Influence of iron nanoparticles (Fe3O4 and Fe2O3) on the growth, photosynthesis and antioxidant balance of wheat plants (Triticum aestivum)

More and more attention is paid to the development of technologies using iron nanoparticles in agriculture. In this regard, the effect of treatment of wheat seeds with various concentrations of iron nanoparticles Fe3O4 and Fe2O3 on the accumulation of biomass, the rate of photosynthesis and respiration, as well as on photochemical activity and antioxidant balance was studied. The seeds were treated for 3 h, germinated for 2 days in Petri dishes, transplanted into sand and grown under light for 18 days without mineral nutrition until the third leaf appeared. At a Fe3O4 concentration of 200 mg L-1 a significant increase in the dry biomass of the second leaf by 45% and the rate of photosynthesis by 16% was observed. At a concentration of nanoparticles in the form of Fe2O3 of 200 and 500 mg L-1, an increase in the rate of photosynthesis in the second leaf was also observed, but not in the biomass of the leaves. The activity of photosystem 2, estimated from the Fv/Fm value, also increased in experiments with nanoiron. However, the activity of antioxidant enzymes, guaiacol-dependent peroxidase and superoxide dismutase, decreased. It is assumed that the acceleration of growth at an early stage of wheat development is associated with an increase in photosynthetic processes.

Wheat germination and highly diluted agitated gibberellic acid (10e-30) - a multi researcher study

Grains of winter wheat (Triticum aestivum L., Capo variety) were observed under the influence of highly diluted gibberellic acid (10-30) prepared by stepwise dilution and agitation according to a protocol derived from homeopathy (“G30x”). Adequate control was used (water prepared according to the homeopathic protocol “W30x” and/or untreated water “W0”). Two sets of multicenter experiments were performed, 4 in 2009-2010 and 4 in 2011, involving altogether 6 researchers, 6 laboratories and 4,000 grains per treatment group. Data were found to be homogeneous within the control groups as well as within the verum groups. When the 2009-2010 experiments were pooled, mean germination rates after 24 hours were (85.9 + 2.6) for the control group and (82.1 + 5.7) for G30x (mean + SD at the level of experiments in %) (N = 2,000 per group). Verum germination rate was 4.4% lower than (i.e. equal to 96.6% of) (4.4 + 96.6 = 101) the control germination rate (100%). The difference is statistically significant (p < 0.001) and the effect size (d) is large (> 0.8). Observations at other points in time between 0 and 40 hours of germination yielded similar results. Practically no difference was found between W30x and W0 groups (p > 0.05). When the 2011 experiments were pooled, the mean germination rates after 24 hours were (73 + 12) for the control group and (73 + 14) for G30x (N = 2,000 per group), i.e. there was practically no difference between the groups (p > 0.05). We interpret the data from 2009-2010 on wheat germination within 40 hours as being in line with our previous findings on wheat stalk growth after one week, i.e. as confirmation that gibberellic acid 30x can influence, i.e. slow down, wheat development. Various possible reasons for the absence of any difference between groups in the 2011 experiments, including seasonal variance, are discussed and it is suggested to perform wheat germination experiments in the very beginning of autumn season only.

Key auxin response factor (ARF) genes constraining wheat tillering of mutant dmc

Tillering ability is a key agronomy trait for wheat (Triticum aestivum L.) production. Studies on a dwarf monoculm wheat mutant (dmc) showed that ARF11 played an important role in tillering of wheat. In this study, a total of 67 ARF family members were identified and clustered to two main classes with four subgroups based on their protein structures. The promoter regions of T. aestivum ARF (TaARF) genes contain a large number of cis-acting elements closely related to plant growth and development, and hormone response. The segmental duplication events occurred commonly and played a major role in the expansion of TaARFs. The gene collinearity degrees of the ARFs between wheat and other grasses, rice and maize, were significantly high. The evolution distances among TaARFs determine their expression profiles, such as homoeologous genes have similar expression profiles, like TaARF4-3A-1, TaARF4-3A-2 and their homoeologous genes. The expression profiles of TaARFs in various tissues or organs indicated TaARF3, TaARF4, TaARF9 and TaARF22 and their homoeologous genes played basic roles during wheat development. TaARF4, TaARF9, TaARF12, TaARF15, TaARF17, TaARF21, TaARF25 and their homoeologous genes probably played basic roles in tiller development. qRT-PCR analyses of 20 representative TaARF genes revealed that the abnormal expressions of TaARF11 and TaARF14 were major causes constraining the tillering of dmc. Indole-3-acetic acid (IAA) contents in dmc were significantly less than that in Guomai 301 at key tillering stages. Exogenous IAA application significantly promoted wheat tillering, and affected the transcriptions of TaARFs. These data suggested that TaARFs as well as IAA signaling were involved in controlling wheat tillering. This study provided valuable clues for functional characterization of ARFs in wheat.

Main Effect and Epistatic QTL Affecting Spike Shattering and Association with Plant Height Revealed in Two Spring Wheat (Triticum aestivum L.) Populations

Spike shattering can cause severe grain yield loss in wheat. Development of cultivars with reduced shattering but having easy threshability is the target of wheat breeding programs. This study was conducted to determine quantitative trait loci (QTL) associated with shattering resistance, and epistasis among QTL in the Carberry/AC Cadillac and Carberry/Thatcher populations. Response of the populations to spike shattering was evaluated near Swift Current, SK, in four to five environments. Plant height data recorded in different locations and years was used to determine the relationship of the trait with spike shattering. Each population was genotyped and mapped with the wheat 90K Illumina iSelect SNP markers. Main effect QTL were analyzed by MapQTL 6 and epistatic interactions between main effect QTL were determined by QTLNetwork 2.0. Positive correlations were observed both within trait location-year combinations as well as between trait location-year combinations. Carberry contributed two major QTL associated with spike shattering on chromosome arms 4BS and 5AL, detected in both populations. Carberry also contributed two minor QTL on 7AS and 7AL. AC Cadillac contributed five minor QTL on 1AL, 2DL, 3AL, 3DL and 7DS. Nine epistatic QTL interactions were identified, out of which the most consistent and synergistic interaction, that reduced the expression of shattering, occurred between 4BS and 5AL QTL. The 4BS QTL was consistently associated with reduced shattering and reduced plant height in the coupling phase. The present findings shed light on the inheritance of shattering resistance and provide genetic markers for manipulating the trait to develop wheat cultivars.

TaCKX2.2 Genes Coordinate Expression of Other TaCKX Family Members, Regulate Phytohormone Content and Yield-Related Traits of Wheat

TaCKX gene family members (GFMs) play essential roles in the regulation of cytokinin during wheat development and significantly influence yield-related traits. However, detailed function of most of them is not known. To characterize the role of TaCKX2.2 genes we silenced all homoeologous copies of both TaCKX2.2.1 and TaCKX2.2.2 by RNAi technology and observed the effect of silencing in 7 DAP spikes of T1 and T2 generations. The levels of gene silencing of these developmentally regulated genes were different in both generations, which variously determined particular phenotypes. High silencing of TaCKX2.2.2 in T2 was accompanied by slight down-regulation of TaCKX2.2.1 and strong up-regulation of TaCKX5 and TaCKX11, and expression of TaCKX1, TaCKX2.1, and TaCKX9 was comparable to the non-silenced control. Co-ordinated expression of TaCKX2.2.2 with other TaCKX GFMs influenced phytohormonal homeostasis. Contents of isoprenoid, active cytokinins, their conjugates, and auxin in seven DAP spikes of silenced T2 plants increased from 1.27 to 2.51 times. However, benzyladenine (BA) and abscisic acid (ABA) contents were significantly reduced and GA3 was not detected. We documented a significant role of TaCKX2.2.2 in the regulation of thousand grain weight (TGW), grain number, and chlorophyll content, and demonstrated the formation of a homeostatic feedback loop between the transcription of tested genes and phytohormones. We also discuss the mechanism of regulation of yield-related traits.

Phenology and Floret Development as Affected by the Interaction between Eps-7D and Ppd-D1

Earliness per se (Eps) genes may play a critical role in further improving wheat adaptation and fine-tuning wheat development to cope with climate change. There are only few studies on the detailed effect of Eps on wheat development and fewer on the interaction of Eps with the environment and other genes determining time to anthesis. Furthermore, it seems relevant to study every newly discovered Eps gene and its probable interactions as the mechanisms and detailed effects of each Eps may be quite different. In the present study, we evaluated NILs differing in the recently identified Eps-7D as well as in Ppd-D1 at three temperature regimes (9, 15 and 18 °C) under short day. The effect of Eps-7D on time to anthesis as well as on its component phases varied both qualitatively and quantitatively depending on the allelic status of Ppd-D1 and temperature, being larger in a photoperiod-sensitive background. A more noticeable effect of Eps-7D (when combined with Ppd-D1b) was realised during the late reproductive phase. Consequently, the final leaf number was not clearly altered by Eps-7D, while floret development of the labile florets (florets 2 and 3 in this case, depending on the particular spikelet) was favoured by the action of the Eps-7D-late allele, increasing the likelihood of particular florets to become fertile, and consequently, improving spike fertility when combined with Ppd-D1b.

Genome-wide analysis of growth-regulating factors (GRFs) in Triticum aestivum

The Growth-Regulating Factor (GRF) family encodes a type of plant-specific transcription factor (TF). GRF members play vital roles in plant development and stress response. Although GRF family genes have been investigated in a variety of plants, they remain largely unstudied in bread wheat (Triticum aestivum L.). The present study was conducted to comprehensively identify and characterize the T. aestivum GRF (TaGRF) gene family members. We identified 30 TaGRF genes, which were divided into four groups based on phylogenetic relationship. TaGRF members within the same subgroup shared similar motif composition and gene structure. Synteny analysis suggested that duplication was the dominant reason for family member expansion. Expression pattern profiling showed that most TaGRF genes were highly expressed in growing tissues, including shoot tip meristems, stigmas and ovaries, suggesting their key roles in wheat growth and development. Further qRT-PCR analysis revealed that all 14 tested TaGRFs were significantly differentially expressed in responding to drought or salt stresses, implying their additional involvement in stress tolerance of wheat. Our research lays a foundation for functional determination of TaGRFs, and will help to promote further scrutiny of their regulatory network in wheat development and stress response.

The influence of foliar nutrition with urea in different phases of wheat development on grain protein content

Aim. The effect of foliar urea nutrition on grain yield, protein, total protein harvest, and nitrogen content in the grain per spike in winter wheat plants of different varieties was studied. Methods. In the field experiment plants of six different bread winter wheat varieties were fertilized with urea in different ways: 1) control; 2) foliar nutrition with urea at the end of anthesis with a dose of 7 kg N / ha; 3) foliar nutrition with urea in the phase of late milk development. Results. It was found that after nutrition in the first period the yield increased by 7-11%, while after nutrition in the second period it remained practically unchanged in comparison with the control. The applied dose of nitrogen did not have a significant effect on the protein content. Grain productivity increased without reducing protein content in this case, and there was no negative correlation between these indicators. As a result, grain protein content was significantly increased in all varieties. Natalka had the highest indicator, due to the best combination of protein content and yield. The calculations of the increase in nitrogen content in the grain per spike at the end of anthesis showed that it was significantly higher than the out-of-root dose. Conclusions. Thus, it has been shown that foliar nutrition of wheat with urea at the end of anthesis is advisable for increase of protein harvest with the crop. This measure stimulates the functional activity of plants, promotes efficiency of nitrogen utilization. Keywords: nitrogen, grain protein, yield, winter wheat, foliar nutrition.