Detection of the mosquitocidal toxin genes encoding Cry11 proteins from Bacillus thuringiensis using a novel PCR-RFLP method Detección de genes que codifican proteínas mosquitocidas Cry11 de Bacillus thuringiensis mediante un método de PCR-RFLP novedoso

A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for detection of cry11 genes from Bacillus thuringiensis was established. Based on the analysis of conserved regions of the cry11 genes, 2 oligonucleotide primers were designed to amplify a 1459-bp fragment of the cry11Aa gene, and a 1471-bp of the cry11Ba and cry11Bb genes. The amplification products were digested with restriction endonuclease HinfI. Exotic B. thuringiensis strains and native isolates collected from soils, leaves and stored product dust of Argentina were analyzed to study the distribution of cry11 genes. The PCR-RFLP patterns revealed the detection of cry11 genes in 3 of 64 exotic strains and in 10 of 107 native B. thuringiensis isolates tested. Just the cry11Aa gene subclass was detected among these bacteria. Since the methodology was also developed to detect cry11Ba and cry11Bb genes, an experimental future confirmation will be required. Based on the results obtained, the PCR-RFLP method presented may be a valuable tool for specific detection of the mosquitocidal toxin genes encoding Cry11 proteins from B. thuringiensis.<br>En el presente estudio se estableció una estrategia basada en la amplificación génica (PCR) y el posterior análisis de restricción (RFLP) para detectar todos los genes cry11 de Bacillus thuringiensis informados hasta ahora. De acuerdo con el análisis de las regiones conservadas en los genes cry11, se diseñaron dos cebadores para amplificar un fragmento de 1459 pb de los genes cry11Aa y un fragmento de 1471 pb de los genes cry11Ba y cry11Bb. Los productos de la amplificación fueron digeridos con la enzima de restricción HinfI. Se analizaron cepas exóticas de B. thuringiensis y aislamientos nativos de Argentina obtenidos a partir de muestras de suelos, hojas y polvillo de silos, para estudiar la distribución de los genes cry11. Los patrones de PCR-RFLP revelaron la presencia de genes cry11 en 3 de las 64 cepas exóticas y en 10 de los 107 aislamientos nativos de B. thuringiensis ensayados. Sólo se detectó la subclase cry11Aa entre estas bacterias. Ya que esta metodología fue también desarrollada para detectar genes cry11Ba y cry11Bb, se requeriría una futura confirmación experimental. Los resultados obtenidos nos permiten inferir que el método de PCR-RFLP constituiría una herramienta valiosa para la detección específica de genes que codifican proteínas mosquitocidas Cry11 de B. thuringiensis

Long-term fertilizer application and cover crops improve soil quality and soybean yield in the Northeastern Pampas region of Argentina

Long-term improvements in soil quality through cover crops (CC) and fertilizer management may provide resilience for temporal water stresses in cropping sequences based on soybean [Glycine max (L.) Merr.]. The objectives of this work were: i) to evaluate the combined effects of CC and fertilizer use on soil properties and ii) to relate soil properties with soybean grain yield in different cropping sequences and contrasting rainfall regimes. Six treatments, combining cropping sequences – fertilization strategy, were studied: soybean monocropping (Sy), fertilized soybean monocropping (Syf), CC/soybean (CC/Sy), CC/fertilized soybean (CC/Syf), N-fertilized CC/fertilized soybean (CCN/Syf), and N-fertilized CC/fertilized soybean in a crop rotation of CCN/Syf-wheat/soybean - maize (CCN/Syf rot). Soil samples were collected in 2015 and 2016 from the 0–5 and 0–15 cm depth intervals, in a long-term field experiment under no-tillage in Paraná, Argentina. Soybean grain yield and soil properties were determined. In both depths, all soil properties increased in treatments that included winter CC (except for CC/Sy). In addition, the soybean yield was 15% greater in treatments that included winter CC and fertilizer use than in monocropping treatments. The CC/Sy treatment performed similarly to soybean monocropping. Under more favorable rainfall conditions, only the soybean yield in CC/Sy was reduced. However, under unfavorable rainfall conditions, the negative effects of the soybean monoccropping were mitigated including CC and fertilization. Significant positive correlations (P < 0.05) between soybean yield and soil properties were found in the average rainfall season, mainly in the 0–5 cm depth. The study highlights the importance of combining high cropping intensity with adequate fertilizer use to maintain or improve the soil quality and, consequently, the soil resilience under reduced water availability.EEA ParanáFil: Fontana, Marianela B. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Novelli, Leonardo Esteban. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sterren, María A. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Uhrich, Walter G. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Benintende, Silvia M. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Barbagelata, Pedro Anibal. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad Ciencias Agropecuarias; Argentin

Cover crop benefit bacteria and increase aggregate-associate soil C and N storage

The aim of this study was to analyze the effect of four crop sequences with different aboveground biomass and crop residue biochemical composition on biological soil variables, fractions of soil organic matter, and soil aggregation. The study was carried out in a long-term experiment under no-till, in the Argentinean Pampas (31°51′ S; 60°32′ W), on an Aquic Argiudoll. The treatments were: i) fertilized soybean monocropping (Syf), ii) winter cover crop (CC)/ fertilized soybean (CC/Syf), iii) N-fertilized winter CC/fertilized soybean (CCN/Syf), and iv) N-fertilized winter CC/fertilized soybean in a crop rotation: CCN/Syf - wheat [Triticum aestivum L.] for grain production/soybean - maize [Zea mays L.] (CCN/Syf rot). Wheat was used as winter CC. Crop residues were sampled in four moments, and were separated into different fractions. Furthermore, crop residue quality was analyzed according to Van Soest (Cellulose, Hemicellulose, Lignin, Non- structural carbohydrates), and %C and %N was also determined. In soil samples obtained at 0–5 cm depth, we determined: soil organic C, total N, particulate organic matter C and N, mineral-associated organic matter C and N, C and N stocks in different aggregate-size classes, microbial biomass C and N (MBC and MBN), fungal and bacterial biomass-C (FBC and BBC), and N released after a 7-d anaerobic incubation. From June to November, Syf exhibited slower decomposition of soybean stems and an increase in the non-identifiable residue biomass. Intensified crop sequences (i.e., with CC) increased MBC (∼38%) and BBC (∼115%), but had no effect on FBC. The BBC was positively correlated with Hemicellulose (r = 0.86, P 2000 μm were 263% and 227% greater in treatments with CC than Syf, respectively, and correlated with improvements in the MBC and MBN (r = 0.87, P < 0.001 and r = 0.88, P < 0.001, respectively), particularly the BBC. Intensification of crop sequences through the incorporation of CC provided crop residues with a higher availability of easily decomposable C compounds. This enhancement stimulated the soil biota responsible for decomposition, particularly bacteria. Our study highlights the importance of increasing cropping intensity and covering the soil with live vegetation, resulting in a healthier soil.EEA ParanáFil: Fontana, Marianela B. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Novelli, Leonardo Esteban. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Novelli, Leonardo Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sterren, María A. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Uhrich, Walter G. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Rondán, Guillermo A. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Rondán, Guillermo A. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barbagelata, Pedro Anibal. Universidad Nacional de Entre Ríos. Facultad Ciencias Agropecuarias; ArgentinaFil: Barbagelata, Pedro Anibal. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Benintende, Silvia M. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; Argentin