Carbon isotope discrimination as a key physiological trait to phenotype drought/heat resistance of future climate-resilient German winter wheat compared with relative leaf water content and canopy temperature

Climate change is expected to influence crop growth through frequent drought and heat extremes, and thus, drought and heat tolerance are of increasing importance as major breeding goals for cereal crops in Central Europe. Plant physiological water status traits are suitable for phenotyping plant drought/heat tolerance. The objective of this study was to determine whether relative leaf water content (RLWC), plant canopy temperature (CT), and carbon isotope discrimination (CID) are suitable for phenotyping the drought/heat resistance of German winter wheat for future climate resilience. Therefore, a comprehensive field evaluation was conducted under drier and warmer conditions in Moldova using a space-for-time approach for twenty winter wheat varieties from Germany and compared to twenty regionally adapted varieties from Eastern Europe. Among the physiological traits RLWC, CT, and CID, the heritability of RLWC showed the lowest values regardless of year or variety origin, and there was no significant correlation between RLWC and grain yield regardless of the year, suggesting that RLWC did not seem to be a useful trait for distinguishing origins or varieties under continental field conditions. Although the heritability of CT demonstrated high values, the results showed surprisingly low and nonsignificant correlations between CT and grain yield; this may have been due to a confounding effect of increased soil temperature in the investigated dark Chernozem soil. In contrast, the heritability of CID in leaves and grain was high, and there were significant correlations between grain yield and CID, suggesting that CID is a reliable indirect physiological trait for phenotyping drought/heat resistance for future climate resilience in German wheat

Interactive Effects of N-, P- and K-Nutrition and Drought Stress on the Development of Maize Seedlings

Global climate change is likely to increase the risk of frequent drought. Maize, as the principal global cereal, is particularly impacted by drought. Nutrient supply may improve plant drought tolerance for better plant establishment during seedling growth stages. Thus, this study investigated the interactive effects of drought and the application of the nutrients N, P and K either individually or in combination. The maize seedlings were harvested between 12 and 20 days after sowing, and the leaf area, shoot fresh and dry weight and root dry weight were determined, and shoot water content and root/shoot dry weight ratio were calculated. Among the N, P and K fertilization treatments applied individually or in combination, the results showed that there was generally a positive effect of combined NPK and/or NP nutrient supply on shoot growth such as leaf area, shoot fresh and dry weight at day 20 after sowing under both well-watered and drought conditions compared with no nutrient supply. Compared with the effect of N and P nutrient supply, it seems that K was not limiting to plant growth due to the mineralogical characteristics of the illitic-chloritic silt loam used, which provided sufficient K, even though soil tests showed a low K nutrient status. Interestingly, the root/shoot ratio remained high and constant under drought regardless of NPK application, while it decreased with NPK applications in the well-watered treatment. This suggests that the higher root/shoot ratios with N, NP, PK and NPK under drought could be exploited as a strategy for stress tolerance in crop plants

Nitrogen Use Efficiency and Carbon Traits of High-Yielding European Hybrid vs. Line Winter Wheat Cultivars: Potentials and Limitations

In contrast to allogamous crops, hybrid wheat has only recently been fostered by breeding companies in Europe. Hybrid cultivars are often associated with higher stress resistance, e.g. under drought conditions, but little is known about the nitrogen (N) use efficiency of modern hybrid wheat cultivars. Therefore, four high-yielding European hybrid and nine line winter wheat (Triticum aestivum L.) cultivars were grown under three N regimes in a high-yielding German environment and compared over 3 years at anthesis and maturity for 53 direct and indirect traits of yield formation and N allocation. Dry matter and N uptake were determined on the plant and plant organ levels. Commercial heterosis, expressing the performance of hybrid in comparison to line cultivars, was positive for about one-third of the 53 direct and indirect N and carbon traits. On average, hybrid cultivars yielded more grain (+5.5%), mainly due to a higher harvest index (+3.5%) together with higher post-anthesis assimilation and more grains per spike. However, grain N content was lower for hybrids (−8.5%), so their grain N uptake was not higher. This went along with comparable trait values for N translocation and the temporal N uptake of the different plant organs. Current wheat hybrids seem to be more efficient in overall N use because they are better at converting (higher N utilization efficiency) comparable amounts of N uptake (N uptake efficiency) into grain biomass. The results suggest that given increased seed costs for hybrids, the yield advantage of hybrid cultivars over locally adapted line cultivars will have to be further increased for establishing hybrids in low-stress, high-yielding environments

Beeinflusst der Boden die N-Freisetzung aus pflanzlichen Düngern?

One consequence of the BSE-crisis is, that animal residue derived N-fertilisers used in organic horticulture are to be replaced. As an alternative plant derived N-fertilisers have been investigated. In an incubation experiment these fertilisers mineralised 40 to 60 % of the total N applied. Net N-mineralisation in the incubation experiment as well as plant N-utilisation in a pot experiment were closely related to the N-content of the fertilisers. Fertilisers increased the N-uptake of plants in any soil. Neither texture nor the content of Corg explained the observed differences in fertiliser use efficiency

Effect of Time of Day and Sky Conditions on Different Vegetation Indices Calculated from Active and Passive Sensors and Images Taken from UAV

Optical sensors have been widely reported to be useful tools to assess biomass, nutrition, and water status in several crops. However, the use of these sensors could be affected by the time of day and sky conditions. This study aimed to evaluate the effect of time of day and sky conditions (sunny versus overcast) on several vegetation indices (VI) calculated from two active sensors (the Crop Circle ACS-470 and Greenseeker RT100), two passive sensors (the hyperspectral bidirectional passive spectrometer and HandySpec Field sensor), and images taken from an unmanned aerial vehicle (UAV). The experimental work was conducted in a wheat crop in south-west Germany, with eight nitrogen (N) application treatments. Optical sensor measurements were made throughout the vegetative growth period on different dates in 2019 at 9:00, 14:00, and 16:00 solar time to evaluate the effect of time of day, and on a sunny and overcast day only at 9:00 h to evaluate the influence of sky conditions on different vegetation indices. For most vegetation indices evaluated, there were significant differences between paired time measurements, regardless of the sensor and day of measurement. The smallest differences between measurement times were found between measurements at 14:00 and 16:00 h, and they were observed for the vehicle-carried and the handheld hyperspectral passive sensor being lower than 2% and 4%, respectively, for the indices NIR/Red edge ratio, Red edge inflection point (REIP), and the water index. Differences were lower than 5% for the vehicle-carried active sensors Crop Circle ACS-470 (indices NIR/Red edge and NIR/Red ratios, and NDVI) and Greenseeker RT100 (index NDVI). The most stable indices over measurement times were the NIR/Red edge ratio, water index, and REIP index, regardless of the sensor used. The most considerable differences between measurement times were found for the simple ratios NIR/Red and NIR/Green. For measurements made on a sunny and overcast day, the most stable were the indices NIR/Red edge ratio, water index, and REIP. In practical terms, these results confirm that passive and active sensors could be used to measure on-farm at any time of day from 9:00 to 16:00 h by choosing optimized indices

Zusammenhang zwischen Ertrag und Proteingehalt im Korn bei homogene und heterogenen Weizensorten aus konventioneller und Ökologischer Züchtung

Feldversuche mit ökologisch und konventionell gezüchteten Weizensorten zeigten, dass die Kornproteinabweichung (GPD) von ökologisch gezüchteten Weizensorten höher war als die von konventionell gezüchteten Sorten. Die GPD von heterogenen Populationen unterschied sich nicht von der von Inzuchtlinien