Eddy Leonard Mangaptche Ngonkeu

Assessment of agronomic parameters of some soybean varieties grown on acidic soil, their total nitrogen content during nodulation, and after pod formation

Linda Manet, Onana Boyomo, Eddy Ngonkeu, Hippolyte Tene Mouafo, Victorine Tomo O. Lombeko, Gabriel Nama Medoua et 1 autre(s)

Agrosystems Geosciences & Environment

Abstract This study, conducted at Nkolbisson in the Centre region of Cameroon, aimed to identify soybean [ Glycine max (L.) Merr.] varieties released by the Pan‐African Soybean Variety Trials (PAT) in 2016 that are adapted to the acidic soil conditions (pH 4.10). A completely randomized block design with three replications was used for experimentation. Fertilizer was not applied to allow each variety to develop its potential under acidic conditions. Quantitative parameters, including plant height, crown diameter, fresh and dry weights of aboveground parts and roots, and total plant dry matter, were measured. The total nitrogen content of the plant during nodulation and after pod formation, as well as the production yields, was also assessed. Results showed that six varieties had plant heights greater than 67 cm (Pan 237, TGX 2010 3F, Pan 3, Maksoy 2N, Songda, and TGX 2001 12F), with the highest height recorded with TGX 2001 12F (85.66 ± 5.68 cm). The highest fresh weights of the aerial parts, ranging from 13.36 ± 3.97 to 44.26 ± 13.95 g, were observed in 19 soybean varieties. Fifteen soybean varieties showed the highest dry matter (95.04%–95.60%). The soybean varieties with the highest total nitrogen content at nodulation and after pod formation were Sentinel (6.00%) and TGX 2011‐3F (4.88%), respectively. Nine varieties achieved yields above 2 t/ha, with TGX 2010 3F scoring the highest yield (2.76 t/ha). This study demonstrated the potential of some varieties of soybeans to thrive in acidic soils, offering a viable alternative for cultivation in areas with edaphic constraints. For that, further studies should be conducted on both the nutritional performance and the symbiotic interactions of these soybean varieties under acidic soil conditions.

• #legume nitrogen fixing symbiosis
• #soybean genetics and cultivation
• #aluminum toxicity and tolerance in plants and animals
• #point of delivery

Effect of Arbuscular Mycorrhizal Fungi Combined with Exogenous Calcium on Papaya (Carica papaya L.) Plant Growth

Adèle Fokou Maffo, Eddy Ngonkeu, Nono Carine Temegne, Clémence Chaintreuil, Godswill Ntsomboh-Ntsefong, Emmanuel Youmbi

Asian Journal of Research in Crop Science

The pawpaw (Carica papaya L.) is a very productive fruit tree but is not widely exploited on the international market due to rapid deterioration of the fruits after harvest. This deterioration is due to a nutritional dysfunction related to the deficiency of nutrients, especially calcium, which is involved in the firmness of fruits in general and the papaya in particular. The symbiotic capacity of arbuscular mycorrhizal fungi (AMF) has been profiled to enhance uptake and regulation of exchangeable calcium ions in the soil. The aim of this study was to reduce losses and improve post-harvest quality of papaya fruits through the potential of arbuscular mycorrhizal fungi (AMF) in calcium uptake for international exploitation. A composite of AMF species identified of papaya rhizosphere in two study sites, combined with different calcium doses (0 µM, 100 µM, 200 µM, 300 µM and 1000 µM) was applied to two papaya varieties (calcium deficiency-resistant V1 Calina papaya IPB9 and calcium deficiency-sensitive V2 Solo N°8) and the effect was evaluated in greenhouse. The frequency and intensity of root colonization were evaluated. The AMF/calcium 1000 µM combination significantly influenced (P = .05) the number of plant height (44%, 68%), leaves (71%; 122%), fresh biomass of leaves (3,3%; 596.3%), roots (159.2%, 265.3%), and stems (910%;4075%) in both varieties V1 and V2 respectively compared to AMF/ calcium 0 µM. Increased absorption of calcium ions (150%) and phytochemicals were recorded in the leaves. The frequency (81%; 85%) and intensity (15%; 21%) of root colonization by AMF respectively was not significantly different (P>.05) in both two varieties (V1 and V2). However, the presence of AMF spores was observed on the roots of papaya plants mycorrhized with the calcium 1000 µM. Inoculation with AMF combined with the high calcium dose (1000 µM) promoted mycorrhizal infectivity of roots, colonization of mycorrhizal spores in the soil and increased roots absorption surface area.

