Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Introduction. Corn ear rot caused by Fusarium verticillioides (F. verticillioides) is one of the most important diseases in the world. In Mexico it causes losses of up to 30 %. The increase in the levels of this disease in the last years requires inspections in producing areas to identify the main strains that damage the grain. Objectives. To determine the morphological and pathogenic variability of F. verticillioides isolates from corn samples from the corn producing area of La Ciénega/Chapala, Mexico, and to identify the best technique for inoculating the pathogen in ears. Materials and Methods. Twenty isolates of F. verticillioides were obtained from samples of corn kernels with disease symptoms. The isolates were used to inoculate, with the use of different inoculation techniques, developing corn cobs (R2) of P-3057 cultivated in Tepatitlán, Jalisco during the Spring/Summer 2019 agricultural cycle under rainfed conditions. The incidence and severity of the disease (SDI) of the isolates and the microscopic morphology of the strains were evaluated. Results. F. verticillioides isolates differed in colony color, mycelial type, abundance, and vegetative mycelial coloration. The incidence and severity were statistically different between F. verticillioides isolates and inoculation techniques tested. Interaction between isolates and inoculation technique was observed. The disease incidence showed values of 82 and 95% with aspersion and toothpick inoculation techniques, respectably. The SDI varied between 8 and 15.5 % with the aspersion and toothpick techniques, in that order. Conclusions. F. verticillioides strains showed variability for pathogenicity and severity of infection. Pathogenicity was related to the inoculation technique used. The toothpick inoculation technique was the one that presented the highest incidence and severity of infection.

Introduction. The fique, “cabuya” or “mecate” are the common names given to the species of the genus Furcraea that are used for the manufacture of biodegradable fibers. Their industrial and social importance in Latin American countries is significant since it is usually related to family and peasant economies. However, for this taxonomic group, the diversity of edaphic conditions in natural habitats or cultivation sites is unknown. Objective. To physicochemically characterize the soils in the productive systems and natural populations of fique, to determine the aspects and factors that best represent their variability. Materials and methods. The work was developed between 2013 and 2014, in 66 municipalities and 108 villages in 11 departments of Colombia. Passport data was recorded at the 121 sites visited, describing site conditions, including georeferencing. In each locality, soil samples were taken in the first 20 cm of depth and subsequently the following variables were determined: texture, pH, organic matter (OM), P, S, K, Mg, Ca, Al+H, CE, cations of change Ca, Mg, K, Na, cationic exchange capacity (ECEC), Ca, Mg, K, and Na. According to georeferencing, 52 agroecological zones were identified. Results. Populations located between 170 to 2,993 m.a.s.l. were found. The most significant factors were agroecological zone and soil texture. Among them, texture was the factor with the greatest capacity for group formation and represented 60.99 % of the variability of the sampled soils. The variables that most contribute to the variability of the soils were (Ca + Mg) / K, exchangeable Mg, K / Mg, exchangeable Ca, and ECEC. Conclusion. The results obtained for wild and cultivated populations indicate that the different taxa survive in diverse tropical soil conditions. It was found that the exchangeable ions had high discriminating power that could indicate diversity to the different conditions and fertility levels of Colombian soils.

Introduction. Edible musaceae are considered strategic crops in the food security of many countries, and important in their economy and diet. However, they are threatened by various phytopathogenic organisms. Objective. To outline the significant features of Banana bunchy top virus (BBTV) caused by a virus of the family Nanoviridae, genus Babuvirus, which represents a potential threat to the musaseae production in Latin America and the Caribbean (LAC). Development. Musaceae are among the main foods and fruits produced in the world (among the six most important), and their commercialization defines them as the most exported fruits. It is estimated that 47 % of the pathogens that originate emerging and re-emerging diseases of global importance are viruses. Among them, BBTV is the most damaging viral disease for musaceae, with potential economic impact, in addition, it limits the international exchange of germplasm. This systemic pathogen is unlikely to be transmitted by agricultural implements, since it is not present in the soil. Its dissemination only occurs through: a) Insect vector Pentalonia nigronervosa, which spreads it over short distance, and b) by infected propagation material that can distribute it between continents, with devastating effects in all the countries where it has been reported. Conclusions. The introduction of new materials (clones) resistant to Foc TR4 (disease present in America) without proper supervision and quarantine measures, can promote the manipulation of in vitro plants carring the virus, which, when exposed to the action of the insect vector present in LAC, condition the entry and spread of the BBTV in this region (main of exporting countries), whose presence could be catastrophic and cause economic losses, similar to those that have occurred in producing countries that have been affected.

