Agricultural monitoring is an important and continuously spreading activity in remote sensing and applied Earth observations. It supplies valuable information on crop condition and growth processes. Much research has been carried out on vegetation phenology issues. In agriculture, the timing of seasonal cycles of crop activity is important for species classification and evaluation of crop development, growing conditions and potential yield. The correct interpretation of remotely sensed data, however, and the increasing demand for data reliability require ground-truth knowledge of the seasonal spectral behaviuor of different species and their relation to crop vigour. For this reason, we performed groundbased study of the seasonal response of winter wheat reflectance patterns to crop growth patterns. The goal was to quantify crop seasonality by establishing empirical relationships between plant biophysical and spectral properties in main ontogenetic periods. Phenology and agr-specific relationships allow to assess crop condition during different portions of the growth cycle and thus effectively track plant development and make yield predictions. The applicability of different vegetation indices for monitoring crop seasonal dynamics, health condition, and yield potential was examined.
► Potential yield of winter wheat simulated with EPIC using weather data from 1960 to 2007 was 6.6–9.1 t ha in the North China Plain (NCP), generally increasing from north to south associated with decreasing low temperature stress. ► Based on county-level data from 2004 to 2007, the yield gap in the NCP was 2.7 t ha , 32% of the potential yield. ► Using 80% of the potential yield as an exploitable level, average actual wheat yields in the NCP could be increased by 1.0 t ha or 18%. ► Yield gaps at the county level were inversely correlated with actual yields ( = 0.82). The North China Plain (NCP) is the most important wheat production area in China, producing about two-thirds of China's total wheat output. To meet the associated increase in China's food demand with the expected growth in its already large population of 1.3 billion and diet changes, wheat production in the NCP needs to increase. Because of the farmland reduction due to urbanization, strategies for increasing wheat production in the NCP should be targeted at increasing current yields. To identify options for increasing wheat yields, we analyzed the yield potentials and yield gaps using the EPIC (Environment Policy Integrated Climate) model, Kriging interpolation techniques, GIS and average farm yields at county level. As most (ca. 82%) of the winter wheat in the NCP is irrigated, it is justified to use potential yield as the benchmark of the yield gap assessment. Wheat potential yields simulated with EPIC using daily weather data from 1960 to 2007 at 43 representative sites varied from 6.6 to 9.1 t ha in the NCP, generally increasing from north to south associated with decreasing low temperature stress. Based on the county-level data (2004–2007), the actual wheat yield varied between 2.4 and 7.7 t ha , while the yield gap was between 0.6 and 5.3 t ha (7–69% of the potential yield) across the NCP and decreased with increase of actual yields ( = 0.82). For the entire region, the weighted average actual yield was 5.7 t ha , while the yield gap was 2.7 t ha or 32% of the potential yield. Using 80% of the potential yield as an exploitable level, the average actual wheat yield in the NCP could be increased by 1.0 t ha or 18%. The results provide an indication of the possibilities to increase wheat yields in the NCP.
Modern genomics approaches rely on the availability of high-throughput and high-density genotyping platforms. A major breakthrough in wheat genotyping was the development of an SNP array. In this study, we used a diverse panel of 172 elite European winter wheat lines to evaluate the utility of the SNP array for genomic analyses in wheat germplasm derived from breeding programs. We investigated population structure and genetic relatedness and found that the results obtained with SNP and SSR markers differ. This suggests that additional research is required to determine the optimum approach for the investigation of population structure and kinship. Our analysis of linkage disequilibrium (LD) showed that LD decays within approximately 5–10 cM. Moreover, we found that LD is variable along chromosomes. Our results suggest that the number of SNPs needs to be increased further to obtain a higher coverage of the chromosomes. Taken together, SNPs can be a valuable tool for genomics approaches and for a knowledge-based improvement of wheat.
Emerson hard red winter wheat (Triticum aestivum L.), a cultivar developed using doubled haploid technology, was registered for western Canadian production in 2012. It is eligible for grades of the Canada Western Red Winter (CWRW) wheat market class. Evaluation across western Canada from 2008 to 2010 was relative to CDC Osprey, AC Bellatrix, Radiant, and CDC Buteo, the CWRW wheat checks in the Western Winter Wheat Cooperative Registration trials. Overall, Emerson had significantly lower grain yield than the mean of these checks; however, in the stem rust, leaf rust and fusarium head blight prone eastern prairies the grain yield of Emerson was not significantly different from CDC Buteo and CDC Falcon, which have been the predominant cultivars in this region. Emerson had good winter survival, intermediate maturity, medium height, strong straw, high test weight, and high grain protein concentration. It expressed improved resistance to fusarium head blight, stem rust, leaf rust, and stripe rust relative to the checks. End-use suitability analysis indicated that Emerson had strong dough rheology, and excellent milling and baking properties.
