Screening for Drought Tolerance: Evaluation of Seed Germination and Seedling Growth for Drought Resistance in Legume Plants

Experiments were performed to evaluate seed germination and seedling growth in simulated drought as screening techniques for drought tolerance raring. Several laboratory screening tests were evaluated for ability to estimate drought resistance in 18 cultivars of legume plants (field bean, soybean, field pea, lupine). Drought was simulated by a water solution of mannitol of chemical water potential ψ= -0.3 and -0.6 MPa. Both solutions significantly affected seed germination (final germination and promptness index) and seedling growth parameters (seedling height, dry matter of shoot and root as well as leaf injury by drought and high temperature). The tested cultivars could be grouped as drought resistant and drought susceptible plants. Drought tolerance ratings of legume plants in the laboratory tests were, on the whole, consistent with the ratings based on estimation of direct effects of soil drought on seed yield in field experiments. Measurements of electroconductivity of leaf diffusate to evaluate invisible injury caused by drought or high temperature were found to be an adequate criterion for drought tolerance rating. It is concluded that tolerance to drought stress in growing seedlings can be screened for by using mannitol containing nutrient solution. According to the results collected in this research, varieties differences in seed germination, seedling growth and leaf injury affected by drought or heat temperature were evident, however, not all treatments appeared to be equally useful for screening of legume species cultivars.     

小麦抗旱性鉴定方法及评价指标研究Ⅳ萌发期抗旱指标的比较研究

为探讨小麦萌发期的抗旱性鉴定指标,采用PEG-6000高渗溶液胁迫剂在小麦种子萌发期进行渗透胁迫试验,并运用灰色关联分析对品种的抗旱性做出评判,依据抗旱性对有关指标进行相关分析。结果表明,种子萌发期抗旱性鉴定方法结果科学、客观,具有较强的操作性和重复性;相对发芽率、贮藏物质转运率、胚芽鞘长可作为鉴定小麦萌发期抗旱性的可靠指标,初生根数可作为参考指标,芽长、主胚根长不宜作为鉴定指标。     

甜菜苗期抗旱性鉴定及指标筛选

为筛选甜菜苗期抗旱种质资源及确定抗旱指标。本研究以国家甜菜种质中期库提供的24份甜菜种质资源为材料,采用PEG-6000模拟干旱胁迫的方法,以正常生长条件的Hoagland水培溶液(CK)为对照,对甜菜幼苗进行7天的6% PEG-6000处理,并测定地上部和地下部的表型指标。结果表明,干旱胁迫对叶鲜重、根鲜重、叶饱和鲜重和叶干重的影响较大,降幅均超过50%;且干旱胁迫后甜菜种质根冠比明显增加。聚类分析将24份甜菜种质分为四类,其中ZT000516单独为一类,是抗旱性最强的种质资源;第二类为抗旱性较强的种质分别为ZT000078、ZT000547、ZT000247;第三类为中等抗旱型种质共7份;第四类为抗旱性弱种质共13份,其中ZT001698、ZT001398为干旱高度敏感型种质资源。通过逐步回归分析筛选出叶干重和叶饱和鲜重与D值极显著相关。ZT000516为抗旱性强种质资源,ZT001698、ZT001398为干旱敏感型种质资源,叶干重和叶饱和鲜重可以作为甜菜苗期干旱胁迫快速准确地鉴定指标。     

Grain Yield and Drought Resistance Indices of Oat Cultivars in Field Rain Shelter and Laboratory Experiments

Oat cultivars (n = 22) varying in origin were examined in laboratory and field tests at Svalöv and Ultuna, Sweden, in 1985 and 1986. Comparisons were made between drought resistance characteristics of juvenile plants and drought responses in yield of crops grown in field. By using automatic, movable rain shelters in combination with drip irrigation systems, both high and low irrigation regimes could be effected in the field experiments.
Black oat cultivars were more stable under water deficiency conditions, particularly on sandy soil. They possessed the highest drought resistance indices both in the laboratory and field. Modern white oat cultivars were found to be most drought sensitive.
Drought resistance index (DRI) and seminal root length (RL), as assessed in seedling stage, were strongly correlated with field drought susceptibility index (S). It is suggested that DRI and RL could be used as selection criteria to increase drought resistance of oats.     

