Effect of Sorghum bicolor mycorrhizae on development of tomato in nursery

Tomato is one of the most important vegetable crops in Burkina Faso. Nevertheless, tomato production is confronted with numerous biotic and abiotic constraints. So, it is essential to find ways of boosting its production, starting at the nursery. In nurseries, the use of mycorrhizal fungi can be an effective means of obtaining vigorous and healthy seedlings. This study was carried out with the aim of assessing the impact of endogenous mycorrhizal fungi on the growth and biomass of tomato in nursery. To do so, sorghum (Sorghum bicolor L.), known as a hypermycotrophic plant, was used for inoculum production of mycorrhizal fungi. In addition, the effect of direct association of sorghum and tomato was studied. The results showed that the application of mycorrhizal fungi from the inoculum significantly improved the emergence, growth and leafing of tomato in the nursery during experimentation. A height of 5.75 cm was observed in mycorrhizal plants as compared to 3.23 cm for non-mycorrhizal control plants. It was also shown that adding mycorrhizal inoculum to the seeds was much more effective than the direct association in the field with the sorghum plant and tomato. The results showed that endogenous mycorrhizal fungi significantly improved the emergence, plant height, leaf formation and biomass production of tomato plants

Quantification of diversity sampling bias resulting from rice root bacterial isolation on popular and nitrogen-free culture media using 16S amplicon barcoding

Culturing bacteria from plant material is well known to be conducive to strong bias compared to the actual diversity in the original samples. This bias is related to the bacterial cultivability, chemical composition of the media and culture conditions. Recovery bias is often observed but has never been quantified on different media using an amplicon barcoding approach whereby plant microbiota DNA extractions are compared to DNA extracted from serial dilutions of the same plant tissues grown on bacterial culture media. In this study, we: i) quantified the bacterial culturing diversity bias using 16S amplicon barcode sequencing by comparing a culture-dependent approach (CDA) focused on rice roots on four commonly used bacterial media (10% and 50% TSA, plant-based medium with rice flour, nitrogen free medium NGN and NFb) versus a culture-independent approach (CIA) assessed with DNA extracted directly from root and rhizosphere samples; ii) assessed enriched and missing taxa detected on the different media; iii) used biostatistics functional predictions to highlight metabolic profiles that could potentially be enriched in the CDA and CIA. A comparative analysis of the two approaches revealed that among the 22 phyla present in microbiota of the studied rice root samples, only five were present in the CDA (Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Verrucomicrobia). The Proteobacteria phylum was the most abundant in all CDA samples, showing high gamma-Proteobacteria enrichment. The diversity of the combined culture media represented about a third of the total microbiota diversity, and its genus diversity and frequency was documented. The functional prediction tool (PICRUSt2) detected nitrogenase enzyme enrichment in bacterial taxa sampled from nitrogen-free media, thus validating its predictive capacity. Further functional predictions also showed that the CDA mostly missed anaerobic, methylotrophic, methanotrophic and photosynthetic bacteria compared to the CIA, thereby generating valuable insight that could enable the design of ad-hoc culture media and conditions to increase the rice-associated microbiota cultivability

Quantification of diversity sampling bias resulting from rice root bacterial isolation on popular and nitrogen-free culture media using 16S amplicon barcoding

International audienceCulturing bacteria from plant material is well known to be conducive to strong bias compared to the actual diversity in the original samples. This bias is related to the bacterial cultivability, chemical composition of the media and culture conditions. Recovery bias is often observed but has never been quantified on different media using an amplicon barcoding approach whereby plant microbiota DNA extractions are compared to DNA extracted from serial dilutions of the same plant tissues grown on bacterial culture media. In this study, we: i) quantified the bacterial culturing diversity bias using 16S amplicon barcode sequencing by comparing a culture-dependent approach (CDA) focused on rice roots on four commonly used bacterial media (10% and 50% TSA, plant-based medium with rice flour, nitrogen free medium NGN and NFb) versus a culture-independent approach (CIA) assessed with DNA extracted directly from root and rhizosphere samples; ii) assessed enriched and missing taxa detected on the different media; iii) used biostatistics functional predictions to highlight metabolic profiles that could potentially be enriched in the CDA and CIA. A comparative analysis of the two approaches revealed that among the 22 phyla present in microbiota of the studied rice root samples, only five were present in the CDA (Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Verrucomicrobia). The Proteobacteria phylum was the most abundant in all CDA samples, showing high gamma-Proteobacteria enrichment. The diversity of the combined culture media represented about a third of the total microbiota diversity, and its genus diversity and frequency was documented. The functional prediction tool (PICRUSt2) detected nitrogenase enzyme enrichment in bacterial taxa sampled from nitrogen-free media, thus validating its predictive capacity. Further functional predictions also showed that the CDA mostly missed anaerobic, methylotrophic, methanotrophic and photosynthetic bacteria compared to the CIA, thereby generating valuable insight that could enable the design of ad-hoc culture media and conditions to increase the rice-associated microbiota cultivability

