How do timing,duration, and intensity of drought stress affect the agronomic performance of winter rye?

Winter rye (Secale cereale L.) will be especially affected by drought induced yield losses in Central and Eastern Europe in the future because it is predominantly cultivated on low-fertile soils with a poor water-holding capacity. In order to examine the performance of winter rye under different drought conditions, field experiments were carried out during the years 2011, 2012, and 2013 near Braunschweig, Germany. Two sets of genotypes were tested under severe, mild, pre-anthesis, and post-anthesis drought stress in rain-out shelters as well as under rainfed and well-watered conditions. The grain, straw, and total above ground biomass yields, harvest index, grain yield components, leaf area index (LAI), and phenological characteristics were examined, as well as phenotypic correlations between grain yield and further characteristics. Drought induced grain yield reduction ranged from 14 to 57%, while straw yield and harvest index were lesser affected by drought than the grain yield. Under drought conditions, fully ripe was reached up to twelve days earlier than under non water-limited conditions. Pre-anthesis drought mainly reduced spikes m⁻² and kernels spike⁻¹ while drought during grain filling reduced the 1000-kernel weight (TKW) only. The grain yield was positively associated with straw yield, spikes m⁻², and kernels spike⁻¹ under water limited conditions while the TWK was only positively associated with grain yield under drought during grain filling. Consequently, high pre-anthesis biomass as well as high numbers of spikes m⁻² and kernels spike⁻¹ are especially important for obtaining high grain yields under water-limited conditions. Focusing on these traits is, therefore, recommendable for developing drought tolerant rye genotypes.     

遮阴对黄淮海玉米主栽品种农艺性状和产量的影响

为分析遮阴对黄淮海玉米主栽品种农艺性状、产量性状和产量的影响,以黄淮海种植面积最大的10个玉米品种为材料,种植在该地区4个省（市）,并设抽雄前遮阴7天和全生育期不遮阴2个处理。研究结果表明遮阴处理对黄淮海玉米主栽品种农艺性状、产量性状及产量均具有显著的影响,10个品种产量均显著的降低,6个品种抽雄吐丝间隔期延长,9个品种吐丝率下降;遮阴后产量降低与行粒数、穗长、穗粗、百粒重变小,秃尖变大有显著的相关性;‘伟科702’在10个品种中耐阴性最好,遮阴后4地点平均产量第一,吐丝率和产量降幅最低,其次为‘郑单958’、‘蠡玉16’和‘隆平206’。因此,生产上应选‘伟科702’等耐阴性较好的品种,耐阴育种方面应将行粒数、穗长、穗粗、百粒重、秃尖长度、吐丝率和抽雄吐丝间隔期等显著相关的性状作为耐阴性鉴定的指标。     

从产量和品质性状的变化分析北方冬麦区小麦品种抗热性

培育抗热性强的品种对应对气候变化,保障小麦稳产性具有重要意义。选用北方冬麦区53份主栽品种和苗头品系,于2008—2009年度分别种植在北京、石家庄、衡水、安阳和泰安5点,各点设正常温度和塑料棚热胁迫处理。结果表明,千粒重可作为抗热性筛选的简易指标。农大189、CA0518和京冬8号的产量和千粒重在正常和热处理环境中均较高,抗热性好;衡观33和CA0736的产量在正常和热处理环境中均较高,但千粒重均表现中等,抗热性较好;农大211、石麦15、济麦22、农大3432和山农2149在正常环境中的产量和千粒重均较高,但在热处理环境中产量和千粒重均较低,抗热性差。53份品种按和面时间和峰值曲线面积可分为强筋、中强筋、中筋、中弱筋和弱筋5大类。热处理使所有类型材料的蛋白质含量和籽粒硬度增加,峰值带高、8min带高和8min带宽降低,并降低强筋、中强筋和中筋类型材料的和面时间与峰值曲线面积,增加中弱筋和弱筋类型材料的和面时间与峰值曲线面积。     

花后干旱和渍水对冬小麦光合特性和物质运转的影响

在温室盆栽条件下，以黑小麦76、皖麦38、扬麦10号、扬麦9号4个蛋白质含量不同的冬小麦(Triticum aestivum L.) 基因型为材料，研究了花后土壤干旱（Soil relative water content, SRWC=45%～50%）、渍水和适宜水分条件（SRWC=75%～80%）下，小麦旗叶净光合速率和叶绿素含量的动态变化，营养器官花前贮藏同化物再运转，花后同     

Contribution of Pre- and Post-anthesis Photosynthates to Grains in Pearl Millet under Water Deficit

When rains end early, grain yield productivity of pearl millet ( Pennisetum glaucum [L.] R. Br.), a rainfed cereal crop of arid and semi-arid regions is limited by water deficits during flowering and grainfilling. Reserves of assimilates present at flowering and available for later remobilization to the grains, could act has buffer under water deficit conditions during flowering and grainfilling. The contribution of pre- and post-anthesis assimilates to grain yield under water-deficit conditions during flowering and grainfilling was investigated by ¹⁴C labeling of leaves at boot and 10 days after anthesis of field-grown plants. Water deficit resulted in 20 percent reduction to grain yield in the main tiller. The distribution pattern of labeled carbon at harvest in various plant parts in water deficit and irrigated control treatments was similar. About 25 percent of the pre-anthesis assimilates was translocated to the grain at harvest, while 95 percent of the post-anthesis (current) assimilates was translocated to the grain. At grain maturity, about 60 percent of the pre-anthesis assimilate was distributed in inflorescence structures, and in upper three inter-nodes which were the active sinks at boot stage. Post-anthesis assimilates were directed towards the grain development which was the active sink after flowering. In conclusion, about 25 percent of the pre-anthesis assimilates are translocated to the grain at harvest and there was no additional contribution under water deficit and post-anthesis assimilates were primarily translocated to the developing grain.     

Relationships between line per se and testcross performance for agronomic traits in two broad-based populations of maize

Degree of the association between line per se performance (LP) and testcross performance (TP) is important in breeding programs and simultaneous improvement of commercial hybrids and their parental lines. This experiment was designed to study genetic variability and genetic correlation for several agronomic traits in two maize (Zea mays L.) broad-based populations (NS12-SG and NS14-SG). Independent trials with 80 entries of S₁ progenies as well as their testcrosses were arranged according to an incomplete block design with replicates in sets. Grain yield, stay green, anthesis-silking interval, stalk water content and grain moisture were evaluated in four environments. The anthesis-silking interval had the highest genetic variation, followed by stay green. High heritability estimates (>0.50) for all traits, pointed out that further selection would be possible. Genetic correlations between line per se and testcross performance were lowest for grain yield (0.396** and 0.592**, for NS12-SG and NS14-SG, respectively), and highest for grain moisture (0.937** and 0.821**, respectively). High correlations between line per se and their testcrosses for stay green, anthesis-silking interval, stalk water content and grain moisture indicated that additive gene action might be more important than dominance in controlling the expression of these traits.     

Genetic gain in yield and changes associated with physiological traits in Brazilian wheat during the 20th century

The objective of this study was to characterize physiologically wheat cultivars released in different decades and identify selection criteria for the continued genetic progress in Brazil. Ten cultivars released from 1940 up to 2009 were tested during 2010 and 2011 crop seasons. The following traits were evaluated: grain yield (GY), thousand-kernel weight (TKW), grain number per m⁻² (GN), plant height (PH), harvest index (HI), above-ground biomass (BIO), relative Chlorophyll content and leaf gas exchanges. The increase in grain yield was 29 kg ha⁻¹ yr⁻¹ a genetic gain of 0.92%, annually. Grain yield improvement was largely associated with HI (0.94^**), number of grains m⁻² (0.93^**), BIO (0.88^**) and reduced PH (−0.93^**). The post-anthesis Chlorophyll content, stomatal conductance and pre/post-anthesis photosynthetic rate were positively correlated with GY. Genetic gains of Brazilian wheat are mainly related to the increases of HI, GN, and BIO. These improvements were achieved by reducing PH and raising gas exchanges and chlorophyll content.     

花后高温胁迫下氮肥追施后移对小麦产量及旗叶生理特性的影响

为探明施用氮肥与减缓小麦花后高温伤害的关系并阐明其生理机制,于2011-2012年和2012-2013年连续两个生长季,选用小麦品种山农16和济麦22,在增温棚中进行花后11~15 d的高温胁迫处理,比较了氮肥全作基肥(T0)、1/2基肥+1/2拔节期追肥(T1)、1/2基肥+1/2孕穗期追肥(T2) 3种施氮方案下的产量、产量构成因素、旗叶光合特性及部分酶的活性。在高温胁迫下,T2方案较T0和T1显著增加籽粒千粒重和产量,提高旗叶谷氨酰胺合成酶(GS)活性,增加旗叶气孔导度和光合速率,提高旗叶过氧化氢酶(CAT)和过氧化物酶(POD)活性,促进花前营养器官干物质向籽粒转运,增加开花后积累的干物质对籽粒的贡献率。两个品种结果基本一致。综合两年结果可以看出,T2处理显著优于T0和T1处理,T2处理能显著缓解高温胁迫的伤害,提高籽粒产量。     

The importance of the period immediately preceding anthesis for grain weight determination in wheat

Although individual grain weight is an important source of variation forgrain yield, there is still poor understanding of the causes determining finalgrain weight. Almost all studies conducted for understanding thedeterminants of grain weight have been focused on the post-anthesis period.However, there is important evidence that pre-anthesis conditions couldalso modify final grain weight. Three experiments including different sowingdates, genotypes and temperature regimes between booting and anthesis,were carried out in Argentina and Mexico to analyse the effect oftemperature and associated traits during the pre- and post-anthesis periodson grain weight under field conditions. In these experiments final grainweight could not be explained by average or maximum temperature duringthe post-anthesis period. However, average temperature between bootingand anthesis was closely related to the observed grain weight differences,probably as a consequence of the effects of this factor on carpel growth.Differences in grain weight between genotypes and grain position weresuccessfully explained by differences in carpel weight at anthesis. Theseresults suggest that our knowledge to determine grain weight could improveif the immediately pre-anthesis period conditions were taken into account.     

非生物胁迫对玉米杂交种及其亲本自交系产量性状的影响

以抗逆性较强玉米杂交种郑单958及其亲本(郑58、昌7-2)和抗逆性较差的杂交种陕单902及其亲本(K22、K12)为材料, 在不同种植密度(45 000株 hm^-2和75 000株 hm^-2)、施氮量(112.5 kg hm^-2和337.5 kg hm^-2)和灌水量(正常灌水和前期干旱控水)条件下, 分析了2个杂交种及其亲本产量及相关生理特性的变化规律。结果表明, 在非生物胁迫条件下(高密度、低氮和前期干旱控水), 与陕单902相比, 品种郑单958叶面积指数、SPAD值、花后干物质积累量和产量的中亲优势值分别增加18%、9%、28%和22%; 与陕单902亲本(K22、K12)比, 郑单958亲本(郑58、昌7-2)叶面积指数、SPAD值、花后干物质积累量和产量的中亲值分别增加45%、36%、51%和45%; 郑单958产量的中亲值和中亲优势显著高于陕单902, 且中亲值增幅高于杂种优势值。玉米杂交种郑单958较陕单902增产的同时, 增强了对非生物逆境适应的能力。玉米杂交种的抗逆性来自亲本自交系。玉米杂交种抗逆性强在于增强了花后叶片光合能力(较高的LAI和SPAD值), 促进了花后干物质积累。     

Reduction in kernel weight as a potential indirect selection criterion for wheat grain yield under terminal heat stress

Heat is an important abiotic stress during wheat (Triticum aestivum L.) grain‐filling in South Asia. A study was undertaken to determine effectiveness of selection for reduction in 1000‐kernel weight (TKWR) under heat stress to increase grain yield. Selection was made for low and high TKWR and selected progenies were evaluated in timely and late seeded trials at two locations in Nepal in 2003. One thousand kernel weight (TKW), biomass yield, grain yield, harvest index (HI), grain‐filling duration (GFD) and area under spot blotch progress curve per day (AUDPC/day) were examined. The low and high TKWR groups did not differ significantly for TKW, biomass yield, grain yield, HI, days to heading, GFD and AUDPC/day under timely seeding. However, low TKWR lines showed higher TKW, biomass yield, grain yield, HI, and GFD and lower AUDPC/day than the lines with high TKWR under late seeding. Realized heritability estimates for TKWR ranged from 0.68 to 0.85. The findings show that selection for low TKWR could be used as an indirect selection criterion to identify high grain yielding lines under terminal heat stress.     

不同穗型小麦花后物质运转及产量对氮肥的响应

在大田条件下,以多穗型小麦‘烟农19’和大穗型小麦‘兰考矮早8’两个不同穗型的冬小麦为材料,研究了不同施氮量及氮肥基追比例对小麦营养器官花前贮藏同化物再运转,花后同化物输入籽粒量,产量及产量构成因素的影响。结果表明,氮肥水平在225~300 kg/hm2范围内,多穗型小麦‘烟农19’和大穗型麦‘兰考矮早8’籽粒产量的形成均以花后绿色器官光合同化为主,其次才是花前积累干物质的再动员分配。大穗型品种‘兰考矮早8’籽粒产量的形成较多穗型品种‘烟农19’更依赖于花后绿色器官同化,积累干物质再运转分配只占籽粒产量的15%左右。两种穗型品种小麦花前贮存物质再动员分配对籽粒产量的贡献都随着氮肥后移而降低。随着施氮量的增加,运转物质对籽粒产量的贡献率呈降低趋势。综合物质运转和产量表现,‘烟农19’施氮量300 kg/hm2,基追比例5:5时较适宜;‘兰考矮早8’施氮量262.5 kg/hm2,氮肥基追比例7:3时较适宜。     

Inheritance of yield and yield-related traits in highland maize hybrids of Uganda

Although many studies have been conducted on gene action of grain yield and yield related traits in maize, none of them focused on highland maize in Uganda. This study was conducted to establish the gene action controlling inheritance of yield and its related traits in highland maize hybrids. Thirty-six F₁ hybrids generated from a 9 x 9 half diallel mating design, were planted with two local checks in three highland locations; Kalengyere, Kachwekano, and Buginyanya with two replications using a 2 x 19 alpha (0, 1) lattice design. Results showed that inheritance of ear length and anthesis-silking interval was controlled by both additive and non-additive gene action while the inheritance of days to anthesis, days to silking was mainly controlled by additive gene action. The inheritance of grain yield and other yield related traits was greatly influenced by environment and genotype x environment interaction. Considering the great influence of the environment and genotype x environment interaction on most of the traits including grain yield, further testing in additional locations over more seasons and broadening the genetic base of the parents is encouraged.     

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.     

吐丝期干旱胁迫对玉米生理特性和物质生产的影响

以玉米品种郑单958 (抗旱性强)和陕单902 (抗旱性弱)为材料,采用抗旱池栽控水试验,研究了叶片光合特性、保护酶活性以及干物质转运对吐丝期干旱胁迫的响应。结果表明,在吐丝期干旱胁迫下2个品种产量分别降低39.10%和44.87%;叶片净光合速率(P_n)和气孔导度(G_s)显著下降,胞间CO₂浓度(C_i)先升后降。PSII最大光化学效率(F_v/F_m)、实际量子产额(Φ_PSII)、光化学猝灭(q_P)降低,非光化学猝灭(q_N)升高;抗氧化酶(SOD、POD和CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高。说明吐丝期干旱胁迫增加了花前营养器官贮藏同化物转运量(率)及其对籽粒转运的贡献率;但郑单958受干旱影响程度小于陕单902。说明抗旱品种郑单958具高抗氧化酶活性清除活性氧,使得膜脂过氧化程度轻,维持较高的光化学效率,延长叶片光合功能期,促进花前营养器官贮藏同化物转运量对籽粒的贡献率。这可能是其在干旱胁迫下仍能获得较高产量的重要原因之一。     

增施氮肥、硼肥对花期遮阴条件下玉米籽粒产量的影响

遮阴已成为影响夏玉米产量的重要因子,提高玉米耐阴性可为高产、抗逆栽培提供理论依据。以‘苏玉29’为试验材料,系统研究了小喇叭口期增施氮肥、硼肥缓解花期遮阴胁迫对夏玉米形态建成、物质积累和产量的影响。结果表明:遮阴处理降低了株高、茎粗、单株叶面积和干物质积累量,并延长了散粉吐丝间隔期。与遮阴处理比,小喇叭口期增施硼肥、氮肥不同程度提高了株高、茎粗、单株叶面积和干物质积累量,且同时增施硼肥、氮肥增幅最大。遮阴处理显著增加了秃尖长,降低了穗粒数和粒重,增施硼肥氮肥缓解了遮阴对突尖长、穗粒数和粒重的影响。增施硼肥、氮肥和同时增施硼肥、氮肥处理产量分别较遮阴处理提高36.7%、8.0%和43.1%。遮阴处理降低叶面积影响干物质积累,产量的降低与突尖增长、穗粒数减少和粒重降低有关。小喇叭口期增施硼肥和氮肥是缓解花期遮阴对产量不利影响的有效措施。     

Genotypic variation and relationships between seedling and adult plant traits in maize (Zea mays L.) inbred lines grown under contrasting nitrogen levels

Genotypes with better root development have good nutrient acquisition capacity and may yield better under limited nitrogen (N) conditions and consequently can help reduce the N fertilization rate and hence mitigate some economic and ecological problems. This study focused on the genotypic variation among diverse maize inbred lines for seedling and adult plant traits under contrasting N levels. Seventy-four lines were screened under high and low N levels in a climate chamber and in the field. High phenotypic diversity was observed for seedling and adult plant traits together with moderate to high broad-sense heritability estimates. Seedling total root length and root dry weight were significantly correlated with other root traits in maize. Of the adult plant traits evaluated in the field, the anthesis-silking interval and the leaf chlorophyll contents were significantly correlated with grain yield under both low and high N levels. In one location, the seminal root length was correlated with grain yield both under low and high N levels and the root dry weight was correlated with grain yield under high N. Selection indices based on secondary root traits along with grain yield could lead to an increase in selection efficiency for grain yield under N stress condition. By identifying lines with better root development, particularly lines with longer SRL, it may be possible to select inbred lines with higher grain yield particularly under low N condition.     

Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphological attributes associated with early-season drought tolerance in spring durum wheat in a mediterranean environment

Impacts of drought during the reproductive development phase of wheat have been thoroughly investigated, while studies of the early-season drought effects are lacking. Field experiments were conducted to study the effect of duration of drought stress during the period from emergence to the end of tillering on the growth and performance of different wheat cultivars, and to identify traits that could be associated with the resistance to early season drought. Experiments were conducted on a Vertic Calcixerol soil in the semiarid cereal-growing region of Morocco in 1995 and 1996. Six spring durum wheat (Triticum durum Desf.) cultivars selected on the basis of variation in morphology, phenology, and zone of adaptation were subjected to four water regimes, including a well-irrigated control. The three water stress treatments were imposed by withholding water during the period from emergence to either the onset, middle, or the end of tillering. Subsequent irrigations provided adequate soil moisture for the remainder of the growing season. Results from both years were generally consistent. The differential responses of the six cultivars was mainly due to differences in numbers of kernels produced. High yields under early-season drought were attributed to high leaf area index under stress and, upon recovery, and to high tiller survival rate. The consistency observed over years in the relationships between grain yield and those traits that proved to be most associated with the resistance to early-season drought, would suggest the usefulness of these traits as selection criteria for breeding for improved drought resistance in a Mediterranean climate type of North Africa. This revised version was published online in July 2006 with corrections to the Cover Date.     

不同春玉米品种花后光合物质生产特点及碳氮含量变化

玉米高产实践表明增加花后干物质生产对于产量的进一步增加具有重要作用。为了探明高产条件下花后干物质生产增加的原因,本研究比较了玉米品种登海661 (DH661)、中单909 (ZD909)和970的产量差异,并利用产量性能分析理论剖析了花后的产量性能参数,分析了花后主要功能叶穗位叶的叶绿素含量、净光合速率和碳、氮含量的变化。结果表明,品种间的产量差异显著,产量较高的品种(DH661和ZD909)具有较高的穗粒重,而DH661具有较多的穗粒数(466.7),ZD909具有较高的粒重(392.7 g);产量较高的品种后期干物质生产及其向籽粒的分配比例高,产量性能分析表明花后的平均叶面积指数(mLAI)及光合势(LAD)与干物质生产及产量均呈显著正相关;产量较高的品种花后穗位叶叶绿素、全碳和全氮含量下降慢,碳氮比值增加慢,光合速率在整个灌浆期相对较高,光合产物不仅向籽粒运转,还能在叶片中以淀粉的形式持续积累,在后期随着光合速率的下降,淀粉才开始降解向籽粒运输。可见玉米花后碳氮代谢协调、光合作用和物质生产能力衰减缓慢对于有效维持较高平均叶面积指数和光合势,进一步提高作物产量具有重要意义。