Screening of Barley Varieties for Drought Resistance

Barley varieties were screened for their efficient drought enduring ability and associated characters which may be useful in breeding programmes. The characters studied were: relative water content, content of proline, chlorophyll stability index (CSI), and percentage grain loss per plant due to water stress subjected to 10 days from jointing to boot stage. Proline and chlorophyll stability index were greatly associated with drought response (r =+0.54; -0.49), flag leaf area (r =+0.69; -0.51) and, to a certain extent, with leaf number (r = -0.35 and +0.34). Among the studied 19 varieties of barley, only three (DL 192, DL 36, DL 3) showed high enduring ability, of these the former two fall in the early, and the last one in the late flowering group. Morphological architecture of DL 192 had gathering type tiller (narrow tiller angle), wider and floppy leaves and it also bears physiological characters (high proline and high relative water content, and low value of chlorophyll stability index) necessary for drought resistance. DL 3 and DL 36 had dispersing type tiller (wider tiller angle) and erect leaf with good leaf area/plant, but unit leaf area was low in DL 3 (relates with shading behaviour reducing water loss). Other relations of drought resistance are briefly discussed in the text. An appraisal of the various traits revealed that high proline content, and low CSI (biochemical characters), earliness, larger flag leaf area and fewer leaves per plant (morphological characters) were directly correlated with productivity of the cultivars under drought conditions. These characters could be used as a guideline for breeding drought resistant cultivars of barley.     

水分胁迫下玉米杂交种光合抗旱指数与抗旱性评价研究

通过筛选抗旱玉米品种和抗旱评价指标,进而对其进行生理生化研究,最终实现干旱半干旱地区玉米抗旱节水,是研究玉米高产高效的重要课题。采用盆栽试验方法,选用辽宁省近几年最新选育的12个玉米杂交种,在水分胁迫条件下,对苗期、抽雄吐丝期和灌浆期玉米形态和光合生理等性状特征进行了研究和分析,找出了不同时期水分胁迫下光合抗旱指数与产量抗旱指数的相关性,筛选出了抗旱性较强的玉米品种。结果如下：苗期水分胁迫缩短了58％供试品种抽雄至散粉期时间,延长了83％供试品种的ASI,而铁研120在水分胁迫处理后ASI比对照短,且和其他品种相比,该品种苗期叶片叶绿素含量较高。相关分析表明,灌浆期水分胁迫处理,光合抗旱指数与产量均呈正相关关系,其中,蒸腾速率抗旱指数与产量抗旱指数相关性较强。不同水分胁迫时期的产量抗旱等级划分结果显示,铁研120和铁研58综合抗旱性较强,在苗期、抽雄吐丝期和灌浆期受到水分胁迫,在籽粒成熟期均能获得较高产量。     

小麦抗旱性鉴定方法及评价指标研究Ⅱ抗旱性鉴定评价技术规程

针对目前小麦品种抗旱性的评价标准不够标准,认识不够统一的问题,介绍了应用于国家旱地小麦品种区试的小麦品种全生育期抗旱性鉴定、幼苗期反复干旱法抗旱性鉴定、种子萌发期PEG胁迫法抗旱性鉴定评价的技术规程,以期能在统一标准下鉴定品种的抗旱性,为小麦抗旱育种和抗旱品种的筛选鉴定及可比性提供依据。     

陆稻苗期抗旱性鉴定指标筛选与评价

为筛选出陆稻苗期抗旱性鉴定指标,以24个云南陆稻品种为材料,采用反复干旱存活率作为标准,分析各测定指标与抗旱性的相关关系并对供试品种的抗旱性进行综合评价。结果表明,心叶下倒1叶长、心叶下倒2叶长、心叶下倒2叶宽、根干重和根冠比等5个形态指标的相对值与反复干旱存活率呈显著或极显著的相关性,可作为苗期抗旱性鉴定的形态指标。以反复干旱存活率为因变量,5个综合指标为自变量建立的回归方程对24个供试品种的抗旱性进行预测,其结果与芽期抗旱鉴定呈显著相关关系。     

小麦抗旱性鉴定方法及评价指标研究Ⅲ综合评价指标的比较研究

为了筛选适宜小麦品种抗旱性鉴定的综合指标,在灌水和旱棚鉴定条件下,以137个品种为试材,研究了小麦品种抗旱性的基因型间差异,对抗旱系数、干旱敏感指数、抗旱指数和抗旱指数DI等抗旱鉴定产量指标进行了比较分析。结果表明,品种间抗旱性存在较大遗传差异。小麦品种抗旱机制和抗旱表现的复杂性要求选择全生育期综合抗旱性评价指标。小麦品种抗旱鉴定与小麦抗旱种质筛选不同。抗旱系数反映材料的稳产性,对于小麦种质抗旱性筛选更直观。抗旱指数DI以对照品种的表现为参照,兼顾品种的相对产量(抗旱系数)和绝对产量,便于与品种区试和品种产量比较试验结合,可操作性强,是目前最适用于小麦抗旱育种和区域试验的综合性抗旱鉴定指标。     

Use of Canopy Temperature Measurements as a Screening Tool for Drought Tolerance in Spring Wheat

