Influencia de las altas temperaturas, la baja luminosidad y la época de siembra sobre el comportamiento fisiológico de dos cultivares de arroz (Oryza sativa L.)

Este trabajo se desarrolló en el Centro de Investigación Las Lagunas de Fedearroz en Saldaña-Colombia, durante los años 2010 y 2011. El primer ensayo consistió en la evaluación de la respuesta fisiológica de las variedades colombianas F50 y F733, a una condición de altas temperaturas (40ºC). La tasa de fotosíntesis disminuyó en los tratamientos de estrés térmico y el efecto fue mayor en F50; la conductancia estomática se vionegativamente afectada por el estrés térmico, mientras que el contenido de clorofila y la máxima eficiencia del PSII (Fv/Fm) no se vieron alterados. La etapa de floración fue la más sensible a altas temperaturas. El segundo ensayo mostró la influencia negativa de la baja luminosidad sobre la tasa de fotosíntesis y la conductancia estomática de las dos variedades. Los valores de clorofila se incrementaron bajo sombra, mientras que Fv/Fm no sufrió alteraciones. En el tercer ensayo se comparó el crecimiento y producción de las dos variedades en tres épocas de siembra. Se encontró una alta correlación de la radiación con la producción de biomasa y grano, así como el beneficio de la mayor producción de biomasa en las etapas finales de cultivo. El efecto fue más evidente en F733.Abstract. Three experiments was performed in El Centro Experimental “Las Lagunas” in Saldaña-Colombia during 2010 and 2011. First and second trials estimated the effect ofthe stress by high temperature (40ºC) and low light intensity (LI) on two Colombian cultivar (ꜞF50ꜞ and ꜞF733ꜞ)at different phenological stages (Initiation of panicle (IP), flowering (F) and Grain filling (GF)). Photosynthesis rate was negatively affected by the thermal stress; the effect was most notorious inꜞ F50ꜞ, causing a diminishing around 50%. Stomatal conductance was also diminished in two cultivars due to high temperature. However, chlorophyll content and maxim efficiency of PSII (Fv/Fm) was not affected. F stage was the most sensitive to the high temperature, causing a percentage of spikelet sterility around 80% and 60% in ꜞF50ꜞ and ꜞF733ꜞ, respectively. Second trialshowed that LI caused a reduction of photosynthesis rate and the stomatal conductance in both cultivars. SPAD readings were higher in plant under LI conditions. Third trial compared the influence of three different sowing dates on the growth and productivity of two cultivars. Biomass and grain yield were highly correlated with solar radiation. The accumulation of biomasswas higher during GF phase in plants planted during growth season 1 (plants sowed on December 1St),being F733 the cultivar that showed a better behavior.Maestrí

Relación de Burkholderia glumae con el rendimiento del cultivo del arroz en Colombia

El vaneamiento del cultivo del arroz viene causando pérdidas en la producción de Colombia. Este hecho se asocia con el reporte hecho en cultivos comerciales de arroz del Caribe Húmedo Colombiano con la enfermedad conocida como añublo bacterial de la panícula causada por la bacteria Burkholderia glumae. Se estudió la relación entre la presencia de la bacteria con la disminución en el rendimiento del cultivo

Physiological Response of Rice Seedlings (Oryza sativa L.) Subjected to Different Periods of Two Night Temperatures

Night temperatures have shown an increase in rice-growing regions due to climate change in Colombia in recent years, causing a reduction in grain yield. The objective of this research was to study the effect of four different periods of exposure to two night temperatures (24°C vs. 30°C) on the physiological behavior of an Indica rice cultivar widely grown in Colombia. Fedearroz 60 (ʻF60ʼ) were grown under greenhouse conditions for forty-five days. After this period, 12 plants in each treatment was established in a growth chamber at 30°C from 18:00 to 24:00 to carry out the duration of the different periods of heat nighttime stress (4, 8, 12, and 16 days respectively). The control plants were kept in a greenhouse at 24°C. The results showed that leaf photosynthesis, carboxylation efficiency, and pigment content decreased in rice seedlings subjected to 30°C. Also, dark respiration and intercellular CO2 concentration increased. These reductions in the variables as mentioned above were more severe during the first four days of exposure to 30°C than 24°C. In conclusion, these results suggest that these physiological variables may be useful to assess the tolerance of rice plants to high nighttime temperatures in plant breeding programs

How does El Niño Southern Oscillation affect rice-producing environments in central Colombia?

