Impact of drought stress on yield,photosynthesis rate,and sugar alcohols contents in wheat after anthesis in semiarid region of Iran

Owing to the importance of after anthesis water deficit in Mediterranean regions (such as Iran), this study has focused on harmful impact of after anthesis drought stress on grain yield (GY), photosynthesis, and some physiological characteristics of wheat. To this aim, a factorial experiment based on randomized complete block design with three replications was used in greenhouse conditions in Razi University in Kermanshah city of Iran, during 2010–2011 growing season. Two bread wheat genotypes, “Zagros” (tolerant to drought) and “Marvdasht” (sensitive to drought) were grown in normal water supply condition (100% of field capacity) and drought stress from anthesis until maturity (50% of field capacity). The results indicated that after anthesis water deficit considerably reduced grain and biological yields, thousand grain weight (TGW) and a number of grains per spike (NGS) among different traits in genotypes. Under well-watered and drought-treated conditions, genotypes in terms of all evaluated traits had considerable variations. Water deficit caused more reduction of net photosynthesis rate (Pn), stomatal conductance (gs), relative water content (RWC) of leaf, chlorophyll a, b (Chl), and soluble proteins content in sensitive genotype; values were respectively 66.3, 73.2, 14.6, 32.1, 46.2, and 25.6%. Better performance of tolerant genotype under water deficit was associated with a great ability in production of some osmoprotectants as inositol, glycerol, and erythritol sugars. Rather adaptation of tolerant genotype to water deficit may be attributable to having maximum soluble protein, sugar alcohols, Chl content, RWC, gs and Pn in drought stress, and with respect to the results, wheat might not be able to synthesize mannitol. Transfer of gene(s) producing mannitol may cause more improvement of growth performance of wheat under stresses.     

羊草干物质积累及叶片气体交换对土壤水分的响应

采用盆栽方法模拟羊草干物质积累和叶片气体交换参数对 5个水分梯度的响应表明 :轻度、中度干旱与对照相比 ,羊草叶片的相对含水量 (RWC )有所升高 ;严重和极严重干旱使RWC显著降低。干旱降低植株生物量 ,后期的降低幅度远远大于前期 ,反映出羊草叶片水分状况对适度的土壤干旱具有良好的适应性 ,而过度干旱对羊草的生长造成威胁。鞘的分配随时间呈下降趋势 ,而根茎的趋势与鞘相反 ,表明鞘的暂储物质有可能向根茎转移。干旱促进早期根的分配和根冠比增加 ,后期降低 ,表明羊草在受到持续干旱后 ,通过增加根部的比重来提高抗旱性的能力逐渐降低。干旱降低了光合速率 ,增加了胞间CO2 浓度 ,但对水分利用率 (WUE )的影响随日进程而波动 ,在上午 10时干旱促进了WUE升高 ,其他时间无显著影响 ,表明光合参数对干旱的响应受日进程影响。     

Long-term effects of mowing on plasticity and allometry of Leymus chinensis in a temperate semi-arid grassland,China

Mowing is an important land management practice for natural semi-arid regions.A growing body of empirical evidence shows that different mowing regimes affect the functioning of grassland ecosystems.However,the responses of plant functional traits to long-term mowing and their allometric scaling under long-term mowing are poorly understood.For a better understanding of the effects of mowing on grassland ecosystems,we analyzed the allometric traits of leaves and stems of Leymus chinensis(Trin.) Tzvel.,a dominant grass species in eastern Eurasian temperate grassland,at different mowing intensities(no clipping,clipping once every two years,once a year and twice a year).Experiments were conducted on plots established over a decade ago in a typical steppe of Xilinhot,Inner Mongolia,China.Results showed that most of the functional traits of L.chinensis decreased with the increased mowing intensity.The responses of leaves and stems to long-term mowing were asymmetric,in which leaf traits were more stable than stem traits.Also significant allometric relationships were found among most of the plant functional traits under the four mowing treatments.Sensitive traits of L.chinensis(e.g.leaf length and stem length) were primary indicators associated with aboveground biomass decline under high mowing intensity.In conclusion,the allometric growth of different functional traits of L.chinensis varies with different long-term mowing practices,which is likely to be a strategy used by the plant to adapt to the mowing disturbances.     

