Abstract:

Non-linear regression (NLR) techniques are used widely to fit weed field emergence patterns to soil microclimatic indices using S-type functions. Artificial neural networks (ANNs) present interesting and alternative features for such modelling purposes. In the present work, a univariate hydrothermal-time based Weibull model and a bivariate (hydro-time and thermal-time) ANN were developed to study wild oat emergence under non-moisture restriction conditions using data from different locations worldwide. Results indicated a higher accuracy of the neural network in comparison with the NLR approach due to the improved descriptive capacity of thermal-time and the hydro-time as independent explanatory variables. The bivariate ANN model outperformed the con- ventional Weibull approach, in terms of RMSE of the test set, by 70·8%. These outcomes suggest the potential applicability of the proposed modelling approach in the design of weed management decision support systems.

Author affiliation: Chantre Balacca, Guillermo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina

Author affiliation: Blanco, Anibal Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (i); Argentina

Author affiliation: Forcella, F.. United States Department Of Agriculture. Agricultural Research Service; Argentina

Author affiliation: Van Acker, R. C.. University Of Guelph; Canadá

Author affiliation: Sabbatini, Mario Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina

Author affiliation: González Andújar, J. L.. Consejo Superior de Investigaciones Cientificas. Instituto de Agricultura Sostenible; España

Abstract:

Para comparar la capacidad de predecir ciclo, rendimiento comercial y diámetro de la pella de modelos de tiempo térmico con modelos basados en temperaturas;se analizaron los rangos térmicos registrados en 11 siembras del híbrido Legacy. Se establecieron 49 combinaciones de temperaturas máximas y mínimas y siete temperaturas mínimas sin umbral superior, para calcular días grado a través del programa Degree Day Utility (DDU) 2.3. Se realizó la regresión de ciclo, rendimiento y diámetro con los días grado y con las temperaturas. Los modelos de tiempo térmico con mayor coeficiente de determinación para rendimiento (R2=0,56) y diámetro (R2=0,53) utilizaron los días grado acumulados desde transplante a diferenciación floral, y los umbrales 10-21 °C y 10-24 °C, respectivamente.Para ciclo, el mejor modelo de tiempo térmico (R2=0,51) incluyó los días grado acumulados entre diferenciación floral y madurez y los umbrales 7-23 °C.Los modelos que utilizaron las temperaturas sin transformar estimaron con mayor precisión los parámetros evaluados que los modelos de tiempo térmico. Los que incluyeron temperaturas medias tuvieron los mayores R2: para rendimiento (R2=0,60) y diámetro (R2= 0,72) participaron los valores medios registrados entre transplante y madurez y para ciclo (R2=0,90) los observados entre diferenciación floral y madurez.

In order to compare the ability of thermal time models based on degree day vs. temperature models to predict cycle, commercial yield and spear diameter; we studied temperature ranges in 11 sowings of the hybrid Legacy. We set up seven minimum temperatures without upper thresholds and 49 minimum and maximum temperature combinations to calculate degree day through the software Degree Day Utility (DDU) 2.3. Cycle, yield and diameter were regressed on degree day and on temperatures. The thermal time models with the highest R2 included degree day in the period transplant-flower differentiation, and the thresholds 10-21° C for yield (R2=0.56) and 10-24° C for diameter (R2=0.53). The best thermal time model to explain the variability in cycle (R2=0.51) included degree day in the period flower differentiation-maturity and the thresholds 7-23° C. The parameters were more precisely estimated by temperature models than by thermal time models. Those including medium temperatures had the largest R2. Yield (R2=0.60) and diameter (R2= 0.72) models included medium temperatures in the period transplant-maturity; and cycle (R2=0.90) models included medium temperatures in the period flower differentiation-maturity.

