Edible coatings have potential to reduce postharvest losses of fruit such as tomato. In this study, the effects of nanolaminate coatings incorporated with extracts of Flourensia cernua, an endemic plant of the arid and semiarid regions of Mexico, has been investigated. Ethanol extracts of F. cernua (FcE) were prepared and incorporated into polyelectrolyte solutions of alginate and chitosan. The nanolaminates were characterized by determining the zeta potential, contact angle and water vapor and oxygen permeabilities. Shelf-life analyses (20°C for 15 d) were carried out with uncoated fruit (UCF), nanolaminate coating (NL) and nanolaminate coating with FcE (NL + FcE). Physicochemical analyses, gas exchange rates of O 2 and CO 2 and ethylene production, as well as microbiological analyses of treated fruit were measured. Zeta potential and contact angle measurements confirmed the successful assembly of successive nanolayers of alginate and chitosan, as well as those with F. cernua. The nanolaminate coatings resulted in decreased permeabilities to water and O 2. The best treatment of NL + FcE, extended the shelf-life of fruit by reducing weight loss and microbial growth, reducing gas exchange and ethylene production, and maintaining firmness and color. The NL + FcE treatment are an alternative to extend the shelf-life of tomato fruit.

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ResumenCon el objetivo de encontrar alternativas para el manejo de patógenos que provocan enfermedades en el sistema radical de las plantas se evaluó el efecto in vitro de bacterias antagonista del género Bacillus aisladas de la rizosfera y de extractos etanolicos de plantas de las especies Larrea tridentata, Flourensia cernua, Opuntia ficus-indica, Agave lechuguilla y Yucca filifera endémicas del desierto Chihuahuense contra el fitopatógeno Rhizoctonia solani. Las bacterias se obtuvieron de la forma esporulada, una suspensión de suelo se calentó 15 min 80 °C para eliminar formas no esporuladas. Los extractos vegetales se obtuvieron por infusión. Como resultado se encontró que las cepas de Bacillus aislados presentan un efecto antagonista in vitro sobre la inhibición micelial de Rhizoctonia solani desde 40 a 67%. La caracterización por secuenciación del gen 16S del ADNr se determinó que los aislamientos pertenecen a las especies de B. subtilis, B. pumilus y a B. atrophaeus, quienes están reportadas con efecto antagónico sobre organismos fitopatógenos. Para el caso de los extractos se encontró un efecto en la inhibición micelial hasta 100% en su mayoría todos los extractos inhibieron el crecimiento del micelio de R. solani al 100% excepto el extracto de Y. filifera que solo tuvo 46% con la dosis más alta evaluada (3 000 ppm). Los extractos de F. cernua muestran que a 160 ppm de polifenoles totales se inhibe completamente a R. solani. AbstractIn order to find alternatives for pathogen management causing diseases in the root system of plants, was evaluated the in vitro effect of antagonistic bacteria of the genus Bacillus isolated from rhizosphere and from ethanolic extracts of plants species Larrea tridentata, Flourensia cernua, Opuntia ficus-indica, Agave lechuguilla and Yucca filifera, that are endemic from the Chihuahua desert against plant pathogen Rhizoctonia solani. Bacteria were obtained as spore form; a soil suspension was heated for 15 min at 80 °C to remove non-sporulating forms. Plant extracts were obtained by infusion. As a result it was found that strains of Bacillus isolates have an in vitro antagonistic effect on mycelia inhibition of Rhizoctonia solani from 40 to 67%. The characterization 16S rDNA gene sequencing determined that the isolates belong to the species of B. subtilis, B. pumilus and B. atrophaeus, that are reported with antagonistic effect on plant pathogenic organisms. In the case of extracts, an effect on mycelial inhibition of up to 100% was found; most extracts inhibited micelial growth of R. solani at 100% except for Y. filifera extract that only obtained 46% with the highest dose evaluated (3 000 ppm). F. cernua extracts show that at 160 ppm of total polyphenols completely inhibited R. solani.Keywords: Rhizoctonia solani, antagonism, bacteria, extracts, mycelial inhibition, plant extract, rhizosphere. IntroducciónUno de los hongos que limita la producción del cultivo de papa en México es Rhizoctonia solani Kühn, la enfermedad que ocasiona es conocida como la costra negra de la pap...

Fusarium oxysporum y Rhizoctonia solani son agentes causales de la marchitez del chile y provocan pérdidas hasta 80% en el cultivo en México. El uso inadecuado de fungicidas químicos ha generado problemas de resistencia, esto no se observó con agentes microbianos, por lo que se evaluaron en el biocontrol de la marchitez del chile en parcelas experimentales donde se identificó a F. oxysporum y R. solani como agentes causales de la enfermedad. Trichoderma spp., Bacillus spp., mezcla de fermento propagativo microbiano, Tiabendazol y testigo, fueron aplicados en una parcela de 800 m2 con seis variedades de chile. Los tratamientos Trichoderma y fermento propagativo mostraron bajos porcentajes de incidencia y severidad, altos rendimiento con Trichoderma en HS- 52 y Coloso (15.67 y 13.89 t ha-1). Los tratamientos Trichoderma y fermento propagativo promueven el biocontrol de la marchitez del chile provocada por F. oxysporum y R. solani e incrementar el rendimiento.

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Problem statement: Plant extracts with polyphenolic compounds obtained with different solvents have been evaluated against plant pathogens. However, most of these extract have been obtained using solvents no allowed under an organic production context. Approach: In the present research was to evaluate the inhibitory effect of polyphenolic extracts from L. graveolens and C. illinoensis, obtained with alternative organic solvents (lanolin and cocoa butter), water and ethanol against R. solani in order to determine the Inhibitory Concentration (IC₅₀) of each extract. Results: The results showed that extracts of both L. graveolens and C. illinoensis obtained with lanolin and ethanol (200 and 3000 ppm of total tannins, respectively) inhibited at 100% growth of R. solani. The IC50 for each extract was highly variable, low IC50 values were obtained with L. graveolens (4.50×10¹) and C. illinoensis (4.33×10²) extract using lanolin and ethanol respectively. Tannins extraction was strongly dependent on plant species and in the solvent used. Conclusion: The alternative organic solvents lanolin and cocoa butter allowed the recovery of polyphenols compounds with antifungal activity against R. solani