resistance against fungal decay, but very low penetration and weak resistance against larvae while the tannin-caprolactam preservatives have shown overall improved biological performances and higher boron fixations. Conclusion The biocidal activity of the caprolactam-added formulations was overall enhanced and therefore these formulations are confirmed to be an interesting alternative for the wood preservation in outdoor environment.

International audience; Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood® treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 °C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 °C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation.

Earthworms, as ecosystem engineers, help to mineralize soil organic matter, construct and maintain soil structure, and often stimulate plant growth and protect plants from pests. The aim of this study was (i) to determine the connection between earthworm traits and indicators of soil ecosystem services and (ii) to identify earthworm “response” traits, which are selected by the landscape or changes in the soil, and “effect” traits, which contribute to soil processes. In the southern portion of the state of Para (eastern Brazilian Amazonia), we sampled earthworms at 135 points distributed among 3 locations, 9 sub-locations and 27 farms (5 sampling points per farm). At each point, three 25 cm × 25 cm soil samples were hand-sorted for earthworms. We measured eight functional traits in 1148 individuals: relative gizzard size, type of typhlosole, length and type of caudal setae, pigmentation, overall length, thickness of septa and musculature in anterior segments. We found a significant, although relatively low, relationship between landscape classes and trait proportions. Earthworm trait proportions significantly covaried with soil parameters and indicators of soil ecosystem services. We did not find significant covariation between earthworm morphospecies and soil ecosystem services. We identified earthworm “response” traits that had been selected and assessed consequences of these changes on effects of earthworm communities (via their “effect” traits) on soil processes and ecosystem services. Typhlosole type, gizzard size and septa thickness were identified as “response” traits selected by soil and landscape conditions. These traits were also identified as “effect” traits for their influence on soil structure. Results indicated a connection between earthworm traits and landscape degradation and soil services, which is a new step toward conceptualizing earthworm ecological studies that go beyond the species level. (Resume d'auteur)

Thermal modification is an attractive alternative to improve the decay durability and dimensional stability of wood. However, thermally modified wood is generally not resistant to termite attacks, limiting the field of application of such materials. One way to overcome this drawback is to combine thermal modification treatment with an additional treatment. One such treatment is the impregnation of a boron derivative associated with appropriate vinylic monomers, which takes advantage of the thermal treatment to polymerise these monomers for boron fixation. Using this strategy, we recently showed that an impregnation of borax (2 or 4% boric acid equivalent) dissolved in a 10% aqueous solution of polyglycerolmethacrylate followed by thermal treatment under nitrogen at 220°C protects wood from both termite and decay degradations, even after leaching. Additionally, wood samples treated with a 10% polyglycerolmethacrylate aqueous solution and subjected to thermal treatment at 220°C presented improved resistance to termites while avoiding boron utilization. Based on these results, we investigate the effect of impregnation with two types of vinylic monomers, which are already used in the presence of boron, followed by thermal treatments at different temperatures. We evaluate termite and decay durability of wood to evaluate if thermal modification associated with light chemical modification could be a solution for utilization of thermally modified materials in termite-infested areas.

Thermal modification is now considered as a new ecofriendly industrial wood modification process improving mainly the material decay resistance and its dimensional stability. Most industrial thermal treatment processes use convection heat transfer which induces sometimes heterogeneous treatment temperature propagation within the oven and lead to the heterogeneity in treatment efficiency. Thus, it is common that treatment is not completely effective on several stack boards, in a same batch. The aim of this paper was to study the decay resistance variability of various European wood species thermally modified. Thermal modifications were performed around 240°C during 4h, on about 10 m3 of 27 x 152 x 2000 mm3 wood planks placed in an industrial oven having a volume of 20 m3, on the following wood species: spruce, ash, beech and poplar. All of the tests concerning the decay resistance were carried out in the laboratory using untreated beech and pine woods as reference materials. An agar block test was used to determine the resistance of thermally modified woods, leached beforehand according to EN 84 standard or not, to brown-rot and white-rot fungi, according to XP CEN/TS 15083-1. A large selection of treated wood samples was tested in order to estimate the variability of treatment efficiency. Thermal treatment increased the biological durability of all leached and un-leached modified wood samples, compared with native wood species. The treatment temperature of 240°C used in this study is sufficient to reach durability classes ''durable'' or ''very durable'' for the four wood species. However, the dispersion of weight loss values, due to the fungal attacks was very important and showed a large variability of the durability of wood which has been treated in a single batch. These results showed that there is a substantial need to develop process control and² indicator in order to insure that the quality of treated timber is properly evaluated with a view to putting this modified timber on the market under a chain of custody.

