Víctor Manuel Ruíz-Valdiviezo

Bacterial community in the roots and rhizosphere of Hypericum silenoides Juss. 1804

Hypericum silenoides Juss. 1804 is an important medicinal plant used in Mexico, but the bacterial community associated with it is unknown. The bacterial communities in the rhizosphere and roots of H. silenoides were isolated and identified by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and ribosomal types were determined by amplified ribosomal rDNA restriction analysis (ARDRA) and 16S rRNA gene sequences. Sixty-six strains were obtained from roots of H. silenoides and 37 were isolated from the rhizosphere. ERIC fingerprinting distinguished 63 genetic patterns with 44 being unique and the remaining 19 containing 59 strains. Eighteen representative strains were distinguished with ARDRA analysis. 16S rRNA gene sequence analysis revealed that the bacteria isolated from the roots and rhizosphere of H. silenoides belonged to the genera Acinetobacter, Enterobacter, Pseudomonas, Sphingobium, Stenotrophomonas, Agrobacterium, Pantoea and Serratia. The largest number of isolates (30) belonged to the genus Agrobacterium. Richness and diversity of bacteria was higher on the roots than in the rhizosphere of H. silenoides.

Bacterial Communities in Soil Under Moss and Lichen-Moss Crusts

Biological soil crusts are symbiotic microbial communities formed by green algae, mosses, fungi, lichens, cyanobacteria and bacteria in different proportions. Crusts contribute to soil fertility and favour water retention and infiltration. However, little is known about the bacterial community structure in soil under the crusts. Soil was sampled under a moss crust (considered the MOSS group), lichen plus moss (considered the LICHEN group) and bare soil (considered the BARE group) and the microbial communities determined using nearly full 16S rRNA gene libraries. Bacteria belonging to seven different phyla were found and the Acidobacteria and Alphaproteobacteria were the dominant in each group. The crusts affected negatively the abundance of the Burkholderiales. The phylogenetic diversity and bacterial community membership were different in the LICHEN group compared to the BARE and MOSS groups, but not species richness and community structure. The beta diversity analysis also revealed a different bacterial community structure beneath the LICHEN and MOSS crusts, suggesting species-specific influence. This is a first insight into the effect of a biological soil crust on the bacterial community structure in an organic matter rich soil of a high altitude mountain forest.

Effect of plant growth-promoting bacteria on the growth and fructan production of Agave americana L.

The effect of plant growth-promoting bacteria inoculation on plant growth and the sugar content in Agave americana was assessed. The bacterial strains ACO-34A, ACO-40, and ACO-140, isolated from the A. americana rhizosphere, were selected for this study to evaluate their phenotypic and genotypic characteristics. The three bacterial strains were evaluated via plant inoculation assays, and Azospirillum brasilense Cd served as a control strain. Phylogenetic analysis based on the 16S rRNA gene showed that strains ACO-34A, ACO-40 and ACO-140 were Rhizobium daejeonense, Acinetobacter calcoaceticus and Pseudomonas mosselii, respectively. All of the strains were able to synthesize indole-3-acetic acid (IAA), solubilize phosphate, and had nitrogenase activity. Inoculation using the plant growth-promoting bacteria strains had a significant effect (p < 0.05) on plant growth and the sugar content of A. americana, showing that these native plant growth-promoting bacteria are a practical, simple, and efficient alternative to promote the growth of agave plants with proper biological characteristics for agroindustrial and biotechnological use and to increase the sugar content in this agave species.

Changes in the Bacterial Community Structure in Stored Wormbed Leachate

Organic wastes, such as cow manure, are often composted with earthworms (vermicomposting) while excess water is drained and collected. This wormbed leachate is nutrient-rich and it has been extensively used to fertilize plants. However, it is derived partially from a not yet finished compost process and could exhibit phytotoxicity or contain potentially hazardous microorganisms. The bacterial community in wormbed leachate derived from vermicomposting of cow manure was studied by pyrosequencing the 16S rRNA gene. The fresh wormbed leachate was rich in Mollicutes, particularly the genus Acholeplasma which contain phytopathogen species. The abundance of the Mollicutes decreased when the leachate was stored, while that of the Rhizobiales and the genus Pseudomonas increased. The bacterial communities changed rapidly in the leachate during storage. The changes in ammonium, nitrate and inorganic carbon content of the wormbed leachate when stored were correlated to changes in the bacterial community structure. It was found that storage of the wormbed leachate might be required before it can be applied to crops as large proportions of potentially plant pathogens were found in the fresh leachate.

