Effect of Heat Stress on Grain Growth, Starch Synthesis and Protein Synthesis in Grains of Wheat (Triticum aestivum L.) Varieties Differing in Grain Weight Stability

The effect of heat stress on the components of grain weight was analysed in wheat ( Triticum aestivum L.) varieties differing in grain weight stability. The wheat varieties PBW154, Sonalika and Hindi62 were raised in the field (New Delhi, India; 77°12' E, 28°40' N, 228.6 m a.s.l.) at three dates of sowing: 19 November 1992 (DOS I), 14 December 1992 (DOS II) and 18 January 1993 (DOS III). The late-sown crop (DOS III) experienced 6–8 °C warmer temperatures during grain development than the crop sown at the normal time (DOS I). The heat susceptibility index (S) revealed that grain weight was less susceptible to heat in Sonalika and PBW154 than in Hindi62. Heat stress reduced both the grain growth duration (GGD) and the grain growth rate (GGR). The grain weight reduction in PBW154 and Sonalika was mainly due to a reduction in GGR, while that of Hindi62 was due to a reduction in GGD. In vivo studies on starch and protein synthesis in excised endosperm at 15, 25 and 35 °C revealed that both processes were more thermotolerant in Hindi62 than in PBW154. The grain starch content was stable in Hindi62 while that in PBW154 was significantly reduced under heat stress. The grain nitrogen content at maturity increased in both varieties under heat stress. It was concluded that the heat susceptibility of grain weight in Hindi62 was mainly due to a reduction in GGD, although GGR, starch and protein synthesis were more thermotolerant in developing grains of Hindi62 than in those of PBW154.     

不同小麦品种产量对冬前积温变化的响应

为确定河北省中部地区小麦品种适播期,筛选耐迟播品种,2011年秋至2014年夏在河北藁城采用播期×品种二因子裂区试验,研究了不同播期对当地12个主栽小麦品种产量的影响以及不同品种对冬前积温的响应。结果表明,播期对小麦产量有显著影响;不同品种对播期响应差异明显,分为迟钝型、中间型和迟播敏感型。迟钝型品种对播期不敏感,适播期长,冬前≥0℃积温范围为324~560℃,迟播后穗数和产量稳定;中间型品种适播期较长,积温范围为362~566℃,迟播后粒数增加,穗数和产量降低;迟播敏感型品种对播期敏感,适播期较短,积温大于511℃,不宜晚播,晚播后穗数和产量明显下降。在试验地区,推荐小麦适播期为迟钝型品种10月7日至22日、中间型品种10月7日至19日、敏感型品种10月5日至10日。     

Effect of Post-Anthesis Water Stress on Accumulation of Dry Matter, Carbon and Nitrogen and Their Partitioning in Wheat Varieties Differing in Drought Tolerance

In four wheat ( Triticum aestivum L.) cultivars of tall (C306 and Narmada) and dwarf (HD2329 and Kundan) type, post-anthesis water stress affected the dry matter accumulation in plant parts with respect to main shoot controls. HD2329 among the dwarf types and Narmada 112 among the tall types were more adversely affected by stress, with greater reductions in their biomass and grain yield. Of the tolerant types, C306 (tall) showed a marginal reduction while Kundan (dwarf) had no reduction in these parameters as a result of stress. The results also indicated a varietal response to carbon and nitrogen accumulation and their partitioning in the main shoot when subjected to post-anthesis stress. In the susceptible dwarf cultivar HD2329, and in the susceptible tall cultivar Narmada 112, carbon and nitrogen contents were reduced in the grains of stressed main shoots. Of the tolerant cultivars, the dwarf type Kundan was not affected by stress, while the tall type C306 registered an increase in carbon content and its partitioning to grain.     

CIMMYT和中国硬质春麦在4种CIMMYT不同处理环境中产量和蛋白品质性状分析

灌溉、播期和垄作等栽培方式对小麦产量和蛋白品质性状具有重要影响。将21个中国和CIMMYT硬质春麦品种于2000—2001和2001—2002年度分别种植在CIMMYT的Obregon试验站4种处理环境中。结果表明，所有性状均受品种和处理环境的显著影响，产量和沉降值同时还受品种和处理环境互作效应的显著作用，在进行产量和品质改良时应考虑品种与处理环境间的互作。充分灌溉和适期播种有利于提高产量，减少灌溉迟播垄作则有利于提高蛋白含量和沉降值。Rayon F 89产量、蛋白含量和沉降值均较高；龙麦26产量、蛋白含量和沉降值显著高于其他光敏感品种。充分灌溉适期播种垄作利于提高Rayon F 89等的产量和Weaver等的沉降值，充分灌溉适期播种平播利于提高Seri M 82等的产量和Attila等的沉降值，充分灌溉迟播垄作利于提高龙麦26等的产量和Super Seri#1等的沉降值，减少灌溉适期播种垄作则利于提高Rayong F 89等的产量和Weaver等的沉降值。     

Temperature Effects on the Duration of the Spikelet Growth Phase and Spikelet Abortion in Barley

Above optimal temperatures in cereals, when measured in thermal time units (°Cd) can lead to underprediction of developmental events by models, particularly when cereals are sown late in Mediterranean-type environments or grown under subtropical conditions. Our objective was to assess the effects of high temperatures on the length of the spikelet growth phase, the number of spikelet nodes per spike and level of spikelet abortion in spring barley (Hordeum vulgare L.). The spikelet growth phase (from the end of the spikelet initiation phase to anthesis) of three cultivars, 'Bandulla', 'Schooner' and 'Weeah' was subjected to two temperature regimes. In the first of two sowings, the mean daily maximum temperature for one regime was 24 °C (maintained for 6 h daily) and the mean daily minimum was 8 °C (24/8 °C). The second temperature regime was 27/17 °C. Corresponding temperatures for the second sowing, which was subjected to slightly longer photoperiods, were 26/8 °C and 26/17°C, respectively. The duration of the spikelet growth phase was longer for 27/17 °C than for 24/8 °C in the first sowing when measured in calendar time (d). In the second sowing, the duration of the spikelet growth phase was slightly shorter under the higher temperature regime (d). The duration of the spikelet growth phase (in°Cd) was greatly increased by the higher temperature treatment in both sowings. In the first sowing, the percentage of aborted spikelets was greater at HT than at LT for Bandulla and Weeah at both sowing times and the duration of the spikelet growth phase increased with higher night temperatures, suggesting that length of the spikelet growth phase was not the sole factor responsible for the proportion of aborted spikelets.     

Grain yield and quality: does there have to be a trade-off?

The effect of agronomic practices and cultivars on grain yield, grain protein and small grain sievings was examined in field experiments over four years in the winter rainfall wheatbelt of Western Australia. Rotation with legume crops and pastures was the main factor responsible for increasing grain protein percent. Grain proteins were increased by 4-5% for crops grown in good legume pasture rotations compared to continuous wheat rotations, but only by 1-2% by factors such as delayed sowing time, applied nitrogen, cultivar or grass weed control. In legume based rotations, wheat crops sown at their highest yielding times produced proteins in the appropriate ranges for premium paying grades. Applying N fertilisers up to the optimum rates for yield did not result in proteins below the levels required for premium paying grades, except for hard wheats at >11.5% grain protein. Legume rotations and appropriate soil types were required for hard wheats to exceed 11.5% at economic N rates. The yield penalty often associated with high quality cultivars has been reduced or eliminated in the modern cultivars used in the experiments. Some longer season cultivars only produced grain proteins >10% if sown after their optimum time for yield, but sowing at optimum time reduced the probability of producing small grain sievings. Some cultivars were more susceptible than others to producing excessive sievings, especially those with inherently smaller than average seed size. Seed rates up to the optimum for grain yield did not result in excessive small grain sievings except where the site was highly fertile, where the crop was sown too late for optimum yield or where too much N fertiliser was used. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of Heat Stress on Grain Starch Content in Diploid, Tetraploid and Hexaploid Wheat Species

Heat stress during grain development adversely affects the starch content of grain in wheat, which results in poor grain quality and yield. Identification of the sources of heat tolerance for grain starch content in wheat species is an important step towards breeding for heat‐tolerant wheat. In this study, 32 wild and cultivated genotypes belonging to diploid (probable donors of B, A and D genomes), tetraploid (BBAA and AAGG genomes) and hexaploid (BBAADD genome) wheat species were evaluated for heat stress tolerance in the field at the Indian Agricultural Research Institute (IARI), New Delhi, India (77°12′ E; 28°40′ N; 228.6 m m.s.l) on two dates, 18 November (normal sowing) and 15 January (heat stress), during 1995–96. The crop sown in January experienced mean maximum temperatures of 31.0–39.3 °C during grain development, which are considered to represent heat stress for wheat grain development. Hexaploids had the highest grain starch content and the lowest heat susceptibility index, followed by tetraploid and diploid species. The heat susceptibility index (S) for grain starch correlated significantly and positively with that of grain weight (Y = 1.259X ? 0.29, R² = 0.8902, P < 0.001) across wheat species, while the actual grain growth duration or the ‘S’ of grain growth duration did not correlate significantly with that of grain weight. Hence, a high mean grain growth rate under heat stress is a better trait for heat tolerance than long grain growth duration. Wide genetic variability for heat tolerance in grain starch content was observed among the wheat species. Hence, the grain weight and quality under heat stress can be improved by using the variability available among wheat species.     

Evaluation of heat stress tolerance in irrigated environment of T. aestivum and related species. I. Stability in yield and yield components

Wheat production is often limited by continual or terminal heat stress. The current study was aimed at the characterization of wild relatives and cultivated Triticum species for their heat tolerance in yield and its analysis in relation to yield components which confer yield stability at the three ploidy levels. Thirty-two non-cultivated and cultivated genotypes belonging to diploid, tetraploid and hexaploid wheat species were evaluated for heat stress tolerance in the field under full irrigation. Wheat species were sown in the field(New Delhi, India; 77°12′E, 28°40′N, 228.6 m m.s.l) at two dates of sowing, November (normal) and January (late Sowing) during winter seasons of 1994–95 and 1995–96. The late sown crop experienced 3°C warmer temperatures than that of the normal sown crop. Wide variability was observed for grain yield stability under heat stress, as the heat susceptibility index (S) ranged from 0.13 to 2.08. Hexaploidy conferred the productive and adaptive advantages as it combined high yield and stability when compared to the tetraploid and diploid groups. However within each ploidy group wide variation was observed for heat tolerance. T. aestivum cv C306 & HI1136, T. dicoccoides, T. monococcum acc. BSP1 and Ae. speltoides ssp. liqustica were highly heat tolerant in their grain yield. Stability in grain no. m- 2 conferred yield stability in all three ploidy levels, although grain weight stability also contributed to yield stability in moderately stable T. turgidum and T. sphaerococcum under heat stress. Higher biomass and grain no. m-2 are the two important traits which could be considered potential selection criteria for yield under heat stress. Of the two components of grain no. m-2, stability in spike no. m-2could be considered more important trait than grain no. spike-1. Since wide variation for heat tolerance of all the yield components are available among the wheat species, these species can be used for improving specific yield components of cultivated wheat. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genotypic Variation in Wheat in Response to Water Stress and Abscisic Acid-Induced Accumulation of Osmolytes in Developing Grains

Two wheat genotypes differing in water stress sensitivity (C306, relatively tolerant; HD2329, relatively susceptible) were water stressed during early grain filling by withholding water for 7 days at watery‐ripe (WR) stage and examined for water status, abscisic acid (ABA) and osmolytes in grains as well as in flag leaf (FL). Both the genotypes differed significantly from each other in endogenous levels of ABA, proline, glycine betaine, total soluble sugars, reducing sugars, sucrose and potassium. The tolerant genotype showed higher content of ABA, proline, glycine betaine, total sugars, reducing sugars and had higher water content in its FL and grains than the susceptible genotype, which contained more of glycine beatine and potassium but had lower ABA and water content in its FL and grains. Although carbohydrates constituted the major amount of all the solutes, proline and glycine betaine increased manifold during stress. Exogenous application of 2 μm ABA at 5 days after anthesis to FL of stressed plants increased the endogenous content of ABA, accelerated the accumulation of osmolytes, improved the water status of FL and grains that resulted in higher grain weight, especially in the susceptible genotype. Differential response of contrasting wheat genotypes to water stress may be governed by ABA‐dependent solute accumulation in grains and FL.     

Seedling survivability as a selection criterion for drought tolerance in wheat

Ninety genotypes of wheat (Triticum aestivum L.) were screened at the seedling stage in wooden boxes in greenhouse conditions (range of temperature 25‐35°C) for moisture stress. Boxes were filled with a mixture of soil : sand : FYM in a 50 : 45 : 5 ratio. Boxes were given equal quantities of water 12 h before sowing to ensure good germination. Seeds were sown in rows at a uniform depth of 3 cm. No irrigation was provided after sowing. When most of the genotypes started wilting, the boxes were irrigated to study the recovery response (seedling survivability) of the genotypes. Based on the days taken for recovery, wheat genotypes, JWS 98, HD 2329, HW 3081, Halna and MP 1136 withered early and were grouped as susceptible, while the genotypes HI 1494, HW 2044, Kundan, NIAW 588, PBW 514 and NI 5439 resumed growth, showed a better response and were classified as drought‐tolerant. The study on mode of inheritance revealed that seedling survivability is controlled by a single dominant gene.     

Mapping quantitative trait loci associated with grain filling duration and grain number under terminal heat stress in bread wheat (Triticum aestivum L.)

Terminal heat stress has the potential negative impact on wheat production across the world, especially in South Asia. Under the threat of terminal heat stress, wheat genotypes with stay green trait would suffer from high temperature stress during their long grain filling duration (GFD). The genotypes with short GFD would be advantageous. To identify quantitative trait loci (QTL) for heat tolerance, a RIL population of K 7903 (heat tolerant) and RAJ 4014 (heat sensitive) wheat genotypes was investigated under timely and late‐sown conditions. Heat susceptibility index of GFD, yield components and traits under late‐sown condition were used as phenotypic data for QTL identification. Stable QTLs associated with these traits were identified on chromosomes 1B, 2B, 3B, 5A and 6B. The LOD value ranged from 2.9 to 5.0 and the corresponding phenotyping variation explained ranged from 12.0–22%. QTL for heat susceptibility index for the grain filling duration were colocalized with QTL for productive tillers under late sown and GFD under late‐sown condition on chromosomes 1B and 5A, respectively. These genomic regions could be exploited for molecular wheat breeding programmes targeting heat tolerance.     

Changes in Hormonal Balance: A Possible Mechanism of Pre‐Sowing Chilling‐Induced Salt Tolerance in Spring Wheat

There is a lack of knowledge about factors contributing to the chilling‐induced alleviatory effects on growth of plants under salt stress. Thus, the primary objective of the study was to determine whether chilling‐induced changes in endogenous hormones, ionic partitioning within shoots and roots and/or gaseous exchange characteristics is involved in salt tolerance of two genetically diverses of wheat crops. For this purpose, the seeds of two spring wheat (Triticum aestivum) cultivars, MH‐97 (salt intolerant) and Inqlab‐91 (salt tolerant) were chilled at 3°C for 2 weeks. The chilled, hydroprimed and non‐primed (control) seeds of the two wheat cultivars were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m^?1 NaCl salinity. Chilling was very effective in increasing germination rate and subsequent growth when compared with hydropriming and control under salt stress. Results from field experiments clearly indicated the efficacy of chilling over hydropriming in improving shoot dry biomass and grain yield in either cultivar, particularly under salt stress. This increase in growth and yield was related to increased net photosynthetic rate, greater potential to uptake and accumulate the beneficial mineral elements (K⁺ and Ca²⁺) in the roots and reduced uptake and accumulation of toxic mineral element (Na⁺) in the shoots of both wheat cultivars when grown under salt stress. Salt‐stressed plants of both wheat cultivars raised from chilled seed had greater concentrations of indoleacetic acid, abscisic acid, salicylic acid and spermine when compared with hydropriming and control. Therefore, induction of salt tolerance by pre‐sowing chilling treatment in wheat could be attributed to its beneficial effects on ionic homeostasis and hormonal balance. The results presented are also helpful to understand the chilling‐induced cross adaptation of plants in natural environments. Moreover, efficacy of pre‐sowing chilling treatment over hydropriming suggested its commercial utilization as a low risk priming treatment for better wheat crop production under stressful environments.     

Traits in Spring Wheat Cultivars Associated with Yield Loss Caused by a Heat Stress Episode after Anthesis

Heat stress resulting from climate change and more frequent weather extremes is expected to negatively affect wheat yield. We evaluated the response of different spring wheat cultivars to a post‐anthesis high temperature episode and studied the relationship between different traits associated with heat tolerance. Fifteen spring wheat (Triticum aestivum L.) cultivars were grown in pots under semifield conditions, and heat stress (35/26 °C) and control treatments (20/12 °C) were applied in growth chambers for 5 days starting 14 days after flowering. The heat stress treatment reduced final yield in all cultivars. Significant variation was observed among cultivars in the reduction in average grain weight and grain dry matter yield under heat stress (up to 36 % and 45 %, respectively). The duration of the grain‐filling period was reduced by 3–12 days by the heat treatment. The reduction in the grain‐filling period was negatively correlated with grain nitrogen yield (r = ?0.60). A positive correlation (r = 0.73) was found between the treatment effect on green leaf area (GLA) and the reduction in yield resulting from heat stress. The amount of stem water‐soluble carbohydrates (WSC) was not related to treatment effects on grain yield or grain weight. However, the treatment effect on stem WSC remobilization was negatively correlated with reduction in grain‐filling duration due to heat stress (r = ?0.74) and positively with treatment effect on grain N yield (r = 0.52). The results suggest that the effect of the heat treatment on GLA was the trait most associated with yield reduction in all cultivars. These findings suggest the importance of ‘stay green’‐associated traits in plant breeding as well as the need for better modelling of GLA in crop models, especially with respect to brief heat episodes during grain filling. There is in particular a need to model how heat and other stresses, including interacting effects of heat and drought, affect duration of GLA after flowering and how this affects source–sink relations during grain filling.     

Differential reaction of wheat cultivars to hot environments

Summary Ten to 20 spring wheat (Triticum aestivum L.) cultivars of Israeli origin were grown in three winter (normal) and two summer (abnormal) growing seasons. During the period of emergence to anthesis mean daily temperature was on the average 12°C higher and photoperiod was about 3 h longer in the summer than in the winter. Data was collected on the durations of the periods from emergence to double-ridge (GS1), double ridge to anthesis (GS2) and anthesis to grain maturation (GS3), as well as on yield and yield components.The duration of all developmental stages was reduced by high temperature. While the duration of GS2 was the most thermo-sensitive, it may also have been reduced by the longer summer photoperiod. The effect of photoperiod on GS2 could not be isolated, but the results were interpreted to show that the effect of photoperiod on the duration of GS2 was relatively small.The most heat-affected yield component was number of grains per spikelet and the least affected component was the number of spikes per plant. High temperature reduced grain weight via reduced grain growth duration and not grain growth rate. A general linear regression model of yield on its components revealed that while variation for number of spikes per plant had the greatest effect on yield variation among cultivars in the winter, variation for number of grains per spikelet and spikelets per spike were by far the most important in the summer. Grain weight was the least important component, in this respect, in all seasons. Varieties which sustained the highest yield in hot environments were able to maintain the longest duration of GS2 and the highest number of grain per spike.     

Independent and Combined Effects of High Temperature and Drought Stress During Grain Filling on Plant Yield and Chloroplast EF‐Tu Expression in Spring Wheat

High temperature and drought stress are among the two most important environmental factors influencing crop growth, development and yield processes. These two stresses commonly occur in combination. Objectives of this research were to investigate the independent and combined effects of high temperature and drought stress during grain filling on physiological, vegetative and yield traits and expression of a chloroplast protein synthesis elongation factor (EF‐Tu) of wheat (Triticum aestivum L.). Two spring wheat cultivars (Pavon‐76 and Seri‐82) were grown at control temperatures (CT; day/night, 24/14 °C; 16/8 h photo/dark period) from sowing to heading. Thereafter, one half of the plants were exposed to high temperature stress (HT; 31/18 °C in Exp. 1 and 34/22 °C in Exp. 2), drought stress (withholding water), or a combination of both HT and drought stress. There were significant influences of HT and/or drought stress on physiological, growth and yield traits. There was no cultivar or cultivar by temperature or cultivar by drought interaction effects on most traits. The decreases in leaf photosynthesis were greater at HT compared with drought alone throughout the stress period, and the combination of HT and drought had the lowest leaf photosynthetic rates. Overall, HT or drought had similar effects (about 48–56 % decrease) on spikelet fertility, grain numbers and grain yield. High temperature decreased grain numbers (by 56 % averaged across both experiments) and individual grain weight (by 25 %), while, respective decreases due to drought were 48 % and 35 %. This suggests that the grain numbers were more sensitive to HT and grain weights to drought for the range of temperatures tested in this research. The interaction between HT and drought stress was significant for total dry weights, harvest index and spikelet fertility, particularly when HT stress was severe (34/22 °C). The combined effects of HT and drought were greater than additive effects of HT or drought alone for leaf chlorophyll content, grain numbers and harvest index. High temperature stress and the combination of HT and drought stress but not drought stress alone resulted in the overexpression of EF‐Tu in both spring wheat cultivars.     

High Temperature-induced Changes in High Molecular Weight Glutenin Subunits of Chinese Winter Wheat and its Influences on the Texture of Chinese Noodles

Post-anthesis temperature affects wheat flour quality, dough properties and end-use quality. In order to investigate the changes in high molecular weight glutenin subunit (HMW-GS) expression caused by elevated temperature and its influences on the texture properties of Chinese noodles, three temperature-induced (<35 °C) treatments were applied to two cultivars with different gluten strengths. The cultivars were grown outside in 0.75 m² containers on the farm of Shandong Agricultural University in 2003–2004. Three post-anthesis temperature treatments, at 15 days after anthesis (DAA), 20 and 25 DAA, respectively, were applied during the grain-filling period by moving the containers from outside into a greenhouse at three replicates per treatment. At maturity, the HMW-GS was extracted. The results indicated that the HMW-GS expression from the wheat with stronger gluten strength appeared to be more tolerant under the different treatments than did that from the weaker dough strength wheat. The same HMW-GS (5 + 10) from different cultivars showed different effects on noodle quality. Moderately high temperature treatments benefited wet noodle texture quality and noodle scores at a different degree. All HMW-GS expression in wheat with the weaker strength appeared to be negatively correlated with wet noodle firmness (WNF) and wet noodle cutting force (WNCF). Some correlation coefficients showed significance. However, HMW-GS expression at Glu-B1 and individual Glu-B1x 14 expression from the strong wheat demonstrated significantly positive correlations with WNF and WNCF. Individual HMW-GS expression of the Glu-B1 and Glu-B1 location and the X-type subunits showed significantly positive correlations with the noodle score. The same HMW-GS at Glu-D1 from varieties with different gluten strength had different contributions to noodle quality.     

Seed Priming Enhances the Performance of Late Sown Wheat (Triticum aestivum L.) by Improving Chilling Tolerance

In rice–wheat systems, late sowing of wheat is the major reason of low yield. This yield reduction is principally due to lower and erratic germination, and poor crop establishment because of low temperature prevailing. The present study was conducted to explore the possibility of improving late sown wheat performance by seed priming techniques. Seed priming strategies were: on‐farm seed priming, hydropriming for 24 h, seed hardening for 12 h and osmohardening with KCl or CaCl₂ for 12 h. Seed priming improved emergence, stand establishment, tiller numbers, allometry, grain and straw yield, and harvest index. However, seed priming techniques did not affect plant height, number of spikelets, number of grains and 1000 grain weight. Osmohardening with CaCl₂ gave more grain and straw yield and harvest index compared with control and other priming treatments, followed by osmohardening with KCl and on‐farm seed priming. Improved yield was attributed principally to better stand establishment and improved number of fertile tillers. Seed priming techniques can be effectively used to improve the performance of late sown wheat.     

淮北地区晚播麦的生育特性研究及配套栽培技术

以不同类型品种小麦为研究对象,通过设置不同播期处理,研究了江苏淮北地区小麦播期推迟对冬前麦苗素质、全生育期及生育进程及产量构成的影响.结果表明：随着播期的推迟,小麦均出现了全生育期缩短,生育进程推迟,穗分化时间缩短的趋势.晚播麦产量构成表现为亩穗数增加,每穗粒数和千粒重减少,最终产量下降,其中每穗粒数的减少是产量下降的主要因素.通过选用穗粒中间型品种,提高播种质量,注重返青期及剑叶露尖期的田间管理,晚播麦仍可获得380kg/667m2左右的产量.     

Long‐Term Field Drought Affects Leaf Protein Pattern and Chloroplast Ultrastructure of Winter Wheat in a Cultivar‐Specific Manner

Recurrent drought periods of varying duration often cause extensive crop damage and affect wheat production in Southern Europe. This study compares biochemical and ultrastructural responses of four wheat (Triticum aestivum L.) cultivars to long‐term field drought, and their contribution to final grain yield. Gel electrophoresis and immunoblotting analyses combined with transmission electron microscopy and grain yield evaluation were employed to assess drought susceptibility of the wheat cultivars. Two of them behaved as drought‐tolerant, the other two presented as drought sensitive. Enhanced degradation of Rubisco large subunit (RLS), Rubisco small subunit (RSS) and Rubisco activase (RA) accompanied by an increased protease activity and reduced levels of heat shock proteins (HSP70) and dehydrins (DHNs) were associated with drought sensitivity. Drought tolerance coincided with relatively stable or increased HSP70 and DHN contents, and unchanged/higher levels of RLS, RSS and RA. Sensitive cultivars were more vulnerable to ultrastructural damages, showing obvious degradation of chloroplast membrane systems and depletion of leaf starch reserves. These drought responses affected yield potential, as tolerant cultivars gave higher yield under intense drought. Thus, our results provide additional insights into the complexity of plant drought responses, identifying multiple interacting traits that may serve as indirect selection criteria for wheat drought tolerance.     

华北低平原不同播种期春玉米的产量表现及其与气象因子的通径分析

针对华北地区种植春玉米面临的灌浆期高温胁迫问题,2011-2012年在河北省吴桥县开展了2个春玉米品种(郑单958播种于2011年,金海5号播种于2012年)的播期试验,以探讨气象因子与玉米产量间的关系,为通过调整播种期减轻春玉米灌浆期的高温胁迫提供理论依据。结果初步表明,不同播种期使春玉米灌浆时期发生变化,因而灌浆期气象因子特征表现出差异。4月上旬播种与其他播种期处理相比,春玉米灌浆期光水资源丰富,降雨量增加5.0~47.4 mm,日照时数增多41.0~70.0 h、气温日较差大0.2~0.6℃,但是,高温胁迫严重(≥33℃天数多达15 d,日均温高达28.4℃);5月中旬播种的玉米灌浆期高温胁迫轻（≥33℃天数仅有8 d,日均温平均26.0℃）,而光水资源相对充足;4月中旬、4月下旬和5月上旬播种的玉米灌浆期高温胁迫相对严重;5月下旬播种的玉米灌浆期高温胁迫相对较轻,但阴雨寡照严重。两年的籽粒产量由高到低的播种期依次是,4月上旬、5月中旬、5月上旬、4月下旬、4月中旬、5月下旬;郑单958和金海5号在4月上旬播种的产量分别达9912 kg hm^-2和11 046 kg hm^-2,在5月中旬播种的产量分别达9906 kg hm^-2和10 852.5 kg hm^-2,其他4个播种期的产量比前两个播种期低6.0%~28.2%。通径分析表明,4月上旬播种的玉米灌浆期气温日较差大、光照时数长,对千粒重和穗粒数的直接正效应大,从而缓解了高温胁迫负效应;5月中旬播种的玉米产量较高是因为躲避了灌浆期高温胁迫,但气温日较差和日照时数的正效应比4月上旬播种期的低,因此比4月上旬播种的产量低;4月中旬、4月下旬、5月上旬、5月下旬各播种处理的千粒重和穗粒数受高温胁迫或阴雨寡照影响较大,且气温日较差和光照时数正效应较小,产量下降明显。针对华北地区种植春玉米面临的灌浆期高温胁迫问题,2011-2012年在河北省吴桥县开展了2个春玉米品种(郑单958播种于2011年,金海5号播种于2012年)的播期试验,以探讨气象因子与玉米产量间的关系,为通过调整播种期减轻春玉米灌浆期的高温胁迫提供理论依据。结果初步表明,不同播种期使春玉米灌浆时期发生变化,因而灌浆期气象因子特征表现出差异。4月上旬播种与其他播种期处理相比,春玉米灌浆期光水资源丰富,降雨量增加5.0~47.4 mm,日照时数增多41.0~70.0 h、气温日较差大0.2~0.6℃,但是,高温胁迫严重(≥33℃天数多达15 d,日均温高达28.4℃);5月中旬播种的玉米灌浆期高温胁迫轻（≥33℃天数仅有8 d,日均温平均26.0℃）,而光水资源相对充足;4月中旬、4月下旬和5月上旬播种的玉米灌浆期高温胁迫相对严重;5月下旬播种的玉米灌浆期高温胁迫相对较轻,但阴雨寡照严重。两年的籽粒产量由高到低的播种期依次是,4月上旬、5月中旬、5月上旬、4月下旬、4月中旬、5月下旬;郑单958和金海5号在4月上旬播种的产量分别达9912 kg hm^-2和11 046 kg hm^-2,在5月中旬播种的产量分别达9906 kg hm^-2和10 852.5 kg hm^-2,其他4个播种期的产量比前两个播种期低6.0%~28.2%。通径分析表明,4月上旬播种的玉米灌浆期气温日较差大、光照时数长,对千粒重和穗粒数的直接正效应大,从而缓解了高温胁迫负效应;5月中旬播种的玉米产量较高是因为躲避了灌浆期高温胁迫,但气温日较差和日照时数的正效应比4月上旬播种期的低,因此比4月上旬播种的产量低;4月中旬、4月下旬、5月上旬、5月下旬各播种处理的千粒重和穗粒数受高温胁迫或阴雨寡照影响较大,且气温日较差和光照时数正效应较小,产量下降明显。