Caracteres fisiológicos y manejo agronómico para maximizar el rendimiento de sorgo ante diferentes tipos de estrés ambiental
Fecha
2020
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Facultad de Ciencias Agrarias-Universidad Nacional de Rosario
Resumen
El cultivo de sorgo es de gran importancia a nivel mundial, con características
favorables para afrontar diversos tipos de estrés. Además representa una gran contribución
a la sustentabilidad de los sistemas productivos por su gran aporte de biomasa luego de la
cosecha. A pesar de estas ventajas, el panorama actual engloba escasa inversión en
programas de mejoramiento, baja ganancia genética y un planteo productivo sin distinción
entre ambientes y con escaso uso de insumos. Esta situación es acentuada por la falta de
una caracterización ambiental específica para sorgo y por la falta de información sobre los
genotipos y prácticas de manejo más acordes para maximizar la producción en diferentes
ambientes. En la presente tesis se estudió la interacción genotipo por ambiente (GxA) para
rendimiento en grano y para posibles caracteres secundarios en híbridos comerciales de
sorgo. Luego, se realizó una caracterización ambiental del área productiva en términos
hídricos y térmicos, y por último se exploraron posibles estrategias de manejo para optimizar
el rendimiento de acuerdo al ambiente.
Se determinó la gran importancia de la interacción GxA para rendimiento (relación
GxA/G=3,48). Ésta fue mayor que los demás caracteres estudiados, relativos a la fenología
y a componentes numéricos y fisiológicos del rendimiento (relación GxA/G<1,05). Además,
se reconocieron caracteres con buena correlación con rendimiento, lo que indica su posible
utilización como caracteres secundarios en programas de mejoramiento. Las diferencias en
fenología entre los genotipos explicaron gran parte de la interacción GxA a través de su
influencia en el peso del grano. Esto demuestra la importancia de la fenología como atributo
secundario.
Se utilizó el modelo de simulación del cultivo APSIM-sorgo para caracterizar el
ambiente de la región central Argentina en términos hídricos y térmicos. Previo a su uso, el
modelo fue calibrado con coeficientes de genotipos locales y validado con información
independiente. El modelo simuló de manera adecuada la fenología, biomasa y rendimiento
en diversidad de condiciones de crecimiento. Se definieron tres patrones de estrés hídrico y
su frecuencia a nivel regional: (i) estrés pre-floración (39%), (ii) estrés terminal leve (38%), y
estrés en llenado de granos (23%). No se encontró un patrón predominante, lo que provoca
dificultades en la mejora genética del cultivo y a la hora de definir un manejo productivo. Se
comprobó que los patrones ayudaron a explicar las interacciones observadas de GxA para
el rendimiento en un conjunto de datos experimentales independientes, lo que demuestra la
importancia de caracterizar los ambientes objetivo y las posibilidades de adaptación
específica. Además brindó información para optimizar las prácticas de manejo en la región,
indicando una buena respuesta al uso de ciclos cortos bajo condiciones de estrés terminal
leve y la capacidad de los ciclos largos en estrés pre-floración de escapar al estrés en la
etapa más crítica, al ubicar su floración en momentos posteriores. Por otro lado, la
frecuencia de estrés térmico (umbral de 33ºC) de la región es relativamente baja
(aproximadamente tres de cada diez años). Ésta probabilidad se reduce considerablemente
cuando se evalúan umbrales mayores (36ºCy 38°C). Además, el estrés térmico no se asoció
claramente con ningún patrón de estrés hídrico.
Por último se exploraron, a través de simulaciones y luego corroborado con datos
experimentales, opciones de fecha de siembra, largo de ciclo y su interacción con los
patrones de estrés anteriormente definidos. Los resultados indicaron que, exceptuando el
Sur de la región, los productores se favorecerían al ajustar la elección de la fecha de
siembra al tipo de estrés presente. Fechas de siembra tempranas (Octubre) fueron
convenientes en los años clasificados como estrés terminal leve y estrés en llenado de
granos. En cambio, en los años en los que hubo estrés en pre-floración las fechas tardías
(Diciembre) fueron más ventajosas.