EEA San Pedro

Author affiliation: Francescangeli, Nora. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentina

Author affiliation: Stoppani, María Inés. Profesional de actividad privada. San Pedro; Argentina

Author affiliation: Martí, Héctor Rubén. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentina

Abstract:

David’s Spurge is an spring-summer annual weed, present in the central area of Buenos Aires Province, Argentina. Field studies were carried out during 2011/12 and 2013/14 to assess demography and population dynamics and determine a thermal time scale of this species. At the experimental site, 1 m² quadrants were established as observational plots, four per cohort. The number of individuals at each phenological stage and from each cohort was recorded weekly. At the end of the experiment, all plots were harvested, and seed production was determined. A thermal time scale was established to identify the occurrence of the different phenological events. Three cohorts were detected, the first one emerged in midOctober, the second one in early November, and the last cohort varied from late November till early January, totalling an average of 1,500 m-2. Over 80% of the evaluated emergences belonged to the first and second cohorts in both periods. Thermal time requirements calculated to reach the 2-4 leaves, 6-8 leaves, branching, and flowering stages, were 192, 370, 515 and 1,155 o Cd, respectively. Average seed production in the first, second and third cohort was 5,700, 6,400 and 1,900 seeds m-2, respectively. However, the total number of propagules from the sum of the three cohorts was similar in both years, about 14,000 seeds m-2. Results from this study will foster a better understanding of the ecophysiology of Euphorbia davidii in the study area, and it may be a valuable contribution from an integrated weed management perspective.

O eufórbio lactífero (em inglês, “David’s Spurge”) é uma planta daninha anual de primavera-verão presente na região central da província de Buenos Aires, Argentina. Estudos de campo foram realizados durante os anos de 2011/12 e 2013/14 para avaliar a demografia e a dinâmica de população, bem como para estabelecer uma escala de tempo térmico para essa espécie. No local do experimento, quatro parcelas de 1 m² foram marcadas para cada coorte de indivíduos. O número de indivíduos de cada coorte, em cada estado fenológico, foi registrado semanalmente. Ao final do experimento, todas as parcelas foram colhidas, e a produção de sementes foi determinada. Uma escala de acumulação de tempo térmico foi estabelecida para identificar a ocorrência de diferentes eventos fenológicos. Foram detectadas três coortes: a primeira surgiu em meados de outubro; a segunda, no início de novembro; e a última, entre o final de novembro e o início de janeiro, totalizando uma média de 1.500 plantas m-2. Mais de 80% das emergências registradas pertenciam à primeira e segunda coortes nos dois períodos de estudo. Os requisitos de tempo térmico calculados para atingir os estádios de 2-4 folhas, 6-8 folhas, ramificação e floração foram de 192, 370, 515 e 1.155 oCd, respectivamente. O rendimento médio na primeira, segunda e terceira coortes foi de 5.700, 6.400 e 1.900 sementes m-2, respectivamente, determinando um número total de mudas de aproximadamente 14.000 sementes m-2, com a soma das três coortes. Os resultados deste estudo permitirão uma melhor compreensão da ecofisiologia de Euphorbia davidii na área de estudo e representarão uma valiosa contribuição para a gestão integrada desta espécie.

Author affiliation: Núñez Fré, F.R.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Author affiliation: Juan, Victor Fabian. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Saint André, H.M.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Chantre Balacca, Guillermo Ruben. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Abstract:

Physical dormancy (PY) has a crucial role in the control of the reseeding process of Vicia villosa Roth, a winter annual species cultivated for pasture and hay, naturalized in several semiarid temperate agroecosystems. As PY is considered a seed trait modulated under natural selection, populations from different origins should show different responses to environmental regulatory factors. The present study aimed to determine the effect of: (i) water availability on PY-break dynamics of a naturalized population from Argentina (ASC) under both laboratory and field conditions; (ii) the seed source on initial PY and dormancy release rate (wet storage at 20ºC) of ASC compared to 45 other populations of V. villosa including wild, naturalized, landraces and cultivars. Water availability increased PY loss rate under both storage and field conditions. ASC PY-break dynamics was adequately described by a Gompertz model with a lower thermal time requirement estimated for dormancy break under fluctuating soil water conditions compared to seeds buried inside impermeable bags. During the field burial experiment, a considerable proportion of seeds (~ 70%) became water permeable during the summer season after dispersal, and retained low levels of residual PY for soil seed bank replenishment. Improved populations (i.e. breeding cultivars) showed the lowest percentages of initial PY compared to landraces, naturalized and wild populations. Naturalized populations of Argentina showed similar initial PY compared to landraces, although PY release rate was lower in the former and might be attributed to local environmental selection. Wild types showed the lowest PY release rates.