The level of hydrogen peroxide (H 2 O 2 ) in plants signalizes the induction of several genes, including that of ascorbate peroxidase (APX-EC 1.11.1.11). APX isoenzymes play a central role in the elimination of intracellular H 2 O 2 and contribute to plant responses to diverse stresses. During the infection process in Theobroma cacao by Moniliophthora perniciosa oxidative stress is generated and the APX action recruited from the plant. The present work aimed to characterize the T. cacao APX involved in the molecular interaction of T. cacao – M. perniciosa . The peroxidase activity was analyzed in protein extracts from cocoa plants infected by M. perniciosa and showed the induction of peroxidases like APX in resistant cocoa plants. The cytosolic protein of T. cacao (GenBank: ABR68691.2 ) was phylogenetically analyzed in relation to other peroxidases from the cocoa genome and eight genes encoding APX proteins with conserved domains were also analyzed. The cDNA from cytosolic APX was cloned in pET28a and the recombinant protein expressed and purified (r Tc -cAPX). The secondary structure of the protein was analyzed by Circular Dichroism (CD) displaying high proportion of α-helices when folded. The enzymatic assay shows stable activity using ascorbate and guaiacol as an electron donor for H 2 O 2 reduction. The pH 7.5 is the optimum for enzyme activity. Chromatographic analysis suggests that r Tc -cAPX is a homodimer in solution. Results indicate that the r Tc -cAPX is correctly folded, stable and biochemically active. The purified r Tc -cAPX presented biotechnological potential and is adequate for future structural and functional studies.

We hypothesized that inducing systemic resistances can contribute to the control of the nematode Rotylenchulus reniformis in pineapple. In greenhouse experiments conducted in Martinique, the pineapple cultivars Smooth Cayenne and MD-2 were treated with methyljasmonate (JAME) and salicylic acid (SA), elicitors of induced systemic resistance (ISR) and systemic acquired resistance (SAR). The efficacy of the elicitors was tested by inoculating plantlets grown in individual pots with a monospecific population of R. reniformis reared on Vigna unguiculata . The final nematode populations, 45 days after inoculation on MD-2 treated with JAME were reduced by 67.0% ( p = 0.006). Nematode populations on MD-2 plants treated with SA were reduced by 55.8% ( p = 0.016). Nematode populations on SC were not reduced by the elicitors. In a second experiment, using split-root systems, JAME was applied to MD-2 plantlets and enzymatic activities involved in plant defense and stress responses were monitored for 14 h after treatment. Additional pots were inoculated with nematodes 24 h after JAME treatment and examined ten days later. Transient stress was observed along with an increase in enzymatic response after inoculation with nematodes. These results showed that the MD-2 was primed through an ISR by JAME. The question now arises whether ISR can be specifically induced only in certain pineapple cultivars. Results are discussed from the perspective of introducing new strategies to manage pineapple nematodes.

Transgenic sorghum plants were produced through particle bombardment and Agrobacterium methods in two elite, but recalcitrant genotypes of Sorghum bicolor L. Moench. Use of target cells from developing tissues (immature embryos and multiple shoot buds), pre-culture of target tissue, small size of target tissue (2-3 mm), and regular subculture improved the selection and regeneration efficiencies. Addition of amino acid l-cysteine during co-cultivation and blotting sheet interface was helpful for complete decontamination of Agrobacterium tumefaciens and regeneration of transgenic plants. We demonstrated production of transgenic sorghum plants expressing a Bacillus thuringiensis lepidopteran toxin, through tailored in vitro protocols. Our results showed that decontamination of agrobacteria employing subtle treatments aided recovery of transgenic plants in recalcitrant genotypes. We generated 14 independent transgenic lines carrying different classes of B. thuringiensis toxin genes, cry1Aa and cry1B. Many single copy events were generated in two elite parental lines, CS3541 and 296B. Accumulation of the B. thuringiensis protein in leaves during the susceptible period of plant growth ranged from 35 to 500 ng/g fresh leaf tissue. Comprehensive insect bioassays for tolerance to spotted stem borer (Chilo partellus) were conducted through leaf disk and whole plant assays. Transgenic progeny plants showed 20-30% of damage as compared to 70-80% in non-transformed controls.

