Agronomic and physiological traits related to the genetic advance of semi-dwarf durum wheat: The case of Spain

Knowledge of the agronomic and physiological traits associated with genetic gains in yield is essential to improve understanding of yield-limiting factors and to inform future breeding strategies. The aim of this paper is to dissect the agronomic and physiological traits related to genetic gain and to propose an ideotype with high yield that is best adapted to Spanish Mediterranean environments. Six semi-dwarf (i.e. modern) durum wheat genotypes were grown in a wide range of growing conditions in Spain during two successive years. Diverse agronomic, physiological and leaf morphological traits were evaluated. Kernels spike−1 was the yield component most affected by the genetic gain. While no interaction between genotype and growing conditions existed for grain yield, the more productive genotypes were characterized by a plant height of around 85 cm, small erect flag leaves, more open stomata, a better balance between N sources and N sinks and a higher capacity to re-fix CO2 respired by the grain. Moreover, in general the non-laminar parts of the plants play a key role in providing assimilates during grain filling. The high heritability of most of the studied parameters allows their consideration as traits for phenotyping durum wheat better adapted to a wide range of Mediterranean conditions

Weather-based predictive modeling of Cercospora beticola infection events in sugar beet in Belgium

Cercospora leaf spot (CLS; caused by Cercospora beticola Sacc.) is the most widespread and damaging foliar disease of sugar beet. Early assessments of CLS risk are thus pivotal to the success of disease management and farm profitability. In this study, we propose a weather-based modelling approach for predicting infection by C. beticola in sugar beet fields in Belgium. Based on reported weather conditions favoring CLS epidemics and the climate patterns across Belgian sugar beet-growing regions during the critical infection period (June to August), optimum weather conditions conducive to CLS were first identified. Subsequently, 14 models differing according to the combined thresholds of air temperature (T), relative humidity (RH), and rainfall (R) being met simultaneously over uninterrupted hours were evaluated using data collected during the 2018 to 2020 cropping seasons at 13 different sites. Individual model performance was based on the probability of detection (POD), the critical success index (CSI), and the false alarm ratio (FAR). Three models (i.e., M1, M2 and M3) were outstanding in the testing phase of all models. They exhibited similar performance in predicting CLS infection events at the study sites in the independent validation phase; in most cases, the POD, CSI, and FAR values were ≥84%, ≥78%, and ≤15%, respectively. Thus, a combination of uninterrupted rainy conditions during the four hours preceding a likely start of an infection event, RH > 90% during the first four hours and RH > 60% during the following 9 h, daytime T > 16 °C and nighttime T > 10 °C, were the most conducive to CLS development. Integrating such weather-based models within a decision support tool determining fungicide spray application can be a sound basis to protect sugar beet plants against C. beticola, while ensuring fungicides are applied only when needed throughout the season

Exploring the potential of Meyerozyma guilliermondii on physiological performances and defense response against Fusarium Crown Rot on Durum Wheat

Coating seeds with bio-control agents is a potentially effective approach to reduce the usage of pesticides and fertilizers applied and protect the natural environment. This study evaluated the effect of seed coating with Meyerozyma guilliermondii, strain INAT (MT731365), on seed germination, plant growth and photosynthesis, and plant resistance against Fusarium culmorum, in durum wheat under controlled conditions. Compared to control plants, seed coating with M. guilliermondii promoted the wheat growth (shoot and roots length and biomass), and photosynthesis and transpiration traits (chlorophyll, ɸPSII, rates of photosynthesis and transpiration, etc.) together with higher nitrogen balance index (NBI) and lower flavonols and anthocyanins. At 21 days post infection with Fusarium, M. guilliermondii was found to reduce the disease incidence and the severity, with reduction rates reaching up to 31.2% and 30.4%, respectively, as well as to alleviate the disease damaging impact on photosynthesis and plant growth. This was associated with lower ABA, flavonols and anthocyanins, compared to infected control. A pivotal function of M. guilliermondii as an antagonist of F. culmorum and a growth promoter is discussed

Carbon Isotope Composition and the NDVI as Phenotyping Approaches for Drought Adaptation in Durum Wheat: Beyond Trait Selection

High-throughput phenotyping platforms provide valuable opportunities to investigate biomass and drought-adaptive traits. We explored the capacity of traits associated with drought adaptation such as aerial measurements of the Normalized Difference Vegetation Index (NDVI) and carbon isotope composition (δ13C) determined at the leaf level to predict genetic variation in biomass. A panel of 248 elite durum wheat accessions was grown at the Maricopa Phenotyping platform (US) under well-watered conditions until anthesis, and then irrigation was stopped and plot biomass was harvested about three weeks later. Globally, the δ13C values increased from the first to the second sampling date, in keeping with the imposition of progressive water stress. Additionally, δ13C was negatively correlated with final biomass, and the correlation increased at the second sampling, suggesting that accessions with lower water-use efficiency maintained better water status and, thus, performed better. Flowering time affected NDVI predictions of biomass, revealing the importance of developmental stage when measuring the NDVI and the effect that phenology has on its accuracy when monitoring genotypic adaptation to specific environments. The results indicate that in addition to choosing the optimal phenotypic traits, the time at which they are assessed, and avoiding a wide genotypic range in phenology is crucial

