Jorge Covarrubias-Prieto

The presence of Bacillus subtilis on tomato roots contributes to plant growth promotion, which depends on its ability to establish in the roots. Edible-film formulations have emerged as effective carriers for beneficial bacteria. In this study, we evaluated film formulations based on guar gum, glycerol, and candelilla wax incorporating B. subtilis for root application in tomato seedlings to stimulate plant development. Sixteen film formulations were prepared and applied to seedling by dipping root; plants were grown under a 16/8 h photoperiod. At 60 days, growth parameters (plant height, leaf number, chlorophyll content, fresh and dry weights) were measured, along with B. subtilis on roots, and the soil degradation of the selected film. Treatments were: seedlings with B. subtilis at two doses (10^6,12 CFU/mL (B6, B12), film without bacteria (P), films with B. subtilis (P1–P16), and untreated (TST). Among the films, formulation 9 (guar gum 0.6%, candelilla wax 0.15%, glycerol 0.15% and B. subtilis 20%, 1 × 10¹²) significantly increased shoot and root biomass and supported higher root colonization of B. subtilis (2.3 × 10⁷ CFU/g). The film degraded in soil within 15 days, while the inoculant maintained high viability (6.3 × 10⁸ CFU/mL) after 8 months at 4 °C. These results highlight film formulation 9 as a promising bioinoculant for tomato cultivation.

Las bacterias patógenas son responsables de grandes afectaciones en los principales cultivos, causan desde daños moderados hasta pérdida total. En plantas de ajo cultivadas durante el ciclo otoño-invierno 2016-2017 en dos localidades, Celaya e Irapuato (estado de Guanajuato, México), se detectaron síntomas de estrías amarillas en el margen de la hoja desde los dos meses después de la siembra. El objetivo de este trabajo fue aislar e identificar los agentes causales asociados a estos síntomas. A partir de 62 muestras de follaje con manifestaciones características de la enfermedad en tres materiales de ajo, se obtuvieron 74 aislados bacterianos puros y se seleccionaron los 13 más representativos, según su morfología colonial, que fueron identificados molecularmente por amplificación y secuenciación del gen ribosomal 16S. Para la localidad de Celaya se identificaron las especies Pantoea agglomerans, Bacillus amyloliquefaciens, Erwinia persicina, Bacillus megaterium y Bacillus mojavensis y para Irapuato Bacillus aryabbattai, B. amyloliquefaciens, B. megaterium, Erwinia persicina. Estas bacterias resultaron ser de importancia fitosanitaria en la fase de desarrollo vegetativo y formación de bulbo, pues se lograron recuperar a partir de tejido dañado obtenido de plantas previamente inoculadas. Hasta donde se sabe, este es el primer reporte de la presencia de dichas bacterias relacionadas con los síntomas descritos en cultivos de ajo y con el deterioro de los bulbos durante su almacenamiento poscosecha.

Crop production of brassicaceous crops in Mexico are affected by the attack of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae). An inadequate application of insecticides indirectly affects the main parasitoid of this pest, the wasp Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae). Eight insecticide treatments and one control were evaluated using a completely randomized design with four replications. The objective of this research was to evaluate, under laboratory conditions, three organic insecticides, five synthetic insecticides and a control, to determine their effectiveness in controlling P. xylostella and its effect on the mortality of the parasitoid D. insulare . Broccoli leaf immersion method in solution with insecticides was used. Pyridalil caused the highest mortality (100%) in the third-instar larval stage of P. xylostella at 48 h after application and mild to moderate mortality (categories 1 and 2 of the IOBC) to D. insulare at 72 hours; Naled obtained 100% mortality in the larva and adult of P. xylostella , but also caused 100% mortality in the parasitoid 24 h after treatment. Among the organic insecticides, Pyrethrin produced the highest mortality in P. xylostella larvae (60%) at 72 h in the two doses used and caused a mortality of 10% in D. insulare . Pyridalil and Emamectin Benzoate insecticides showed high effectiveness for the control of the insect-pest and had low impact on the parasitoid.

Germination is a process of high metabolic activity in plants that involves the use of storage components present in seeds for seedling development. Chemical induction is a process in which different types of compounds are used to promote the activation of secondary metabolic pathways. The objective of the present study was to determine the effect of chemical induction with salicylic acid (SA) (1 and 5 mM) on chickpea seed germination, germination percentage, radicle length and protein content in seedlings. Soluble protein fractions and trypsin inhibitory activity were quantified in the seedlings, and protein patterns were identified by polyacrylamide gel electrophoresis. Treatment with 5 mM salicylic acid decreased both the germination percentage and the length of the radicle. The albumin fraction content of the seedlings was reduced with 1 mM SA. The trypsin inhibitory activity in the globulin fraction decreased in seedlings treated with both SA treatments. Protein electrophoretic patterns from SA-induced seedlings remained similar to those without induction. In a dose-dependent manner, chickpea seedlings exhibited changes in seedling development, concentration of protein fractions, and reduced trypsin inhibitory activity.

In seed technology, the use of biocompatible materials, such as chitosan, has been demonstrated to improve the germination process and establishment of seedlings. This research is focused on the effect of a chitosan coating on the germination and development of sesame and bean plantlets. The seeds were treated with different coating techniques and combinations of chitosan: chitosan solutions at 0.1, 0.5 and 1% were used in film coating, chitosan flakes with particle sizes of 1.19 mm and 0.71 mm were used as a crusted coating, and chitosan flakes with a size of 1.19 mm were used for coating with acrylic resin. Images of the coatings were obtained by means of scanning electron microscopy; the effect on germination, germination speed, vigor index, length and root area of plantlets were also determined. Chitosan treatments increased germination by 26% in bean and 16% in sesame compared with the control; the germination speed index showed an increase of 61% in bean and 58% in sesame. The treatments with chitosan increased the length of the root in bean by 77%, and in sesame four times more, compared with the control treatments. Different forms of chitosan coatings improve germination and seedling establishment; however, the response to the type of coating at a given stage of seedling development will depend on the crop species.

Chitosan is a biopolymer obtained from deacetylation of chitin; it has multiple applications in agriculture as an antifungal, soil conditioner, inducer of defense mechanisms, fruits postharvest coating, leaves and seeds, among others. The objective in this research was to evaluate the effect of chitosan coatings mixed with fungicide (dithiocarbamate) on the germination and germination speed of bean and maize seeds in storage and to determine the retention capacity of the fungicide in the coated seeds under different times of imbibition. Two coating treatments at concentrations of 0.1 and 0.5% chitosan in water, two coatings treatments at 0.1 and 0.5% chitosan supplemented with 0.5% fungicide and a coating without chitosan using only 0.5% fungicide in water were used in bean and maize seed; and as control seeds imbibed in distilled water were used; after treatments, germination percentage and germination speed were determined, also fungicide release were determined at 0, 1, 2 and 6 h of imbibition, and the effect of storage time on germination and germination speed was determined at 30, 60, 90, 120, 150 and 180 days of storage at 4 °C and 45% relative humidity. The fungicide release effect was determined by inhibiting Fusarium oxysporum conidia germination. There were no negative effects of coatings on seed germination after storage. The treatment that provided both greater retention of the fungicidal agent and released it gradually, was 0.5% chitosan mixed with fungicide concentration. Chitosan coating seeds mixed with fungicide do not cause negative changes in seed germination or germination rate.

In Guanajuato, Mexico, water deficits have dramatically increased in recent years due to over-exploitation of this resource. The objective was to identify high yielding wheat (Triticum spp.) varieties under two irrigation regimes. The experiments were planted at Celaya, Guanajuato, for two consecutive (2013-2014 and 2015-2016) growing seasons (GS). Eleven commercial varieties and nine experimental lines were evaluated under 3 or 4 irrigation regimes; split-plot design with 4 replicates was considered; data on yield performance and its components were measured. There were significant differences between GS and number of irrigation regimes (p ≤ 0.01) for most evaluated traits. ANOVA showed significant differences for all traits in the study, except for the 1000-grains weight. Growing seasons affected yield, grains number m^-2 and biomass, mainly; on last cropping season, grain yield was higher (1.8 t ha^-1) than first one; strong gluten genotypes were more stable, as compared with the soft gluten genotypes. Some experimental varieties exceeded commercial varieties, which means success in wheat breeding. Genotypes Experimental Line D and control ‘Bárcenas F2002’ under 3 irrigations regime treatment showed the highest grain yield (7.7 and 7.0 t ha^-1, respectively). On 4 irrigations regime, the best yielding genotypes were experimental lines D, and H, with 6.5 and 6.1 t ha^-1, respectively. Based on regression deviations the most stable and predictable wheat genotypes were strong gluten genotypes.