北部冬麦区小麦新品种(系)的节水生理特性与综合评判

为了研究不同灌溉条件下北部冬麦区小麦新品种的节水生理特性和选择节水品种,以北部冬麦区有代表性的30个小麦品种（系）为研究对象,在节水处理和正常灌溉处理下,对主要生理和农艺性状进行了分析。研究结果表明:不同小麦品种（系）间的植被归一化指数（Normalized Difference Vegetation Index,NDVI）在拔节期以后的不同生育时期存在着显著差异,抽穗期的NDVI出现拐点,此时期保证水分供给,有利于延长叶片功能期。在不同灌溉处理条件下,NDVI、叶面积指数和光截获的变异系数存在差异,和其他性状相比广义遗传力较低,分别为48.61%、58.51%和72.84%,受环境影响较大。由灰色关联度分析可知：NDVI、冠层温度和光截获与产量的关联性较高,位于前列;在正常灌溉条件下,最好的品种（系）为：CA0391-1、中麦998、农大211、中麦175、 CA0958、中优206、农大5181、航麦247、 CA1146、中麦818和京冬17;在节水处理下,最好的品种（系）为：中麦175、中麦818、 CA0391-1 、CA1091、中优206、轮选1690。因此,可根据NDVI值判断小麦受干旱胁迫的影响,将NDVI、冠层温度和光截获作为评价品种（系）抗旱性主要性状指标,在进行抗旱小麦选育时,可将CA0391-1、中麦175、中优206和中麦818作为抗旱选育亲本加以利用。     

外来入侵植物长芒苋在中国不同地区的表型变异与环境适应性

长芒苋(Amaranthus palmeri)是近年来入侵我国的超级杂草,已在我国从南到北的多个点定殖,一旦大面积扩散势必会对农业生产和生物多样性保护等构成极大威胁。长芒苋在我国入侵点的纬度跨度大于其原产地北美洲的分布,探明其在我国不同纬度的地理种群的环境适应机制,对评估扩散潜能、建立早期监测预警等防控措施具有重要意义。本研究在同质种植园实验条件下,通过测定长芒苋不同纬度地理种群的生活史、形态及生物量等11个性状指标来分析其在我国的表型变异与环境适应性。结果表明,在同质园条件下,长芒苋不同地理种群间株高等7个表型性状指标差异不显著,而开花和发芽时间、花序长以及比叶鲜重4个指标具有显著差异(p<0.01),且它们的表型变异随年平均温度(纬度)线性增加或降低。开花时间随纬度的升高而缩短,发芽时间、花序长和比叶鲜重随纬度的升高而增加。基于长芒苋不同纬度地理种群间表型性状的异同,我们推断表型可塑性促进了其在我国不同地理环境中的定殖,表型变异(如高纬度种群开花时间提前)可促进其环境适应性进化,拓展其在我国的适生性分布区,增强其向原产地适应环境梯度之外地区入侵和扩散蔓延的潜力。     

基于GGE双标图法的西瓜抗旱性鉴定评价方法

以7个已知抗旱性的西瓜品种为试材,大田条件下测定其在正常供水、轻度和中度水分胁迫下的经济产量及产量构成性状。选用7种评价方法对试材的经济产量进行评价比较,利用GGE-bioplot双标图分析系统,筛选西瓜抗旱性评价的适宜方法。结果表明:随水分胁迫加剧,供试西瓜材料的产量逐渐降低,降幅具有明显的品种间差异;抗旱品种为了实现最大可能性的产量产出,单果重与单株坐果数间存在权衡效应,而干旱敏感性品种的单果重与单株坐果数间并无权衡关系,果型大小比较不稳定,且单株坐果数变幅较大,不能够保障产量丰收;在GGE-bioplot分析系统中利用折合公顷产量分析试材间抗旱性的相似性,所得结果与已知品种抗旱性强弱规律一致;以折合公顷产量为基准,试材和评价方法位于GGE-bioplot双标图不同的扇区内,与已知抗旱性强的试材位于同一扇区的评价方法即为筛选出适宜的评价方法;在轻度和中度水分胁迫下,筛选出YSI(抗旱系数)、DRI(抗旱指数)、MP(平均产量)、STI(耐旱指数)与GMP(几何平均产量)为西瓜抗旱性评价的适宜方法,其中MP、STI与GMP属同一类评价方法,YSI与DRI属同一类。本研究结果对西瓜抗旱资源筛选和新品种抗旱性鉴定具有理论指导意义。     

Development of a Scale for Evaluation of Tomato yellow leaf curl virus Resistance Level in Tomato Plants