The plant-transpiration response to vapour pressure deficit (VPD) in durum wheat is associated with differential yield performance and specific expression of genes involved in primary metabolism and water transport

The regulation of plant transpiration was proposed as a key factor affecting transpiration efficiency and agronomical adaptation of wheat to water-limited Mediterranean environments. However, to date no studies have related this trait to crop performance in the field. In this study, the transpiration response to increasing vapor pressure deficit (VPD) of modern Spanish semi-dwarf durum wheat lines was evaluated under controlled conditions at vegetative stage, and the agronomical performance of the same set of lines was assessed at grain filling as well as grain yield at maturity, in Mediterranean environments ranging from water stressed to good agronomical conditions. A group of linear-transpiration response (LTR) lines exhibited better performance in grain yield and biomass compared to segmented-transpiration response (STR) lines, particularly in the wetter environments, whereas the reverse occurred only in the most stressed trial. LTR lines generally exhibited better water status (stomatal conductance) and larger green biomass (vegetation indices) during the reproductive stage than STR lines. In both groups, the responses to growing conditions were associated with the expression levels of dehydration-responsive transcription factors (DREB) leading to different performances of primary metabolism-related enzymes. Thus, the response of LTR lines under fair to good conditions was associated with higher transcription levels of genes involved in nitrogen (GS1 and GOGAT) and carbon (RCBL) metabolism, as well as water transport (TIP1.1). In conclusion, modern durum wheat lines differed in their response to water loss, the linear transpiration seemed to favor uptake and transport of water and nutrients, and photosynthetic metabolism led to higher grain yield except for very harsh drought conditions. The transpiration response to VPD may be a trait to further explore when selecting adaptation to specific water conditions

Increasing genotypic productivity in post Green Revolution durum wheat: the case of Spain

[eng] It is of strategic importance for Mediterranean agriculture to develop new varieties of durum wheat with greater production potential, together with a better adaptation to adverse environmental conditions and better quality of grain. While durum wheat, which is the most strategic crop in the south Mediterranean agriculture, has benefited as other cereals of the Green Revolution, genetic progress in recent decades has been less evident, partly masked by climate change, and the underlying physiological mechanisms are not evident. For this propose, the objective is to evaluate whether there have been agronomic and physiological changes associated with the genetic improvement of durum wheat grown in Spain after the Green Revolution and the environmental conditions where breeding gains have been higher. The study was based on a collection of 20 commercial varieties, grown in Spain between the beginning of the 70s of the last centuries and the present. The set was readapted during the last two cropping cycles and increased to a total of 23 cultivars, including more recent cultivars, released during the present decade. Cultivars were compared through consecutive years in wide range growing conditions secured by growing in three different sites differing in latitude and temperature, together with the implementation of support irrigation and different planting times. Changes in the genetic gain of the yield were evaluated between 2014 and 2016. Change in the agronomic and physiological parameters related to the genetic progress was evaluated between 2015- 2016, and the changes caused by the improvement in the adaptation patterns through the study of the genotype by environment (GE) interaction was evaluated between 2017 and 2018. It has been observed that the rate of genetic progress in the yield of durum wheat in Spain after the Green Revolution has been low it was estimated on 24 kg ha-1 y-1 (0.44% y-1 in term of relative gain) between 1980 and 2003 and has even stopped during the last decade until 2010. It was mainly due to increases in the number of kernels per spike (117 kernels m-2 y-1), and spikes per unit area (0.24 kernels spike-1 y-1), while no clear trend in some grain quality traits (TKW and grain N concentration). Moreover, areal biomass at harvest and grain nitrogen yield increased with the year of release of the cultivars for the entire period. In addition, it has been observed that the more productive genotypes were characterized by a plant height of around 85 cm, small erect flag leaves, more open stomata, a better balance between N sources and N sinks and a higher capacity to re-fix CO2 respired by the grain. Moreover, in general the non-laminar parts of the plants play a key role in providing assimilates during grain filling. Also, that the high heritability of most of the studied parameters allows their consideration as traits for phenotyping durum wheat better adapted to a wide range of Mediterranean conditions. On the other hand, an improvement in genetic yield has been reported in warm environments and under optimal water conditions, environments similar to those of from where the germplasm provenance release or origin. The adaptation of semi-dwarf durum in Spain has shown a tendency to specific adaptation rather than large-scale adaptation. Two different patterns of selection have been reported due the G×E interaction and change in the ranking of genotypes: in the high yielding environments, plant favors more water uptake, with more transpiration and more open stomata (more negative value of δ13C, whereas, in low yielding environments, plant close stomata and favors more water use efficiency (positive value of δ13C).[spa] El trigo duro, que es el cultivo más estratégico en la agricultura del sur del Mediterráneo, se ha beneficiado como otros cereales de la Revolución Verde, el progreso genético en las últimas décadas ha sido menos evidente, en parte enmascarado por el cambio climático, y los mecanismos fisiológicos subyacentes no son evidentes. Se ha observado que la tasa de progreso genético en el rendimiento del trigo duro en España después de la Revolución Verde ha sido baja, se estimó en 24 kg ha-1 año-1 entre 1980 y 2003 e incluso se detuvo durante la última década hasta 2010. Se debió principalmente al aumento en el número de granos por espiga, y espigas por unidad de área, aunque no hay una tendencia clara en algunos rasgos de calidad de grano (TKW y concentración de N de grano). Además, la biomasa área en la cosecha y el rendimiento de nitrógeno en grano aumentó con el año de liberación de los cultivares durante todo el período. Además, se ha observado que los genotipos más productivos se caracterizaron por una altura de planta de alrededor de 85 cm, pequeñas hojas de bandera erectas, estomas más abiertos, un mejor equilibrio entre las fuentes de N y los sumideros de N y una mayor capacidad para re-fijar CO2 Respirado por el grano. Además, en general, las partes no laminares de las plantas juegan un papel clave en el suministro de asimilados durante el llenado del grano. Por otro lado, se ha informado una mejora en el rendimiento genético en ambientes cálidos y en condiciones óptimas de agua, ambientes similares a los de donde se origina el germoplasma. La adaptación del durum semi-enano en España ha mostrado una tendencia a la adaptación específica en lugar de la adaptación a gran escala. Se han informado dos patrones diferentes de selección debido a la interacción G × E: en los entornos de alto rendimiento, la planta favorece una mayor absorción de agua, con más transpiración y más estomas abiertos, mientras que, en entornos de bajo rendimiento, planta estomas cercanos y favorece una mayor eficiencia en el uso del agua

