A sand culture experiment was conducted to answer the question whether or not exogenous KNO can alleviate adverse effects of salt stress in winter wheat by monitoring plant growth, K /Na accumulation and the activity of some antioxidant enzymes. Seeds of two wheat cultivars (CVs), DK961 (salt-tolerant) and JN17 (salt-sensitive), were planted in sandboxes and controls germinated and raised with Hoagland nutrient solution (6 mM KNO , no NaCl). Experimental seeds were exposed to seven modified Hoagland solutions containing increased levels of KNO (11, 16, 21 mM) or 100 mM NaCl in combination with the four KNO concentrations (6, 11, 16 and 21 mM). Plants were harvested 30 d after imbibition, with controls approximately 22 cm in height. Both CVs showed significant reduction in plant height, root length and dry weight of shoots and roots under KNO or NaCl stress. However, the combination of increased KNO and NaCl alleviated symptoms of the individual salt stresses by improving growth of shoots and roots, reducing electrolyte leakage, malondialdehyde and soluble sugar contents and enhancing the activities of antioxidant enzymes. The salt-tolerant cultivar accumulated more K in both shoots and roots compared with the higher Na accumulation typical for the salt-sensitive cultivar. Soluble sugar content and activities of antioxidant enzymes were found to be more stable in the salt-tolerant cultivar. Our findings suggest that the optimal K /Na ratio of the nutrient solution should be 16:100 for both the salt-tolerant and the salt-sensitive cultivar under the experimental conditions used, and that the alleviation of NaCl stress symptoms through simultaneously applied elevated KNO was more effective in the salt-tolerant than in the salt-sensitive cultivar.
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.
Improvement of water use efficiency (WUE) in crops is important for almost all agricultural practices around the world. Numerous studies have addressed WUE on a grain yield basis, but few on a photosynthesis basis and a biomass basis. Based on a 2-year field experiment (2002–2004), we analyzed wheat WUE not only on grain yield basis, but also on photosynthesis basis and biomass basis, and then discussed the effects of irrigation regimes on wheat WUE. We found that: (1) irrigation regimes had considerable effects on wheat transpiration, total evapotranspiration, and canopy temperature; (2) wheat WUE ranged 2.1–3.3 μmol CO /mmol H O on a photosynthesis basis, 1.0–2.6 kg m and 1.1–2.1 kg m on a biomass and a grain yield basis, respectively. The maximum WUE appeared during the jointing and the milking stage, when suitable water management could be crucial to improve wheat WUE; (3) it was hypothesized by farmers and local water managers that more water supply over the conventional irrigation regime during the growing season could significantly increase both WUE and grain yield of the winter wheat in the north China plain (NCP). However, our results showed that with the increase of irrigation times and amount of irrigation water per growing season, wheat WUE was generally decreased and grain yield was not increased, although the evapotranspiration was significantly increased. Reduction in irrigation times and amount of irrigation water could be considered for saving water in the NCP; (4) WUE of winter wheat at photosynthesis and biomass levels were positively related with WUE at grain yield level.
Understanding of the effects of climatic change on phenological phases of a crop species may help optimize management schemes to increase productivity. This study determined the trend of climatic changes during the period of 1981–2004 in northwest China and assessed the impacts of climatic changes on phenological phases and productivity of winter wheat ( L.) and spring cotton ( L.) at two locations. There was a clear trend of climate warming during the study period, leading to the earliness of pseudo stem elongation, booting, anthesis, and ripening stages of winter wheat by 13.2, 9.8, 11.0, and 10.8 d during the 24-year period, respectively. The growth period from seedling emergence to stem elongation shortened 16.1 d, but the growth period from anthesis to milk prolonged 8.2 d during the 24-year period. In cotton, the dates of seedling emergence, budding, anthesis, and boll-opening stages became earlier by, respectively, 10.9, 9.0, 13.9, and 16.4 d during the period of 1983–2004. However, the growth periods from five-leaf stage to budding, budding to anthesis, and anthesis to boll-opening stages were prolonged by 2.4, 12.0, and 9.0 d, respectively, for every 1 °C of rise in minimum temperature during their respective growth period. Increasing minimum temperatures during the vegetative period positively affected winter wheat growth but increases in maximum temperatures during the reproductive period negatively affected kernel weight and grain yield. Consequently, the grain yield of winter wheat had decreased, but the yield of cotton had increased during the study period. The trend of climate warming appeared to be favourable for cotton production but unfavourable for winter wheat in northwest China.
