Tolerance Of Winter Wheat Research Articles

Effect of the transgenerational exposure to elevated CO2 on low temperature tolerance of winter wheat: Chloroplast ultrastructure and carbohydrate metabolism

AbstractThe transgenerational effect of elevated atmospheric CO2 concentration (e[CO2]) on low temperature response in wheat is still little investigated, through the interaction of e[CO2], and low‐temperature stress has been reported in a single generation. Here, the low temperature‐induced modifications of chloroplast ultrastructure and carbohydrate metabolism in wheat after four generations continuously grown under ambient CO2 concentration (a[CO2]) and e[CO2] (2014–2018) were investigated. The results indicated that the transgenerational exposure to e[CO2] increased the number of grana lamellae and the amounts of osmiophilic lipid droplets, attenuating the negative effect of low temperature on chloroplast ultrastructure. The transgenerational e[CO2] enhanced the activities of antioxidant enzymes (i.e. SOD, POD and CAT) and concentrations of osmotic substances (i.e. proline and soluble sugar), which alleviated the low temperature‐induced oxidative damage to the chloroplast ultrastructure. In addition, transgenerational exposure of wheat to e[CO2] increased activities of vacInv and cwInv, while decreased fructokinase activity, which affected the sucrose metabolism in wheat leaf. These findings elucidated that transgenerational exposure to e[CO2] could improve low temperature tolerance of winter wheat, which provide novel insights to the response of wheat to future climate change.

Foliar-Applied GR24 and Salicylic Acid Enhanced Wheat Drought Tolerance

Phytohormones salicylic acid and strigolactones play critical roles in mediating plant responses to environmental stress including drought stress. This study investigated whether foliar application of salicylic acid and strigolactones in the form of GR24 will improve the drought tolerance of winter wheat (T-riticum aestivum L.) plants. Exogenous application of strigolactone and salicylic acid increased proline and soluble sugar content as well as stomatal conductance, photosynthesis and transpiration rate of wheat plants. Higher amounts of all above mentioned characteristics are indicative of the higher drought tolerance of hormone-treated plants. In this experiment, application of hormones decreased the drought-induced rise in the content of H2O2 a factor known to lead to membrane lipid peroxidation, toxicity, and cell death. Hormones external application dampened leaf water potential that contributes to plant-level physiological drought tolerance. Drought tolerance features magnified when we used both hormones together. Our finding suggests that hormonal application can improve osmotic adjustment and decrease adverse effects of drought stress on wheat plants.

Molybdenum Application Regulates Oxidative Stress Tolerance in Winter Wheat Under Different Nitrogen Sources

Molybdenum (Mo), an essential microelement, may enhance the oxidative stress tolerance in plants. However, the efficacy of Mo might be variable with different forms of nitrogen (N) fertilizer. The present study was conducted to investigate the role of Mo application in regulating oxidative stress tolerance in winter wheat under different N sources. A hydroponic study was carried out comprising of two winter wheat cultivars ‘97003’ and ‘97014’ as Mo efficient and Mo inefficient, respectively, under two Mo levels (0 and 1 μM) and three different N sources (NO3, NH4NO3, or NH4+). Winter wheat plants supplied with different N sources accumulated superoxide anions (O2−), and malonaldehyde (MDA) contents in the order of NH4+ > NO3 > NH4NO3, suggesting that sole application of either N sources, especially sole NH4+ source, may induce oxidative stress in winter wheat. However, Mo application decreased the MDA contents by 20.02%, 15.11%, and 25.89% in Mo-efficient cultivar and 30.75%, 23.79%, and 37.76% in Mo-inefficient cultivar under NO3, NH4NO3, and NH4+ sources, respectively, while increased antioxidant enzyme activities and carotenoids and abscisic acid (ABA) contents up-regulated the expressions of TaAO and TaAba3 genes. Mo application regulated oxidative stress tolerance in winter wheat under different N sources through enhancing ABA production and ROS-scavenging enzymes. Mo-efficient ‘97003’ winter wheat cultivar possesses a wider range of adaptability to withstand Mo-deficient conditions than Mo-inefficient ‘97014’ cultivar.