Growth, Phenolic Content and Antioxidant Activity in Chincuya (Annona purpurea Moc & Sesse ex Dunal) Cultivated with Vermicompost and Phosphate Rock

ABSTRACT The aim of this investigation was to determine the effect of vermicompost and phosphate rock on plant growth, total phenols, flavonoids, flavanones, and antioxidant activity in Annona purpurea Moc & Sesse ex Dunal leaves. Annona purpurea seedlings were planted according to factorial 32 experimental design with nine repetitions. The factors were vermicompost (0, 50, and 100 g plant−1) and phosphate rock (0 and 10 g plant−1). Plant height, stem diameter, number of leaves, and chorophyll content were determined one month after application of the different treatments and total phenols, flavonols, flavanones, total flavonoids, and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity in dry leaves after 4 months. Plant height and stem diameter increased by phosphate rock, but not by vermicompost. Total phenols in leaves decreased by vermicompost. Flavonol content decreased by rock phosphate, whereas flavanones increased by vermicompost. Antioxidant activity decreased by vermicompost addition.

Symbiotic potential and survival of native rhizobia kept on different carriers

Native rhizobia are ideal for use as commercial legume inoculants. The characteristics of the carrier used to store the inoculants are important for the survival and symbiotic potential of the rhizobia. The objective of this study was to investigate the effects of peat (PEAT), perlite sugarcane bagasse (PSB), carboxymethyl cellulose plus starch (CMCS), and yeast extract mannitol supplemented with mannitol (YEMM) on the survival, nodulation potential and N2 fixation capacity of the native strains Sinorhizobium mexicanum ITTG R7T and Rhizobium calliandrae LBP2-1T and of the reference strain Rhizobium etli CFN42T. A factorial design (4 × 3) with four repetitions was used to determine the symbiotic potential of the rhizobial strains. The survival of the strains was higher for PEAT (46% for strain LBP2-1T, 167% for strain CFN42T and 219% for strain ITTG R7T) than for the other carriers after 240 days, except for CFN42T kept on CMCS (225%). All the strains kept on the different carriers effectively nodulated common bean, with the lowest number of nodules found (5 nodules) when CFN42T was kept on CMCS and with the highest number of nodules found (28 nodules) when ITTG R7T was kept on PSB. The nitrogenase activity was the highest for ITTG R7T kept on PEAT (4911 μmol C2H4 per fresh weight nodule h−1); however, no activity was found when the strains were kept on YEMM. Thus, the survival and symbiotic potential of the rhizobia depended on the carrier used to store them.

Evaluation of Worm-Bed Leachate as an Antifungal Agent against Pathogenic Fungus, Colletotrichum gloeosporioides

ABSTRACT Worm-bed leachate is a nutrient-rich by-product of composting organic wastes with earthworms. Worm-bed leachate was stored and characterized while its possible antifungal activity towards the pathogenic fungus Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. was investigated in vitro. The pH decreased from 9.6 at the onset of the storage to 8.9 after 28 days, while the total N and C nearly halved. The surfactin concentration in the worm-bed leachate reached 10.8 μg L−1 at day 10, while that of iturin A and iturin A homologues increased towards the end of the storage. Sterilized worm-bed leachate had little effect on the growth of C. gloeosporioides, but unsterilized worm-bed leachate inhibited growth 100%. It was found that unsterilized worm-bed leachate inhibited growth of C. gloeosporioides, but sterilizing the worm-bed leachate strongly reduced the inhibitory effect indicating that the microorganisms in the worm-bed leachate out-competed the fungus for nutrients or were antagonistic towards it.

