Susceptibility of Diaphorina citri to dimethoate and chlorpyrifos in commercial citrus orchards of Veracruz, Mexico

There are reports of Diaphorina citri resistance in the state of Veracruz to chlorpyrifos and dimethoate due to the excessive use of these products for the control of pests, among them D. citri. The purpose of this work was to diagnose the susceptibility of D. citri adults to chlorpyrifos and dimethoate in commercial citrus orchards of the municipality of Martinez de la Torre, Veracruz. For this, 200 adults of D. citri were collected in each of 30 orchards, and topical application bioassays were performed with dimethoate at 0.0090% concentration and chlorpyrifos at 0.0085% concentration. Diaphorina citri adults without chemical control during 10 years were used as a control. Mortality of D. citri with dimethoate and chlorpyrifos averaged 85%, in contrast the control mortality was 99% and 98.8% with dimethoate and chlorpyrifos, respectively. According to these results, it can be inferred that D. citri has some resistance to organophosphate insecticides in the orchards of Martinez de la Torre, Veracruz. This information can be used to decide the type of insecticides to apply in the study area.

Biochemical and immune response in red tilapia (Oreochromis mossambicus × O. niloticus) with dietary chitosan supplementation

The use of biostimulants in fish diets is a promising strategy to reduce the use of antibiotics, enhance the biochemical and immune response, which contributes to improving productive yields and reducing economic losses. The biochemical and immune response was evaluated in juvenile red tilapia (Oreochromis mossambicus × O. niloticus), with different levels: 0 (control), 1, 2, 3, 4 and 5% chitosan in diet. 270 animals (7.53 ± 0.50 g of initial weight), distributed in a completely randomized design of 6 treatments with 3 replicates and 45 tilapia.treatment-1, were sown in 18 tanks with 90 L of water in a closed system. The juveniles were fed for 55 days with the experimental diets and at the end of the bioassay the tissue and blood plasma samples were taken. Differences were found (p<0.05) in the variables evaluated responses, where the content of lipids, triglycerides, cholesterol, carbohydrates and glucose showed higher levels (p<0.05) at lower chitosan concentrations. However, for protein content, a better response (p<0.05) was found at higher levels of chitosan in the diet. Regarding dry matter and ash, no differences were found (p˃0.05). While superoxide dismutase and leukocytes were found in higher concentration (p<0.05) when supplemented with chitosan by 3 and 4%. It was concluded that the juvenile biochemical and immune response of red tilapia was favored with dietary chitosan supplementation.

Effect of anisosmotic stress on the structural and functional integrity of the plasma and acrosomal membrane of ram sperm

The integrity of the plasma membrane (MP) and the acrosome (MA) have been two of the most studied seminal evaluation parameters due to their role as a cell boundary and because they are responsible for interactions between cells effective. To assessing more objectively the effects of osmotic stress on the integrity of the PM and MA, as well as the rate of change that occurred during seminal cryopreservation, five freshly collected ejaculates were evaluated, refrigerated at 5 ºC and thawed per ram/session during 5 consecutive weeks. Using eosin-nigrosin (EN) staining, vitality (VIT), morpho abnormalities and cellular response were evaluated after performing osmotic resistance (ORT) and endosmosis (HOST) tests. The direct effect of anysosmosis and cryopreservation on the dependent variables were analyzed using the GLM procedure (SAS®) and when differences were observed, the effects were quantified using the LSMEANS. All the sperm quality values studied were significantly affected (P <0.001) by cryopreservation (VIT, ORT, HOST). The ORT demonstrated how the acrosome was one of the structures most affected by cryopreservation (P <0.001). In conclusion, the present study confirms that anysosmotic stress affects the sperm cell in an important way, compromising the reference values that quantify semen quality, especially MA and MP.