Evaluating Selection of a Quantitative Trait: Snow Mold Tolerance in Winter Wheat

Core Ideas Six quantitative trait loci for snow mold tolerance were detected in a winter wheat recombinant inbred line population. Marker‐assisted selection to incorporate QTL is unlikely to help breed for highly quantitative traits. Genomic selection could replace initial phenotyping for quantitative traits. Selection for snow mold tolerance (SMT) in winter wheat (Triticum aestivum L.) is complicated by the influence of numerous quantitative trait loci (QTL) and of environmental conditions. The goals of this study were to identify QTL for SMT, determine the effectiveness of marker‐assisted selection (MAS), and model the effectiveness of genomic prediction for SMT. Quantitative trait loci analysis of a recombinant inbred line (RIL) subpopulation, derived from a cross between Xerpha and Münstertaler, detected six unique QTL. Progeny from the same cross were advanced by MAS and compared with the unselected subpopulation to evaluate the efficacy of MAS. No significant difference was found between the SMT means (p = 0.41). Similarly, genomic selection had very poor accuracy (−0.07) in the Xerpha–Münstertaler (XM) RIL subpopulation. This contrasts with the apparent effectiveness of genomic selection (0.65) in a Finch–Eltan RIL population, also evaluated for SMT. The failure of selection tools to improve SMT in the XM population is likely due to the challenges of rating a quantitative trait that requires highly specific environmental conditions for phenotype development.

Genome-Wide Association Mapping of Seedling Heat Tolerance in Winter Wheat.

Heat stress during the seedling stage of early-planted winter wheat (Triticum aestivum L.) is one of the most abiotic stresses of the crop restricting forage and grain production in the Southern Plains of the United States. To map quantitative trait loci (QTLs) and identify single-nucleotide polymorphism (SNP) markers associated with seedling heat tolerance, a genome-wide association mapping study (GWAS) was conducted using 200 diverse representative lines of the hard red winter wheat association mapping panel, which was established by the Triticeae Coordinated Agricultural Project (TCAP) and genotyped with the wheat iSelect 90K SNP array. The plants were initially planted under optimal temperature conditions in two growth chambers. At the three-leaf stage, one chamber was set to 40/35°C day/night as heat stress treatment, while the other chamber was kept at optimal temperature (25/20°C day/night) as control for 14 days. Data were collected on leaf chlorophyll content, shoot length, number of leaves per seedling, and seedling recovery after removal of heat stress treatment. Phenotypic variability for seedling heat tolerance among wheat lines was observed in this study. Using the mixed linear model (MLM), we detected multiple significant QTLs for seedling heat tolerance on different chromosomes. Some of the QTLs were detected on chromosomes that were previously reported to harbor QTLs for heat tolerance during the flowering stage of wheat. These results suggest that some heat tolerance QTLs are effective from the seedling to reproductive stages in wheat. However, new QTLs that have never been reported at the reproductive stage were found responding to seedling heat stress in the present study. Candidate gene analysis revealed high sequence similarities of some significant loci with candidate genes involved in plant stress responses including heat, drought, and salt stress. This study provides valuable information about the genetic basis of seedling heat tolerance in wheat. To the best of our knowledge, this is the first GWAS to map QTLs associated with seedling heat tolerance targeting early planting of dual-purpose winter wheat. The SNP markers identified in this study will be used for marker-assisted selection (MAS) of seedling heat tolerance during dual-purpose wheat breeding.

Heat Priming During Early Reproductive Stages Enhances Thermo-Tolerance to Post-anthesis Heat Stress via Improving Photosynthesis and Plant Productivity in Winter Wheat (Triticum aestivum L.).

