Isela Quintero-Zapata

Se evaluó la lechuga (Lactuca sativa) como dieta única para la crianza en laboratorio de Spodoptera exigua durante cuatro generaciones. Se determinó el crecimiento y peso de larvas y pupas. El tamaño larval varió de 2.44 (L1) a 21.03 mm (L5), y el peso, entre 190 y 217 mg. La longitud de pupa entre 14.70 y 18.13 mm, mientras que su peso fue 61 a 104 mg. La duración desde el primer estado larvario hasta pupa fue en promedio de 20.5 días. Estos resultados demuestran que S. exigua logró sobrevivir favorablemente con solamente L. sativa ya que el incremento en longitud y peso fue paulatino y alcanzó su punto máximo en la cuarta generación, logrando además completar su ciclo de vida en cada generación analizada.

Environmental pollution caused by petroleum-derived plastics continues to increase annually. Consequently, current research is interested in the search for eco-friendly bacterial polymers. The importance of Bacillus bacteria as producers of polyhydroxyalkanoates (PHAs) has been recognized because of their physiological and genetic qualities. In this study, twenty strains of Bacillus genus PHA producers were isolated. Production was initially evaluated qualitatively to screen the strains, and subsequently, the strain B12 or Bacillus sp. 12GS, with the highest production, was selected through liquid fermentation. Biochemical and molecular identification revealed it as a novel isolate of Bacillus cereus. Production optimization was carried out using the Taguchi methodology, determining the optimal parameters as 30 °C, pH 8, 150 rpm, and 4% inoculum, resulting in 87% and 1.91 g/L of polyhydroxybutyrate (PHB). Kinetic studies demonstrated a higher production within 48 h. The produced biopolymer was analyzed using Fourier-transform infrared spectroscopy (FTIR), confirming the production of short-chain-length (scl) polyhydroxyalkanoate, named PHB, and differential scanning calorimetry (DSC) analysis revealed thermal properties, making it a promising material for various applications. The novel B. cereus isolate exhibited a high %PHB, emphasizing the importance of bioprospecting, study, and characterization for strains with biotechnological potential.

In this research, muffin-type bakery products were developed based on wheat flour (WF) and mesquite flour (MF) in the following proportions: WFMF 90:10, WFMF 75:25, and WFMF 50:50. The products were characterized based on various properties in which it was possible to observe that the water activity (aw) did not show a significant change with the increase in the concentration of MF. In addition, the increase in the concentration of MF modified the sensory properties (color, odor, flavor, texture, and acceptance), further decreasing the luminosity and increasing the values of the a* and b* coordinates. Moreover, in the texture profile analysis, it was found that the increase in the MF concentration increased hardness, fracturability, and gumminess and decreased adhesiveness and cohesiveness. All the previously mentioned changes were more evident in the WFMF50:50 and, to a lesser degree, in WFMF75:25. In general, in most evaluations realized, the WFMF90:10 treatment was the most similar to the control (without MF). However, WFMMF75:25 provided a higher protein and fiber content and a lower fat content. Finally, it is possible to use the flour obtained from the mesquite fruit to make bakery products since it is an important source of food due to the wide distribution of mesquite in the country.

Spodoptera exigua Hübner (Lepidoptera: Noctuidae) is considered a polyphagous pest distributed worldwide with a wide range of hosts, and is also considered a serious plague for vegetables and ornamentals. The objective of this study was to explore the occurrence of entomopathogenic fungi in agricultural soils from Mexico and to evaluate its virulence and effect on the life cycle of S. exigua. Selected isolates (HEB1 and γ01) were used to perform toxicity bioassays on neonatal larvae of S. exigua; additionally, the GHA (Beauveria bassiana), Pfr-612 (Cordyceps fumosorosea), Ma, and 2 isolates HIB-11 and HIB-12 (Metarhizium anisopliae) were included to obtain the median lethal concentration (LC50) and the median lethal time (LT50). Also, the life cycle of the surviving individuals was followed up after treatment to document the effects of the entomopathogenic fungi application. The isolates belong to 2 different species, which are Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) and Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae) (formerly Isaria fumosorosea). In toxicity tests, the isolate HIB-12 of Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Cordycipitaceae) showed better mortality results against S. exigua than the other fungi evaluated with LC50 of 3.17 × 106 conidia per mL. The lethal time of LT50 oscillated between 3 to 5 d and the HIB-12 isolate had the lowest lethal time (3.15 d). During the monitoring of the biological cycle after treatment, the greatest interruption of the metamorphosis was caused by the GHA strain, while the Ma strain was the one that induced the slightest interruption of the biological cycle. These results show the feasibility of using strains of M. anisopliae for control of larval stages of S. exigua and their possible formulation for agricultural use, as well as opening a way for the exploration and research of mechanisms or metabolites involved in the interruption of metamorphosis due to the application of entomopathogenic fungi, specifically B. bassiana.

