Scanner-Based Minirhizotrons Help to Highlight Relations between Deep Roots and Yield in Various Wheat Cultivars under Combined Water and Nitrogen Deficit Conditions

Undergoing lignin-coated seeds to cold plasma to enhance the growth of wheat seedlings and obtain future outcome under stressed ecosystems

Climate changes threat global food security and food production. Soil salinization is one of the major issues of changing climate, causing adverse impacts on agricultural crops. Germination and seedlings establishment are damaged under these conditions, so seeds must be safeguard before planting. Here, we use recycled organic tree waste combined with cold (low-pressure) plasma treatment as grain coating to improve the ability of wheat seed cultivars (Misr-1 and Gemmeza-11) to survive, germinate and produce healthy seedlings. The seeds were coated with biofilms of lignin and hash carbon to form a protective extracellular polymeric matrix and then exposed them to low-pressure plasma for different periods of time. The effectiveness of the coating and plasma was evaluated by characterizing the physical and surface properties of coated seeds using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and wettability testing. We also evaluated biological and physiological properties of coated seeds and plants they produced by studying germination and seedling vigor, as well as by characterizing fitness parameters of the plants derived from the seeds. The analysis revealed the optimal plasma exposure time to enhance germination and seedling growth. Taken together, our study suggests that combining the use of recycled organic tree waste and cold plasma may represent a viable strategy for improving crop seedlings performance, hence encouraging plants cultivation in stressed ecosystems.

The geophysical toolbox applied to forest ecosystems - A review

Studying the forest subsurface is a challenge because of its heterogeneous nature and difficult access. Traditional approaches used by ecologists to characterize the subsurface have a low spatial representativity. This review article illustrates how geophysical techniques can and have been used to get new insights into forest ecology. Near-surface geophysics offers a wide range of methods to characterize the spatial and temporal variability of subsurface properties in a non-destructive and integrative way, each with its own advantages and disadvantages. These techniques can be used alone or combined to take advantage of their complementarity. Our review led us to define three topics how near-surface geophysics can support forest ecology studies: 1) detection of root systems, 2) monitoring of water quantity and dynamics, and 3) characterisation of spatial heterogeneity in subsurface properties at the stand level. The number of forest ecology studies using near-surface geophysics is increasing and this multidisciplinary approach opens new opportunities and perspectives for improving quantitative assessment of biophysical properties and exploring forest response to the environment and adaptation to climate change.

Root Electrical Capacitance Can Be a Promising Plant Phenotyping Parameter in Wheat

As root electrical capacitance (CR*) was assumed to depend on the stem properties, the efficiency of measuring CR* at flowering for whole-plant phenotyping was assessed in five wheat cultivars in three replicate plots over two years. Linear regression analysis was used to correlate CR* with plant-size parameters and flag-leaf traits (extension and SPAD chlorophyll content) at flowering, and with yield components at maturity. The plot-mean CR* was correlated with the plot leaf area index (LAI), the chlorophyll quantity (LAI×SPAD), and the grain yield across years. At plant scale, CR* was found to show the strongest positive regression with total chlorophyll in the flag leaf (flag leaf area × SPAD; R2: 0.65−0.74) and with grain mass (R2: 0.55−0.70) for each cultivar and year (p < 0.001). Likewise, at plot scale, the regression was strongest between CR* and the LAI×SPAD value (R2: 0.86−0.99; p < 0.01) for the cultivars. Consequently, CR* indicated the total plant nutrient and photosynthate supply at flowering, which depended on root uptake capacity, and strongly influenced the final yield. Our results suggested that the polarization of the active root membrane surfaces was the main contributor to CR*, and that the measurement could be suitable for evaluating root size and functional intensity. In conclusion, the capacitance method can be applied for nondestructive whole-plant phenotyping, with potential to estimate root and shoot traits linked to the nutrient supply, and to predict grain yield. CR* can be incorporated into allometric models of cereal development, contributing to optimal crop management and genetic improvement.

Genetic Analysis of Platform-Phenotyped Root System Architecture of Bread and Durum Wheat in Relation to Agronomic Traits

Roots are essential for water and nutrient uptake but are rarely the direct target of breeding efforts. To characterize the genetic variability of wheat root architecture, the root and shoot traits of 200 durum and 715 bread wheat varieties were measured at a young stage on a high-throughput phenotyping platform. Heritability of platform traits ranged from 0.40 for root biomass in durum wheat to 0.82 for the number of tillers. Field phenotyping data for yield components and SNP genotyping were already available for all the genotypes. Taking differences in earliness into account, several significant correlations between root traits and field agronomic performances were found, suggesting that plants investing more resources in roots in some stressed environments favored water and nutrient uptake, with improved wheat yield. We identified 100 quantitative trait locus (QTLs) of root traits in the bread wheat panels and 34 in the durum wheat panel. Most colocalized with QTLs of traits measured in field conditions, including yield components and earliness for bread wheat, but only in a few environments. Stress and climatic indicators explained the differential effect of some platform QTLs on yield, which was positive, null, or negative depending on the environmental conditions. Modern breeding has led to deeper rooting but fewer seminal roots in bread wheat. The number of tillers has been increased in bread wheat, but decreased in durum wheat, and while the root-shoot ratio for bread wheat has remained stable, for durum wheat it has been increased. Breeding for root traits or designing ideotypes might help to maintain current yield while adapting to specific drought scenarios.