Author affiliation: Renzi, Juan Pablo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Hilario Ascasubi; Argentina

Author affiliation: Chantre Balacca, Guillermo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentina

Author affiliation: Cantamutto, Miguel Angel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Hilario Ascasubi; Argentina

Abstract:

Olive production has expanded significantly from the Mediterranean Basin into the New World over the last two decades. In some cases, cultivars of European origin have been introduced at a large commercial scale with little previous evaluation of potential productivity. The objective of this study was to evaluate whether a temperature-driven simulation model developed in the Mediterranean Basin to predict normal flowering occurrence and flowering date using cultivar-specific thermal requirements was suitable for the low latitude areas of Northwest Argentina. The model was validated at eight sites over several years and a wide elevation range (350–1200 m above mean sea level) for three cultivars (‘Arbequina’, ‘Frantoio’, ‘Leccino’) with potentially different chilling requirements. In ‘Arbequina’, normal flowering was observed at almost all sites and in all years, while normal flowering events in ‘Frantoio’ and ‘Leccino’ were uncommon. The model successfully predicted if flowering would be normal in 92% and 83% of the cases in ‘Arbequina’ and ‘Frantoio’, respectively, but was somewhat less successful in ‘Leccino’ (61%). When flowering occurred, the predicted flowering date was within ± 7 days of the observed date in 71% of the cases. Overall, the model results indicate that cultivar-specific simulation models may be used as an approximate tool to predict whether individual cultivars will be successful in new growing areas. In Northwest Argentina, the model could be used to identify cultivars to replace ‘Frantoio’ and ‘Leccino’ and to simulate global warming scenarios.

Author affiliation: Aybar, Vanesa E.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Catamarca-la Rioja. Estación Experimental Agropecuaria Catamarca; Argentina

Author affiliation: Melo Abreu, J. Paulo De. Universidade de Lisboa. Instituto Superior de Agronomia; Portugal

Author affiliation: Searles, Peter Stoughton. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; Argentina

Author affiliation: Matias, Angel C.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Catamarca-La Rioja. Estación Experimental Agropecuaria Catamarca; Argentina

Author affiliation: del Río, Carmen. Instituto de Investigación y Formación Agraria y Pesquera; España

Author affiliation: Caballero, Juan M.. Instituto de Investigación y Formación Agraria y Pesquera; España

Author affiliation: Rousseaux, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; Argentina

Abstract:

In the mid 1970s, there was a shift in peanut cultivars used in Argentina, from cultivars with erect growth habit (CEGH) to those with procumbent growth habit (CPGH), which improved seed yield, but also lengthened growth cycle. However, there is no information on (i) the partitioning of thermal time (TT) requirements between vegetative and reproductive phases, as well as between reproductive sub-phases representative of the seed set and seed-filling periods, and (ii) the effect of developmental changes on growth traits. Field experiments were performed to compute TT, grain yield determinants (i.e., seed number and seed weight), and other related physiological traits. Eight cultivars released between 1948 and 2004 were evaluated. The introduction of CPGH produced a lengthening (31%) of peanut growth cycle (S–R8), which was more pronounced for the reproductive phase (+39% for R1–R8) than for the vegetative phase (+17% for S–R1). This trend held for pod-set (R3–R6.5: +37%) and seed filling (R5–R8: +57%) sub-phases. It also held (CPGH > CEGH) for the rate of flower production (+80%), total flower number (+36%) and number of pods per plant (+117%), and consequently for the fertility index (+56%). The enhanced seed number of CPGH was related to (r2 = 0.55, P < 0.001) the variation in crop growth rate during the seed set period (CGRR3–R6.5), but not to the duration of this period. Variations in CGRR3–R6.5 were partially explained by differences in cumulative IPAR, which were linked to the duration of the R3–R6.5 period as well as to maximum light interception fraction. These trends may have management as well as breeding origins. Introduction of the procumbent habit enhanced seed weight (CPGH > CEGH) and seed-filling duration markedly, but had no effect on seed-filling rate. Seed weight, however, was positively related to this rate (P < 0.01) and exhibited a negative trend in response to the duration of the period. Lack of source limitations on seed filling suggest that future breeding efforts should focus on the increase of seed numbers and the reduction of seed filling duration.

Author affiliation: Haro, Ricardo J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi; Argentina

Author affiliation: Baldessari, Jorge. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi; Argentina

Author affiliation: Otegui, Maria Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Abstract:

Models based on thermal-time approaches have been a useful tool for characterizing and predicting seed germination and dormancy release in relation to time and temperature. The aims of the present work were to evaluate the relative accuracy of different thermal-time approaches for the description of germination in Lithospermum arvense and to develop an after-ripening thermal-time model for predicting seed dormancy release.