Introduction. Traditional livestock production systems generate soil degradation, so it is important to implement silvopastoral systems as an alternative for meat and dairy cattle production. Objective. To quantify the production of leaf litter of perennial woody species (Gmelina arborea - Melina, Tabebuia rosea - Oak, Acacia mangium - Acacia) and the potential contribution of nutrients to the soil (nutrient cycling) within silvopastoral systems. Materials and methods. The production and decomposition of leaf litter of forest species was evaluated in fields planted with a variety of grasses of the genus Brachiaria, in the middle Sinu valley, Colombia, during May to September 2013. A randomized complete block design with three replications was used. The treatments used were Pr= Brachiaria hybrid cv. Mulato II, SSP1= Tabebuia rosea + Brachiaria cv. Mulato II, SSP2= Acacia mangium + Brachiaria cv. Mulato II, and SSP3= Gmelina arborea + Brachiaria cv. Mulato II. Results. The greater production of leaf litter in forest species within the silvopastoral systems was evidenced. The forest species G. arborea had the highest potential nutrient inputs in litterfall with the following descending pattern in kg ha-1: C 4069,6> Ca 96,47> N 62,46> K 37,48> Mg 23,60> P 14,57. Mulato II pasture litter and the forest species G. arborea exhibited higher decomposition rates (k= 1.87 and k=1.77, respectively) than the rest of the species evaluated. Conclusions. The forest species evaluated improved soil quality through a higher leaf litter input and a higher potential nutrient input.

Introduction. Studies on the structural characteristics of the ovary associated with the quality of the cumulus-oocyte complex (COCs) in cattle contribute to the definition of strategies to improve reproductive efficiency. Objective. To determine the weight and size of the ovaries, follicle quality, and COCs in Zebu females, in order to establish differences between the right and left ovary. Materials and methods. Between March and July 2017, 52 ovaries were obtained from twenty-six Zebu cows. The ovaries and follicles were weighed and measured. The follicles were grouped into three categories: a) <3 mm (TFI), b) 3-6 mm (TFII) and c) >6 mm (TFIII). The follicles quality was determined by the irrigation-translucency technique (TIT) and the COCs by the characteristics of the cytoplasm and cumulus cells as good (CI), fair (CII), and poor (CIII), and by cresyl brilliant blue test were categorized as BCB+ and BCB-. Results. Ovarian length, width and weight were 2.7 ± 0.6 cm, 1.8 ± 0.5 cm, and 7.0 ± 3 g, respectively, with differences for length and weight between the right and left ovary (p<0.01). The highest number of follicles were obtained in TFI (p<0.05). The 88.56 % of the follicles evaluated were of good quality. A total of 52 % and 44.2 % of COCs were classified as CI and BCB+, respectively. When follicle size and COC quality were considered, it was shown that in the TFI group 22 % were IC, 34 % CII, and 44 % CIII, and in the TFII group 31 % were IC, 21 % CII and 48 % CIII. No differences were observed between left and right ovary. Conclusion. The right ovary presented a greater size and weight, a greater number of follicular structures and a greater number of good quality CCOs.

Introduction. Water erosion is a natural phenomenon accelerated by human activity, which facilitates soil degradation and sediment transport to other areas. Objective. To quantify the surface runoff and erosion rate at the plot scale, under natural precipitation events in an Entisol soil cultivated with shaded coffee (Coffea arabica) and to determine the temporal dynamics and the influence of the main factors associated with this process. Materials and methods. The study was developed in Llano Brenes, Alajuela, Costa Rica. Nine runoff plots were installed, the data was collected between May 2018 and November 2019, each plot had a runoff meter and a container for collecting sediment samples. Three-time domain reflectometry sensors were installed for surface soil moisture content measurements. Data analysis was carried out on a monthly-annual, inter-event and intra-event scale. At the intra-event scale, the Diskin & Nazimov infiltration model was applied. Results. In the years 2018 and 2019, the following annual results were obtained, respectively: a) total runoff sheet of 90.99 and 102.66 mm, b) sediment concentration of 2.14 and 1.88 g L-1, and c) soil loss of 1612 and 1692 g m-2. The highest soil loss values were obtained in October of each year. The intra-event analysis explained the runoff generation based on the precipitation sheet and the initial moisture content in the event. Conclusion. The mean annual erosion rate and runoff were 1652 g m-2 and 96.8 mm. The precipitation sheet, intensities, and initial surface soil moisture content played an important role in runoff generation and soil loss.