• #mycorrhizal fungi and plant interactions
• #carica
• #arbuscular mycorrhizal fungi
• #biology

Effect of Inoculation With Two Strains of Rhizobium sp. on the Agronomic Performance of Three Soybean Varieties ( Glycine max L.) Cultivated in Mbalmayo, Cameroon

Linda Manet, Eddy Ngonkeu, Onana Boyomo, Hippolyte Tene Mouafo, Gabriel Nama Medoua, Aimé Didier Boyogueno Begoudé

Legume Science

ABSTRACT Soybean inoculation with Rhizobium strains is a sustainable and eco‐friendly strategy to enhance productivity, particularly in countries where agriculture is hampered by some issues, including acidic soils and the high cost of chemical fertilizers. This study assessed the effect of inoculating three soybean varieties with two Rhizobium strains on nitrogen fixation, plant growth parameters, and productivity. Rhizobium S1 and Rhizobium S2 were used to inoculate seeds of three soybean varieties: TGX 1910 14F, Maksoy 4N, and TGX 1835 10E. The agronomic performance of inoculated soybean seeds was compared with noninoculated seeds over a 120‐day field growth period. We found that the total nitrogen content of the var. TGX 1910 14F increased following inoculation with strains S1 (2.93 ± 0.06% vs. 2.53 ± 0.12%) and S2 (3.34 ± 0.05% vs. 2.53 ± 0.12%). A similar trend was observed for the root fresh weight of TGX 1910 14F. Maksoy 4N inoculated with strain S1 exhibited increases in plant height, above‐ground biomass, and both fresh and dry root weights. The highest number of nodules was recorded in the inoculated seeds, with strain S2 being the most effective across all soybean varieties. Regarding yield, strain S1 was most efficient for TGX 1910 14F (169.66 ± 75.56 seeds per plant equivalent to 1.35 ± 0.60 tons/ha) and Maksoy 4N (106.0 ± 2.64 seeds per plant equivalent to 0.84 ± 0.02 tons/ha), while strain S2 was most effective for TGX 1835 10E, achieving the highest seeds per plant (174.33 ± 42.91 seeds per plant equivalent to 1.39 ± 0.34 tons/ha). This study presents a practical solution for enhancing the sustainability of farming systems, contributing to the achievement of sustainable development goals, and addressing climate change.

• #legume nitrogen fixing symbiosis
• #agronomic practices and intercropping systems
• #soybean genetics and cultivation
• #glycine

Unveiling the Biofertilizer Potential of Two Rhizobium sp. Strains on the Secretion of Phytochemical Compounds, Antioxidant Activity, and Nutritional Quality of Three Soybean Varieties ( Glycine max L.)

Linda Manet, Onana Boyomo, Eddy Ngonkeu, Hippolyte Tene Mouafo, Ferdinand Lanvin Ebouel Edoun, Gabriel Nama Medoua et 1 autre(s)

International Journal of Agronomy

Optimizing agricultural methods to enhance the nutritional quality of crops is crucial for achieving the global sustainable development goals. This study examined the impact of inoculation of seeds from three soybean varieties with Rhizobium sp. S1 and Rhizobium sp . S2, on the secretion of phytochemical compounds, antioxidant activity, and nutritional quality of the harvested seeds. Seeds from three varieties of soybean were inoculated with Rhizobium sp. S1 and Rhizobium sp . S2. The inoculated seeds were grown over 120 days and compared with non‐inoculated seeds used as controls. Analyses focused on phytochemical compounds (polyphenols, flavonoids, saponins, tannins, and alkaloids), antioxidant activity assessed through iron‐reducing capacity and total antioxidant capacity (TAC), and the nutritional quality of harvested seeds. The results showed that inoculation has significantly ( p < 0.05) improved phytochemical concentrations of seeds independent of the strain and soybean variety. Maksoy 4N seeds inoculated with Rhizobium sp . S1 scored the highest polyphenols (408.66 ± 12.48 μg GAE/g DM), flavonoids (76.62 ± 5.02 μg QE/g DM), and alkaloids (147.28 ± 2.96 μg QuiE/g DM). While Maksoy 4N seeds inoculated with Rhizobium sp . S2 showed the highest tannins (5.98 ± 0.22 μg TAE/g DM) and saponins (4116.67 ± 17.55 μg SaE/g DM). Significant ( p < 0.05) enhancement of the TAC independent of the soybean variety was recorded following seed inoculation compared to controls. The highest proteins (39.51 ± 0.19 g/100 g DM) and total sugars (9.04 ± 0.28 g/100 g DM) were noticed with seeds from Maksoy 4N inoculated with Rhizobium sp . S2, while seeds from TGX 1835 10E inoculated with Rhizobium sp . S1 showed the highest fiber content (8.83 ± 0.08 g/100 g DM). This study demonstrates that inoculation with Rhizobium sp. S1 and Rhizobium sp . S2 strains enhanced the content of bioactive compounds, antioxidant activity, and the nutritional quality of seeds, thus suggesting the use of these strains as biofertilizers for sustainable agriculture, leading to nutritious products and health benefits.