All bananas cultivated for export are Cavendish cultivars and are considered to be very susceptible to both the burrowing nematode Radopholus similis and the lesion nematode Pratylenchus coffeae . Twelve cultivars of Musa spp. genome AAA cv. Grande Naine from mass field selections in Martinique and Guadeloupe were cloned and micro-propagated in tissue culture. Resistance of these sibling cultivars to nematodes was tested in two growth chamber trials and in one 2-year field trial in a former banana field heavily infested with nematodes and without control methods (no guying or nematicide applications). The field trial also included a new synthetic hybrid FB920 that has tolerance to yellow and black Sigatoka and partial resistance to nematodes. Trends were similar in growth chamber and field trials in that all Cavendish cultivars were susceptible to nematode species, although some differences in susceptibility were detected, and in particular roots of the selected cultivar MA13 contained fewer R. similis than the most susceptible cultivars of Cavendish (cvs. Petite naine, Poyo and L93). Cultivar MA13 was also less susceptible than most commercial cultivars to P. coffeae in the growth chamber trials, and a similar but insignificant trend was documented in the field trial. In the field trial, all cultivars experienced severe damage (lengthening of vegetative and reproductive stages, uprooting and reduced yield), which was attributed to the high level of nematode infestation. Although tolerance to nematodes in the field trial was greater for the synthetic new hybrid FB920 than for the Cavendish cultivars, FB920 produces small bunches and tall plants that will prevent its development as a banana for export (but will not prevent its production by small holders). In summary, this study shows that there is useful variation in tolerance to R. similis and P. coffeae among sibling Cavendish cultivars and that growth chamber trials with in vitro -cultivated plants are useful for screening for such susceptibility.

A l'intérieur du genre Musa, il existe des variétés immunes et des variétés très sensibles aux attaques de Cercospora musae. Des études ont été faites en Guinée pour comparer le degré de résistance au Cercospora des variétés de la collection du Centre guinéen de recherches fruitières aux résultats obtenus par différents auteurs dans d'autres régions, pour des travaux du même ordre. On a recherché, en outre, quelle pouvait être l'influence de la variété sur la germination et la pénétration des ascospores, chez quatre clones de Musa. A la suite de ces essais, on peut affirmer que la résistance des différentes variétés de Musa à la Cercosporiose est un facteur lié aux conditions de développement du parasite à l'intérieur de la plante. Un certain nombre d'hybrides de Gros Michel présentant une résistance assez bonne ont été obtenus par les chercheurs de l'Imperial College à Trinidad. Il n'est pas possible d'envisager d'hybridations à partir des variétés du type Cavendish, car la production de graines s'est avérée nulle dans tous les essais entrepris

Growers of Bacillus thuringiensis (Bt) crops often use refuges of non-Bt plants to delay pest resistance, but plant-to-plant gene flow between Bt and non-Bt crops could affect this strategy. Here we used simulation modeling to explore the consequences of pollen- and seed-mediated gene flow in cotton fields on the evolution of resistance in a generic pest. We modeled a landscape of 0.5-ha fields where growers used farm-saved seed, as could often occur in the developing world. Specifically, we examined the effects of moderate and high gene flow rates, larval feeding behavior, dominance of resistance, refuge type and abundance, and the interactions among these factors. With either completely dominant or completely recessive inheritance of resistance, gene flow among plants and larval feeding behavior had limited practical impact on resistance evolution. With intermediate dominance, however, moderate or high gene flow among plants substantially accelerated resistance evolution in some simulations where non-Bt cotton refuges were 5 or 20% of the cotton acreage. The acceleration was usually greater when larvae moved and fed indiscriminately among Bt and non-Bt cotton plants than when larvae were sedentary or discriminated among plant types. Adding alternative host plant refuges to the landscape delayed resistance, while increasing the non-Bt cotton refuge from 20 to 50% of the cotton acreage had positive, negative, or neutral effects, depending on dominance, the amount of alternative host plant refuges, and larval feeding behavior. The results suggest that, under certain conditions, reducing gene flow between refuges and Bt crops could help delay pest resistance.

