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

Information regarding the productive potential of Hibiscus sabdariffa in different environments and planting densities is scarce. The objective of the study was to evaluate the effect on the calyxes of the Alma Blanca, Escarlata, Quinba and Sudán varieties, in various  environments  (Guerrero, Oaxaca, Puebla and Quintana Roo States)  and  densities  of  15625,  20833,  31250 and  41666 pl ha-1. A randomized block design, with four repetitions, and 4x4x4 factorial arrangement of the treatments was used. The results indicate that at 200 days after transplant more than 85 % of mature calyxes (with red color and separation of bracts) were obtained. The Sudan variety developed calyxes with a larger diameter and dry weight per calyx (7.42 cm and 2.61 g, respectively), and up to 20 seeds per fruit in Quintana Roo at 15625 pl·ha-1. The pH (2.88) and acidity (24 %) of the extracts were higher in Alma Blanca, in Oaxaca at 41666 pl·ha-1; while total soluble solids (85 %) and anthocyanins (4.0 mg·g-1) were higher in Sudan, in Oaxaca at 15625 pl·ha-1. The most important anthocyanins  found  were  delphinidin-3-sambubioside  and  cyanidin-3-sambubioside,  with 62.56 and 25.49 %, respectively; these compounds were obtained in Sudan, in Guerrero at 15625 pl·ha-1. It is concluded that the variety, the production environment, and the plant density influence the quality and chemical composition of the calyxes.

Quinoa is a crop with high economic and social potential in the Puno Region, Peru; however, its production is affected by low soil fertility. One way to deal with this problem, without affecting the environment, is through the use of beneficial microorganisms. The objective of the study was to evaluate the effect of Trichoderma sp. on N, P and K levels in plants and soil. The research was carried out in the Phytopathology Laboratory and greenhouse of the Professional School of Agricultural Engineering in the city of Puno, from January to July 2015. Five strains of Trichoderma sp. were inoculated in quinoa var. Salcedo-INIA plants by soil application or using pelleted seed. At the end of the crop cycle (six months), the levels of N, P and K were evaluated both in the plant tissue and in soil. No effects of Trichoderma inoculation on soil nutrient levels were detected, but the inoculated plants showed higher P and K contents than the control (p≤0.05). The results did not support the thesis of the solubilizing effect of Trichoderma on soil nutrients, but support the idea that the plant improved its efficiency in nutrient absorption attributed to the greater growth of the root system.

Sugar mango (Mangifera indica L.) is cultivated in the department of Magdalena, municipalities of Santa Marta and Cienaga mainly, where it expresses its best agronomic behavior and best fruit quality. Its high demand has generated the need to increase the cultivation areas; however, there are no defined criteria to identify potential areas for its establishment. The study consisted of constructing a soil quality index for sugar mango production, based on twelve physical and fifteen chemical indicators of the soil. In six sugar mango farms in the department of Magdalena, three plots per farm of 350 m2 were selected and the properties of the soils were characterized in each plot. The characteristics of the soil where the cultivar expresses its highest yield and fruit quality were the reference indicators. The soil quality indicator was formulated based on the variables that explained greater variability and were more redundant based on their correlations. Additionally, a weight was given to each variable depending on its importance for agronomic behavior of the cultivar. The soil indicators showed variation, especially the nutrients Zn, Cu, Fe, S, and P in the chemical properties and infiltration and structure index in the physical properties. The chemical and physical variables with the greatest weight were pH and sand content, respectively. The proposed soil quality index turned out to be a good method to classify soil quality for sugar mango production based on physical and chemical soil indicators.

By using hydroponics makes possible to increase the use of nutrients by crops; however, the balance of the nutrient solution (NS) must be adequate, otherwise the plant response may be negatively affected. The objective of this research was to determine during three stages the growth of lettuce plants under hydroponics, using macronutrients (NO3-, H2PO4-, SO42- and K+, Ca2+, Mg2+) in the following five respective proportions: 60:5:35 and 35:45:20 (NS-1-control), 80:2.5:17.5 and 35:45:20 (NS-2), 40:7.5:52.5 and 35:45:20 (NS-3), 60:5:35 and 43.7: 38.9:17.3 (NS-4) and 60:5:35 and 20:55.4:24.6 (NS-5). The trial was conducted in a randomized block design with six replicates. The chlorophyll index (CI), foliar area (FA) and plant fresh weight (PF), as well as dry weight of leaves (LDW), bud (BDW) and root (RDW) were determined. The NS-2 showed to be superior than other proposed treatments in the three stages in the variables of FP, FA and IC, and in certain stages it was superior to the control treatment. In the dry weight variables, there were only differences in the final stage for LDW and RDW in which NS-2 outperformed other proposed NS, although did not differ from Steiner's NS (control). The treatment with a high proportion of nitrate (NS-2) outperformed the rest of the treatments in different variables, as well as eventually Steiner's NS, so it should be considered in future evaluations of nutrient solutions for leafy crops.

Various bacterial diseases affect rice (Oryza sativa L.), causing foliar lesions and grain discoloration, symptoms observed in rice-growing areas of Venezuela. The objective of this study was the characterization, inoculation and evaluation of the main symptoms produced by bacterial strains in rice, belonging to the Danac Foundation's collection of pathogens. The strains were reactivated and presumptive, physiological and biochemical tests carried out, based on a descriptive evaluation of the symptoms. The conventional characterization allowed to corroborate the presence of Xanthomonas oryzae pv. oryzae (Xoo), Acidovorax avenae, Pantoea agglomerans and Burkholderia glumae, which were positive (100%) in the pathogenicity tests. Since P. agglomerans is the most frequent and ubiquitous species in the rice-growing areas of Venezuela, three different inoculation methods were tested on it, as well as the effect of the different strains on the size of the lesion in leaves. In addition, the percentage of grains stained by the effect of inoculation with the different bacterial species was measured in the panicle. A completely randomized design with three replicates was used. The largest size of the lesion on the leaves was detected by the scissor and spray methods, being the variety 'Colombia 21' the most affected. In the evaluation of the panicle, the strains of B. glumae and Xoo showed a higher percentage of stained grains, without significant differences between them, while the variety of rice 'IR8' was the most susceptible, regardless of the strains inoculated.

The frequent application of pesticides in horticultural crops can generate residues with adverse consequences on the health of consumers. The objective of this research was to determine the residual and dissipation of lufenuron applied on peas (Pisum sativum L.), and its hazard and risk index by ingestion. The study was carried out in an open field in a semi-arid zone located in Arequipa, Peru. The treatments were the application of three doses of the active ingredient lufenuron (12, 24 and 30 g·ha-1) in two opportunities (every 4 and 8 days), conforming six treatments applied via foliar in a completely randomized design, with three replications (18 plots). Lufenuron residues were detected in pea pods and grains by HPLC in samples collected 4, 8 and 16 days after the last application. Dissipation kinetics, half-life, ingestion hazard or health hazard index (HI) were calculated. The highest half-life values were 13.4 days in pods and 4.8 days in grains with the dose 24 g·ha-1 and frequency of 8 days. The application frequency was more relevant than the lufenuron dose, and the difference was detected at 4 days after the last application. It was found that lufenuron residues in grains at 4 days of sampling exceeded the maximum residue limits in all treatments; however, under the conditions of this trial, ingestion of pea grains with lufenuron residues did not represent a health hazard and risk of population.

