Reiner Rincón-Rosales

Fruit Characteristics of Bell Pepper Cultivated in Sheep Manure Vermicompost Substituted Soil

ABSTRACT The effects of earthworm-processed sheep manure (vermicompost) on growth, productivity, and characteristics of bell pepper fruits (Capsicum annum) (cv ‘Ancho supremo’) were investigated in a greenhouse experiment. Six treatments were applied combining vermicompost and soil in 0:1, 1:1, 1:2, 1:3, 1:4, and 1:5 (v/v) ratios. Plant characteristics were measured 21 and 90 days after transplanting. Addition of vermicompost increased plant size significantly with 8 cm in the 1:3 vermicompost: soil treatment compared to the unamended soil after 21 days, but no significant differences were found after 90 days. Seven more flowers were found in the 1:2 vermicompost: soil treatment and four in the 1:3 vermicompost: soil treatment compared to the unamended soil after 90 days. The number of marketable fruits per plant was significantly 1.5 and 1.9 times greater in the 1:2 and 1:3 vermicompost: soil treatments compared to plants cultivated in unamended soil after 90 days. The addition of vermicompost to soil increased soluble solids in pepper fruits > 2 Brix compared to fruits from plants cultivated in unamended soil while their pH was significantly lower. The nitrogen (N) content of the pepper fruits was significantly higher in the 1:4 vermicompost: soil mixture compared to the other treatments, whereas the fruits obtained from plants cultivated in the 1:3 and 1:4 vermicompost: soil treatments had higher titratable acidity values than in those from other treatments. It was found that amounts and characteristics of pepper fruits from plants cultivated in soil supplemented with vermicompost were generally better than those from plants grown in soil only.

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.

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.

Structure and Diversity of the Bacterial Communities in the Acid and Thermophilic Crater-Lake of the Volcano “El Chichón”, Mexico

Abstract El Chichón is an active volcano located in the Chiapas Volcanic Arc characterized by high temperatures, low pH, and large heavy metal concentrations. High temperatures are known to affect microorganisms, so the bacterial community structure was investigated in crater-lake sediment at a ‘low’ 50 °C and a ‘high’ 92 °C by sequencing the 16S rRNA bacterial gene. Most metal concentrations, and bacterial richness, and diversity indexes were higher at 50 °C than at 92 °C. Fifteen phyla were found in the sediment at 50 °C dominated by Actinobacteria (33.1%), Proteobacteria (29.1%) and Acidobacteria (20.1%). Nine phyla dominated by Firmicutes (52.7%, mostly Alicyclobacillus and Sulfobacillus) and Proteobacteria (44.8%, mostly Bradyrhizobium, Methylobacterium, Sediminibacterium) were detected in the sediment at 92 °C. The predictive functional profiling indicated metabolic pathways related to amino acid metabolism, membrane transport, replication, and repair as the most important. It was found that although a large number of bacterial groups were well adapted to 92 °C, the higher temperature reduced strongly, the bacterial diversity and species richness in the El Chichón volcano crater-lake system, and altered the bacterial community structure and their functionality.

Plant growth regulators optimization for maximize shoots number in Agave americana L. by indirect organogenesis

Los protocolos actuales para la micropropagacion de Agave americana L. tienen limitaciones para su aplicacion comercial debido al bajo numero de plantas producidas por cada explante. La organogenesis indirecta podria ser una alternativa, sin embargo, es necesario optimizar los reguladores de crecimiento vegetal para maximizar el numero de plantas. El objetivo del trabajo fue optimizar la concentracion de acido 2,4-diclorofenoxiacetico (2,4-D) y de 6-bencil adenina (BA) sobre la induccion de callos embriogenicos en A. americana usando meristemos apicales como explante para maximizar el numero de brotes por callo, utilizando un diseno experimental de superficie de respuesta. Se utilizo el medio Murashige Skoog (MS) adicionado con 30 g l-1 de sacarosa, y con 0,11;0,18; 0,45 o 2,26 μM de 2,4-D, y 11,0; 22,0; 38,2 o 44,0 μM de BA. Se implementaron 9 tratamientos con 3 repeticiones y el numero de brotes por callo fue evaluado despues de 4, 16, 20 y 36 semanas. Se indujo el enraizamiento in vitro usando medio MS adicionado con acido indolbutirico (AIB). Se obtuvo un maximo de 74 plantulas por callo, usando 2,26 μM de 2,4-D y 38,2 μM de BA. En conclusion, la organogenesis indirecta podria ser una alternativa para la micropropagacion de A. americana L con fines comerciales.

Aluminium tolerance in the tropical leguminous N2-fixing shrub Acaciella angustissima (Mill.) Britton & Rose inoculated with Sinorhizobium mexicanum

La leguminosa tropical Acaciella angustissima inoculada con o sin la cepa Sinorhizobium mexicanum ITTG R7T fue cultivada en un suelo tratado con (Al) para estudiar la tolerancia a este metal. Las plantas de A. angustissima fueron crecidas en el suelo con 0, 2, 4 y 6 mg de Al kg-1. Se hizo un seguimiento del efecto de Al e inoculacion en el crecimiento, la nodulacion, el contenido de nitrogeno y el contenido de taninos en las plantas. La altura, el peso seco total y el peso seco de la raiz de las plantas decremento significativamente cuando el suelo fue tratado con Al, pero incremento cuando fue inoculado. El Al disminuyo el numero de nodulos. El inoculo incremento el N total y el contenido de taninos de las plantas. En este experimento fue encontrado que el Al reduce el crecimiento de la leguminosa arbustiva tropical fijadora de N2 A. angustissima, mientras la inoculacion con S. mexicanum ITTG R7T estimula el crecimiento e incrementa el contenido de taninos y nitrogeno.