Heat stress during grain filling substantially decreases wheat productivity; thus, to ensure food security, heat tolerance in wheat needs to be developed. In this study, we evaluated the effect of heat priming applied during the stem-elongation stage, booting and anthesis, followed by 5 days of severe heat stress (a 7.86°C rise in temperature) during the grain-filling stage on physiological activities and grain yield of winter wheat in pot experiments during the 2015-2017 growing seasons using the winter wheat cultivars Yangmai 18 (a vernal type) and Yannong 19 (a facultative type). Compared with the damage observed in non-primed plants, heat priming during the stem-elongation stage and booting significantly prevented the grain-yield damage caused by heat stress during grain filling. Heat-primed plants displayed higher sucrose contents and sucrose-phosphate activity in leaves and greater above-ground dry matter than non-primed plants. Priming during stem elongation and booting led to increased photosynthetic capacity, stomatal conductance and chlorophyll contents in comparison with non-priming. Improved tolerance to heat stress due to the enhanced activities of antioxidant enzymes superoxide dismutase and peroxidase and reductions in reactive oxygen species and malondialdehyde production was observed in primed plants compared with non-primed plants of both cultivars. The positive effect of heat priming on the response to heat stress during grain filling was more pronounced in plants primed at the booting stage than in those primed at the stem-elongation or anthesis stage. Moreover, the vernal-type Yangmai 18 benefited more from heat priming than did Yannong 19, as evidenced by its higher productivity. We conclude that heat priming during early reproductive-stage growth can improve post-anthesis heat tolerance in winter wheat.

Coronatine enhances drought tolerance in winter wheat by maintaining high photosynthetic performance

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae. Its structure is similar to those of jasmonates (JAs), which play diverse roles in multiple plant biotic and abiotic defenses. However, the biological activity of COR is 1000 times greater than the activity of JA. In addition to being involved in the JA pathway, COR affects plant photosynthetic efficiency. In this study, we examined wheat blade pretreatment with COR. Blades treated with COR remained green longer than those of control plants under drought stress conditions, resulting in less yield loss with COR treatment. To investigate the mechanism of COR in drought resistance further, we employed two-dimensional gel electrophoresis technology and matrix-assisted laser desorption/ionization mass spectrometry to sequester and identify key proteins. Six COR-inducible proteins that are located in the chloroplast and involved directly in photosynthesis were found. The wheat homologue of protein gi|326509937 is degradation of periplasmic proteins 1 (DEGP1) in Arabidopsis, which is a response to photosystem II reparation, and was maintained at a low level with COR treatment. Finally, we measured levels of chlorophyll and photosynthetic performance to reveal the phenotypic effect of COR. Taken together, the results demonstrate that COR enhances drought tolerance by maintaining high photosynthetic performance.

Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain then progressively lose freezing tolerance. Exposing the plants to freeze–thaw cycles of −3/3 °C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This study was conducted to determine to what extent the length of time that a plant is grown at low temperatures influenced the effectiveness of this freeze–thaw enhancement of freezing tolerance. Plants from six winter wheat lines were grown at 4 °C for 1–18 wk, exposed to 0–2 cycles of freezing to −3 °C for 24 h, then thawed for 24 h at 3 °C, then tested for their ability to tolerate freezing to −10 °C to −17 °C. The freeze–thaw treatments resulted in increased freezing tolerance after 6–12 wk of growth at low temperatures, but had no significant effect before or after that time period. Two cycles of −3/3 °C freeze–thaw was consistently more effective than one cycle. Variation in the extent and timing of the effective...

Estimation of Crown Temperature of Winter Wheat and the Effect on Simulation of Frost Tolerance

AbstractAccurate estimation of winter wheat frost kill in cold‐temperate agricultural regions is limited by lack of data on soil temperature at wheat crown depth, which determines winter survival. We compared the ability of four models of differing complexity to predict observed soil temperature at 2 cm depth during two winter seasons (2013‐14 and 2014‐15) at Ultuna, Sweden, and at 1 cm depth at Ilseng and Ås, Norway. Predicted and observed soil temperature at 2 cm depth was then used in FROSTOL model simulations of the frost tolerance of winter wheat at Ultuna. Compared with the observed soil temperature at 2 cm depth, soil temperature was better predicted by detailed models than simpler models for both seasons at Ultuna. The LT50 (temperature at which 50 % of plants die) predictions from FROSTOL model simulations using input from the most detailed soil temperature model agreed better with LT50 FROSTOL outputs from observed soil temperature than what LT50 FROSTOL predictions using temperature from simpler models did. These results highlight the need for simpler temperature prediction tools to be further improved when used to evaluate winter wheat frost kill.