A pathogenesis-related (PR) protein from Theobroma cacao (TcPR-10) was identified from a cacao–Moniliophthora perniciosa interaction cDNA library. Nucleotide and amino acid sequences showed homology with other PR-10 proteins having P loop motif and Betv1 domain. Recombinant TcPR-10 showed in vitro and in vivo ribonuclease activity, and antifungal activity against the basidiomycete cacao pathogen M. perniciosa and the yeast Saccharomyces cerevisiae. Fluorescein isothiocyanate-labeled TcPR-10 was internalized by M. perniciosa hyphae and S. cerevisiae cells and inhibited growth of both fungi. Energy and temperature-dependent internalization of the TcPR-10 suggested an active importation into the fungal cells. Chronical exposure to TcPR-10 of 29 yeast mutants with single gene defects in DNA repair, general membrane transport, metal transport, and antioxidant defenses was tested. Two yeast mutants were hyperresistant compared with their respective isogenic wild type: ctr3Δ mutant, lacking the high-affinity plasma membrane copper transporter and mac1Δ, the copper-sensing transcription factor involved in regulation of high-affinity copper transport. Acute exposure of exponentially growing yeast cells revealed that TcPR-10 resistance is also enhanced in the Snq2 export permease-lacking mutant which has reduced intracellular presence of TcPR-10.

L'acarien du cocotier (Aceria guerreronis Keifer) constitue maintenant une menace importante pour les producteurs et transformateurs du cocotier (Cocos nuciferaL.) en Inde. Les moyens de lutte chimique et biologique se sont avérés coéteux, inefficaces et indésirables sur le plan écologique. L'emploi de cultivars résistants é l'acarien est la méthode la plus efficace pour prévenir les pertes de rendement et constituerait l'assise principale de tout programme de lutte intégrée. Des génotypes du cocotier, tant des accessions résitantes que sensibles, ont été collectés dans diverses régions du Sud de l'Inde. Trente-deux paires d'amorces SSR et sept amorces RAPD ont été employées pour réaliser des études moléculaires. Sur la base d'analyses ponctuelles, neuf marqueurs SSR et 4 marqueurs RAPD associés é la résistance aux acariens ont été identifiés. Suite é des régressions multiples par palliers sur les marqueurs SSR, une combinaison de six marqueurs a montré une parfaite association (100%) avec la réaction aux mites. Une analyse semblable sur les marqueurs RAPD a révélé que la combinaison de trois marqueurs expliquait 83,86% de la résistance au sein des lignées é l'étude. Des régressions multiples combinées effectuées sur les marqueurs SSR et RAPD ont montré que la combinaison de cinq marqueurs expliquait 100% de l'association avec la résistance aux acariens chez le cocotier. Les marqueurs associés é la résistance aux acariens sont importants dans les programmes de sélection chez le cocotier et faciliteront la sélection précoce de génotypes résistants et de géniteurs dans le cadre des efforts d'amélioration génétique.