• #legume nitrogen fixing symbiosis
• #soybean genetics and cultivation
• #plant nutrient uptake and metabolism
• #phytochemical

Agro-Morphology Evaluation and Gluten Content Estimation of Wheat (<i>Triticum aestivum </i>L.) in the Western Highland of Cameroon

Liliane Ngoune Tandzi, Aminatou Fanche Mongoue, Eddy Ngonkeu

Agricultural Sciences

Agriculture is amongst the major occupations in Cameroon where over 70% of citizens are involved and it contributes enormously to the economy of the country. Wheat is one of the most consumed cereals in Cameroon with very high importation rate. However, the adoption of wheat production in the cropping system could have the potential to pull farmers out of poverty. It is essential in human foods and animal feeds. This study aims to investigate on the adaptability of wheat varieties based on growth traits and yield as well as to estimate the gluten content in each of the tested variety in the North-West region. Eight wheat varieties (five from CIMMYT, two from IRAD and one local variety) were evaluated in a factorial design with two types of fertilization (organic and inorganic), in two site (Santa and UBa farm) and five environments. Agro-morphological data were collected and were subjected to the analysis of variance using R software. The gluten content related to the baking quality of wheat flour was estimated per tested variety. Highly significant differences were observed among varieties, sites, environment and fertilization for all parameters estimated. The general mean of all the traits evaluated was significantly higher when using organic fertilizer than inorganic, meaning that the application of organic fertilizer provides better performance of wheat growth. The elevated number of tillers found in Santa could inform on the high level of soil fertility for wheat production in that area. Environment 1 was found to be the best follow by environment 3 and 5. IRAD I gave the highest yield followed by Alexander Wonder and IRAD II. 11SATYND and 29SAWYT were promising introduced varieties in term of grain weight when using organic fertilization. Wet and dry gluten yield varied from 3.8 (ALEXANDER Wonder) to 5.5 (IRAD I) and from 3.7 (IRAD II) to 7.9 (IRAD I) respectively. All the introduced wheat varieties expressed low wet and dry gluten yield as compare to the check Amigo. IRAD I was the best variety to be produced for industrial purposes taken into account the high level of gluten content. IRAD I, 42ESWYTB and IRAD II were found to have their moisture content percentage of flour below that of the check (Amigo) and therefore could be recommended for manufactured foods.

• #food composition and properties
• #seed and plant biochemistry
• #wheat and barley genetics and pathology
• #gluten

Comparative genomics and transcriptomic response to root exudates of six rice root-associated Burkholderia sensu lato species

Adrian Wallner, Agnieszka Klonowska, Ludivine Guigard, Eoghan King, Isabelle Rimbault, Eddy Ngonkeu et 3 autre(s)

Peer Community Journal

Beyond being a reliable nutrient provider, some bacteria will perceive the plant as a potential host and undertake root colonization leading to mutualistic or parasitic interactions. Bacteria of the Burkholderia and Paraburkholderia genera are frequently found in the rhizosphere of rice. While the latter are often described as plant growth promoting species, Burkholderia are often studied for their human opportunistic traits. Here, we used root exudate stimulation on three Burkholderia and three Paraburkholderia strains isolated from rice roots to characterize their preliminary adaptation to the rice host at the transcriptomic level. Instead of the awaited genus-dependent adaptation, we observed a strongly species-specific response for all tested strains. While all bacteria originate from the rice environment, there are great disparities in their levels of adaptation following the sensing of root exudates. We further report the shared major functions that were differentially regulated in this early step of bacterial adaptation to plant colonization, including amino acids and putrescine metabolism, the Entner-Doudoroff (ED) pathway as well as cyclic diguanylate monophosphate (c-di-GMP) cycling.

• #legume nitrogen fixing symbiosis
• #plant-microbe interactions and immunity
• #plant pathogenic bacteria studies
• #biology

Comparative genomics and transcriptomic response to root exudates of six rice root-associated Burkholderia sensu lato species

Adrian Wallner, Agnieszka Klonowska, Ludivine Guigard, Eoghan King, Isabelle Rimbault, Eddy Ngonkeu et 3 autre(s)

bioRxiv (Cold Spring Harbor Laboratory)

Abstract Beyond being a reliable nutrient provider, some bacteria will perceive the plant as a potential host and undertake root colonization leading to mutualistic or parasitic interactions. Bacteria of the Burkholderia and Paraburkholderia genera are frequently found in the rhizosphere of rice. While the latter are often described as plant growth promoting species, Burkholderia are often studied for their human opportunistic traits. Here, we used root exudate stimulation on three Burkholderia and three Paraburkholderia strains isolated from rice roots to characterize their preliminary adaptation to the rice host at the transcriptomic level. Instead of the awaited genus-dependent adaptation, we observed a strongly species-specific response for all tested strains. While all bacteria originate from the rice environment, there are great disparities in their levels of adaptation following the sensing of root exudates. We further report the shared major functions that were differentially regulated in this early step of bacterial adaptation to plant colonization, including amino acids and putrescine metabolism, the Entner-Doudoroff (ED) pathway as well as cyclic diguanylate monophosphate (c-di-GMP) cycling.