Effect of Early-Stage Regulated Deficit Irrigation on Stem Lodging Resistance, Leaf Photosynthesis, Root Respiration and Yield Stability of Winter Wheat under Post-Anthesis Water Stress Conditions

A field micro-plot experiment was conducted to study the effect of early-stage regulated deficit irrigation (RDI) on the stress tolerance of winter wheat in the late growth stage. Plants were subjected to two RDI treatments: proper water deficits (45-55% field water capacity) were imposed during tillering—the beginning of the spring growth stage (T1) and during the beginning of spring growth to the end of the stem elongation stage (T2). The control plants (CK) were maintained with an adequate water supply until anthesis. The results showed that T1 and T2 shortened the length of the first and second internodes, and increased their weight per unit length, and thereby enhanced stem lodging resistance. Although post-anthesis drought and waterlogging lowered leaf photosynthetic rate and root respiration rate, the two RDI treatments improved significantly compared to the control. The two RDI treatments had no significant effects on grain yield under post-anthesis well-watered conditions but increased grain yield and yield stability of wheat under post-anthesis water stress. In addition, T1 and T2 significantly reduced water consumption and increased water productivity (WP) of wheat compared to the control. In summary, this study shows that appropriate RDI at early growth stages increased grain yield and yield stability through improving population characteristics, root respiration and photosynthesis of plants under post-anthesis water stress conditions. Copyright © 2016 John Wiley & Sons, Ltd.

Genetic characterization of aluminum tolerance in winter wheat

Aluminum toxicity in acidic soils is a major constraint to winter wheat productivity in the southern Great Plains, USA. In this study, a population of recombinant inbred lines generated from a cross between two winter wheat cultivars, ‘Jagger’ with high acidic soil tolerance and ‘2174’ with moderate acidic soil tolerance, was used to map genes for acidic soil tolerance in the field. As expected, a major QTL centered on TaALMT1 on chromosome 4DL was observed. Further sequencing, however, indicated that Jagger carried an allele having Type V of triplicated sequence repeats in TaALMT1-1, whereas 2174 carried an allele having Type IV of two (A–B) block sequences in TaALMT1-2. The Jagger TaALMT1-1-V allele was expressed at a significantly higher level than the 2174 TaALMT1-2-IV allele not only in roots as reported in previous studies but also in leaves found in this study. No sequence was found for genes to be homoeologous to TaALMT1 in any of the recently released genomic sequences of diploid, tetraploid, or hexaploid wheat, suggesting that neither TaALMT1-A nor TaALMT1-B exists in wheat. Therefore, TaALMT1 is a gene unique to genome D. In addition, Jagger had the favorable allele at a QTL mapped on chromosome 2DL, whereas 2174 had the favorable allele at a QTL mapped on chromosome 7BL. The combination of these three complementary QTLs/genes/alleles may help to generate winter wheat lines that confer greater tolerance to acidic soils.

Winter wheat (Triticum aestivum L.) response to herbicides as affected by application timing and temperature

Robinson, M. A., Letarte, J., Cowbrough, M. J., Sikkema, P. H. and Tardif, F. J. 2015. Winter wheat (Triticum aestivum L.) response to herbicides as affected by application timing and temperature. Can. J. Plant Sci. 95: 325–333. Field studies were conducted to determine the effects of cold temperatures and physiological growth stage at the time of application on the tolerance of winter wheat (Triticum aestivum L.) to 10 herbicides used in Ontario, Canada. Herbicides were applied: early during a frost event (when forecasted temperatures ≤ 0°C); at a normal timing (Zadoks 21–29); and a late timing (Zadoks 39). Visible injury, yield, plant height at maturity, test weight and 1000-kernel weight were measured to determine if environmental conditions or growth stage at the time of herbicide application influenced wheat tolerance. Cold temperatures at the time of herbicide application resulted in injury with three treatments: 2,4-D, dicamba/MCPA/mecoprop and dichlorprop/2,4-D. Visible injury was greatest at 14 d after treatment (DAT); it was, however, transient and yield, plant height, test weight and 1000-kernel weight were not affected. The herbicides 2,4-D, dichlorprop/2,4-D, and fenoxaprop-p-ethyl caused visible injury 14 DAT when applied at the normal timing, while 2,4-D at this timing, also caused injury 7 DAT. Dicamba/MCPA/mecoprop was the most injurious herbicide, causing 4% injury at the normal timing and 11% injury at the late application timing (42 DAT). Dicamba/MCPA/mecoprop caused yield reductions of 11 to 24% at two locations in 2010 when applied at the normal timing. Dicamba/MCPA/mecoprop reduced yield at 6 of the 8 site-years when applied late, and also reduced plant height. Cold temperatures at the time of application did not affect tolerance of winter wheat; however, visible injury was more likely to occur when herbicides were applied at later growth stages. In most cases, herbicide injury was transient and no impact on yield was observed. Dicamba/MCPA/mecoprop was the most injurious herbicide, causing prolonged injury at all application timings and reducing yields when applied at the normal timing. In addition, yield and plant height were affected negatively when this herbicide was applied late.

Winter wheat (Triticum aestivum L.) response to herbicides as affected by application timing and temperature

Robinson, M. A., Letarte, J., Cowbrough, M. J., Sikkema, P. H. and Tardif, F. J. 2015. Winter wheat (Triticum aestivum L.) response to herbicides as affected by application timing and temperature. Can. J. Plant Sci. 95: 325-333. Field studies were conducted to determine the effects of cold temperatures and physiological growth stage at the time of application on the tolerance of winter wheat (Triticum aestivum L.) to 10 herbicides used in Ontario, Canada. Herbicides were applied: early during a frost event (when forecasted temperatures ≤ 0°C); at a normal timing (Zadoks 21-29); and a late timing (Zadoks 39). Visible injury, yield, plant height at maturity, test weight and 1000-kernel weight were measured to determine if environmental conditions or growth stage at the time of herbicide application influenced wheat tolerance. Cold temperatures at the time of herbicide application resulted in injury with three treatments: 2,4-D, dicamba/MCPA/mecoprop and dichlorprop/2,4-D. Visible injury was greatest at 14 d...

Responses of Winter Wheat to Herbicide-Fungicide Tankmixes

Tankmixing herbicides with fungicides could improve production efficiency and reduce application costs. A total of six field trials were conducted from 2012 to 2014 in Ontario to study the tolerance of winter wheat to herbicide (fenoxaprop-p-ethyl/mefenpyr, prosulfuron + bromoxynil and fluroxypyr + MCPA ester) plus fungicide tankmixes (pyraclostrobin/metconazole, tri-floxystrobin/propiconazole, azoxystrobin/propiconazole and picoxystrobin) applied alone and as a tankmix. At 1 WAT, fenoxaprop-p-ethyl/mefenpyr applied alone or in tankmix with tri-floxystrobin/propiconazole or azoxystrobin/propiconazole fungicides caused minimal visible injury (up to 1.3%) in winter wheat but caused no significant injury when applied as a tankmix with pyraclostrobin/metconazole or picoxystrobin fungicides. There was no effect on visible injury in winter wheat with other herbicide and fungicide tankmixes. Fenoxaprop-p-ethyl/mefenpyr applied alone with no fungicide reduced winter wheat height 3% but had no adverse effect on height when tankmixed with fungicides evaluated. Prosulfuron + bromoxynil or fluroxypyr + MCPA ester herbicides applied alone with no fungicide or tankmixed with pyraclostrobin/metconazole, tri-floxystrobin/propiconazole, azoxystrobin/propiconazole and picoxystrobin fungicides had no adverse effect on winter wheat height. There was no adverse effect of herbicide plus fungicide treatments on winter wheat yield. Co-application of fenoxaprop-p-ethyl/mefenpyr, prosulfuron + bromoxynil and fluroxypyr + MCPA ester herbicides with pyraclostrobin/metconazole, tri-floxystrobin/pro- piconazole, azoxystrobin/propiconazole and picoxystrobin fungicides could provide winter wheat growers with a single-pass treatment for the control of weeds and diseases.

Impacts of Crop Variety and Time of Inoculation on the Susceptibility and Tolerance of Winter Wheat to Wheat streak mosaic virus.

Plant genotype, age, size, and environmental factors can modify susceptibility and tolerance to disease. Understanding the individual and combined impacts of these factors is needed to define improved disease management strategies. In the case of Wheat streak mosaic virus (WSMV) in winter wheat, yield losses and plant susceptibility have been found to be greatest when the crop is exposed to the virus in the fall in the central and southern Great Plains. However, the seasonal dynamics of disease risk may be different in the northern Great Plains, a region characterized by a relatively cooler fall conditions, because temperature is known to modify plant-virus interactions. In a 2-year field study conducted in south-central Montana, we compared the impact of fall and spring WSMV inoculations on the susceptibility, tolerance, yield, and grain quality of 10 winter wheat varieties. Contrary to previous studies, resistance and yields were lower in the spring than in the fall inoculation. In all, 5 to 7% of fall-inoculated wheat plants were infected with WSMV and yields were often similar to uninoculated controls. Spring inoculation resulted in 45 to 57% infection and yields that were 15 to 32% lower than controls. Although all varieties were similarly susceptible to WSMV, variations in tolerance (i.e., yield losses following exposure to the virus) were observed. These results support observations that disease risk and impacts differ across the Great Plains. Possible mechanisms include variation in climate and in the genetic composition of winter wheat and WSMV across the region.

Tolerance of Winter Wheat to Co-application of Postemergence Broadleaf Herbicides Using Urea Ammonium Nitrate as the Carrier

Tolerance of Winter Wheat to Co-application of Postemergence Broadleaf Herbicides Using Urea Ammonium Nitrate as the Carrier

Tolerance of Winter Wheat to Co-application of Postemergence Broadleaf Herbicides Using Urea Ammonium Nitrate as the Carrier

Spring application of post-emergence (POST) broadleaf herbicides in a urea ammonium nitrate (UAN) as the carrier may provide winter wheat growers with a one-pass option for weed control and nitrogen application. Winter wheat tolerance to bromoxynil/MCPA, dichlorprop/2,4-D, thifensulfuron/tribenuron + MCPA amine or pyrasulfotole/bromoxynil applied using 28% UAN at various carrier volumes (0, 100, 200, 300 and 400 L ha-1) was evaluated in field experiments planted in the fall of 2008, 2009 and 2010 at Exeter and Ridgetown Ontario, Canada. Generally, winter wheat injury was greater as the carrier volume of UAN increased. Injury due to bromoxynil/MCPA, dichlorprop/2,4-D, thifensulfuron/tribenuron + MCPA amine and pyrasulfotole/bromoxynil was as much as 8, 11, 18 and 9% at 7 days after treatment (DAT); the injury observed was transient and was 1, 2, 4 and 1% at 28 DAT, respectively. Winter wheat height and yield were not reduced by the herbicides evaluated, excepting bromoxynil/MCPA which reduced yield by 2%, and thifensulfuron/tribenuron + MCPA amine, which reduced height 3% and yield 2%. The establishment of underseeded red clover was decreased by at least 50% for all herbicide treatments assessed, except bromoxynil/MCPA. Based on this study, there is potential for spring co-application of UAN and bromoxynil/MCPA, dichlorprop/2,4-D, thifensulfuron/tribenuron + MCPA amine or pyrasulfotole/bromoxynil in winter wheat. However, growers that underseed red clover may not fully benefit as carrier UAN significantly reduced clover establishment.

Time and Temperature Interactions in Freezing Tolerance of Winter Wheat

ABSTRACTTo survive the temperature fluctuations that occur during the winter months, winter wheat (Triticum aestivum L.) plants must tolerate episodes of freezing of varying intensity and duration. In this study, the ability of six wheat cultivars to survive exposure to −13.5 to −16.5°C for 2, 3, or 4 h was measured. Tolerance was described as the percentages of plants surviving after time intervals at −10°C or less. The average survival of the six cultivars significantly decreased by about 50% as length of exposure to −10°C or less was increased from 325 to 525 min. Surprisingly, survival then increased with longer exposure times such that the percentages of plants surviving were similar after 675, and after 325 min at −10°C or less. The greater survival after longer exposure times to −10°C or less compared with shorter exposure times suggested that certain freezing tolerance mechanism(s) in wheat are activated only after sufficient exposure to subfreezing temperatures for a sufficient amount of time. Lesser exposure to either temperature or time apparently does not activate this mechanism, leading to greater plant death. Further characterization of this mechanism and its genetic control may lead to development of wheat lines with enhanced ability to survive harsh freezing conditions and thus improved winterhardiness.

Tolerance of Winter Wheat (<i>Triticum aestivum</i> L.) and Under Seeded Red Clover (<i>Trifolium pretense</i> L.) to Fall Applied Post-Emergent Broadleaf Herbicides

The fall application of post-emergent (POST) herbicides on winter wheat provided effective control of emerged winter annual, biennial, and perennial broadleaf weeds. In recent years, wheat producers have seen a shift to these weeds, due in part, to the adoption of reduced-and no-tillage practices and the use of non-residual herbicides such as glyphosate in the preceding soybean and corn crops. The tolerance of winter wheat to ten herbicides, applied POST in the fall, was evaluated between 2008 and 2011 at Exeter and Ridgetown, Ontario. Winter wheat yield was not reduced by applications of MCPA ester, dicamba/ MCPA/ mecoprop, clopyralid, bromoxynil/ MCPA, thifensulfuron /tribenuron +MCPA ester, fluroxypyr +MCPA ester, and pyrasulfotole/ bromoxynil. In contrast, 2,4-D ester and dichlorprop/2,4-D, caused visible injury in June and July of the following year and consistently decreased winter wheat yield by at least 10%. Applications of 100 g a.i. ha-1 saflufenacil also decreased winter wheat yield in two of the four harvest years examined. None of the herbicide options examined were safe on red clover when it was under seeded the spring following winter wheat planting. All herbicides significantly decreased red clover dry biomass one month after wheat harvest.

Nonsense-mediated decay of sucrose synthase 1 mRNA with induced premature chain termination codon during cold acclimation in winter wheat

Cold acclimation induces the expression of cold-regulated genes needed to protect plants against freezing damage. Fourteen candidate genes were identified as being differentially expressed (presence/absence) between cold acclimated and nonacclimated crown and leaf tissues of 2 winter wheat lines using the cDNA-AFLP method. Two TILLING populations originating from the 2 winter wheat lines were further developed in order to create mutant forms of the candidate genes to verify their role in freezing-tolerance formation. Exon 8 of the identified differentially expressed sucrose synthase 1 (Ss1) gene was chosen for mutation detection by high-resolution melting analysis. A total of 75.68 kb of DNA was screened and 2 novel alleles of the Ss1 gene were identified, of which 1 was silent and 1 was a nonsense (premature stop codon) mutation. qRT-PCR analysis showed that premature stop codon mutation has a strong negative effect on Ss1 gene expression in nonacclimated leaves as well as in crowns and leaves collected at 2, 4, and 6 weeks of cold acclimation compared with the wild-type winter wheat line. Further work will reveal the effect of the mutation on cold tolerance of winter wheat and will enable the assessment of the role of Ss1 in the cold acclimation process.