Search

The aim of this study was to isolate and characterize the culturable rhizobacteria associated with native cacti from Caatinga biome, testing their potential in plant growth promotion and abiotic stress tolerance. Bacterial isolates were examined for plant growth promotion traits and for in vitro abiotic stress tolerance. Promising isolates were 16S rRNA sequenced, tested under greenhouse conditions for plant growth promotion and induction of water deficit tolerance in maize plants. Analysis of variance was used to assess differences among treatments and, when significant, followed by the Scott-Knott?s test. The highest culturable population density was found in Melocactus zehntneri and the most promissing isolates belonged to the genus Bacillus. Under recommended conditions of irrigation, plants inoculated with the isolates CF12.2, CF8.2, and P12.2 presented an increment in root length, leaf number and root and shoot dry weight. Additionally, isolates CF6.1, CF3.1, CF8.2 and P12.2, increased shoot dry weight under water deficit conditions. In this study we identified bacterial taxa for further validation and application as biostimulants in crops grown in drylands. Made available in DSpace on 2020-09-30T09:12:13Z (GMT). No. of bitstreams: 1 8221-21729-1-PB-1.pdf: 2416262 bytes, checksum: f60acd7dcc9723d1795176e62fd34e4a (MD5) Previous issue date: 2020

Seeds are reproductive structures able to carry and transfer microorganisms that play an important role in plant fitness. Genetic and external factors are reported to be partly responsible for the plant microbiome assemblage, but their contribution in seeds is poorly understood. In this study, wheat, canola, and lentil seeds were analyzed to characterize diversity, structure, and persistence of seed-associated microbial communities. Five lines and 2 generations of each crop were subjected to high-throughput amplicon sequencing of the 16S rRNA and internal transcribed spacer (ITS) regions. Bacterial and fungal communities differed most by crop type (30% and 47% of the variance), while generation explained an additional 10% and 15% of the variance. The offspring (i.e., generation harvested in 2016 at the same location) exhibited a higher number of common amplicon sequence variants (ASVs) and less variability in microbial composition. Additionally, in every sample analyzed, a “core microbiome” was detected consisting of 5 bacterial and 12 fungal ASVs. Our results suggest that crop, genotype, and field environmental conditions contributed to the seed-associated microbial assemblage. These findings not only expand our understanding of the factors influencing the seed microbiome but may also help us to manipulate and exploit the microbiota naturally carried by seeds.

Seed are reproductive units that transfer genetic information to the next generation and harbor microbial communities that may interact with a host plant at all stages of its development. Here, we assessed the effect of the environment and plant genotype on the seed microbiome of eight spring Brassica napus lines harvested from four site years in Saskatchewan, Canada: one location each in 2016 and 2017 and two additional locations in 2017. Seed microbiomes were characterized using high-throughput amplicon sequencing of the bacterial 16S ribosomal RNA and fungal internal transcribed spacer regions. Our results revealed that microbial communities were predominantly shaped by the environment, with location explaining 34% of bacterial and 43% of fungal total variance. Meanwhile, genotype had a smaller effect, accounting for only 9% of bacterial and 13% of fungal variance. The seed microbiome of B. napus predominantly contained members of Enterobacteriales and Pseudomonadales bacterial orders as well as Pleosporales and Capnodiales fungal orders. Additionally, common taxa, including Enterobacteriales, Pseudomonadales, Micrococcales, Sphingomonadales, Pleosporales, Capnodiales, Tremellales, Filobasidiales, and Sporidiobolales, were detected across all site years. Our results demonstrate that the environment plays a dominant role in shaping spring B. napus seed microbiomes, with more subtle contributions related to host plant genotype. Information collected in this study may contribute to the development of novel and sustainable breeding and agricultural strategies that consider microorganisms carried by seed.

The aim of this study was to isolate, quantify, identify and characterize the culturable diazotrophic bacterial community associated with sisal (Agave sisalana P.) and assess its potential for plant growth promotion and tolerance to abiotic stress. Nitrogen-free Burk’s medium was used for bacteria isolation and quantification. Isolates carrying the nifH gene were typed by BOX-PCR and sequenced for the 16S rRNA region. Additionally, the bacteria was tested for growth promotion in maize plants and for salinity tolerance in cucumber seedlings. The representative isolates were identified as members of Pantoea, Rhizobium, Burkholderia, Leifsonia and Bacillus genera. All isolates were positive for at least two of the nine plant growth promoting (PGP) traits tested. All isolates showed positive traits for tolerance to abiotic stress. Leifsonia sp. (S1.5) significantly increased root length, stem length and total fresh matter, and it was involved in the reduction of deleterious salt effects (60 mM NaCl) in cucumber seedlings. Diazotrophic bacterial community associated with sisal plants is genetically diverse, exhibits several plant growth-promoting traits and shows potential to support plant growth in adverse environments (salinity).

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of fungal communities in the root and rhizosphere of Brassica napus, the world's second largest oilseed crop, weekly in eight diverse lines at one site and every three weeks in sixteen lines, at three sites in 2016 and 2017 in the Canadian Prairies. 14,944 unique amplicon sequence variants (ASV) were detected based on the internal transcribed spacer region, with an average of 43 ASVs per root and 105 ASVs per rhizosphere sample. Temporal, site-to-site, and line-driven variability were key determinants of fungal community structure. This dataset is a valuable resource to systematically extract information on the belowground microbiome of diverse B. napus lines in different environments, at different times in the growing season, in order to adapt effective varieties for sustainable crop production systems.

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of bacterial and fungal communities in the root and rhizosphere of Brassica napus, the world's second largest oilseed crop, weekly in eight diverse lines at one site and every three weeks in sixteen lines, at three sites in 2016 and 2017 in the Canadian Prairies. We sequenced the bacterial 16S ribosomal RNA gene generating a total of 127.7 million reads and the fungal internal transcribed spacer (ITS) region generating 113.4 million reads. 14,944 unique fungal amplicon sequence variants (ASV) were detected, with an average of 43 ASVs per root and 105 ASVs per rhizosphere sample. We detected 10,882 unique bacterial ASVs with an average of 249 ASVs per sample. Temporal, site-to-site, and line-driven variability were key determinants of microbial community structure. This dataset is a valuable resource to systematically extract information on the belowground microbiome of diverse B. napus lines in different environments, at different times in the growing season, in order to adapt effective varieties for sustainable crop production systems.

Enterobacter and Bacillus are common endophytes in many plants. Endophytic Enterobacter cloacae 344 and Bacillus amyloliquefaciens 629 from cacao had their colonization patterns assessed in different plants and organs. The 344’s colonization in all plants was ~12x higher than those observed for 629. CFU countings were 16 and 3 times lower for 344 and 629, respectively, in non-sterile than in sterile conditions. The results suggested that 344 is a better endophytic colonizer than 629, but this seems a better competitor than 344. Indigenous endophytic fungi interfered with the colonization levels of both strains in all plants. Plant species, tissue and competing microbes appear to define the levels of endophytic colonization by these bacteria. Key words: Cacao, endophytic bacteria, population densities.

Papaya ( Carica papaya L.) is susceptible to various production diseases, therefore, studies are needed to reduce them. Papaya fruit rot ( Phytophthora palmivora (Butler) Butler) is one of the fungal diseases present in producing regions (Bahia and Espirito Santo) of Brazil. This study aimed to evaluate the variability of aggressiveness and virulence of Phytophthora palmivora that influence the severity of fruit rot in postharvest in vitro and in vivo. The following mycelial growth characteristics were evaluated: (a) mycelial growth speed index (MGSI); (b) mycelial growth speed potential (%MGSI); (c) spore production (SP); (d) spore production potential (%SP) and (e) growth potential (%GP) of 21 strains. The maximum mycelial growth after 120 hours of cultivation in strains of P. palmivora ranged between 27 and 81 mm for strains 355 and 356, respectively. Strains 356, 363, 839, 1056, 1060 and 1189 showed the highest MGSI values. These strains have a high colonization speed and, therefore, good capacity to settle on the substrate. Among them, strains 356, 1060, 839 and 363 showed better %MGSI when compared with the other strains. The most virulent were: 356, 357, 358, 359, 361, 363, 839, 1055, 1056, 1057, 1060 and 1189, whereas the most aggressive were 356 and 1060. Additional keywords: mycelial growth; spore production; fungal rot.