• #legume nitrogen fixing symbiosis
• #plant-microbe interactions and immunity
• #nematode management and characterization studies
• #biology

GWAS identifies a wheat orthologue of the rice D11 gene as an important contributor to grain size in an international collection of hexaploid wheat

Honoré Tekeu, Eddy Ngonkeu, Sébastien Bélanger, Pierre François Djocgoue, Amina Abed, Davoud Torkamaneh et 5 autre(s)

Research Square

Abstract Grain size is a key agronomic trait that contributes to grain yield in hexaploid wheat. Grain length and width were evaluated in an international collection of 159 wheat accessions. These accessions were genetically characterized using a genotyping-by-sequencing (GBS) protocol that produced 73,784 single nucleotide polymorphism (SNP) markers. GBS-derived genotype calls obtained on Chinese Spring proved extremely accurate when compared to the reference (> 99.9%) and showed > 95% agreement with calls made at SNP loci shared with the 90K SNP array on a subset of 71 Canadian wheat accessions for which both types of data were available. This indicates that GBS can yield a large amount of highly accurate SNP data in hexaploid wheat. The genetic diversity analysis performed using this set of SNP markers revealed the presence of six distinct groups within this collection. A GWAS was conducted to uncover genomic regions controlling variation for grain length and width. In total, seven SNPs were found to be associated with one or both traits, identifying three quantitative trait loci (QTLs) located on chromosomes 1D, 2D and 4A. In the vicinity of the peak SNP on chromosome 2D, we found a promising candidate gene (TraesCS2D01G331100), whose rice ortholog (D11) had previously been reported to be involved in the regulation of grain size. These markers will be useful in breeding for enhanced wheat productivity.

• #wheat and barley genetics and pathology
• #genetic mapping and diversity in plants and animals
• #genetics and plant breeding
• #biology

Effect of Arbuscular Mycorrhizal Fungi Used as Biofertilizer for the Vegetative Propagation of Prunus africana (Hook.f.) Kalkman

J D Kamko, Yves H. Tchiechoua, Eddy Ngonkeu, Justine Germo Nzweundji, M. Tchatat, D Eloumou et 8 autre(s)

International Journal of Plant Research

Prunus africana is a medicinal plant species whose exploitation became abusive over the years due to the high properties of its bark. It faces multiple challenges: the recalcitrance of its seeds and the irregular fruiting which makes its sexual regeneration difficult. Therefore, asexual regeneration has been set as the appropriate corridor for its domestication. Nonetheless, this way has encountered difficulties, particularly in the continuous growth of cuttings due to the weak development of its root systems. The optimization of plant mycorrhizal symbiosis is a key factor to overcome this constraint. This justifies the aim of this work which was to develop a method of producing P. africana cuttings inoculated with its native Arbuscular mycorrhizal fungi (AMF) to improve its regeneration. To undergo this purpose, soils samples were collected in three Mounts (Cameroon, Oku and Manengouba), then, isolation and characterization of AMF species was done after the fungi trapping culture followed by a pre-germination, multiplication and evaluation of their growth efficiency. To see their real efficiency on Prunus root system, each AMF species multiplied has been used as biofertilizer on Prunus cuttings in a frame, where indol butyric acid (AIB) was used as positive control and water was applied as a negative control. The result revealed the presence of six species of AMF belonging to the genera Gigaspora (1), Glomus (3) and Acaulospora (2). Each AMF species showed a great capacity of growth improvement and self-multiplication. Inoculated AM fungi increased the root density of Prunus africana cuttings with an average root number of 35 for the more efficient species (Gigaspora margarita), compared to the positive control which had an average root number of 10 and the negative control 4. These results can contribute to the improvement of P. africana regeneration.

• #mycorrhizal fungi and plant interactions
• #plant pathogens and fungal diseases
• #banana cultivation and research
• #cutting

Genomic analyses of Burkholderia cenocepacia reveal multiple species with differential host-adaptation to plants and humans

Adrian Wallner, Eoghan King, Eddy Ngonkeu, Lionel Moulin, Gilles Béna

BMC Genomics

BACKGROUND: Burkholderia cenocepacia is a human opportunistic pathogen causing devastating symptoms in patients suffering from immunodeficiency and cystic fibrosis. Out of the 303 B. cenocepacia strains with available genomes, the large majority were isolated from a clinical context. However, several isolates originate from other environmental sources ranging from aerosols to plant endosphere. Plants can represent reservoirs for human infections as some pathogens can survive and sometimes proliferate in the rhizosphere. We therefore investigated if B. cenocepacia had the same potential. RESULTS: We selected genome sequences from 31 different strains, representative of the diversity of ecological niches of B. cenocepacia, and conducted comparative genomic analyses in the aim of finding specific niche or host-related genetic determinants. Phylogenetic analyses and whole genome average nucleotide identity suggest that strains, registered as B. cenocepacia, belong to at least two different species. Core-genome analyses show that the clade enriched in environmental isolates lacks multiple key virulence factors, which are conserved in the sister clade where most clinical isolates fall, including the highly virulent ET12 lineage. Similarly, several plant associated genes display an opposite distribution between the two clades. Finally, we suggest that B. cenocepacia underwent a host jump from plants/environment to animals, as supported by the phylogenetic analysis. We eventually propose a name for the new species that lacks several genetic traits involved in human virulence. CONCLUSION: Regardless of the method used, our studies resulted in a disunited perspective of the B. cenocepacia species. Strains currently affiliated to this taxon belong to at least two distinct species, one having lost several determining animal virulence factors.

