Study of yield components under heat stress conditions in wheat

High temperature tolerance can be characterised by measuring various plant productivity traits in different developmental stages. The present work investigated the effect of exposure to high temperature (30-35°C) at first node appearance, during early embryo development and in the grain-filling stage on the yield parameters of two winter wheat varieties. Periods of high temperature had diverse effects on wheat plants in different phenophases. The greatest differences between the various developmental stages were found for grain number, grain yield and thousand-kernel weight. Heat stress was demonstrated to have the least effect on total grain number and number of grains per spikelet on the main spike during the grain-filling period. The most pronounced reductions in the traits examined were detected when heat stress was applied during the early embryo development stage

EFFECT OF HEAT STRESS ON THE PHYSIOLOGICAL PROCESSES OF WHEAT

Stress tolerance is associated with the activation of antioxidant compounds and enzyme systems that are capable of neutralising the reactive oxygen species (ROS) continually produced in response to stress. The present experiment was designed to compare the heat tolerance of four winter wheat varieties in the shooting and grain-filling stages by investigating changes detected in antioxidant enzyme activity and yield components in response to heat stress. Heat treatment was found to cause a significant rise in the activity of the glutathione- S-transferase and catalase enzymes, while there was usually a less intense decline in the activity of guaiacol peroxidase. An analysis of yield data revealed that heat stress had a more pronounced effect during grain filling in this experiment than at the beginning of shooting, as shown by the greater reduction in thousand-kernel weight and yield

Investigation of the Stress Tolerance of Winter Wheat Genotypes Under Natural Rain-Fed and Irrigated Conditions

AbstractDrought around the world is one of the most important yield reducing factor. From the cross of winter wheat varieties (Plainsman V x Mv Magma) doubled haploid (DH) population was created consisting of 174 lines to investigate the drought tolerance of the genotypes exposed to two treatments; natural rain-fed and well-watered conditions in the field.The object of the experiment was to determine the yield production capacity of the DH lines under natural rain-fed conditions and to compare the effect of changes in the yield components due to irrigation. After ripening, the wheat plants were harvested from both treatments. The plant height, the length of last internode, number of spikelets, seed number, seed weight on the main stem; the number of reproductive tillers, seed number and weight per plant was determined.The effect of irrigation was investigated on the morphological parameters and yield properties which changed due to well watered conditions in the wheat plants. Averaged over the DH lines, the heading date was significantly affected by irrigation. Irrigation significantly increased all the morphological parameters. Not only the average, but also the minimum and maximum values increased significantly for spikelet number, reproductive tiller number and plant height. Changes in the morphological parameters resulted in significant alterations in the yield components. The irrigation significantly increased the total grain number per plant, the thousand kernel weight and the grain yield averaged over the DH lines.The results showed that the morphological parameters and yield components can still be some of the most effective features to estimate the tolerance of wheat in response to stress factors. This project was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences and the project DROPS (EU-FP7 No. 244374)

Effect of different sowing times on the plant developmental parameters of wheat (Triticum aestivum L.)

Studies on plant development phases and yield component patterns of wheat are essential for a better understanding of adaptation in wheat. Our main aim was to carry out detailed phenological analyses of 18 wheat genotypes in three sowing times for determining the effect of sowing date on individual phenophases, and yield components. Sowing date had the single greatest effect on the start of intensive stem elongation. The longer vegetation period had a favourable effect on main spike length and on the spikelet number per spike, but had no influence on thousand-kernel weight and grain number per spike. The time between the first node appearance and start of intensive stem elongation had a significant effect on the number of reproductive tillers. A close association (R2 = 0.191) was observed during the second phase of intensive stem elongation between the boot stage-to-heading interval and the number of spikelets per spike. Two-way analysis of variance on the yield components showed that the sowing date, as a main factor, had a weaker effect on the phenophases than on morphological and developmental parameters. The insensitive allele of the Ppd-D1 gene shortened the time required for first node appearance and heading both in autumn and spring sowing

Hőmérséklet szerepének vizsgálata a gabonafélék virágzásában = Evaluating the role of ambient temperature in determining flowering in cereals

Az árpa egyedfejlődését és így a földrajzi adaptációs képességét elsődlegesen a vernalizációs igény, valamint a nappalhossz érzékenység mértéke szabja meg. E két komponens alapján kialakított árpa csoportokon belül azonban nagy variabilitás mutatkozik a fajták egyedfejlődési mintázatában és virágzási idejében. Kísérleteinkkel célunk volt e variabilitást kiváltó környezeti tényezők egyedfejlődésre gyakorolt hatásának részletes elemzése, valamint ezekre a környezeti tényezőre adott válaszreakciók genetikai szabályozásában közreműködő komponensek azonosítása. Vizsgáltuk a környezeti hőmérséklet szerepét a vernalizációs folyamatokat és a hőstresszt kiváltó hőmérsékletek közti intervallumban, az állandó és a napi fluktuáló tényezők (fény, hőmérséklet) egymáshoz viszonyított hatását, valamint a fény minőségének a szerepét. Meghatároztuk e környezeti tényezőkre adott válaszreakciók természetes variabilitásának mértékét a termesztett árpafajták körében, kontrasztos reakciójú fajtákat azonosítottunk a további kísérletek céljaira. Kétszülős árpa populációkra alapozott QTL elemzéssel, és nagy fajtakört magába foglaló gyűjteményre alapozott teljes genomra kiterjedő fenotípus – genotípus asszociációs elemzésekkel azonosítottuk a szabályozásban szerepet játszó főbb genetikai komponenseket. Nyomon követtük a főbb egyedfejlődési gének génexpressziós mintázatainak változását mesterséges (kontrollált klímakamra) és természetes (szántóföldi vegetációs periódus) környezetben, több vetésidőben. | In cereals, plant development and thus the ecological adaptation is basically determined by the vernalization requirement and photoperiod sensitivity. Large variation in flowering time exists however between the cultivars within the various groups of these two factors. Our major aims were to identify the additional environmental cues responsible for this variation, to characterise their effects on plant developmental patterns and to evaluate the genetic determinants participating in the regulation pathways of these environmental cues. Thus we studied the effects of ambient temperature on plant development in the range between its function as a vernalising agent and being an abiotic stress factor, the effects of daily fluctuating factors (light and temperature) compared to constant environment, and the effects of the quality of light. We characterised the natural variation present in cultivated barley for these environmental factors and identified contrasting types for further studies. The evaluation of the genetic components involved was carried out partly by QTL studies in bi-parental mapping populations and partly by genome wide association mapping in a multi-parental barley collection. Changes in the expression levels of the major plant developmental genes were also followed both in controlled environmental tests and under field conditions during the vegetation period with the application of different sowing time

Allele frequencies in the VRN-A1, VRN-B1 and VRN-D1 vernalization response and PPD-B1 and PPD-D1 photoperiod sensitivity genes, and their effects on heading in a diverse set of wheat cultivars (Triticum aestivum L.)

Heading of cereals is determined by complex genetic and environmental factors in which genes responsible for vernalization and photoperiod sensitivity play a decisive role. Our aim was to use diagnostic molecular markers to determine the main allele types in VRN - A1 , VRN - B1 , VRN - D1 , PPD - B1 and PPD - D1 in a worldwide wheat collection of 683 genotypes and to investigate the effect of these alleles on heading in the field. The dominant VRN - A1 , VRN - B1 and VRN - D1 alleles were present at a low frequency. The PPD - D1a photoperiod-insensitive allele was carried by 57 % of the cultivars and was most frequent in Asian and European cultivars. The PPD - B1 photoperiod-insensitive allele was carried by 22 % of the genotypes from Asia, America and Europe. Nine versions of the PPD - B1 -insensitive allele were identified based on gene copy number and intercopy structure. The allele compositions in PPD - D1 , PPD - B1 and VRN - D1 significantly influ- enced heading and together explained 37.5 % of the phenotypic variance. The role of gene model increased to 39.1 % when PPD - B1 intercopy structure was taken into account instead of overall PPD - B1 type (sensitive vs. insensitive). As a single component, PPD - D1 had the most important role (28.0 % of the phenotypic variance), followed by PPD - B1 (12.3 % for PPD - B1 _overall, and 15.1 % for PPD - B1 _intercopy) and VRN - D1 (2.2 %). Significant gene interactions were identified between the marker alleles within PPD - B1 and between VRN - D1 and the two PPD1 genes. The earliest heading genotypes were those with the pho- toperiod-insensitive allele in PPD - D1 and PPD - B1 , and with the spring allele for VRN - D1 and the winter alleles for VRN - A1 and VRN - B1 . This combination could only be detected in genotypes from Southern Europe and Asia. Late-heading genotypes had the sensitivity alleles for both PPD1 genes, regardless of the allelic composition of the VRN1 genes. There was a 10-day difference in heading between the earliest and latest groups under field conditions

Rising atmospheric CO2 concentration may imply higher risk of Fusarium mycotoxin contamination of wheat grains

2 Abstract Increasing atmospheric CO2 concentration not only has a direct impact on plants but also affects plant-pathogen interactions. Due to economic and health-related problems, special concern was given thus in the present work to the effect of elevated CO2 (750 μmol mol-1) level on the Fusarium culmorum infection and mycotoxin contamination of wheat. Despite the fact that disease severity was found to be not or little affected by elevated CO2 in most varieties, as the spread of Fusarium increased only in one variety, spike grain number and/or grain weight decreased significantly at elevated CO2 in all the varieties indicating that Fusarium infection generally had a more dramatic impact on the grain yield at elevated CO2 than at the ambient level. Likewise, grain deoxynivalenol (DON) content was usually considerably higher at elevated CO2 than at ambient level in the single-floret inoculation treatment, suggesting that the toxin content is not in direct relation to the level of Fusarium infection. In the whole-spike inoculation, DON production did not change, decreased or increased depending on the variety × experiment interaction. Cooler (18°C) conditions delayed rachis penetration while 20°C maximum temperature caused striking increases in the mycotoxin contents, resulting in extreme high DON values and also in a dramatic triggering of the grain zearalenone contamination at elevated CO2. The results indicate that future environmental conditions, such as rising CO2 levels, may increase the threat of grain mycotoxin contamination. Keywords: deoxynivalenol, elevated CO2, Fusarium culmorum, mycotoxin, Triticum aestivum, zearalenon