Genetic improvement programs in cacao (Theobroma cacao L) have focused on obtaining new varieties with high yield and resistance to diseases. However, drought tolerance response has not been considered enough in order to face the climate change emergency. Events such as prolonged droughts or excessive rainfall can affect the pollen production of cacao flowers and others reproductive characteristics. Hence, this study was proposed to learn about the hydric deficit influence on pollen production of four Ecuadorian cacao genotypes. The results indicated statistical differences between CCN-51 and the "National" clones (P≤0.05). CCN-51 reached the highest pollen production values in the wettest treatment (26,546 ±100) compared to the “National” clones, which had no differences among them. There was a positive correlation between pollen production and the highest irrigation treatments (r=0.78), observing that while the water level was the highest, the pollen grain formation (PGF) increased, and the opposite when the water level diminished. It is concluded that the adequate water amount in the soil can increase pollen production. However, it is essential to emphasize the strong genetic influence on drought tolerance traits that could be severely affected by climatic changes. The CCN-51 and EET-575 clones should be considered when planning to develop drought-tolerant hybrids of cacao.

Ectomycorrhizal fungi are considered to play an essential role in the development of forest ecosystems and can protect plant against pathogenic infections. Among other factors, soil pH may affect the successful inoculation of forest seedlings in nurseries. The effect of pH on the growth rate of strains of nine species of edible ectomycorrhizal (ECM) fungi was evaluated in vitro. In the experiments, Boletus edulis, B. aereus, B. pinophilus, B. fragrans, Amanita rubescens, Xerocomus ferrugineus, Lactarius deliciosus, Lactarius sanguifluus and Suillus luteus were grown in Petri dishes containing modified Melin Norkrans medium and adjusted at seven different pH levels. Colony area was measured at 7-day intervals for 8 weeks. Final fungal biomass and residual pH of the medium at 8th week were also measured. The optimum pH levels and pH tolerance ranges for the tested ECM fungal species are presented and discussed in the text. The results showed that the greatest growth in vitro was produced by A. rubescens and S. luteus at high pH levels (between 6.5-8.5), and by X. ferrugineus  at low pH (3.5-6.5). Almost all the strains acidified the medium where they were grown after eight incubation weeks.

In recent years there has been a growing need in agriculture to reduce and replace the use of synthetic chemicals with the application of plant extracts and essential oils in crops for the control of phytopathogens. The objective of this work was to evaluate the in vitro effect of the essential oil and aqueous extract of the plant species Lippia palmeri W. collected in the state of Sonora, Mexico. The antifungal activity was carried out by means of the agar diffusion method on the phytopathogenic fungi on Fusarium oxysporum and Thanatephorus sp. The percentage of inhibition of mycelial growth of the different concentrations was determined and analyzed, an analysis of variance (ANOVA) and comparison of Tukey means (p ≤ 0.05) were made. The essential oil and the carvacrol of L. palmeri managed to inhibit the growth of Fusarium oxysporum by 100 %, the aqueous extract had a result between 20 and 100 %. While Thanatephorus sp had an inhibition between 90 and 100 % using essential oil and carvacrol, the aqueous extract had an inhibition between 10 and 100 %.

Calcium carbonate is present in many biological structures such as bivalve shell, which is composed mainly of two CaCO3 polymorphs: calcite and aragonite. However, exist other forms of calcium carbonate like vaterite and amorphous calcium carbonate (ACC) that are not commonly reported. Polymorph selection is influenced by salt concentration, cofactor ions, and the presence of shell matrix proteins (SMPs) which regulates calcium carbonate deposition, among other factors. In this study, calcium carbonate crystallization in vitro of four different saline solutions at two molarities was evaluated with increased concentrations of the Ps19 protein, an insoluble extracted protein from the shell of Pteria sterna, previously described as a promotor of aragonite platelet crystallization. In vitro crystallizations showed that Ps19 is capable to induce aragonite and calcite deposition in a dose-dependent manner, but also vaterite under ciertan conditions, acting as a promoter and inhibitor of crystallization. The results contribute to understand how Ps19 control precipitation of calcium polymorphs in the growth of the prismatic and nacre layer of the shell of P. sterna.