The edibility of different Elaeis sp. breeding populations present in Benin was tested for the leaf miner Coelaenomenodera lameensis Berti (Coleoptera: Chrysomelidae), a major oil palm pest in Africa. Experiments carried out in sleeves revealed the oviposition capacities of females and the mortality rates for the different developmental stages by comparing the populations found on two breeding populations of Elaeis oleifera (HBK) Cortes, four of Elaeis guineensis Jacquin and four ( E. guineensis × E. oleifera ) × E. guineensis backcrosses. Females laid their eggs similarly on all breeding populations, with a preference for the E. guineensis La Me origin. The average hatching rate reached 80% for the La Me origin as opposed to 28% for the Deli origin. The mortality rates for the larval instars were greater on E. oleifera , on certain backcrosses and on the Deli origin of E. guineensis . Development at the second- and third- larval instars was the most affected, with a mortality rate of three to five times greater than that seen on La Me. Epidermis and cuticle measurements indicated which breeding populations were suitable or unsuitable for the development of C. lameensis . E. guineensis, with its thin epidermis (12 µm) and cuticle (2 µm), proved to be highly susceptible to C. lameensis attacks. On the other hand, E. oleifera , which is very resistant, exhibited a thicker epidermis (17 µm) and cuticle (4 µm). The breeding populations were thus classified according to the positive or negative influence they exerted on the insect’s egg laying and feeding. RESUME. La comestibilite de differents materiels vegetaux d’ Elaeis sp. presents au Benin est testee pour Coelaenomenodera lameensis Berti (Coleoptera: Chrysomelidae), important ravageur du palmier a huile en Afrique. Des experimentations en manchons ont permis de determiner les capacites d’oviposition des femelles et les taux de mortalite des differents stades de developpement (œufs, larves, nymphes et adultes) en comparant les populations observees sur deux origines d’ Elaeis oleifera (HBK) Cortes, quatre origines d’ Elaeis guineensis Jacquin et quatre Backcross ( E. guineensis × E. oleifera ) × E. guineensis . Les femelles pondent indifferemment sur tous les types de materiel vegetal avec une preference pour l’origine La Me d’ E. guineensis . Le taux moyen d’eclosion atteint 80% pour l’origine La Me contre 28% pour l’origine Deli. Le taux de mortalite des stades larvaires est plus important sur E. oleifera , sur certains Backcross et sur l’origine Deli d’ E. guineensis . Le developpement des deuxieme et troisieme stades larvaires sont les plus affectes avec un taux de mortalite 3 a 5 fois superieur a celui observe sur La Me. Des mesures d’epiderme et de cuticule mettent en evidence l’existence de materiel vegetal favorable ou defavorable au developpement de C. lameensis . E. guineensis dont l’epiderme (12 µm) et la cuticule (2 µm) sont peu epais se revele etre tres sensible aux attaques de C. lameensis . Au contraire, E. oleifera presente un epiderme (17 µm) et une cuticule (4 µm) plus epais et est tres resistants. Le materiel vegetal est ainsi classe suivant l’influence positive ou negative qu’ils exercent sur la ponte et l’alimentation des insectes.

In order to assess the resistance of phenol-formaldehyde (PF) modified wood to subterranean termites (Reticulitermes flavipes), laboratory no-choice tests following the standard EN 117 (2013) were performed for 8 weeks. Scots pine (Pinus sylvestris L.) sapwood specimens were modified with low molecular weight PF-resin in two concentrations. After vacuum-pressure impregnation and curing, the wood specimens were subjected to an accelerated aging test according to the standard EN 84 (1997). Five replicates per each concentration group were exposed to termites as well as unmodified wood. Following exposure, the specimens were evaluated for termite damage using a visual rating system and mass losses were also recorded. All treated samples showed higher resistance to termites than the controls. After testing period, 100 % termite mortality was found for modified wood. PF-resin treatment significantly reduced the feeding activity of termites and the mass losses caused.

Equipe DGB - ex-UMR PIA; International audience; Puroindolines form the molecular basis of wheat grain hardness. However, little is known about puroindoline gene regulation. We previously reported that the Triticum aestivum puroindoline-b gene (PinB) promoter directs beta-glucuronidase gene (uidA) seed-specific expression in transgenic rice. In this study, we isolated a puroindoline-a gene (PinA), analyzed PinA promoter activity by 5' deletions and compared PinA and PinB promoters in transgenic rice. Seeds of PinA-1214 and PinB-1063 transgenic plants strongly expressed uidA in endosperm, in the aleurone layer and in epidermis cells in a developmentally regulated manner. The GUS activity was also observed in PinA-1214 embryos. Whereas the PinB promoter is seed specific, the PinA promoter also directed, but to a lower level, uidA expression in roots of seedlings and in the vascular tissues of palea and pollen grains of dehiscent anthers during flower development. In addition, the PinA promoter was induced by wounding and by Magnaporthe grisea. By deletion analysis, we showed that the "390-bp" PinA promoter drives the same expression pattern as the "1214-bp" promoter. Moreover, the "214-bp" PinA promoter drives uidA expression solely in pollen grains of dehiscent anthers. The presence of putative cis-regulatory elements that may be related to PinA expression is discussed from an evolutionary point of view. By electrophoretic mobility shift assay, we showed that putative cis-elements (WUN-box, TCA motifs and as-1-like binding sites) whose presence in the PinA promoter may be related to wounding and/or the pathogen response form complexes with nuclear extracts isolated from wounded wheat leaves