Phenolics from Lippia multiflora Moldenke as potential bioactive agents against peanut pathogens

International audienceThe phenolic composition of aqueous extract from dried leaves of Lippia multiflora Moldenke was analyzed by liquid chromatography- mass spectrometry (LC-MS) before inverse solid phase fractionation. The crude extract and the different fractions (from FL1 to FL5) obtained after fractionation were then tested in vitro for their effect on two fungi responsible of peanut foliar diseases, Phaeoisariopsispersonata and Pucciniaarachidis. The chemical analysis of the aqueous L. multiflora crude extract indicated the presence of seven phenolic compounds (nuomiosideA, isonuomiside A, samioside, verbascoside, isoverbascoside, alyssonoside and leucoseptoside A) and one monoterpene (geniposide). The antifungal activity, estimated by the efficient rate of the fungal appressorium formation, varied from 33.33% to 58.33% and 5.56% to 38.89% for P. personataand P. arachidis spores, respectively. By spraying the different fractions on artificially contaminated leaves, the best antifungal activity was noticed using FL3 and FL4 fractions, the only one in which the presence of samioside was described. The results of this study suggest that the protecting effect of Lippiaextracts against peanut pathogens may be related to the presence of four phenylethanoid glucosides: verbascoside, nuomoside A, leucoseptoside A and samiosid

Phytochemical analysis of Ziziphus mucronata Willd. extract and screening for antifungal activity against peanut pathogens

International audienceChemical analysis of aqueous extract of Ziziphus mucronata Willd. was determined by liquid chromatography–mass spectrometry (LC-MS) analysis. Among the 11 compounds found, catechin, rutin (quercetin 3-O-rutinoside), delphinidin-3-glucoside, isoquercetin (hyperoside) and quercitrin (quercetine3,7-O-L-dirhanmopyranoside) were identified as the major phenolics components in this aqueous plant extract. To elute the target compounds, the fractionation of crude extract was carried out on solid phase extraction (SPE) columns. The different fractions (from FZ1 to FZ5) obtained after fractionation were evaluated in vitro against economically important foliar fungal pathogens of peanut, including Cercospora arachidicola, Phaeoisariopsis personata and Puccinia arachidis. The treatments with Z. mucronata fractions were compared with negative control (water) and standard solutions of cathechin and rutin (1 mg/mL). All the fractions recorded an inhibitory effect, firstly on conidial germination and germ tube elongation, secondly on disease evolution on peanut leaves previously inoculated by fungi; the level of efficiency of inhibition varied from 40.55 (FZ1 against C. arachidicola) to 57.14% (FZ2 and FZ3 against P. arachidis). Then, spores of P. arachidis seemed to be more sensitive to the treatment

Diversity and plant growth promoting ability of rice root-associated bacteria in Burkina-Faso and cross-comparison with metabarcoding data.

Plant-associated bacteria are essential partners in plant health and development. In addition to taking advantage of the rapid advances recently achieved in high-throughput sequencing approaches, studies on plant-microbiome interactions require experiments with culturable bacteria. A study on the rice root microbiome was recently initiated in Burkina Faso. As a follow up, the aim of the present study was to develop a collection of corresponding rice root-associated bacteria covering maximum diversity, to assess the diversity of the obtained isolates based on the culture medium used, and to describe the taxonomy, phenotype and abundance of selected isolates in the rice microbiome. More than 3,000 isolates were obtained using five culture media (TSA, NGN, NFb, PCAT, Baz). The 16S rRNA fragment sequencing of 1,013 selected isolates showed that our working collection covered four bacterial phyla (Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes) and represented 33% of the previously described diversity of the rice root microbiome at the order level. Phenotypic in vitro analysis of the plant growth promoting capacity of the isolates revealed an overall ammonium production and auxin biosynthesis capacity, while siderophore production and phosphate solubilisation were enriched in Burkholderia, Ralstonia, Acinetobacter and Pseudomonas species. Of 45 representative isolates screened for growth promotion on seedlings of two rice cultivars, five showed an ability to improve the growth of both cultivars, while five others were effective on only one cultivar. The best results were obtained with Pseudomonas taiwanensis ABIP 2315 and Azorhizobium caulinodans ABIP 1219, which increased seedling growth by 158% and 47%, respectively. Among the 14 best performing isolates, eight appeared to be abundant in the rice root microbiome dataset from previous study. The findings of this research contribute to the in vitro and in planta PGP capacities description of rice root-associated bacteria and their potential importance for plants by providing, for the first time, insight into their prevalence in the rice root microbiome