In the last decades, the use of entomopathogenic fungi for the control of pest insects has increased globally, however a key step to achieve the successful application of fungal propagules as biocontrol agents depends of various factors, inoculum production being one of the essential stages for these microorganisms to be used in pest management programs. The objective of this study was to evaluate the production of conidia by solid fermentation and biphasic culture in different sporulation matrices for four native isolates and a strain of Isaria fumosorosea that have been shown potential for the control of various insects at the laboratory level. The experimental design was completely randomized, two propagation methods were used with six treatments and ten repetitions per treatment; the data were analyzed using an analysis of variance and the means were compared using the Tukey test (p≤ 0.05). In the production by solid fermentation the minimum value of 5.30 × 105 conidia g-1 was registered with the pericarp of peanut and the maximum of 2.35 × 107 conidia g-1 in the corn grain; in the biphasic culture the minimum of 7.60 × 105 conidia g-1 was observed in birdseed and the maximum of 2.07 × 107 conidia g-1 in rice. The differences were significant (p ≤ 0.05) in the production by method and by substrate, in solid fermentation 6.84 × 106 conidia g-1 and in biphasic culture 8.85 × 106 conidia g-1. In the production by substrate, the rice showed 1.75 × 107 conidia g-1 and the lesser canary seed concentration (7.80 × 105 conidia g-1). The average production per isolate and / or strain was of the order of 106 and significant difference was registered (p ≤ 0.05) among the fungi, the isolate HIB-9 showed concentration in average higher in the production (7.90 × 106 conidia g-1) and the isolated HIB-19 was the least effective, with only 1.08 × 106 conidia g-1. The results obtained show marked differences between the isolates with respect to their capacity to use the different substrates used as propagation media to obtain conidia of I. fumosorosea.

The aim of this study was to evaluate pathogenicity and effect of four isolated native and a strain of Isaria fumosorosea on beet armyworm, Spodoptera exigua (Hübner), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). Bioassays in a laboratory used neonate larvae of beet armyworm and corn earworm reared on artificial diet, which were inoculated by spraying or immersing with suspensions of 1 × 10⁸ ml^-1 conidia of I. fumosorosea, and subsequently incubated at 26°C, 65 ± 5% relative humidity, and 14:10 light: dark hours. Isolated HIB-30 killed the most immersed corn earworms, but fewest beet armyworms. HIB-30 most disrupted metamorphosis, 40%, by immersing beet armyworms, while HIB-29 and Pfr-612 least interrupted metamorphosis (8%), by spraying and immersing, respectively.

A total of 142 soil samples was collected from different Mexican states: Campeche (13), Michoacán (15), Nuevo León (25), San Luis Potosí (25), Sinaloa (17), Sonora (17), Tabasco (5), Tamaulipas (20), and Yucatán (5). Larvae of the greater wax moth, Galleria mellonella (L.), were used as bait to detect, trap, and multiply entomopathogenic fungi in vivo. Twenty-three percent of the soil samples processed were positive for the presence of entomopathogenic fungi according to the macroscopic and microscopic characteristics: Beauveria bassiana (Bals.-Criv.) Vuill. was detected in 12% (17 isolates), Metarhizium anisopliae (Metchnikoff) Sorokin in 1% (2 isolates), and Isaria fumosorosea (Wize) in 10% (14 isolates). Genetic variability of the fungi was analyzed using the sequences of internal transcribed ribosomal genes (ITS-5.8S-ITS2) and digested with the enzyme Haelll. PCR results generated fragments of 600 bp for B. bassiana and M. anisopliae, and more than 600 bp for I. fumosorosea. Both reference strains and field isolates produced similar restriction patterns. Genera of native entomopathogenic fungi were found in the diverse citrus areas of Mexico, opening the possibility for biological control of pests affecting citrus in each region. Se colectaron 142 muestras de suelo de diferentes estados de la República Mexicana: Campeche (13), Michoacán (15), Nuevo Leán (25), San Luis Potosí (25), Sinaloa (17), Sonora (17), Tabasco (5), Tamaulipas (20), y Yucatán (5). Las larvas de Galleria mellonella (L.) fueron utilizadas como cebo para detectar, atrapar y multiplicar hongos entomopatogénicos in vivo. Con base a las características macroscópicas y microscópicas se obtuvo un 23% de las muestras de suelo positivas a la presencia de hongos entomopatógenos. Beauveria bassiana (Bals.-Criv.) Vuill. fue detectado en un 12% (17 aislados), Metarhizium anisopliae (Metchnikoff) Sorokin en 1% (2 aislados) e Isaria fumosorosea (Wize) en un 10% (14 aislados). La variabilidad genética de los hongos se analizó mediante la amplification por PCR de las secuencias de los espaciadores transcriptos internos (ITS-5.8S-ITS2) de los genes ribosomales y posterior digestión enzimática con Hae III. Como producta de la PCR se obtuvieron fragmentas de aproximadamente 600 pb para B. bassiana y M. anisopliae. Para el caso de /. fumosorosea, se amplifieó un fragmenta por arriba de 600 pb. Tanto en cepas de referencia como en aislados se generaron patrones de restricción similares. Los généros de hongos entomopatógenos fueron encontrados en las diferentes áreas citrícolas de México; Io que abre el campo para el control biológico de plagas que afectan los cítricos en cada región.