• #cystic fibrosis research advances
• #bacterial biofilms and quorum sensing
• #infections and bacterial resistance
• #biology

Breeding Maize for Tolerance to Acidic Soils: A Review

Liliane Ngoune Tandzi, Charles Shelton Mutengwa, Eddy Ngonkeu, Vernon Gracen

Agronomy

Acidic soils hamper maize (Zea mays L.) production, causing yield losses of up to 69%. Low pH acidic soils can lead to aluminum (Al), manganese (Mn), or iron (Fe) toxicities. Genetic variability for tolerance to low soil pH exists among maize genotypes, which can be exploited in developing high-yielding acid-tolerant maize genotypes. In this paper, we review some of the most recent applications of conventional and molecular breeding approaches for improving maize yield under acidic soils. The gaps in breeding maize for tolerance to low soil pH are highlighted and an emphasis is placed on promoting the adoption of the numerous existing acid soil-tolerant genotypes. While progress has been made in breeding for tolerance to Al toxicity, little has been done on Mn and Fe toxicities. More research inputs are therefore required in: (1) developing screening methods for tolerance to manganese and iron toxicities; (2) elucidating the mechanisms of maize tolerance to Mn and Fe toxicities; and, (3) identifying the quantitative trait loci (QTL) responsible for Mn and Fe tolerance in maize cultivars. There is also a need to raise farmers’ and other stakeholders’ awareness of the problem of Al, Mn, and Fe soil toxicities to improve the adoption rate of the available acid-tolerant maize genotypes. Maize breeders should work more closely with farmers at the early stages of the release process of a new variety to facilitate its adoption level. Researchers are encouraged to strengthen their collaboration and exchange low soil pH-tolerant maize germplasm.

• #aluminum toxicity and tolerance in plants and animals
• #plant micronutrient interactions and effects
• #plant stress responses and tolerance
• #germplasm

Antagonism of Trichoderma asperellum against Phytophthora megakarya and its potential to promote cacao growth and induce biochemical defence

Séverin Nguemezi Tchameni, Modeste Lambert Sameza, Anthonia O’Donovan, Raymond Fokom, Eddy Ngonkeu, Louise Wakam Nana et 2 autre(s)

Mycology&#58 An International Journal on Fungal Biology

This work aimed to assess the antagonism effects of four different Trichoderma asperellum isolates against Phytophthora megakarya and their ability to enhance cacao growth and biochemical defence. Results showed that In paired culture, all the isolates of T. asperellum used were antagonistic to P. megakarya by means of mycoparasitism. In pot experiments, leaf number, plant height, shoots and root dry matter were significantly increased by T. asperellum. Similarly, chlorophyll rate, P uptake and acid phosphatase activities were also increased. These antagonists reduced significantly the effects of P. megakarya in the leaves of cacao plants. Amino acid and phenolic components content increased in either healthy or infected leaves from cacao plants inoculated with T. asperellum. There was negative correlation between both phenolic compounds and disease severity and amino acids and disease severity. This suggests that these compounds are involved in disease resistance. In fact, the induction of specific amino acids such as alanine, glutamic acid and methionine may play an important role in the adaptation of cacao plant to P. megakarya infection. These findings demonstrated that Trichoderma asperellum (PR10, PR11, PR12 and PR659-7) could be used to improve the development of cacao plants and protect the plant against Phytophthora megakarya.

• #cocoa and sweet potato agronomy
• #plant-microbe interactions and immunity
• #plant parasitism and resistance
• #biology

Screening of Maize (Zea mays L.) Genotypes for Adaptation on Contrasted Acid Soils in the Humid Forest Zone of Cameroon

Carine Petmi, Eddy Ngonkeu, Liliane Ngoune Tandzi, Zachée AMBANG, Onana Boyomo, Joseph Martin Bell et 4 autre(s)

Journal of Experimental Agriculture International

International audience

• #crop yield and soil fertility
• #agricultural science and fertilization
• #rice cultivation and yield improvement
• #zea mays

Effects of Nitrogen Levels and Arbuscular Mycorrhizal Fungi on Biomass Production, Mineral Nutrition, Sugar and Total Phenolic Content of Two Zea mays Cultivars

Louise Nana Wakam, Alvine Nanhou, Raymond Fokom, Séverin Nguemezi Tchameni, Eddy Ngonkeu, Pierre Eke et 2 autre(s)