Genetic analysis of salinity tolerance in wheat (Triticum aestivum L.)

Understanding the genetics of salt tolerance is of utmost need to combat the rising prevalence of soil salinity through employing tolerant cultivars. The current study was carried out to investigate the quantitative genetic basis of agronomical and physiological-related traits of salinity-stressed plants using seven generations (parental cultivars, F₁, F₂, F₃, BC₁, and BC₂) of wheat grown in the field under normal and saline conditions. The combined analysis of variance showed highly significant effects of salinity and genotypes (generations) on all the traits. The scaling tests did not support the three-parameter model (additive-dominance model); hence, the six-parameter model was used to assess the genetic effects governing the traits in this study. The epistatic gene effects were crucial, as were additive and dominance gene effects for plant height, K/Na, and yield in salinity stress conditions. The highest heritability was observed for total chlorophyll, carotenoid, SPAD chlorophyll, and K/Na ratio in saline conditions. The additive genetic variance was more important than the dominance variance for grain weight, K, K/Na in salinity conditions. The findings of the current study may have important implications in the quantitative genetics of salinity tolerance and the development of cultivars tolerant to salinity in wheat.

Electrical Capacitance versus Minirhizotron Technique: A Study of Root Dynamics in Wheat-Pea Intercrops

This study evaluated the concurrent application and the results of the root electrical capacitance (C_R) and minirhizotron (MR) methods in the same plant populations. The container experiment involved three winter wheat cultivars, grown as sole crops or intercropped with winter pea under well-watered or drought-stressed conditions. The wheat root activity (characterized by C_R) and the MR-based root length (RL) and root surface area (RSA) were monitored during the vegetation period, the flag leaf chlorophyll content was measured at flowering, and the wheat shoot dry mass (SDM) and grain yield (GY) were determined at maturity. C_R, RL and RSA exhibited similar seasonal patterns with peaks around the flowering. The presence of pea reduced the maximum C_R, RL and RSA. Drought significantly decreased C_R, but increased the MR-based root size. Both intercropping and drought reduced wheat chlorophyll content, SDM and GY. The relative decrease caused by pea or drought in the maximum C_R was proportional to the rate of change in SDM or GY. Significant linear correlations (R²: 0.77-0.97) were found between C_R and RSA, with significantly smaller specific root capacitance (per unit RSA) for the drought-stress treatments. C_R measurements tend to predict root function and the accompanying effect on above-ground production and grain yield. The parallel application of the two in situ methods improves the evaluation of root dynamics and plant responses.

Response of Two Different Wheat Varieties to Glow and Afterglow Oxygen Plasma

Cold plasma technology has received significant attention in agriculture due to its effect on the seeds and plants of important cultivars, such as wheat. Due to climate change, wherein increasing temperatures and droughts are frequent, it is important to consider novel approaches to agricultural production. As increased dormancy levels in wheat are correlated with high temperatures and drought, improving the germination and root growth of wheat seeds could offer new possibilities for seed sowing. The main objective of this study was to evaluate the influence of direct (glow) and indirect (afterglow) radio-frequency (RF) oxygen plasma treatments on the germination of two winter wheat varieties: Apache and Bezostaya 1. The influence of plasma treatment on seed surface morphology was studied using scanning electron microscopy, and it was observed that direct plasma treatment resulted in a high etching and nanostructuring of the seed surface. The effect of plasma treatment on germination was evaluated by measuring the germination rate, counting the number of roots and the length of the root system, and the fresh weight of seedlings. The results of this study indicate that the response of seeds to direct and indirect plasma treatment may be variety-dependent, as differences between the two wheat varieties were observed.

Image-Based, Organ-Level Plant Phenotyping for Wheat Improvement

Wheat was one of the first grain crops domesticated by humans and remains among the major contributors to the global calorie and protein budget. The rapidly expanding world population demands further enhancement of yield and performance of wheat. Phenotypic information has historically been instrumental in wheat breeding for improved traits. In the last two decades, a steadily growing collection of tools and imaging software have given us the ability to quantify shoot, root, and seed traits with progressively increasing accuracy and throughput. This review discusses challenges and advancements in image analysis platforms for wheat phenotyping at the organ level. Perspectives on how these collective phenotypes can inform basic research on understanding wheat physiology and breeding for wheat improvement are also provided.