The price elasticity of the demand and revenue increase for some Mexican planting seeds

The study of the price elasticity of demand (PED) has been and is a current research topic, as it greatly helps the managers of companies to make decisions about the price of their products and the expected repercussions in changing them. The objective of this study was to estimate PED and its impacts on the variation of income (VI) of six planting seed crops from Mexico, such as yellow corn, other corn (except yellow and sweet corn), sorghum, chickpea, pumpkin and cucumber. The data were gathering from the Foreign Agriculture Service (FAS) (1998-2018 period) through the tables provided and published on the Internet (secondary data). In this study, the arc method was applied to calculate PED and VI = ((Pf * Qf * 100) / (Pi * Qi)) - 100. Five of six the planting seed products have a relatively elastic demand price in most of the years, on the contrary the revenue increase had positive and negative values, without a defined trend. Sorghum planting seed has in some cases elastic demand and in other inelastic demand. It is concluded that there are no clear effects of the PED on the sales revenue of the aforementioned products; an aspect that contradicts the theory of PED and its impact on income.

Characterization of rhizospheric bacteria isolated from soil cultivated with sugarcane in Tamaulipas state, Mexico

The state of Tamaulipas, Mexico, has two important sugar mills, with plantations of sugarcane (Saccharum officinarum L.) of more than 50 years, the objective of the study was the identification and bacterial characterization in the production of indole-3-acetic acid (IAA), the solubilization of phosphorus and plant growth of bacterial isolates from the rhizosphere of sugarcane. The isolation and morphological characterization were in 30 rhizosphere soil samples of the sugarcane variety CP 72-2086 using the Luria-Bertani media, Congo Red Agar and Potato Dextrose Agar. The molecular characterization was with the 16S rRNA gene and the bacterial inoculation consisted of seedlings of the variety CP 72-2086. 121 strains (38 species) were isolated, being Bacillus sp. most frequently, 14 species were positive for phosphorus solubilization: Bacillus sp. (6), Pseudomonas spp. (5), Paenibacillus (2) Streptomyces venezuelae (1) stand out. The greater phosphorus solubilization was Pseudomonas mediterranea (21.6 mm). Nine bacteria showed production close to 5 ppm IAA: Bacillus aryabhattai (6 ppm), Bacillus pumilus (5.8 ppm) and Ensifer adhaerens (5.6 ppm). Bacillus megaterium showed a higher percentage of chlorophyll and foliar nitrogen. In the present analysis, 38 bacterial species associated with the rhizosphere of the sugarcane variety CP 72-2086 were identified, so these results showed the potential to select native bacteria that have the ability to stimulate plant growth of the variety CP 72-2086.

Antagonism of Trichoderma harzianum and Trichoderma viride on isolates of Fusarium spp. from Nicotiana tabacum

Tobacco production is a key line in the Cuban economy and generates the largest income in the agricultural sector. Within phytopathogens affecting this plant, Fusarium spp., constitutes a pest of interest, due to vascular involvements that cause deterioration of the commercial value of the leaf. Therefore, the research was carried out with the aim of determining the antagonistic activity in vitro of native strains of Trichoderma harzianum and T. viride on isolates of Fusarium oxysporum and F. phyllophylum, from Nicotiana tabacum L. in Granma province, Cuba. The work was carried out at the Laboratory of Agricultural Microbiology, University of Granma. Half dextrose potato agar was prepared to establish the dual crops of Trichoderma spp. vs. Fusarium spp. Once the treatments were established and the incubation time had elapsed, the percentage inhibition of mycelial growth, antagonistic capacity and mycoparasitic activity was determined. A fully randomized design with four replicas per treatment was used and a two factorial ANOVA and Tukey test (p≤0.05) were used for statistical processing. It was shown that the strains of Trichoderma spp., recorded intermediate values of phytopathogenic inhibition, the competitiveness of the antagonist was mostly located in class two of the Bell scale and it was found that penetration, winding, vacuolization, deformation and granulation constitute the main forms of mycoparasitism. Which points to this biocontrol method as an alternative to consider for the management of Fusarium spp., in tobacco agroecosystems.