Journal of Experimental Agriculture International

International audience

• #bioeconomy and sustainability development
• #crop yield and soil fertility
• #agronomy
• #cultivar

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

Honoré Tekeu, Eddy Ngonkeu, Liliane Ngoune Tandzi, Pierre François Djocgoue, Joseph Martin Bell, Hortense A. Mafouasson et 3 autre(s)

International Journal of Biological and Chemical Sciences

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

• #crop yield and soil fertility
• #randomized block design
• #hybrid
• #lime

Desirò et al., 2013 - Detection of a Novel Intracellular Microbiome Hosted in AMF

Alessandro Desirò, Alessandra Salvioli, Eddy Ngonkeu, Stephen J. Mondo, Sara Epis, Antonella Faccio et 3 autre(s)

• #gut microbiota and health
• #oral microbiology and periodontitis research
• #microbiome
• #chemistry

Etude de la relation fonctionnelle bactéries endospores-mycorhizes à arbuscules des sols acides du Cameroun : Session 7- Stress abiotiques et interactions des plantes-bactéries

Eddy Ngonkeu, Clémence Chaintreuil, Caroline Bournaud, Michel Lebrun, O. Boyomo, P.F. Djocgoué et 5 autre(s)

Agritrop (Cirad)

Les Champignons mycorhiziens à arbuscules (CMA) hébergent dans leur cytoplasme sporal deux types d'endobactéries majeures : Candidatus Glomeribacter gigasporarum (CaGg) et des bactéries Mollicutes (Mre). Ces bactéries présentes dans les spores sont des endosymbioles obligatoires de Gigaspora margarita (Gim) en particulier, et auraient un rôle majeur dans la croissance du champignon dans les premières étapes de la symbiose avec la plante (Lum in i et al. 2007). Une étude fonctionnelle visant à comprendre celte relation symbiotique a été initiée afin d'évaluer l'impact de l'inoculation des spores contenant ces populations d'endobactéries sur la symbiose avec le riz. Pour cela, un recensement global de la communauté bactérienne (extérieur et intérieur de la spore) a été effectuée par étude du polymophisme par ARISA (Ribosomal Intergenic Spacer Analysis). Cette approche a été complétée par l'étude de la coexistence des deux endosymbiotes dans le cytoplasme sporal des CMA par différents approches (phylotypage moléculaire, microscopie électronique, hybridation ill situ Ouorescente (F ISH) ct PCR quantitative)(Desi ro ct al 2013). L'inoculation du riz à l'aide des spores provenant du Camero un et du japon a permis d'évaluer l'impact de la présence des bactéries sur les performances symbiotiques des CMA. Globalement, une communauté bactérienne dominée par les Actinobactéries, les Firmicutes et Burkholderia ont été recensés à l'extérieur et intérieur des spores. Dans l'espace cytoplasmique, une spore est susceptible d'héberger les deux types d'endobactéries à la fois (CaGg el Mre) avec une abondance variable de population de mollicutes el de CaGg en fonction de l'origine des CMA Ces découvertes révèlent ainsi pour la première fois que les champignons tolèrent un microbiome bactérien intracellula re dans lequel des types distincts d'endobactéries coexistent au se in d'une seule cellule. Une très faible abondance des CaGg observée dans les spores du Cameroun (1/20 à 11200 par rapport à l'espèce de référence provenant du japon) s'accompagne d'une forte présence des mollicutes (Mre). Une réponse plus importante a été notée sur la croissance et le développement du riz inoculé en serre avec les spores du Cameroun par rapport à celle du Japon, suggérant un effet positif de ces bactéries et un potentiel intéressant dans la tolérance des spores de CMA aux sols acides et la croissance du riz.

• #plant pathogens and fungal diseases
• #mycorrhizal fungi and plant interactions
• #plant-microbe interactions and immunity
• #biology

Detection of a novel intracellular microbiome hosted in arbuscular mycorrhizal fungi

Alessandro Desirò, Alessandra Salvioli, Eddy Ngonkeu, Stephen J. Mondo, Sara Epis, Antonella Faccio et 3 autre(s)

The ISME Journal

Arbuscular mycorrhizal fungi (AMF) are important members of the plant microbiome. They are obligate biotrophs that colonize the roots of most land plants and enhance host nutrient acquisition. Many AMF themselves harbor endobacteria in their hyphae and spores. Two types of endobacteria are known in Glomeromycota: rod-shaped Gram-negative Candidatus Glomeribacter gigasporarum, CaGg, limited in distribution to members of the Gigasporaceae family, and coccoid Mollicutes-related endobacteria, Mre, widely distributed across different lineages of AMF. The goal of the present study is to investigate the patterns of distribution and coexistence of the two endosymbionts, CaGg and Mre, in spore samples of several strains of Gigaspora margarita. Based on previous observations, we hypothesized that some AMF could host populations of both endobacteria. To test this hypothesis, we performed an extensive investigation of both endosymbionts in G. margarita spores sampled from Cameroonian soils as well as in the Japanese G. margarita MAFF520054 isolate using different approaches (molecular phylotyping, electron microscopy, fluorescence in situ hybridization and quantitative real-time PCR). We found that a single AMF host can harbour both types of endobacteria, with Mre population being more abundant, variable and prone to recombination than the CaGg one. Both endosymbionts seem to retain their genetic and lifestyle peculiarities regardless of whether they colonize the host alone or together. These findings show for the first time that fungi support an intracellular bacterial microbiome, in which distinct types of endobacteria coexist in a single cell.