Introduction. The plant growth-promoting rhizobacteria (PGPR) could be used as an alternative source to the use of conventional nitrogen fertilizers in banana (Musa AAA) cultivation. It is necessary to search for bacteria adapted to Costa Rican soil conditions and banana cultivation. Objective. To evaluate the effect of the inoculation of four Bacillus cereus isolates on the growth and nitrogen (N) content of banana seedlings under greenhouse conditions. Materials and methods. Two simultaneous experiments were carried out between April and September 2020 at the Corporacion Bananera Nacional (CORBANA) Research Center, La Rita, Limon, Costa Rica. Four isolates of B. cereus were inoculated into banana plants that were fertilized with four doses of nitrogen weekly. The design consisted of divided plots, where the main plot consisted of four levels of N: 0, 33, 66, 100 % of the dose; and the small plot consisted of the bacterial isolates and the control. The variables measured were plant height, chlorophyll content, leaf area of the third leaf, fresh and dry weight of roots, corm, pseudostem, and leaves, as well as the nitrogen content in each organ. Results. In experiment 1: the plants inoculated with the SER-23 isolate presented the highest total dry weight. In experiment 2: the highest total dry weight was observed in seedlings inoculated with the BF-98 isolate. The application of SER-23 and BF-98 bacteria significantly increased the nitrogen content in all the organs evaluated. Conclusions. The inoculation of Bacillus cereus isolates SER-23 and BF-98 stimulated the increase in biomass and nitrogen content in banana plants, this increase depended on the nitrogen availability and soil type.

Introduction. Aquaculture wastewater is an important resource that can be used for irrigation of agricultural land. Objective. To evaluate the physical, chemical, and biological properties of soils with continuous irrigation of aquaculture wastewater and to identify the variables that provide more information in regarding their behavior under irrigation. Materials and methods. The treatments were three agricultural soils, located in the south of the state of Tlaxcala, Mexico, in 2018 soil sampling was performed at a depth of 0-30 cm and nine replicates to determine: pH, organic matter, electrical conductivity, nitrate, ammonium, total N, phosphorus, potassium, calcium, magnesium, texture, apparent density, and microbial activity, with which a principal component analysis (PCA) was applied. Results. Irrigation with aquaculture wastewater increased the concentration of phosphorus, potassium, calcium, ammonium, and nitrates. Through linear correlation analysis and PCA, it was obtained that the first principal component explained 76 % of the total variance, associated with pH, organic matter, sand, total N, potassium, magnesium, and ammonium, while the second component explained 23 % of the total variance, linked to phosphorus and adsorption by the exchange complex provided by the clay. Conclusion. Irrigation with aquaculture wastewater improved soil fertility and with the principal component analysis (PCA) phosphorus, clay particle, and magnesium were identified as indicator variables that will support the management of soils irrigated with aquaculture wastewater.

Introduction. The ferns of the genus Pteridium are characterized by their wide habitat and adaptive power that allows their establishment in various types of soils and altitudes. They have the ability to produce a toxin called ptaquiloside. Objective. To gather a current body of updated knowledge on the ptaquiloside toxin present in ferns of the genus Pteridium. Development. The ferns of the genus Pteridium produce ptaquiloside biotoxin, especially in young phenological stages and in the fronds. The hydrolysis of this toxin at the biological level generates compounds with cytotoxic and genotoxic properties. Ptaquiloside can produce enzootic bovine hematuria, be deposited in the milk of the animal that consumes it and affects the health of dairy consumers. The biotoxin has an immunosuppressive effect in cattle, which can favor the papilloma virus, and also causes blindness in sheep. It is associated with esophageal and gastric cancer in humans living in areas populated by ferns of the genus Pteridium. The carcinogenic effect of ptaquiloside is generated because it causes DNA alkylation at N3 adenine or N7 guanine, 24 h after ingestion. For the eradication of ferns in pastures, mechanical control, biological control, and chemical control, are the most important. Conclusion. The biotoxin ptaquiloside represents a risk to human and animal health, which can spread to soil, water bodies, and food. More research is needed to take measures to reduce its effects.