ABSTRACT We have developed a scale of differential hosts that enables the determination and comparison of level of resistance to Tomato yellow leaf curl virus (TYLCV) expressed by resistant tomato lines or by individual plants in a segregating population. The scale is composed of seven different homozygous tomato genotypes that exhibit different levels of TYLCV resistance, ranging from fully susceptible to highly resistant. The differential hosts composing the scale were inoculated with TYLCV under greenhouse conditions. Four weeks after inoculation the plants were evaluated for disease symptom severity, and virus DNA titer was determined. The different genotypes were arranged in the scale according to symptom severity score. The different genotypes were then tested under different environmental conditions, inoculated at different ages, and tested in a field experiment assaying TYLCV-induced yield reduction. While the symptom severity score of each individual resistant genotype changed under different environmental conditions, the relative position on the scale did not alter, except for one genotype. Thus, to evaluate disease resistance of a given tomato genotype, the genotype in question should be inoculated alongside the differential hosts composing the scale, and within 4 weeks one can determine the relative level of resistance of the tested genotype.     

Characterization of Drought Tolerance in Bread Wheat Genotypes Using Physiological Indices

Wheat (Triticum aestivum L.) is a staple food in many countries and is regarded as a vital source of nutrition. Drought is one the most prevalent limitations to wheat growth and development. Herein a two year study was conducted using 25 diverse wheat genotypes obtained from the gene pool of various research institutes of Pakistan to characterize their drought tolerance using various physiological indices like relative water content (RWC), relative dry weight (RDW), water saturation deficit (WSD), relative water loss (RWL), flag leaf area (LA), chlorophyll content index (CC) and their association with the grain yield (GY). Analysis of variance (ANOVA) indicated the presence of significant amount of differences and genetic diversity among genotypes under study. Correlation analysis exposed positive association of CC and LA with GY. However, RWC was shown to have a highly significant and negative association with WSD and RWL. Principal component analysis (PCA) showed that out of the 7 PCs only 2 were significant having eigenvalues >?1; cumulatively accounting for 88.70% and 73.03% of the total variation under control and drought stress conditions, respectively. Strikingly the results of the PCA biplots and cluster heat map exposed G1 (Barani-17), G2 (Dharabi-11), G3 (Ehsan-16), G4 (Chakwal-50), G17 (Ujala-2016) and G23 (Kohistan-97) as potential drought tolerant genotypes. Selection of the positively associated indices would be fruitful and the tolerant genotypes having drought tolerance potential could be utilized in future wheat breeding programs to develop high yielding and drought tolerant genotypes.

     

小麦族6种根茎型牧草叶表皮气孔特性与抗旱性的研究

本文对小麦族 6种根茎型牧草叶的气孔特性与抗旱性的关系进行了研究 ,结果表明 :6种禾草间气孔特性存在着基因型的本质差异 ;赖草属中 ,赖草叶对水分的蒸腾、气体交换的调控功能强于羊草和大赖草 ,其抗旱性强 ;在偃麦草属中 ,中间偃麦草叶的水分的蒸腾、气体交换的调控功能弱于其他 2种 ;在同种不同品种中 ,巴顿硬叶偃麦草叶的抗旱性强于茹莎娜硬叶偃麦草 ;6种禾草中 ,赖草属植物抗旱性强于偃麦草属植物。     

Impact of Cuscuta australis infection on the photosynthesis of the invasive host,Mikania micrantha,under drought condition

Cuscuta species (dodders) are widespread stem holoparasites that depend on host plants for their entire mineral and water and most carbohydrate requirements. Dodders negatively affect host photosynthesis but precise information on their impact on hosts in the presence of environmental stress factors (i.e. drought) is little known. In a pot experiment, the leaf traits, gas exchange and chlorophyll a fluorescence of the invasive climber, Mikania micrantha, parasitized by Cuscuta australis, were investigated in order to study variations of host photosynthesis in response to parasitism and drought. The results showed that the concomitant presence of C. australis infection and drought significantly impacted the leaf traits (i.e. increased leaf dry mass content), gas exchange (i.e. decreased stomatal conductance and transpiration rates and increased water‐use efficiency) and quantum yield of chlorophyll a fluorescence of M. micrantha. The presence of a single stress factor (C. australis infection or drought), however, only significantly affected the leaf traits and gas exchange of M. micrantha. These results suggested that the combined additive effects of C. australis parasitism and drought significantly suppressed the photosynthesis of M. micrantha in relation to both stomatal and non‐stomatal limitation of host photosynthesis. This study provides insights into Cuscuta–host interactions under drought conditions in the tropics.     

不同基因型小麦NDVI值与产量的关系

在旱地保护性耕作条件下,以11个不同基因型小麦(Triticum aestivumL.)品种为材料,研究了植被归一化指数(NDVI,Normalized difference vegetation index)与产量构成和抗旱性的关系。结果表明,不同基因型小麦各生育期的归一化植被指数(NDVI)存在显著性差异;小麦抽穗期NDVI值与其干旱产量指数呈正相关,抽穗期NDVI值较高的小麦品种其干旱产量指数也较高;本试验条件下,石麦15、石家庄8号和烟Blu6439三个小麦品种的干旱产量指数较高。     

玉米大斑病菌毒素对玉米叶肉细胞脂氧合酶活性的影响

 玉米大斑病菌2号小种粗毒素(HT-C)和标准毒素(5-羟甲基-2-呋喃甲醛,HT-I)处理玉米叶片,都能诱导3种供试基因型玉米叶片中脂氧合酶活性增高,但是不同基因型玉米对HT-C和HT-I的反应不同,HT-I对含有Ht1基因的品系诱导时间早,水平高,HT-C对于不带Ht基因的品系LOX的影响略高于HT-I;不同浓度的HT-I在OH43和OH43Ht1玉米叶片中诱导的LOX酶活性不同,高浓度HT-I和HT-C对LOX酶活诱导时间早,水平高,浓度降低诱导水平降低;外源H₂O₂对HT-I和HT-C在OH43叶片中LOX酶活性诱导作用的影响不同。     

Genetic analysis of partial resistance to bacterial leaf streak (Xanthomonas campestris pv. cerealis) in wheat

Genetic variability of partial resistance to bacterial leaf streak was investigated in hexaploid winter wheat ( Triticum aestivum. ), using 16 parental genotypes and 48 pure lines (F10) derived from a composite cross programme. Two experiments were undertaken in a controlled growth chamber. Seeds of all genotypes were grown under controlled conditions using a randomized block design with three replications. Each replication consisted of a row of 20 seedlings of each parent and pure line. An Iranian strain of bacterial leaf streak was used for the inoculation of 12-day-old seedlings. In a third experiment, eight genotypes from parents and F10 pure lines representing a large variability for partial resistance were inoculated with four other Iranian strains of bacterial leaf streak. A large genetic variability was observed amongst the 64 genotypes for partial resistance to the disease. Partial resistance heritability estimates were rather high (70%), indicating that the resistance factors may be transmitted by crossing. Amongst all genotypes investigated, 'DC²-30-N2' and 'IBPT-66' displayed the highest partial resistance to the disease. Significant correlations between strains in the third experiment show that a genotype resistant or susceptible to one strain will have similar reactions with other strains. No significant genetic gain was observed for partial resistance in the best pure line of the 48 lines studied, when compared with the best parental line. Increasing the number of pure lines is likely to result in the identification of genotypes that might prove to be more resistant.     

羊草(Leymus chinensis)与灰色赖草(Leymus cinereus)及其杂交种(F1)的抗旱生理特性比较

用不同浓度的聚乙二醇(PEG6000)进行根际水分胁迫处理，研究羊草(Leymus chinensis)、灰色赖草(Leymuscinereus)及其杂交种的抗旱生理特性。结果表明，在15%PEG、25％PEG、35％PEG不同处理下，两亲本及其杂交种叶片相对舍水量(RWC)逐渐降低；相对电导率、丙二醛含量(MDA)逐渐增加；超氧化物歧化酶活性(SOD)15％PEG、25%PEG处理下，活性逐渐增加，在35%PEG处理下，活性开始下降。而且在15%PEG、25％PEG处理下，杂交种的抗旱(耐旱)性与亲本羊草相近，明显大于另一亲本灰色赖草。     

Increased crop diversity reduces the functional space available for weeds

There is a drive to improve the sustainability of agricultural systems including the biodiversity component. Cultivar mixtures offer yield benefits from the same land area, but the mechanisms behind this overyielding have not been completely worked out. One potential mechanism is improved competition with weeds. We use an experimental approach of varying barley (Hordeum vulgare L.) genotypic and phenotypic diversity to test the hypothesis that increases in diversity have an impact on weed growth strategies and community assembly, or if responses are driven by barley performance. There was no effect of increasing barley mixture diversity on weed traits, either in terms of species means or the community-weighted mean. However, Functional Richness of the weed community decreased with increasing barley mixture diversity mainly as a result of reduced specific leaf area Functional Richness. This pattern was driven by a reduction in species richness of the weed community rather than by reduced variation within species. Whilst barley phenotype had different impacts on weed traits, there were no specific mixtures of phenotypes or genotypes that had consistent effects on community assembly or weed species responses. The competitive exclusion of weed species could have agronomic and environmental benefits, through better targeting or less frequent use of herbicides. Growing crop mixtures is one of many strategies available to improve agricultural sustainability and resilience, and one that has clear benefits.     

紫花苜蓿苗期抗旱性鉴定指标筛选及综合评价

以21份紫花苜蓿种质为研究材料,通过室内盆栽试验,在苗期反复干旱胁迫下,测定了与抗旱性有关的8项形态指标,通过主成分分析法筛选出了叶片长度、叶片宽度、根冠比胁迫指数、地下生物量胁迫指数、干物质含量胁迫指数等5个与存活率密切相关的指标作为紫花苜蓿苗期抗旱性鉴定的指标;并运用隶属函数法对21份紫花苜蓿种质进行综合评价,确定了苗期抗旱性较强的种质为:ZXY04P-44、ZXY04P-10、ZXY04P-32。     

内陆河湿地芦苇叶功能性状特征及其对土壤环境因子的响应

植物功能性状是连接植物与外界环境的重要桥梁,其在不同环境梯度下的变化表现出了对异质环境的适应机制。本文以敦煌西湖国家级自然保护区克隆植物芦苇(Phragmites australis)为研究对象,设置了未退化、轻度退化、中度退化和重度退化4个梯度样地,研究环境异质条件下芦苇叶功能性状特征及其对土壤环境因子的响应。结果表明:①各环境梯度下,芦苇叶功能性状特征变化显著(P <0. 05),叶长、叶宽、叶面积、叶干重随环境梯度退化呈下降趋势,比叶面积随梯度退化呈上升趋势;②芦苇各叶功能性状间呈协同变化的特征,叶长、叶宽、叶面积、叶干重之间呈极显著正相关(P <0. 01),比叶面积与叶长、叶干重呈显著负相关(P <0. 05);③叶长、叶宽、叶面积、叶干重与土壤表层(0~30 cm)、中层(30~60 cm)水分呈显著正相关(P <0. 05),而与土壤表层、中层含盐量呈显著负相关(P <0. 05),说明土壤表层与中层的水分与盐分是芦苇叶功能性状最主要的驱动力。研究结果对干旱区内陆河湿地的保护、生态恢复及管理具有重要的指导意义。     

玉米杂交种耐旱性状的因子分析

在干旱地区大田条件下,通过2a调查4个大面积推广玉米杂交种在4个不同干旱处理下与耐旱性有关的14个生长发育性状,选择差异显著的性状进行农艺性状和产量性状的因子分析。结果表明,影响玉米杂交种耐旱性和耐旱稳定性的主要性状是株高、结实长度、成穗率和出籽率,可利用其预测玉米杂交种的耐旱性。     

利用叶绿素含量及荧光动力学参数评价青贮玉米耐旱关键指标研究

利用叶绿素荧光仪测定了26份青贮玉米自交系和105个组合的叶绿素含量及荧光动力学参数,对其生理性状关键耐旱指标进行主成分及相关分析,并进行配合力及遗传参数分析。青贮玉米Fv/Fm的影响因素大 小依次为：叶片Fv>叶片Fm>叶片Fo>叶片Area>叶片SPAD>苞叶Fv/Fm>苞叶SPAD。筛选出了5个关键指 标(叶片Fm、叶片Fv、叶片Area、叶片Fv/Fm、叶片SPAD)及一般配合力(GCA)较高的9份自交系和特殊配合力(SCA)较高的19个组合。在F₁吐丝期,叶片Fo、叶片Area主要受基因加性效应支配;叶片Fm、叶片Fv的加性与 非加性效应相当;叶片Fv/Fm、叶片SPAD主要受基因非加性效应支配。狭义遗传力(h²N,)大小依次为：叶片SPAD>叶片Area>叶片Fo>叶片Fv>叶片Fm>叶片Fv/Fm。通过对叶片Fv的早代正向直接选择、叶片Fo的早代 负向直接选择,以及对叶片Fv/Fm的杂种优势利用,可提高旱区青贮玉米单位面积生物产量。叶绿素含量及荧光 动力学参数可用于青贮玉米的耐旱性筛选。