RESUMO
Soil microbial communities are key players of ecosystem processes and important for crop and soil health. The Humid Pampas region in Argentina concentrates 75% of the national soybean production, which is based on intensive use of agrochemicals, monocropping and no-till. A long-term field experiment under no-till management in the southeast of the Argentinean Pampas provides a unique opportunity to compare soybean under monocropping with cultivation including alternating cover crops or in a three-phase rotation. We hypothesized that cropping regimes and season affect soil microbial community composition and diversity. Amplicon sequencing of 16S rRNA genes and internal transcribed spacer fragments showed a stronger microbial seasonal dynamic in conservation regimes compared to monocropping. In addition, several bacterial (e.g. Catenulispora, Streptomyces and Bacillus) and fungal genera (e.g. Exophiala) with cropping regime-dependent differential relative abundances were identified. Despite a temporal shift in microbial and chemical parameters, this study shows that long-term cropping regimes shaped the soil microbiota. This might have important implications for soil quality and soybean performance and should therefore be considered in the development of sustainable agricultural managements.
Assuntos
Microbiota , Solo , Argentina , RNA Ribossômico 16S/genética , Microbiologia do Solo , Glycine maxRESUMO
Species of the genus Trichoderma are economically important as biocontrol agents, serving as a potential alternative to chemical control. The applicability of Trichoderma isolates to different ecozones will depend on the behavior of the strains selected from each zone. The present study was undertaken to isolate biocontrol populations of Trichoderma spp. from the Argentine wheat regions and to select and characterize the best strains of Trichoderma harzianum by means of molecular techniques. A total of 84 out of the 240 strains of Trichoderma were able to reduce the disease severity of the leaf blotch of wheat. Thirty-seven strains were selected for the reduction equal to or greater than 50% of the severity, compared with the control. The percentage values of reduction of the pycnidial coverage ranged between 45 and 80%. The same last strains were confirmed as T. harzianum by polymerase chain reaction amplification of internal transcribed spacers, followed by sequencing. Inter-simple sequence repeat was used to examine the genetic variability among isolates. This resulted in a total of 132 bands. Further numerical analysis revealed 19 haplotypes, grouped in three clusters (I, II, III). Shared strains, with different geographical origins and isolated in different years, were observed within each cluster. The origin of the isolates and the genetic group were partially related. All isolates from Paraná were in cluster I, all isolates from Lobería were in cluster II, and all isolates from Pergamino and Santa Fe were in cluster III. Our results suggest that the 37 native strains of T. harzianum are important in biocontrol programs and could be advantageous for the preparation of biopesticides adapted to the agroecological conditions of wheat culture.
Assuntos
Antibiose , Controle Biológico de Vetores/métodos , Doenças das Plantas/prevenção & controle , Trichoderma/isolamento & purificação , Trichoderma/fisiologia , Triticum , Argentina , DNA Fúngico/química , DNA Fúngico/genética , DNA de Plantas/química , DNA de Plantas/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , Trichoderma/classificação , Trichoderma/genéticaRESUMO
Fusarium Head Blight is an important wheat disease in the Argentine Pampas region, being Fusarium graminearum the predominant pathogen. DNA polymorphism of the isolates was analyzed by IGS-RFLP and ISSR. IGS-RFLP and ISSR profiling were carried out using six endonucleases and eight primers, respectively. IGS-RFLP yielded 41 bands, 30 of which were polymorphic while ISSR produced 87 bands with 47 polymorphic bands. Both markers showed genetic variability among the analyzed isolates; however, IGS-RFLP was more efficient than ISSR, showing a higher polymorphic average (59.91%) than the latter (44.11%). The averages of polymorphic information content (PIC) were 0.211 and 0.129, respectively. Twenty haplotypes were identified by IGS-RFLP and 15 haplotypes by ISSR. Genotype clustering within dendrograms was different for both types of markers. The genetic groups obtained by IGS-RFLP showed a partial association to geographic origin. This is the first report on genetic variability of F. graminearum isolates from wheat in Argentina using IGS-RFLP and ISSR markers.
Assuntos
Fusarium/genética , Doenças das Plantas/microbiologia , Triticum/microbiologia , Argentina , DNA Fúngico/genética , DNA Fúngico/isolamento & purificação , DNA Intergênico , Fusarium/isolamento & purificação , Genes Fúngicos , Marcadores Genéticos , Variação Genética , Genótipo , Haplótipos/genética , Repetições de Microssatélites , Polimorfismo de Fragmento de RestriçãoRESUMO
La fusariosis de la espiga de trigo es una importante enfermedad para la región pampeana Argentina; Fusarium graminearum es el principal patógeno asociado. Se estudió el polimorfismo del ADN de un conjunto de aislamientos utilizando las técnicas de IGS-RFLP e ISSR. La técnica de IGS-RFLP produjo 41 bandas, 30 de ellas fueron polimórficas. El análisis de los ISSR mostró 87 bandas con 47 bandas polimórficas. La primera de estas metodologías fue más eficiente, ya que detectó mayor promedio polimórfico (59,91%) que la segunda (44,11%). Los valores promedio del contenido de información polimórfica (PIC) fueron 0,211 y 0,129, respectivamente. Se identificaron 20 haplotipos por IGS-RFLP, mientras que el análisis de los ISSR reveló 15 haplotipos. La agrupación de genotipos obtenida en ambos dendrogramas fue diferente. Los grupos genéticos obtenidos por la técnica de IGS-RFLP mostraron una asociación parcial con el origen geográfico. Este es el primer reporte que analiza la variabilidad genética en poblaciones de F. graminearum de trigo empleando marcadores IGS-RFLP e ISSR en Argentina
Fusarium Head Blight is an important wheat disease in the Argentine Pampas region, being Fusarium graminearum the predominant pathogen. DNA polymorphism of the isolates was analyzed by IGS-RFLP and ISSR. IGS-RFLP and ISSR profiling were carried out using six endonucleases and eight primers, respectively. IGS-RFLP yielded 41 bands, 30 of which were polymorphic while ISSR produced 87 bands with 47 polymorphic bands. Both markers showed genetic variability among the analyzed isolates; however, IGS-RFLP was more efficient than ISSR, showing a higher polymorphic average (59.91%) than the latter (44.11%). The averages of polymorphic information content (PIC) were 0.211 and 0.129, respectively. Twenty haplotypes were identified by IGS-RFLP and 15 haplotypes by ISSR. Genotype clustering within dendrograms was different for both types of markers. The genetic groups obtained by IGS-RFLP showed a partial association to geographic origin. This is the first report on genetic variability of F. graminearum isolates from wheat in Argentina using IGS-RFLP and ISSR markers