• #mycorrhizal fungi and plant interactions
• #plant pathogens and fungal diseases
• #plant-microbe interactions and immunity
• #biology

Détection des études des communautés bactériennes du cytoplasme sporal des mycorhizes à arbuscules provenant de sols acides à toxicité aluminique et manganique du Cameroun

Eddy Ngonkeu, Clémence Chaintreuil, Caroline Bournaud, Michel Lebrun, Amougou Akoa, O. Boyomo et 4 autre(s)

Agritrop (Cirad)

Récemment, des bactéries ont été détectées dans le cytoplasme sporal de certains champignons mycorhiziens à arbuscules (CMA). En général représentées par l'espèce Candidatus Glomeribacter gigasporarum (CGg) (Biancotto et al., 2003, Salvioli et al., 2008), ces bactéries présentes dans les spores sont des endosymbiotes obligatoires de Gigaspora margarita (Gim) en particulier, et auraient un rôle majeur dans la croissance du champignon dans les premières étapes de la symbiose avec la plante (Lumini et al., 2007). L'objectif de cette étude est de comparer les communautés bactériennes des spores de Gim provenant de zones géographiques du Cameroun contrastées par rapport à la toxicité des sols (aluminique ou manganique, impactant fortement la croissance de plantes), afin d'étudier l'impact de ces stress sur ces communautés et leur possible rôle dans l'adaptation du champignon. Les spores de Gim isolées de différents sites du Cameroun à toxicité Al et Mn ont été purifiées et utilisées pour la détection directe des bactéries à l'intérieur du cytoplasme. L'amplification de l'ADNr 16S (amorces universelles ou spécifiques de taxons bactériens) couplée aux observations des spores au microscope confocal, ont révélé la présence de trois groupes de bactéries: CGg, Burkholderia et des Firmicutes, dont la répartition varie en fonction du site d'origine des spores. Une très faible abondance des CGg a été observée dans les spores de Gim isolés des sols acides (1/20 à 1/200 par rapport à l'espèce de référence Gim BEG34 provenant de sol tempéré). En revanche, cette faible abondance de CGg s'accompagne d'une forte présence des Burkholderia et des Firmicutes, qui semblent montrer un potentiel intéressant dans la tolérance des spores de CMA aux sols acides. En effet, une germination rapide des spores (2 jours) et une croissance importante des hyphes (> 80011m) ont été observées et mesurées sur milieu gélosé (0,7%) à pH 4 et contenant des concentrations en Al (600 µM) et Mn (600 µM). L'étude des relations fonctionnelles entre bactéries et champignons au cours de la symbiose, ainsi que l'impact de l'inoculation de spores contenant ces populations d'endobactéries sur la symbiose mycorhizienne avec le maïs, en fonction de la toxicité du substrat, est en cours.

• #plant pathogens and fungal diseases
• #mycorrhizal fungi and plant interactions
• #plant-microbe interactions and immunity
• #biology

Inoculation with Rhizobium etli enhances organic acid exudation in common bean ( Phaseolus vulgaris L.) subjected to phosphorus deficiency

Maureen Fonji Atemkeng, Roseline Remans, Jan Michiels, Appolinaire Tagne, Eddy Ngonkeu

Lirias

sponsorship: This study was supported by a Vlaamse Interuniversity Raad (VLIR) Own Initiative project which is in collaboration with Centre of Microbial Plant Genetics, Belgium (CMPG) International Centre of Tropical Agriculture, Columbia (CIAT), Centre of Genomic science, Mexico (CCG) and La Renee (Cuba). (Vlaamse Interuniversity Raad (VLIR), Centre of Microbial Plant Genetics, Belgium (CMPG) International Centre of Tropical Agriculture, Columbia (CIAT), Centre of Genomic science, Mexico (CCG) and La Renee (Cuba))

• #legume nitrogen fixing symbiosis
• #plant nutrient uptake and metabolism
• #agronomic practices and intercropping systems
• #phaseolus

Biological control of cocoa black pod disease by fungi agents : arbuscular mycorrhizal fungi and Trichoderma asperellum

N.S. Tchameni, Louise Nana Wakam, A.D. Owona, R. Fokom, Tertulaine Tchana, Joseph Bienvenu Mbarga et 11 autre(s)

Agritrop (Cirad)

• #cocoa and sweet potato agronomy
• #phytoplasmas and hemiptera pathogens
• #plant pathogenic bacteria studies
• #trichoderma

