Impacto ambiental por uso de plaguicidas en tres áreas de producción de melón en la Comarca Lagunera, México / Environmental impact by usage of pesticides in three melon producing areas in the Comarca Lagunera, Mexico

RESUMEN El uso intensivo de plaguicidas altamente tóxicos, en la producción de cultivos hortofrutícolas especializados, conlleva riesgos ambientales y sociales, que pueden medirse mediante indicadores de riesgo de plaguicidas, para evaluar el potencial de impacto negativo de estos productos en los ecosistemas y comparar los logros de la implementación de prácticas agrícolas sustentables, en términos de reducción de riesgos, por la utilización de plaguicidas. El objetivo de esta investigación fue estimar el potencial impacto ambiental, por uso de plaguicidas, en las tres áreas de mayor producción de melón en la Comarca Lagunera. Se realizó un estudio descriptivo transversal, mediante la aplicación de una encuesta en 19 predios, seleccionados mediante muestreo no probabilístico. El Impacto Ambiental (IA) se evaluó mediante el modelo del Cociente de Impacto Ambiental (CIA), que se basa en el cálculo del CIA y el Cociente de Impacto Ambiental en Campo (CIAC). Los resultados muestran que los plaguicidas que contribuyeron con la mayor carga ambiental en las áreas de estudio fueron: clorotalonil (49 %), azufre elemental (11 %) y endosulfan (10 %), en Mapimí; carbofuran (19 %), endosulfan (18 %) y carbendazim (12 %), en Matamoros-Viesca; y oxicloruro de cobre (20 %), endosulfan (17 %) y mancozeb (17 %), en Tlahualilo. Los sistemas de producción, con los valores del IA más altos, se identificaron en fechas de siembra intermedias (199 a 500) y tardías (201 a 701), en Mapimí, y fechas tardías (132 a 383) en MatamorosViesca. El modelo del CIA permitió identificar a los plaguicidas y los sistemas de producción con el mayor impacto ambiental negativo en las tres principales áreas de producción de melón en la Comarca Lagunera, además de proporcionar una escala cuantificable, que permitirá evaluar y comparar futuros cambios en el uso regional de plaguicidas.

ABSTRACT The intensive use of highly toxic pesticides in the production of specialized horticultural crops entails environmental and social risks that can be measured through pesticide risk indicators to assess the potential negative impact of these products on ecosystems. In addition, this measurement enables the comparison of the achievements that result from the implementation of sustainable agricultural practices in terms of risk reduction due to the use of pesticides. The objective of this research was to estimate the potential environmental impact due to the use of pesticides in three melon production areas in the Comarca Lagunera. A cross-sectional descriptive study was carried out by applying a survey in 19 properties selected by non-probabilistic sampling. The Environmental Impact (EI) was evaluated using the Environmental Impact Quotient (EIQ) model, which is based on the calculation of the EIQ and the Environmental Impact Quotient in the Field (EIQF). The results show that the pesticides that contributed with the greatest environmental burden in the study areas were: Chlorothalonil (49 %), elemental sulfur (11 %) and endosulfan (10 %) in Mapimí; carbofuran (19 %), endosulfan (18 %) and carbendazim (12 %) in Matamoros-Viesca, and copper oxychloride (20 %), endosulfan (17 %) and mancozeb (17 %) in Tlahualilo. The production systems with the highest AI values were identified on intermediate (199 to 500) and late (201 to 701) sowing dates in Mapimí and late dates (132 to 383) in Matamoros-Viesca. The EIQ model allowed the identification of pesticides and production systems with the greatest negative environmental impact in the main areas of melon production in the Comarca Lagunera and provides a quantifiable scale that will allow the evaluation and comparison of future changes in the regional use of pesticides.

Microbiology of high-sugar must fermentation by novel yeasts from the chihuahuan desert.

This work reports important results of aromatic profiles produced by native yeasts isolated from desert-grown wine grapes from the south of Chihuahua, México. These grapes stand very high temperatures during the ripening season, developing high sugar concentration and high pH. Yeast species found in grapes were identified by polymerase chain reaction and sequence analysis of the 5.8S internal transcribed spacer ribosomal RNA region. Aureobasidium namibiae, Sporobolomyces johnsonii, Candida apicola, Hanseniaspora uvarum, Candida thaimueangensis, Hanseniaspora opuntiae were identified. All of them can grow at glucose concentration of 35% (w/v) and 100 ppm of SO2, and produce low volatile acidity (0.2-1.0 g acetic acid/L). Volatile organic compounds analysis showed that C. thaimueangensis and one strain of C. apicola produce high levels of esters, and Hanseniaspora species produces high levels of higher alcohols and carbonyl compounds. The results of this study contribute to the knowledge about yeast communities associated with desert-grown winegrape yeasts.

Changes in Trichoderma asperellum enzyme expression during parasitism of the cotton root rot pathogen Phymatotrichopsis omnivora.

The present study determined the activity of hydrolytic enzymes and the gene expression during direct interaction of the novelTrichoderma asperellumstrains TC74 (high antagonistic capacity) and Th1 (low antagonistic capacity) with the plant pathogenic fungusPhymatotrichopsis omnivora. TheT. asperellumstrains produced the lytic enzymes endochitinase, N-acetylglucosaminidase and ß-1,3-glucanase when grown on two different carbon sources. The response of strain TC74 was more rapid than that of strain Th1. When directly exposed toP. omnivora, theT. asperellumstrains expressed one endochitinase and one N-acetylglucosaminidase, as shown by RT-PCR experiments. The strains also expressed two ß-1,3-exoglucanases (designated as exg290 and exg343). TC74 and Th1 were able to express their chitinases and ß-1,3-exoglucanase activities when grown on the different carbon sources tested. When theT. asperellumstrains were grown in the presence ofP. omnivora, qRT-PCR experiments revealed that mycoparasitism-related genes were first expressed prior to contact between the antagonist and the pathogen's mycelium. As a general response, the transcription level of these genes was increased at the post-contact stage. Although TC74 and Th1 both express the assayed genes when grown in direct contact withP. omnivora, significant differences in the time, intensity and kinetics of the response were observed.

Enzyme activity of extracellular protein induced in Trichoderma asperellum and T. longibrachiatum by substrates based on Agaricus bisporus and Phymatotrichopsis omnivora.

Antagonistic Trichoderma spp. are used throughout the world for the biological control of soil-borne plant diseases. This approach has stimulated an on-going search for more efficient mycoparasitic strains with a high potential for producing extracellular lytic enzymes. This study compares the production of lytic enzymes by native strains of Trichoderma asperellum and Trichoderma longibrachiatum on substrates of differing complexity. The quantity of protein induced by Agaricus bisporus-based medium was higher than that induced by Phymatotrichopsis omnivora-based medium. In P. omnivora medium, T. asperellum exhibited higher chitinolytic and ß-1,3-glucanolytic activities than T. longibrachiatum. The enzyme profile was related to the previously reported ability of these strains to inhibit the growth of several soil-borne plant pathogens. NAGase production was similar among the tested indigenous strains of T. longibrachiatum; T479 and T359 produced more endochitinase, T479 produced more glucanase, and T341 and T359 produced more ß-1,3-glucanase. The detected variations in glucanase and ß-1,3-glucanase activities suggest that the production of these enzymes is strongly influenced by the substrate. Strains T397 and T359 exhibited xylanase activity, which triggers defence mechanisms in plants. Thus, these strains may utilise an additional mechanism of biocontrol.