The genetic parameters of several agronomic traits were estimated in #Coffea canephora# in a triangular diallel with six parents and in a partial diallel with 18 parents. The yield data came from harvests obtained over 14 years divided into an initial 6-year cycle, a second cycle of 5 years after cutting back and a third cycle of 3 years after topping. Risk incidence was also observed over several years. The general combining abilities (GCA) were the principal sources of variation for the various traits considered. Parents derived from the Yangambi selections (Democratic Republic of Congo) proved to be best for yields in the three cropping cycles. The rank correlations between the GCA of the various traits indicated that first-cycle production was still not enough to predict the GCA for yield over 14 years. Susceptibility to leaf anthracnose and to drought could lead to modifications in successive classifications, with a more significant impact on production during the first cycle. The differences in susceptibility to Coffee Berry Borers had an impact on yield, which increased in line with coffee tree age. There was a rather good relation between inherent values and values in parent combinations and it was thus possible to choose parents on their own performance.

International audience; In order to meet growing demand for chocolate products, numerous initiatives have been launched over the last 10 years with a view to increasing cocoa production. These initiatives continue to promote the input-intensive model advocated since the 1960s, even though this model has reached its agronomic, socio-economic, and environmental limits. Hence the proposal to learn from agroforestry in order to develop the current model: introducing fruit and forest tree species into cocoa plantations contributes to the agro-ecological intensification of cocoa production, while improving flexibility and resilience, which are essential to smallholder farmers, who grow 95% of the world’s cocoa.; Para satisfacer el incremento en el consumo de productos con chocolate, se tomaron varias iniciativas en la última decena para aumentar la producción de cacao. Esas iniciativas siguen promoviendo el modelo intensivo en insumos recomendado desde los años 1960, aun si este modelo ha alcanzado sus límites agronómicos, socio-económicos y ambientales. A raíz de esto se elaboró la propuesta de inspirarse de la Agroforestería para influenciar la evolución del modelo actual: introducir árboles frutales y maderables en las plantaciones de cacao contribuye a la intensificación agroecológica del cultivo del cacao, aportando al mismo tiempo la flexibilidad y la resiliencia necesarias a los pequeños agricultores quienes producen el 95% del cacao en el mundo.; Pour satisfaire la consommation croissante de produits chocolatés, de nombreuses initiatives ont été lancées depuis une décennie afin d’augmenter la production de cacao. Ces initiatives continuent de promouvoir le modèle intensif en intrants préconisé depuis les années 1960, alors que ce modèle a atteint ses limites agronomiques, socio-économiques et environnementales. D’où la proposition de s’inspirer de l’agroforesterie pour faire évoluer le modèle actuel : introduire des arbres fruitiers et forestiers dans les cacaoyères contribue à l’intensification agroécologique de la cacaoculture, tout en apportant souplesse et résilience, nécessaires aux petits agriculteurs, qui produisent 95 % du cacao mondial.

International audience; In order to meet growing demand for chocolate products, numerous initiatives have been launched over the last 10 years with a view to increasing cocoa production. These initiatives continue to promote the input-intensive model advocated since the 1960s, even though this model has reached its agronomic, socio-economic, and environmental limits. Hence the proposal to learn from agroforestry in order to develop the current model: introducing fruit and forest tree species into cocoa plantations contributes to the agro-ecological intensification of cocoa production, while improving flexibility and resilience, which are essential to smallholder farmers, who grow 95% of the world’s cocoa.; Para satisfacer el incremento en el consumo de productos con chocolate, se tomaron varias iniciativas en la última decena para aumentar la producción de cacao. Esas iniciativas siguen promoviendo el modelo intensivo en insumos recomendado desde los años 1960, aun si este modelo ha alcanzado sus límites agronómicos, socio-económicos y ambientales. A raíz de esto se elaboró la propuesta de inspirarse de la Agroforestería para influenciar la evolución del modelo actual: introducir árboles frutales y maderables en las plantaciones de cacao contribuye a la intensificación agroecológica del cultivo del cacao, aportando al mismo tiempo la flexibilidad y la resiliencia necesarias a los pequeños agricultores quienes producen el 95% del cacao en el mundo.; Pour satisfaire la consommation croissante de produits chocolatés, de nombreuses initiatives ont été lancées depuis une décennie afin d’augmenter la production de cacao. Ces initiatives continuent de promouvoir le modèle intensif en intrants préconisé depuis les années 1960, alors que ce modèle a atteint ses limites agronomiques, socio-économiques et environnementales. D’où la proposition de s’inspirer de l’agroforesterie pour faire évoluer le modèle actuel : introduire des arbres fruitiers et forestiers dans les cacaoyères contribue à l’intensification agroécologique de la cacaoculture, tout en apportant souplesse et résilience, nécessaires aux petits agriculteurs, qui produisent 95 % du cacao mondial.