Potential use of Lupinus exaltatus Zucc. (Leguminosae) as green manure in soils of Jalisco, Mexico

The environmental impact generated by agriculture with excessive use of fertilizers has led to the search for alternatives to improve soil fertility. This study aimed to evaluate the potential of Lupinus exaltatus in terms of decomposition and mineralization of nitrogen (N) when incorporated into the soil as green manure (GM) and its effect on the growth of Triticum aestivum L. seedlings. Litter bags were used, with a total of 216 nylon bags (10 × 5 cm), in each bag were placed 5 g dry base of GM in the vegetative stage and flowering. Subsequently, the GM bags were placed separately Vertisol and Regosol soil at a depth of 5 cm; and every three weeks until the end of the incubation, three bags were recovered per treatment. For evaluation of the effect GM on T. aestivum growth experiment was established in pots with soil Regosol, it consisted of incorporating 50 and 34 g dry base of the GM (equivalent to 10 and 15 t.ha-1). The GM in the vegetative stage lost an average of 83,52 % of its initial weight, while in flowering the loss was 76,49 %, the mineralized N was higher in Regosol soil than in Vertisol with 74,02 % and 70,58 % respectively. The wheat seedlings presented 30 % more dry matter and N with GM than the control treatment. L. exaltatus had a rapid decomposition and mineralization of N in the first stages of incubation.

Weed discrimination based on the spectral response of the corn crop, Manabí, Ecuador

Precision agriculture allows to gain efficiency, sustainability and profitability, since it provides great benefits in reducing the environmental impact of agriculture, economic risks and at the same time contributes to controlling the vigor of crops and improving the quality of their yield. The objective of this research is to discriminate weeds within the corn crop, based on their spectral response. For this, the advanced EBEE SQ agricultural drone was used, with which multispectral images were captured through its Parrot Sequoia camera. The images were processed with software in Geographic Information Systems (GIS). With the multispectral bands, different vegetation indices were calculated such as NDVI, NDVIAS, NGRDI, NDRE, GNDVI, using map algebra tools in specialized programs. A supervised classification was applied to the different indices to discriminate the different land covers, which obtained a precision of 93% and a Kappa index of 0.93. The results allowed to clearly differentiate the coverage of crops, weeds and bare soil. The data showed that both early-growing and developed weeds occupy 38% of the crop area. With this information, it is possible to improve the planning of agronomic practices, adding the herbicide at the specific site of the weeds.

Leaves drying kinetics of the species Zanthoxylum sprucei (Rutaceae) and Melampodium divaricatum (Asteraceae)

The study of the drying of the plants is important for the extraction methods of the active principles, since it provides benefits both for the efficiency and for the stability. The objective of this research is to study the drying kinetics of the leaves of Zanthoxylum sprucei (Rutaceae) and Melampodium divaricatum (Asteraceae) species from the Manabí province. Eight empirical models derived from Fick's law with adjustment and the STATISTICA software as modeler was used. The model was made by applying the ORIGIN Pro fit curve. The kinetic results were obtained experimentally in a laboratory scale tunnel dryer with a temperature of 40°C, at 1 atm of pressure and a speed air of 8.47 m.s-1. To determine the model that best fits the experimental data, it relies on the correlation coefficient (R2), mean square error (ERMS) and chi-square (X2). The mathematical model that best describes the drying process is the logarithmic for Zanthoxylum sprucei and the Wang and Singh model for Melampodium divaricatum.

Growth of four types of Capsicum spp. in substrates under a protected environment

Plant growth depends on environmental conditions, management conditions and soil conditions, which is why in this research we evaluated the growth of chili peppers in a sand-based substrate, under a protected environment. The treatments evaluated were: 1) soil (control), 2) sand, 3) sand-perlite (4:1) and 4) sand-perlite (1.5:1), which were established under a completely randomized design with six replications. The species used were Capsicum annuum L. Hungarian, serrano and jalapeño types, and Capsicum pubescens Ruiz & Pav. apple type. The sand-perlite mixtures benefited the growth of the chili peppers, with respect to soil and sand. Therefore, sand-perlite mixtures should be considered as an alternative to produce chili peppers in containers.