International audienceThe rice industry plays an important role in the agricultural economy of Colombia and its success dependents largely on weather conditions. Rice farmers, policymakers and other stakeholders thus need to understand and manage the risks associated with climate variability, including those related to El Nino Southern Oscillation (ENSO) - the most important source of variability affecting Colombian climates. The objectives of this study were to (1) assess the ENSO influence on the spatio-temporal variability of agro-climatic conditions (crop water requirements, dry and wet spells, and heatwaves) and rice yield across the central producing region of Colombia; and (2) identify the main agro-climatic factors driving crop yield variability. Results showed that rice irrigation water requirements under positive ENSO phases (El Nino) increased by up to 14% compared to the long-term average. These increases were associated with less total precipitation, more dry days and longer dry spells, together with a greater number of day-and-night heatwave episodes. During negative phases (La Nina), on the other hand, irrigation requirements decreased by 16% with respect to the long-term average due to longer and more frequent wet spells, and more total precipitation. Analyses of simulated yields indicated that El Nino years reduce crop yield in about 86% of the study region, while La Nina affects 62% of the region positively. The number of heat nights (i.e. nights with minimum temperature > 23 degrees C) during the growing season was the most important agro-climatic factor causing yield losses during ENSO events. Our results represent an important step towards understanding the interaction between climate variability and rice production in Colombia, which is useful for improving climate risk management at local levels

Assessing weather-yield relationships in rice at local scale using data mining approaches

Seasonal and inter-annual climate variability have become important issues for farmers, and climate change has been shown to increase them. Simultaneously farmers and agricultural organizations are increasingly collecting observational data about in situ crop performance. Agriculture thus needs new tools to cope with changing environmental conditions and to take advantage of these data. Data mining techniques make it possible to extract embedded knowledge associated with farmer experiences from these large observational datasets in order to identify best practices for adapting to climate variability. We introduce new approaches through a case study on irrigated and rainfed rice in Colombia. Preexisting observational datasets of commercial harvest records were combined with in situ daily weather series. Using Conditional Inference Forest and clustering techniques, we assessed the relationships between climatic factors and crop yield variability at the local scale for specific cultivars and growth stages. The analysis showed clear relationships in the various location-cultivar combinations, with climatic factors explaining 6 to 46% of spatiotemporal variability in yield, and with crop responses to weather being non-linear and cultivar-specific. Climatic factors affected cultivars differently during each stage of development. For instance, one cultivar was affected by high nighttime temperatures in the reproductive stage but responded positively to accumulated solar radiation during the ripening stage. Another was affected by high nighttime temperatures during both the vegetative and reproductive stages. Clustering of the weather patterns corresponding to individual cropping events revealed different groups of weather patterns for irrigated and rainfed systems with contrasting yield levels. Best-suited cultivars were identified for some weather patterns, making weather-site-specific recommendations possible. This study illustrates the potential of data mining for adding value to existing observational data in agriculture by allowing embedded knowledge to be quickly leveraged. It generates site-specific information on cultivar response to climatic factors and supports on-farm management decisions for adaptation to climate variability

Boxplots of the yield distributions by cultivar in Saldaña.

<p>(a) Cluster 2 and (b) cluster 10. Cultivars are sorted from left to right in decreasing order of yield median value. Lowercase letters above the boxplots show the results of the Kruskal-Wallis test, with statistically similar cultivars grouped by the same letter.</p

Boxplots of conditional permutation based VI scores using CIF for specific cultivars.

<p>In Saldaña for (a) cultivars F733 and (b) F60, and in Villavicencio for (c) cultivar F174. Lowercase letters to the right of the boxplots show the results of the Kruskal-Wallis test, with statistically similar variables grouped by the same letter.</p

List of the variables used in the models.

<p>List of the variables used in the models.</p