Pour satisfaire la consommation croissante de produits chocolatés, de nombreuses initiatives ont été lancées depuis une décennie afin d'augmenter la production de cacao. Ces initiatives continuent de promouvoir le modèle intensif en intrants préconisé depuis les années 1960, alors que ce modèle a atteint ses limites agronomiques, socio-économiques et environnementales. D'où la proposition de s'inspirer de l'agroforesterie pour faire évoluer le modèle actuel : introduire des arbres fruitiers et forestiers dans les cacaoyères contribue à l'intensification agroécologique de la cacaoculture, tout en apportant souplesse et résilience, nécessaires aux petits agriculteurs, qui produisent 95 % du cacao mondial.

International audience; The root-knot nematode Meloidogyne incognita is widely distributed and a major pathogen of cotton (Gossypium spp.) worldwide. The objectives of this study were to assess the genetic variability and aggressiveness of Brazilian populations of M. incognita in cotton. Five populations of M. incognita and one isolate of M. enterolobii (outgroup) were used in the molecular analysis. Our results showed that only 2.7 % of the RAPD and AFLP fragments were polymorphic. Despite the existence of two races (races 3 and 4) and two esterase phenotypes (I1 and I2), a low genetic variability among populations was observed, which might be due to the mitotic parthenogenetic mode of reproduction of this pathogen. The aggressiveness/virulence among populations towards different cotton genotypes was also studied. None of the populations was virulent to the resistant cotton genotypes M-315 RNR, TX-25, CIR1343, Wild Mexican Jack Jones and CIR1348 (reproduction factor < 1). Two populations of M. incognita from the states of Mato Grosso do Sul and Parana (Umuarama) (races 4 and 3, respectively) were highly aggressive to the susceptible control FM966 and virulent to the accessions LA-887 and Clevewilt-6 that showed moderate resistance to other populations tested.

Plant proteinase inhibitors (PIs) are considered as candidates for increased insect resistance in transgenic plants. Insect adaptation to PI ingestion might, however, compromise the benefits received by transgenic expression of PIs. In this study, the maize proteinase inhibitor (MPI), an inhibitor of insect serine proteinases, and the potato carboxypeptidase inhibitor (PCI) were fused into a single open reading frame and introduced into rice plants. The two PIs were linked using either the processing site of the Bacillus thuringiensis Cry1B precursor protein or the 2A sequence from the foot-and-mouth disease virus (FMDV). Expression of each fusion gene was driven by the wound- and pathogen-inducible mpi promoter. The mpi-pci fusion gene was stably inherited for at least three generations with no penalty on plant phenotype. An important reduction in larval weight of Chilo suppressalis fed on mpi-pci rice, compared with larvae fed on wild-type plants, was observed. Expression of the mpi-pci fusion gene confers resistance to C. suppressalis (striped stem borer), one of the most important insect pest of rice. The mpi-pci expression systems described may represent a suitable strategy for insect pest control, better than strategies based on the use of single PI genes, by preventing insect adaptive responses. The rice plants expressing the mpi-pci fusion gene also showed enhanced resistance to infection by the fungus Magnaporthe oryzae, the causal agent of the rice blast disease. Our results illustrate the usefulness of the inducible expression of the mpi-pci fusion gene for dual resistance against insects and pathogens in rice plants., BLG was a researcher from the Ministerio de Ciencia e Innovación (MICINN), Spain (‘Ramon y Cajal’). We are grateful to M. Coca (CRAG, Spain) for her collaboration in this work and M. Royer (CIRAD, BGPI unit, France) for providing us with the C region of the Cry1B sequence synthesized in the framework of an UNDP-funded project. We are also grateful to C. Halpin, Dundee University, UK) for providing us with the pGUS2AGFP plasmid). This work was supported by grants BIO2003-04936-C02-01/BIO2012-32838 to B.S.S and AGL2010-16847 to B.L-G from Ministerio de Economía y Competitividad (MINECO). We also thank the Consolider-Ingenio CSD2007-00036 to CRAG and the Generalitat de Catalunya (Xarxa de Referencia en Biotecnología and SGR 09626) for substantial support.