Excessive nitrogen (N) fertilizer application is very common in the North China Plain. Diagnosis of in-season N status in crops is critical for precision N management in this area. Remote sensing, as a timely and nondestructive tool, could be an alternative to traditional plant testing for diagnosing crop N status. The objectives of this study were to determine which vegetation indices could be used to estimate N status in winter wheat ( L.) under high N input conditions, develop models to predict winter wheat N uptake using spectral vegetation indices and validate the models with data from farmers’ fields. An N rate experiment and a variety-N experiment were conducted in Huimin, Shandong Province from 2005/2006 to 2006/2007 to develop the models. Positive linear relationships between simple ratio vegetation indices (red vegetation index, RVI and green vegetation index, GVI) and N uptake were observed independent of growth stages and varieties ( , 0.48–0.74). In contrast, the relationships between normalized difference vegetation indices (NDVI and GNDVI), red and green normalized difference vegetation index (RGNDI), and red and green ratio vegetation index (RGVI) were exponentially related to N uptake ( , 0.43–0.79). Subsequently, 69 farmers’ fields in four different villages were selected as datasets to validate the developed models. The results indicated that the prediction using RVI had the highest coefficient of determination ( , 0.60), the lowest root mean square error (RMSE, 39.7 kg N ha ) and relative error (RE, 30.5%) across different years, varieties and growth stages. We conclude that RVI can be used to estimate nitrogen status for winter wheat in over-fertilized farmers’ fields before heading.
The main objective of this study was to elucidate the roles of silicon (Si) in enhancing tolerance to freezing stress (−5 °C) in two contrasting wheat ( L.) cultivars: i.e. cv. Yangmai No. 5, a freezing-susceptible cultivar and cv. Linmai No. 2, a freezing-tolerant cultivar. Shoot dry weight of the freezing-susceptible wheat was significantly lower under freezing stress than in controls, but increased significantly with Si amendment. The freezing treatment did not affect shoot dry weight of the freezing-tolerant cultivar. The leaf water content was considerably decreased by freezing stress in the freezing-susceptible cultivar, but was significantly increased by Si amendment. In contrast, freezing treatment did not significantly reduce leaf water content in the freezing-tolerant cultivar and Si played no role in water retention in this cultivar. The concentrations of H O and free proline along with malondialdehyde (MDA) were progressively enhanced by freezing stress in the two wheat cultivars used, but were significantly suppressed by amendment with Si. The major antioxidant enzyme activities and non-enzymatic antioxidants (i.e. glutathione and ascorbic acid) in the leaves of freezing-stressed plants were decreased, but were stimulated significantly by the exogenous Si. The possible mechanisms for Si-enhanced freezing stress may be attributed to the higher antioxidant defense activity and lower lipid peroxidation through water retention in leaf tissues.
Fusarium head blight (FHB) resistance is of particular importance in wheat breeding programmes due to the detrimental effects of this fungal disease on human and animal health, yield and grain quality. Segregation for FHB resistance in three European winter wheat populations enabled the identification of resistance loci in well-adapted germplasm. Populations obtained from crosses of resistant cultivars Apache, History and Romanus with susceptible semi-dwarfs Biscay, Rubens and Pirat, respectively, were mapped and analysed to identify quantitative trait loci (QTL) for FHB severity, ear emergence time and plant height. The results of the present study together with previous studies in UK winter wheat indicated that the semi-dwarfing allele Rht-D1b seems to be the major source for FHB susceptibility in European winter wheat. The high resistance level of the cultivars Romanus and History was conditioned by several minor resistance QTL interacting with the environment and the absence of Rht-D1b. In contrast, the semi-dwarf parents contributed resistance alleles of major effects apparently compensating the negative effects of Rht-D1b on FHB reaction. The moderately resistant cultivar Apache contributed a major QTL on chromosome 6A in a genome region previously shown to carry resistance loci to FHB. A total of 18 genomic regions were repeatedly associated with FHB resistance. The results indicate that common resistance-associated genes or genomic regions are present in European winter wheats.
The North China Plain (NCP) is one of the most water stressed areas in the world. The water consumption of winter wheat accounts for more than 50% of the total water consumption in this region. An accurate estimate of the evapotranspiration (ET) and crop water productivity (CWP) at regional scale is therefore key to the practice of water-saving agriculture in NCP. In this research, the ET and CWP of winter wheat in 83 counties during October 2003 to June 2004 in NCP were estimated using the remote sensing data. The daily ET was calculated using SEBAL model with NOAA remote sensing data in 17 non-cloud days whereas the reference daily crop ET was estimated using meteorological data based on Hargreaves approach. The daily ET and the total ET over the entire growing season of winter wheat were obtained using crop coefficient interpolation approach. The calculated average and maximum water consumption of winter wheat in these 83 counties were 424 and 475 mm, respectively. The calculated daily ET from SEBAL model showed good match with the observed data collected in a Lysimeter. The error of ET estimation over the entire growing stage of winter wheat was approximately 4.3%. The highest CWP across this region was 1.67 kg m , and the lowest was less than 0.5 kg m . We observed a close linear relationship between CWP and yield. We also observed that the continuing increase of ET leads to a peaking and subsequent decline of CWP, which suggests that the higher water consumption does not necessarily lead to a higher yield.