En esta tesis se generó información de utilidad para los mejoradores de sorgo en
ambientes templados, tanto por la descripción de caracteres secundarios como por la
caracterización de ambientes en términos hídricos y térmicos que permitirían hacer más
eficientes los programas de mejora. También se generaron estrategias de manejo
específicas para los patrones de estrés más frecuentes, aportando al proceso de toma de
decisiones del productor
Sorghum is grown worldwide. This crop has favorable characteristics that provides tolerance under different types of stresses. It also contributes to the sustainability of production systems due to its great amount of produced biomass. However, the current context encompasses poor investment in terms of breeding programs and management. Genetic gain is low and management is similar across the productive central region, and is mainly based on low inputs. There is lack of knowledge about which genotype and management practices are ideal to maximize production in different environments. In the present thesis, genotype by environment (GxE) interaction for grain yield and possible secondary traits were studied for sorghum commercial hybrids. Additionally, an environmental characterization in terms of water and heat stress was done for different sites across the central region. Finally, some management strategies to optimize grain yield according to the environment were explored. An important GxE interaction for grain yield was detected (ratio GxE/G=3.48). This interaction was greater than the rest of the studied traits, including phenology, physiological and numerical components (ratio GxE/G<1). Traits associated with grain yield were identified, which could be used as secondary traits in breeding programs. Genotypic differences in phenology explained a large proportion of the GxE interaction through their influence on grain weight, demonstrating the relevance of phenology as a secondary trait. The sorghum crop model of the APSIM software was used for the environmental characterization of the Argentinean central region. Prior to its use, the model was calibrated for local materials, and tested with independent information. Good fit was obtained between observed and simulated phenology, biomass and yield data. It was found that the central productive region is characterized by three water stress patterns with similar frequencies: (i) pre-flowering stress (39%), (ii) low terminal stress (38%), and (iii) grain filling stress (23%). In the context of no predominant pattern, dealing with seasonal variability in breeding programs and for defining crop managements will be challenging. Defined water stress patterns helped explain the observed GxE interactions for grain yield. This shows the relevance of characterizing target environments and the possibility of selecting for specific adaptation. In addition, this results provided information of how enhance management in the region, showing a good yield response of short maturity genotypes in low terminal stress environments, and the capacity of late maturity genotypes of avoiding pre-flowering stress by placing the flowering afterwards. Thermal stress frequency (33°C threshold) was relatively low (about 3 every 10 years). This probability is greatly reduced when considering higher thresholds (36°C). Thermal stress was not associated with any of the defined water stress patterns. Lastly, sowing date and maturity types management options and its interaction with previously defined water stress patterns were explored through simulations and later tested with experimental data. The results indicated that, excepting the South of region, farmers should chose sowing dates according to the type of stress. Early sowings (October) improved grain yield under low terminal, and grain filling stress. Instead, late sowings (December) were more convenient under pre-flowering stress. In this thesis, useful information was generated for sorghum breeders in temperate environments, via the identification of secondary traits and via an environmental characterization in terms of water and heat stress that could help to increase the efficiency of breeding programs. Specific management strategies to increase yield according to the water stress pattern were also generated, facilitating farmers’ management decisions
Sorghum is grown worldwide. This crop has favorable characteristics that provides tolerance under different types of stresses. It also contributes to the sustainability of production systems due to its great amount of produced biomass. However, the current context encompasses poor investment in terms of breeding programs and management. Genetic gain is low and management is similar across the productive central region, and is mainly based on low inputs. There is lack of knowledge about which genotype and management practices are ideal to maximize production in different environments. In the present thesis, genotype by environment (GxE) interaction for grain yield and possible secondary traits were studied for sorghum commercial hybrids. Additionally, an environmental characterization in terms of water and heat stress was done for different sites across the central region. Finally, some management strategies to optimize grain yield according to the environment were explored. An important GxE interaction for grain yield was detected (ratio GxE/G=3.48). This interaction was greater than the rest of the studied traits, including phenology, physiological and numerical components (ratio GxE/G<1). Traits associated with grain yield were identified, which could be used as secondary traits in breeding programs. Genotypic differences in phenology explained a large proportion of the GxE interaction through their influence on grain weight, demonstrating the relevance of phenology as a secondary trait. The sorghum crop model of the APSIM software was used for the environmental characterization of the Argentinean central region. Prior to its use, the model was calibrated for local materials, and tested with independent information. Good fit was obtained between observed and simulated phenology, biomass and yield data. It was found that the central productive region is characterized by three water stress patterns with similar frequencies: (i) pre-flowering stress (39%), (ii) low terminal stress (38%), and (iii) grain filling stress (23%). In the context of no predominant pattern, dealing with seasonal variability in breeding programs and for defining crop managements will be challenging. Defined water stress patterns helped explain the observed GxE interactions for grain yield. This shows the relevance of characterizing target environments and the possibility of selecting for specific adaptation. In addition, this results provided information of how enhance management in the region, showing a good yield response of short maturity genotypes in low terminal stress environments, and the capacity of late maturity genotypes of avoiding pre-flowering stress by placing the flowering afterwards. Thermal stress frequency (33°C threshold) was relatively low (about 3 every 10 years). This probability is greatly reduced when considering higher thresholds (36°C). Thermal stress was not associated with any of the defined water stress patterns. Lastly, sowing date and maturity types management options and its interaction with previously defined water stress patterns were explored through simulations and later tested with experimental data. The results indicated that, excepting the South of region, farmers should chose sowing dates according to the type of stress. Early sowings (October) improved grain yield under low terminal, and grain filling stress. Instead, late sowings (December) were more convenient under pre-flowering stress. In this thesis, useful information was generated for sorghum breeders in temperate environments, via the identification of secondary traits and via an environmental characterization in terms of water and heat stress that could help to increase the efficiency of breeding programs. Specific management strategies to increase yield according to the water stress pattern were also generated, facilitating farmers’ management decisions
Descripción
Palabras clave
Sorgos, Rendimiento de cultivos, Aumento del rendimiento, Interacción genotipo ambiente, Fenología, Estrés