1. Predators can provide a valuable ecosystem service by suppressing crop pests. However, intraguild predation, where predators compete for the same prey resource whilst consuming each other, may destabilize population dynamics and increase the risk of pest outbreaks. Very little is known about intraguild predation in open fields or the strengths of trophic links between predators which may negatively affect pest control. 2. We tested the null hypothesis that predation by the epigeal predator Pterostichus melanarius (Coleoptera: Carabidae) on different spiders is species-independent (proportional to density). A combination of population monitoring in winter wheat, molecular identification of juvenile spiders, molecular analysis of predator gut contents and a Monte Carlo simulation model were used to analyse prey choice. 3. Pterostichus melanarius were pitfall-trapped over three months, and 622 individuals were screened for the remains of four spider species. Predation rates on spiders were 43·6% in June and 33·3% in August and showed clear evidence of prey choice. 4. Predation on the web-dependent Tenuiphantes tenuis (Linyphiidae) was significantly greater than predicted from a random choice model, while predation on Bathyphantes gracilis (Linyphiidae) was significantly lower. The beetles may be selecting the most abundant species disproportionately (switching) or responding in some cases to spatial niche separation (T. tenuis locate their webs marginally lower than B. gracilis). However, two itinerant hunters, Erigone spp. (Linyphiidae) and Pachygnatha degeeri (Tetragnathidae), were consumed in proportion to their density. 5. Synthesis and applications. High levels of intraguild predation were revealed using molecular diagnostics. The gut analysis approach provided invaluable data that will inform the future design of appropriate pest management and integrated farming strategies that encourage these predators. The data showed strong evidence of prey choice. Managers can, however, probably encourage high densities of all these known aphid predators (spiders and carabids) because disproportionately high rates of predation on the most common spiders at our field sites (T. tenuis) were not sufficient to prevent strong growth in the density of this species between June and August (adults increased × 1·6 and juveniles × 8·6). Such work is essential if we are to reveal the processes behind functional biodiversity in crops.
Abiotic stress tolerance in plants is pivotal to increase yield stability, but its genetic basis is still poorly understood. To gain insight into the genetic architecture of frost tolerance, this work evaluated a large mapping population of 1739 wheat (Triticum aestivum L.) lines and hybrids adapted to Central Europe in field trials in Germany and finger-printed the lines with a 9000 single-nucleotide polymorphism array. Additive effects prevailed over dominance effects. A two-dimensional genome scan revealed the presence of epistatic effects. Genome-wide association mapping in combination with a robust cross-validation strategy identified one frost tolerance locus with a major effect located on chromosome 5B. This locus was not in linkage disequilibrium with the known frost loci Fr-B1 and Fr-B2. The use of the detected diagnostic markers on chromosome 5B, however, does not allow prediction of frost tolerance with high accuracy. Application of genome-wide selection approaches that take into account also loci with small effect sizes considerably improved prediction of the genetic variation of frost tolerance in wheat. The developed prediction model is valuable for improving frost tolerance because this trait displays a wide variation in occurrence across years and is therefore a difficult target for conventional phenotypic selection.
Enhanced ultraviolet-B (UV-B) is one of the most important abiotic stress factors that can influence almost every aspect of plant. Selenium (Se) can increase the tolerance of plants to stressful environment. The paper mainly reported the effects of enhanced UV-B, Se supply and their combination on agronomical characters of winter wheat under field conditions. Enhanced UV-B caused a marked decrease in chlorophyll content, plant height, spike length, weight per spike, grain yield and protein content, grain nitrogen (N) and iron (Fe) concentration, and increased hydrogen peroxide (H O ), malondialdehyde (MDA) and proline content, and grain zinc (Zn) and manganese (Mn) concentration under without supplemental Se supply. However, it also decreased plant height, spike length, weight per spike, grain yield and Fe concentration, and increased H O content, grain potassium (K), Zn and Mn concentration under supplemental Se supply. On the other hand, Se supply induced an evident increase in chlorophyll content, spike length, weight per spike, grain yield, grain protein content, grain N, Fe, copper (Cu), and Se concentration under both UV-B levels. Moreover, significant UV-B×Se interaction was found on plant height, chlorophyll, MDA, H O and proline content, and grain protein, N, K, Cu and Mn concentrations in wheat. The obtained results supported the hypothesis that Se supply increased the yield and improved the quality of winter wheat exposed to enhanced UV-B to some extent.
This study was conducted to determine whether grain yield and nitrogen-use efficiency (NUE) of winter wheat ( L.) could be improved by managing the seeding rate. During the 2010–2011 and 2011–2012 crop seasons, two winter wheat cultivars (Tainong18 with lower tillering capability and Shannong15 with higher tillering capability) were evaluated to investigate the effect of seeding rate on grain yield and NUE. Significant increases in root length density (RLD), absorbed N from fertiliser (N ) and soil (N ), above-ground N uptake (AGN), N uptake efficiency (UPE), NUE and grain yield, as well as a significant reduction in N utilisation efficiency (UTE), were observed as the seeding rate increased from 135 to 405 seeds m for Tainong18 and from 90 to 345 seeds m for Shannong15. NUE was positively correlated with UPE but not with UTE, indicating that optimising the seeding rate improved NUE mainly by raising UPE due to increased AGN as a result of optimised RLD and a synchronous increase in N and N . Therefore, the seeding rate could be a factor useful to obtain higher grain yield and NUE in winter wheat.
Crop growth models have been applied successfully in forecasting crop yield at a local scale, while satellite remote sensing has the advantage of retrieving regional crop parameters. The new assimilation method of integrating the crop growth model with remote sensing has presented great potential in regional crop yield assessment. In this study, the Moderate Resolution Imaging Spectrometer (MODIS) leaf area index (LAI) data product was assimilated into the World Food Studies (WOFOST) crop growth model. Using the Extended Fourier Amplitude Sensitivity Test (EFAST) global sensitivity analysis approach, several local and regional crop parameters were identified to be recalibrated. The Shuffled Complex Evolution (SCE) optimization algorithm was used to estimate the emergence date, initial biomass and initial available soil water by minimizing the differences between the corrected MODIS-LAI and simulated LAI. Results indicated that the accuracy of water-limited crop yield was improved significantly after the assimilation. The root mean square error (RMSE) reduced from 983 kg/ha to 474 kg/ha and 667 kg/ha respectively in two different optimization schemes.