Author affiliation: Chantre Balacca, Guillermo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Author affiliation: Batlla, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Sabbatini, Mario Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Author affiliation: Orioli, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Abstract:

Sunflower genotypes with increased concentration of stearic and oleic acids have been developed to fulfil industrial specific requirements. Fatty acid composition of membranes has been widely described to affect seed germination, but the effect of composition of reserve lipids on germination is still unknown. Two experiments were conducted including: traditional (high linoleic), high stearic–high oleic, high stearic–high linoleic and high oleic genotypes. Thermal and hydrotime analyses were performed on germination data obtained from the incubation of seeds at different temperatures and water potentials. Fatty acid composition affected the parameters values of thermal time model. Base temperature was inversely related to linoleic acid concentration. Genotypes with high linoleic acid concentration germinated earlier at low temperatures, while no significant differences among genotypes at temperatures above 15 °C were found. High stearic–high oleic genotypes showed lower thermal time requirement for 50% germination than traditional and high stearic–high linoleic genotypes. The parameters of hydrotime model were not affected by fatty acid composition, but at low water potentials and high temperatures thermo-dormancy was induced and strongly reduced final seed germination in all genotypes studied. In conclusion, breeding for higher oleic acid and lower linoleic acid concentration in sunflower oil may affect seed germination performance at low temperatures.

Author affiliation: González Belo, Raúl. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Author affiliation: Tognetti, Jorge Alberto. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Author affiliation: Benech-arnold, Roberto Luis. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Izquierdo, Natalia Gabriela. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

The possibility of accurately predicting timing and extent of seedling emergence from natural seed soil banks has long been an objective of both ecologist and agriculturalist. However, as dormancy is a common attribute of many wild seed populations, we should first be able to predict dormancy changes if we intend to predict seedling emergence in the field. In this paper, we discuss the most relevant environmental factors affecting seed dormancy of natural seed soil banks, and present a conceptual framework as an attempt to understand how these factors affect seed-bank dormancy level. Based on this conceptual framework we show approaches that can be used to establish quantitative functional relationship between environmental factors regulating dormancy and changes in the seed-bank dormancy status. Finally, we briefly explain how we can utilize population-based threshold models as a framework to characterize and quantify changes in seed sensitivity to environmental factors as a consequence of dormancy loss and/or induction. © 2010 Springer Science+Business Media B.V.

Author affiliation: Batlla, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Benech-Arnold, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Abstract:

Seeds integrate environmental cues that modulate their dormancy and germination.Although many mechanisms have been identified in laboratory experiments, their contribu-tion to germination dynamics in existing communities and their involvement in definingspecies habitats remain elusive.By coupling mathematical models with ecological data we investigated the contribution ofseed temperature responses to the dynamics of germination of three Nothofagus species thatare sharply distributed across different altitudes in the Patagonian Andes.Seed responsiveness to temperature of the three Nothofagus species was linked to the ther-mal characteristics of their preferred ecological niche. In their natural distribution range, therewas overlap in the timing of germination of the species, which was restricted to mid-spring.By contrast, outside their species distribution range, germination was temporally uncoupledwith altitude. This phenomenon was described mathematically by the interplay between inter-specific differences in seed population thermal parameters and the range in soil thermic envi-ronments across different altitudes.The observed interspecific variations in seed responsiveness to temperature and its environ-mental regulation, constitute a major determinant of the dynamics of Nothofagus germinationacross elevations. This phenomenon likely contributes to the maintenance of patterns ofspecies abundance across altitude by placing germinated seeds in a favorable environment forplant growth

Author affiliation: Arana, Maria Veronica. Instituto Nacional de Tecnologia Agropecuaria. Centro Reg.patagonia Norte. Estacion Exptal.agrop.s.c.de Bariloche; Argentina

Author affiliation: Gonzalez Polo, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina

Author affiliation: Martinez Meier, Alehandro. Instituto Nacional de Tecnologia Agropecuaria. Centro Reg.patagonia Norte. Estacion Exptal.agrop.s.c.de Bariloche; Argentina

Author affiliation: Gallo, Leonardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina

Author affiliation: Benech-arnold, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Sánchez, Roberto Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Batlla, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina