VARIABILITÉ PHÉNOTYPIQUE ET SÉLECTION DES CARACTÈRES AGRONOMIQUES DU BLÉ DUR (Triticum durum Desf.) SOUS CONDITIONS SEMI-ARIDES

Genetic improvement of agronomic traits related to yield performance and adaptation to the production environments is conditioned by the presence of phenotypic variability of the targeted characters in the plant material subjected to selection. This research was conducted to assess the magnitude of phenotypic variability, the heritability and the expected genetic gain of selection of agronomic traits in 18 durum wheat (Triticum durum Desf) varieties and segregating lines. The results showed the presence of significant variability for the measured traits. The degree of genetic determination had values greater than 70% for the duration of the vegetative phase and plant height, and below 50% for yield and aboveground biomass. The expected genetic gain ranged from 4.8% for the duration of the vegetative phase to 45.9% for grain yield. Single-character selection identified 6 desirable genotypes which brought increases of 14.9% in harvest index, 3.7 g in 1000 kernel weight, 4.8% in relative water content, and declines of 18.6% in percent cells injury, 2.1 g in yield per plant, 2.1 cm in spike length, and 12.9 grains per spike, and a gain of 1.7 spikes associated to 8.8 g of biomass. Relatively to Bousselam, the check cultivar, the selected lines brought a grain yield advantage ranging from 53.8 to 161.5%. This yield gain is associated with a desirable improvement in heat stress tolerance, and an undesirable reduction in thousand kernel weight. The study of th

VARIABILITÉ PHÉNOTYPIQUE ET SÉLECTION DES CARACTÈRES AGRONOMIQUES DU BLÉ DUR (Triticum durum Desf.) SOUS CONDITIONS SEMI-ARIDES

Genetic improvement of agronomic traits related to yield performance and adaptation to the production environments is conditioned by the presence of phenotypic variability of the targeted characters in the plant material subjected to selection. This research was conducted to assess the magnitude of phenotypic variability, the heritability and the expected genetic gain of selection of agronomic traits in 18 durum wheat (Triticum durum Desf) varieties and segregating lines. The results showed the presence of significant variability for the measured traits. The degree of genetic determination had values greater than 70% for the duration of the vegetative phase and plant height, and below 50% for yield and aboveground biomass. The expected genetic gain ranged from 4.8% for the duration of the vegetative phase to 45.9% for grain yield. Single-character selection identified 6 desirable genotypes which brought increases of 14.9% in harvest index, 3.7 g in 1000 kernel weight, 4.8% in relative water content, and declines of 18.6% in percent cells injury, 2.1 g in yield per plant, 2.1 cm in spike length, and 12.9 grains per spike, and a gain of 1.7 spikes associated to 8.8 g of biomass. Relatively to Bousselam, the check cultivar, the selected lines brought a grain yield advantage ranging from 53.8 to 161.5%. This yield gain is associated with a desirable improvement in heat stress tolerance, and an undesirable reduction in thousand kernel weight. The study of th

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.Peer reviewe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains

Data Descriptor: A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment