The association of specific target traits for drought resistance (early flowering, high accumulation of stem water soluble carbohydrate (WSC) reserves, presence of awns and high green flag-leaf area persistence) with yield performance under late-season drought was analyzed utilizing two doubled-haploid (DH) populations derived from crosses between Beaver × Soissons and Rialto × Spark in two seasons 2000/2001 and 2001/2002. The aim was to quantify associations between target traits and yield responses to drought, and to prioritize traits for drought resistance. Flowering time variation had a neutral effect on the absolute yield loss under drought, suggesting there may be a trade-off between water-saving behaviour in the shorter pre-flowering period with early flowering and a reduced capacity to access water associated with a smaller rooting system. The presence of awns also had a neutral effect on yield loss under drought amongst lines of the Beaver × Soissons population. The potential advantages of awns for increasing water-use efficiency and sensible heat transfer responsible for a cooler canopy appeared to be of less significance under moderate droughts in the UK than under severe droughts in other regions worldwide. The value of large stem soluble carbohydrate reserves for drought environments alone could not be confirmed in the UK environment. Stem WSC was positively associated with grain yield under both irrigation and drought. The genetic trait which showed the clearest correlation with the ability to maintain yield under drought was green flag-leaf area persistence. Averaged across years, the positive phenotypic correlation of this trait with yield under drought amongst DH lines of the Beaver × Soissons population ( = 0.49; ≤ 0.001) indicated the potential use of this trait as a selection criterion for yield under drought. It is suggested that screens for this trait including marker-assisted selection would have value in future breeding programmes aimed at improving yields in high yielding, rainfed environments, but where drought can also be a problem, such as the UK.
Cadmium (Cd) is a toxic heavy metal which to a relatively large extent is ingested via wheat-based products. Conflicting results have been reported on how the application of nitrogen (N) fertilizers to winter wheat ( L.) affects the Cd concentration in grain. The objectives of this study were to investigate how and to what degree application of N fertilizer affected the Cd concentration in winter wheat grain under field conditions and how consistent such effects were between sites and cultivars. Two wheat cultivars fertilized with four rates of nitrate of lime (100, 145, 190 and 235 kg N ha ) were investigated in field trials, where the fertilizer was applied on two occasions as is common for bread wheat. In addition, data on Cd and N concentrations in grain of wheat, oats and barley from a Swedish soil monitoring programme were evaluated. In the field trials the grain Cd concentration increased with increasing N rate, irrespective of the Cd concentration in soil and grain. Each 10 kg increase in N application gave an increased Cd concentration in grain of approximately 0.001–0.003 mg kg . The relative increase in Cd concentration as a function of N rate varied between 6 and 14% across sites and cultivars when the N rate was increased from 145 to 175 kg N. The grain Cd concentration was also positively correlated to the grain N concentration. The data from the Swedish soil monitoring programme showed a significant positive correlation between the N and Cd concentrations in grain of winter wheat, oats and barley. A possible explanation for the increase in grain Cd concentration could be ion exchange reactions in the soil solution, where an increased concentration of the fertilizer cation Ca may have caused an increased concentration of Cd in soil solution and eventually in wheat grain.
Knowledge of changes associated with advances in crop productivity is essential for understanding yield limiting factors and developing strategies for future genetic improvement. The objectives of this study are to understand genetic gain for grain yield and associated traits in the Northern China Winter Wheat Region (NCWWR). Four trials, comprised of 47 leading common wheat (Triticum aestivum L.) cultivars from the NCWWR from 1960 to 2000, were conducted during 2001 to 2003 using a completely randomized block design of three replicates under controlled field environments. Molecular markers were used to detect the presence of dwarfing genes and the 1B/1R translocation. Results showed that average annual genetic gain in grain yield ranged from 32.07 to 72.11 kg ha(-1)yr(-1) or from 0.48 to 1.23% annually in different provinces. The most significant increase in grain yield occurred in the early 1980s, largely because of the successful utilization of dwarfing genes and the 1B/1R translocation. There was no common trend across trials in terms of changes in spikes m(-2), kernels per spike, 1000-kernel weight (TKW), or biomass. The genetic improvement in grain yield was primarily attributed to increased grain weight per spike, reduced plant height, and increased harvest index (HI). The dwarfing allele Rht-D1b was the most frequent (68.0%) among the cultivars, followed by Rht 8 (42.0%) and Rht-B1b (16.0%). The frequency of 1B/1R translocation cultivars was 42.6%. The future challenge of wheat breeding in this region is to maintain the genetic gain in grain yield and to improve grain quality, without increasing inputs for the wheat-maize double cropping system.
Ozone (O 3 ) concentrations in periurban areas in East Asia are sufficiently high to decrease crop yield. However, little is known about the genotypic differences in O 3 sensitivity in winter wheat in relation to year of cultivar release. This paper reports genotypic variations in O 3 sensitivity in 20 winter wheat cultivars released over the past 60 years in China highlighting O 3 ‐induced mechanisms. Wheat plants were exposed to elevated O 3 (82 ppb O 3 , 7 h day −1 ) or charcoal‐filtered air (<5 ppb O 3 ) for 21 days in open top chambers. Responses to O 3 were assessed by the levels of antioxidative activities, protein alteration, membrane lipid peroxidation, gas exchange, leaf chlorophyll, dark respiration and growth. We found that O 3 significantly reduced foliar ascorbate (−14%) and soluble protein (−22%), but increased peroxidase activity (+46%) and malondialdehyde (+38%). Elevated O 3 depressed light saturated net photosynthetic rate (−24%), stomatal conductance (−8%) and total chlorophyll (−11%), while stimulated dark respiration (+28%) and intercellular CO 2 concentration (+39%). O 3 also reduced overall plant growth, but to a greater extent in root (−32%) than in shoot (−17%) biomass. There was significant genotypic variation in potential sensitivity to O 3 that did not correlate to observed O 3 tolerance. Sensitivity to O 3 in cultivars of winter wheat progressed with year of release and correlated with stomatal conductance and dark respiration in O 3 ‐exposed plants. O 3 ‐induced loss in photosynthetic rate was attributed primarily to impaired activity of mesophyll cells and loss of integrity of cellular membrane as evidenced by increased intercellular CO 2 concentration and lipid peroxidation. Our findings demonstrated that higher sensitivity to O 3 in the more recently released cultivars was induced by higher stomatal conductance, larger reduction in antioxidative capacity and lower levels of dark respiration leading to higher oxidative damage to proteins and integrity of cellular membranes.
Association mapping in populations relevant for wheat breeding has a large potential for validating and fine-mapping QTLs identified in F2- or DH (double haploid)-derived populations. In this study, associations between markers in the region of QSng.sfr-3BS, a major QTL for resistance to Stagonospora nodorum glume blotch (SNG), and SNG resistance were investigated by linkage and association analyses. After increasing marker density in 240 F5:7 recombinant inbred lines (RILs), QSng.sfr-3BS explained 43% of the genetic variance and peaked 0.6 cM proximal from the marker SUN2-3B. Association between SNG resistance and markers mapped in the region of QSng.sfr-3BS was investigated in a population of 44 modern European winter wheat varieties. Two genetically distinct subpopulations were identified within these lines. In agreement with linkage analyses, association mapping by a least squares general linear model (GLM) at marker loci in the region of QSng.sfr-3BS revealed the highest association with SNG resistance for SUN2-3B (p < 0.05). Association mapping can provide an effective mean of relating genotypes to complex quantitative phenotypes in hexaploid wheat. Linkage disequilibrium (r 2) in chromosome 3B extended less than 0.5 cM in 44 varieties, while it extended about 30 cM in 240 RILs, based on 91 SSR and STS marker-pair comparisons. This indicated that the association mapping population had a marker resolution potential at least 390-fold higher compared to the RIL population.
In the semi-humid to arid loess plateau areas of North China, water is the limiting factor for rain-fed crop yields. Conservation tillage has been proposed to improve soil and water conservation in these areas. From 1999 to 2005, we conducted a field experiment on winter wheat ( L.) to investigate the effects of conservation tillage on soil water conservation, crop yield, and water-use efficiency. The field experiment was conducted using reduced tillage (RT), no tillage with mulching (NT), subsoil tillage with mulching (ST), and conventional tillage (CT). NT and ST improved water conversation, with the average soil water storage in 0–200 cm soil depth over the six years increased 25.24 mm at the end of summer fallow periods, whereas RT soil water storage decreased 12 mm, compared to CT. At wheat planting times, the available soil water on NT and ST plots was significantly higher than those using CT and RT. The winter wheat yields were also significantly affected by the tillage methods. The average winter wheat yields over 6 years on NT or ST plots were significantly higher than that in CT or RT plots. CT and RT yields did not vary significantly between them. In each study year, NT and ST water-use efficiency (WUE) was higher than that of CT and RT. In the dry growing seasons of 1999–2000, 2004–2005 and the low-rainfall fallow season of 2002, the WUE of NT and ST was significantly higher than that of CT and RT, but did not vary significantly in the other years. For all years, CT and RT showed no WUE advantage. In relation to CT, the economic benefit of RT, NT, and ST increased 62, 1754, and 1467 yuan ha , respectively, and the output/input ratio of conservation tillage was higher than that of CT. The overall results showed that NT and ST are the optimum tillage systems for increasing water storage and wheat yields, enhancing WUE and saving energy on the Loess Plateau.
Fusarium head blight (FHB) of wheat has become a serious threat to wheat crops in numerous countries. In addition to loss of yield and quality, this disease is of primary importance because of the contamination of grain with mycotoxins such as deoxynivalenol (DON). The Swiss winter cultivar Arina possesses significant resistance to FHB. The objective of this study was to map quantitative trait loci (QTL) for resistance to FHB, DON accumulation and associated traits in grain in a double haploid (DH) population from a cross between Arina and the FHB susceptible UK variety Riband. FHB resistance was assessed in five trials across different years and locations. Ten QTL for resistance to FHB or associated traits were detected across the trials, with QTL derived from both parents. Very few of the QTL detected in this study were coincident with those reported by authors of two other studies of FHB resistance in Arina. It is concluded that the FHB resistance of Arina, like that of the other European winter wheat varieties studied to date, is conferred by several genes of moderate effect making it difficult to exploit in marker-assisted selection breeding programmes. The most significant and stable QTL for FHB resistance was on chromosome 4D and co-localised with the Rht–D1 locus for height. This association appears to be due to linkage of deleterious genes to the Rht-D1b (Rht2) semi-dwarfing allele rather than differences in height per se. This association may compromise efforts to enhance FHB resistance in breeding programmes using germplasm containing this allele.
Simulation of the timing of anthesis in wheat crops is achieved using two very different approaches. The older of these simulates progress to flowering by calculating the duration of phases between significant events on the shoot apex. The alternative method tracks development through leaf appearance, using the prediction of final mainstem leaf number to control the duration of the phase from emergence to flowering. Although these methods appear to differ substantially, we show in this paper that the number of leaves on the mainstem when the stage of terminal spikelet occurs is extremely tightly coupled to final mainstem leaf number. We conclude that accurate prediction of the terminal spikelet stage or similar prediction of mainstem leaf number amount to the same thing, so reconciling the methods.
Field experiments were conducted at an experimental station of Farmland Irrigation Research Institute of Chinese Academy of Agricultural Sciences in the Huang-Huai-Hai plain of China (HPC) during 2005–2006. The experiment comprised planting winter wheat in three patterns, namely, furrow irrigated raised bed-planting (FIRB), mulched ridge and furrow planting (MRFP) and conventional flat planting (FP). The study indicated that the FIRB and MRFP patterns had lower water consumption than the FP pattern due to decrease of irrigation amount and control of evaporation from topsoil. The water consumption was 354.5 mm for FIRB and 323.6 mm for MRFP, which were 12.3 and 20.0% lower than that in FP, respectively. The yield of FIRB and MRFP were respectively, 5.2% higher and 7.8% lower than FP. The water use efficiency (WUE) for FIRB and MRFP was 2.26 and 2.16 kg m , which was 20.2 and 14.9% higher over FP, respectively. Combining water consumption yield and WUE, it could be concluded that the FIRB system had higher yield than WUE, MRFP and FP, which will offer a sound opportunity for sustainable farming in HPC.
Irrigation plays an important role in increasing food production in China. The impact of irrigation on crop yield (Y), crop water productivity (CWP), and production has not been quantified systematically across regions covering the whole country. In this study, a GIS-based EPIC model (GEPIC) was applied to simulate Y and CWP for winter wheat (Triticum aestivum L.) in China at a grid resolution of 5 arc-minutes and to analyze the impacts of reducing irrigation water on wheat production. The findings show that irrigation is especially important in improving CWP of winter wheat in the North China Plain (NCP), the “bread basket” of China. On average, the provincial aggregate CWP was 56% higher under the irrigated than that under the rainfed conditions. The intensification of water stress and the associated increase in environmental problems in much of the NCP require critical thoughts about reducing water allocation for irrigated winter wheat. Two scenarios for irrigation reduction in the NCP provinces are presented: reducing irrigation depth (S1), and replacing irrigated winter wheat by rainfed winter wheat (S2). The simulation results show that S1 and S2 have similar effects on wheat production when the reduction in irrigation water supply is below 20% of the current level. Above this percentage, S2 appears to be a better scenario since it leads to less reduction in wheat production with the same amount of water saving.