Agronomic and physiological traits related to the genetic advance of semi-dwarf durum wheat: The case of Spain

14 Pág.Knowledge of the agronomic and physiological traits associated with genetic gains in yield is essential to improve understanding of yield-limiting factors and to inform future breeding strategies. The aim of this paper is to dissect the agronomic and physiological traits related to genetic gain and to propose an ideotype with high yield that is best adapted to Spanish Mediterranean environments. Six semi-dwarf (i.e. modern) durum wheat genotypes were grown in a wide range of growing conditions in Spain during two successive years. Diverse agronomic, physiological and leaf morphological traits were evaluated. Kernels spike-1 was the yield component most affected by the genetic gain. While no interaction between genotype and growing conditions existed for grain yield, the more productive genotypes were characterized by a plant height of around 85 cm, small erect flag leaves, more open stomata, a better balance between N sources and N sinks and a higher capacity to re-fix CO2 respired by the grain. Moreover, in general the non-laminar parts of the plants play a key role in providing assimilates during grain filling. The high heritability of most of the studied parameters allows their consideration as traits for phenotyping durum wheat better adapted to a wide range of Mediterranean conditions.This study was supported by the Spanish project AGL2016-76527-R from MINECO, Spain. Fadia Chairi is the recipient of an FPI doctoral fellowship from the same institution. Jose Luis Araus acknowledges the support from the ICREA Academia of the Catalan Government, Spain.Peer reviewe

The plant-transpiration response to vapour pressure deficit (VPD) in durum wheat is associated with differential yield performance and specific expression of genes involved in primary metabolism and water transport

The regulation of plant transpiration was proposed as a key factor affecting transpiration efficiency and agronomical adaptation of wheat to water-limited Mediterranean environments. However, to date no studies have related this trait to crop performance in the field. In this study, the transpiration response to increasing vapor pressure deficit (VPD) of modern Spanish semi-dwarf durum wheat lines was evaluated under controlled conditions at vegetative stage, and the agronomical performance of the same set of lines was assessed at grain filling as well as grain yield at maturity, in Mediterranean environments ranging from water stressed to good agronomical conditions. A group of linear-transpiration response (LTR) lines exhibited better performance in grain yield and biomass compared to segmented-transpiration response (STR) lines, particularly in the wetter environments, whereas the reverse occurred only in the most stressed trial. LTR lines generally exhibited better water status (stomatal conductance) and larger green biomass (vegetation indices) during the reproductive stage than STR lines. In both groups, the responses to growing conditions were associated with the expression levels of dehydration-responsive transcription factors (DREB) leading to different performances of primary metabolism-related enzymes. Thus, the response of LTR lines under fair to good conditions was associated with higher transcription levels of genes involved in nitrogen (GS1 and GOGAT) and carbon (RCBL) metabolism, as well as water transport (TIP1.1). In conclusion, modern durum wheat lines differed in their response to water loss, the linear transpiration seemed to favor uptake and transport of water and nutrients, and photosynthetic metabolism led to higher grain yield except for very harsh drought conditions. The transpiration response to VPD may be a trait to further explore when selecting adaptation to specific water conditions