Potentiel des agents de lutte biologique contre les maladies et ravageurs des cultures

Tertulaine Tchana, Jean Kuaté, Pierre R. Tondje, Eddy Ngonkeu, E. Nyemb Tshomb, B.A.D. Begoude et 21 autre(s)

Agritrop (Cirad)

• #animal disease management and epidemiology
• #agricultural pest management studies
• #zoonotic diseases and public health
• #medicine

Responses of maize grain yield to changes in acid soil characteristics after soil amendments

C. Thé, Henri Calba, Célicard Zonkeng, Eddy Ngonkeu, Victor O. Adetimirin, Hortense A. Mafouasson et 2 autre(s)

Plant and Soil

• #aluminum toxicity and tolerance in plants and animals
• #clay minerals and soil interactions
• #plant micronutrient interactions and effects
• #lime

Long term effect of organic and inorganic amendment on acid soil maize yield and corresponding change in soil characteristics

Henri Calba, Célicard Zonkeng, Eddy Ngonkeu, S. S. Meka, Walter J. Horst

An experiment was conducted from 1997 to 2000 in Cameroon, on acid soil with low pH (4.63), high Aluminium (Al), low calcium (Ca), low magnesium (Mg), and low phosphorus supply (P), to assess the effectiveness of an acid tolerant maize (Zea mays L.) cultivar compared to the use of organic and inorganic fertilizer to correct soil acidity. The experiment was a 2x2x3x2 factorial in a randomised complete block design with six replications. The factors were: phosphorus rate (0 and 60 kg.ha-1 applied as diammonium phosphate), dolomitic lime rates (0 and 2 tons .ha-1), organic manure (0 and 4 tons.ha-1 of poultry manure, 4 tons.ha-1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y an acid soil tolerant, and Tuxpeno Sequia an acid susceptible). Each replication consisted of 4 blocks of 7 treatments with a local maize (CMS 8501) augmented in each block. On non amended acid soil, maize grain yield of ATP-SR-Y, the soil acidity-tolerant cultivar, was 61% higher than grain yield of Tuxpeno Sequia, the soil acidity susceptible cultivar. Continuous maize cultivation on acid soil without amendment further increase soil acidity. This was evident by a decrease in pH (0.23 unit), Ca (31%) and Mg (36%) and by an increase in AI3+ (20%). The yearly application of 60 kg.ha-1 of P for 3 years did not increase the grain yield of the acidity-tolerant cultivar significantly (7%). The 42% grain yield increase obtained with the soil acidity susceptible cultivar on acid soil was partly attributed to increase in available P (35%) of the soil and to the fact that Tuxpeno sequia was AI3+ susceptible but P use efficient. Soil amendment with sole diamonium phosphate tended to increase soil acidity through increases in AI3+ (8%) and H+ (16%) concentration and a decrease in Ca (30%), Mg (11%) and pH (0.07 unit) Lime application, except in the first year resulted in a significant increase in grain yield of both the tolerant (82%) and the susceptible cultivar (208%). The grain yield increase was associated with a significant decrease in exchangeable AI3+ (43%), H+ (51%), and increase in pH (0.27 unit) CEC (5%), and available Ca (154%) and Mg (481%) contents of the soil planted to both the tolerant and the susceptible cultivar. Manure application (poultry and leaves of senna spectabilis) on acid soil, generally resulted in significant (p>0.05) grain yield increase for both the soil acidity tolerant and susceptible cultivars. Poultry manure was more efficient than senna leaves manure producing on average 38% more grain yield. On plot planted to the tolerant cultivar ATP-SR-Y, poultry manure application led to higher increase than did senna leaves in pH (0.24 vs 0.14 unit) in available plant nutrient Ca, Mg and P and in higher decrease in AI3+ (31% vs 09%). On plot planted to the susceptible cultivars, senna spectabilis as compared to poultry manure resulted in higher increase in pH (0.17 vs 0.03 unit), Mg (29% vs 14%) and in higher decrease in AI3+ (15% vs 2%). The available Ca and P were however, better on plot planted to the tolerant cultivar. It was partially concluded that manure application could in a long run decrease the acidity of the soil: However, compared to lime application, the rate in soil characteristic change was slow, suggesting that soil acidity correction with manure would take longer time than the present three yearly application of 4 tons ha-1 investigated in this study. In general, grain yield increase due to soil acidity correction was more related to the decrease in exchangeable AI3+ (R2 = 0.79**) and increase in Ca+ (R2 = 0.74**), than to pH (R2 = 0.52***). However exchangeable AI3 was the main factor determining pH (R2 = 0.66**). These findings suggested that maize cultivation on acid soil must focus on greater understanding of AI3+, Ca+ and Mg dynamics and their management and that breeding maize for AI3+ tolerant and for an efficient use of Ca and Mg from organic manure application is advisable for the acid soil type of C

• #plant micronutrient interactions and effects
• #crop yield and soil fertility
• #phytase and its applications
• #diammonium phosphate