Effects of Vermicompost and Vermiwash on Plant, Phenolic Content, and Anti-oxidant Activity of Mexican Pepperleaf (Piper auritum Kunth) Cultivated in Phosphate Rock Potting Media

ABSTRACT The aim of this investigation was to determine the effect of vermicompost, vermiwash, and phosphate rock on plant, total phenols, flavonoids, and anti-oxidant activity in Piper auritum Kunth leaves. P. auritum plants were obtained from cuttings and were planted according to the Box-Behnken experimental design with three repetitions at the central point. The factors and levels were vermicompost (10, 20, and 30 g plant−1), vermiwash (5, 10, and 15 mL plant−1), and phosphate rock (1, 2, and 3 g plant−1). Plant growth parameters (plant height, stem diameter, leaves number) and chlorophyll content were measured 1 month after treatment applications. Total phenols, total flavonoids, and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity was measured after 4 months. Vermicompost, vermiwash, and phosphate rock had no statistically significant effect on plant growth. Plant height, stem diameter, leaves number, chlorophyll, innermost number, fresh weight stem, fresh weight leaves, fresh weight root, dry weight stem, dry weight leaves, and dry weight root were not different among treatments. Total phenolic compounds were statistically affected for both vermiwash and phosphoric rock (p < 0.05) and the anti-oxidant activity decreased by vermicompost addition. The application of 15 mL plant−1 vermiwash, 1 g phosphate rock, and 20 g vermicompost plant−1 increased the total phenol content.

Fatty Acids Profile, Phenolic Compounds and Antioxidant Capacity in Elicited Callus ofThevetia peruviana (Pers.) K. Schum

The aim of this study was analyze the effect of jasmonic acid (JA) and abscisic acid (ABA) as elicitors on fatty acids profile (FAP), phenolic compounds (PC) and antioxidant capacity (AC) in callus of Thevetia peruviana. Schenk & Hildebrandt (SH) medium, supplemented with 2 mg/L 2, 4-dichlorophenoxyacetic (2, 4-D) and 0.5 mg/L kinetin (KIN) was used for callus induction. The effect of JA (50, 75 and 100 μM) and ABA (10, 55 and 100 μM) on FAP, PC and AC were analyzed using a response surface design. A maximum of 2.8 mg/g of TPC was obtained with 100 plus 10 µM JA and ABA, respectively, whereas AC maximum (2.17 μg/mL) was obtained with 75 plus 100 µM JA and ABA, respectively. The FAP was affected for JA but not for ABA. JA increased cis-9, cis-12-octadecadienoic acid and decreased dodecanoic acid. Eight fatty acids were identified by GC-MS analysis and cis-9-octadecenoic acid (18:1) was the principal fatty acid reaching 76 % in treatment with 50 μM JA plus 55 μM ABA. In conclusion, JA may be used in T. peruviana callus culture for obtain oil with different fatty acids profile.

Greenhouse Gas Emissions and Growth of Wheat Cultivated in Soil Amended with Digestate from Biogas Production

Abstract Digestate, the product obtained after anaerobic digestion of organic waste for biogas production, is rich in plant nutrients and might be used to fertilize crops. Wheat (Triticum spp. L.) was fertilized with digestate, urea, or left unfertilized and cultivated in the greenhouse for 120 d. Emissions of greenhouse gasses (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) were monitored and plant growth characteristics were determined at harvest. The digestate was characterized for heavy metals, pathogens, and C and N mineralization potential in an aerobic incubation experiment. No Salmonella spp., Shigella spp., or viable eggs of helminths were detected in the digested pig slurry, but the number of faecal coliforms was as high as 3.6 × 104 colony-forming units (CFU) g−1 dry digestate. The concentrations of heavy metals did not surpass the upper limits established by US Environmental Protection Agency (EPA). After 28 d, 17% of the organic C (436 g kg−1 dry digestate) and 8% of the organic N (6.92 g kg−1 dry digestate) were mineralized. Emissions of CO2 and CH4 were not significantly affected by fertilization in the wheat-cultivated soil, but digestate significantly increased the cumulative N2O emission by 5 times compared to the urea-amended soil and 63 times compared to the uncultivated unfertilized soil. It could be concluded that digestate was nutrient rich and low in heavy metals and pathogens, and did not affect emissions of CH4 and CO2 when applied to a soil cultivated with wheat, but increased emission of N2O.