Remotely sensed infrared canopy temperatures provide an efficient method for rapid, non-destructive monitoring of whole-plant response to water stress. Field studies were conducted in 1992 and 1993 to evaluate the potential for using canopy temperatures to screen for drought tolerance in wheat. In both years, 12 spring wheat (Triticum aestivum L.) genotypes were grown under two irrigation levels (well-watered and moisture-stressed) imposed between tillering and anthesis with a line-source sprinkler irrigation system. Canopy temperature measurements were taken in well-watered and moisture-stressed plots between 1330 and 1430 h (MDT) on five clear days in 1992 and seven clear days in 1993 during the late vegetative and early reproductive growth periods following closure of the plant canopy. Genotypes exhibited differences in mean canopy temperatures across the two irrigation levels and two years. Klasic consistently had the highest canopy temperature under moisture-stressed conditions, while Bannock and Pondera had the lowest. Bannock, Yecora Rojo and Klasic had the warmest canopies under well-watered conditions, while Vandal, Amidon and Rick had the coolest. Plot-to-plot variation in canopy temperature under water stress conditions was evident for differences in grain yield. Significant correlations between canopy temperature and yield under moisture-stress conditions and drought susceptibility index values indicated the potential for screening wheat genotypes for drought response.     

接骨木无性系苗期干旱胁迫响应及抗旱性综合评价

为揭示不同种接骨木无性系的抗旱性,探讨其对干旱环境的适应能力,为干旱瘠薄山地造林提供材料。采用盆栽法进行自然干旱胁迫试验,运用主成分分析对不同处理下各无性系生理指标进行综合评价。结果表明:干旱胁迫下,无性系PT-1的生物量增量最大,PT-2的根冠比最大。在干旱胁迫逐增情况下,细胞膜透性逐增,当干旱达到中、重度时,无性系PT-1和PT-2的细胞膜透性最小。叶绿素含量及超氧化物岐化酶活性均随干旱程度增加呈先增后降趋势。随干旱胁迫增加可溶性糖和脯氨酸均随之增大。在重度干旱胁迫下,无性系PT-1的可溶性糖含量最大。主成分分析得出,各无性系抗旱能力由强到弱为:XY-2、JY-1、XY-1、XY-3、PT-1、PT-3、PT-2。其中,XY-2、JY-1具有较强抗旱性,可初步作为抗旱材料进行后续研究。     

玉米抗旱化学调控技术研究进展

干旱是影响玉米生长发育及产量的主要气象因子之一。为了找到有效的减灾保产途径,提高玉米的抗旱性,本研究介绍了玉米抗旱化学调控技术,总结了干旱胁迫对玉米种子萌发及幼苗生理生化的影响,概述了植物的抗旱机制,并归纳了化学调控技术在玉米抗旱性方面的应用。最后指出化学调控技术应用过程中存在的问题,并提出了应注重混合剂型的研发及应用的建议。     

作物对干旱胁迫的响应机制及提高作物抗旱能力的调控措施研究进展

干旱是影响作物生长发育和产量的最主要非生物胁迫之一,在气候变化背景下,作物遭受干旱胁迫的风险越来越大。为了应对干旱,作物表现出一系列的抵御机制,包括形态特征和生理生化（抗氧化酶、渗透调节物质、内源激素）特性改变。本研究从上述2个方面总结了作物对干旱胁迫的响应机制,并对提高作物抗旱能力的调控措施进行了论述,主要包括：（1）筛选抗旱性品种,促进对深层土壤贮水的吸收利用;（2）地面覆盖,有利于降低土壤蒸发,增加土壤含水量;（3）节水灌溉技术,如微喷灌、滴灌等灌溉方式能实现少量多次灌溉,根区局部灌溉有利于调节气孔关闭,减少奢侈蒸腾,降低土壤蒸发;（4）抗蒸腾剂,在作物枝干及叶面表层形成超薄透光的保护膜,抑制作物水分过度蒸腾;（5）植物生长调节剂,调控植物生理代谢,增强抗旱性;（6）纳米肥料,改变作物生理生化反应,促进植株生长发育;（7）生物炭,有利于土壤通气保水,改善土壤的物理性质和土壤的持水能力。本研究系统地对以上7种措施提高作物抗旱能力的作用机理、应用前景及存在问题进行了论述,以期为应对干旱胁迫提供理论依据和技术参考。     

A Comparison of Screening Criteria for Salt Tolerance in Wheat under Field and Controlled Environmental Conditions

Although many screening criteria have been suggested to distinguish between genotypes for their salt tolerance under controlled environmental conditions, there is a need to test these criteria in the field. Saline soils are often complex and, therefore, unlikely to show a simple relationship to controlled conditions. To address this deficit, different agronomic and physiological screening criteria for salt tolerance in wheat at different stages were examined under both field and controlled conditions. Four wheat genotypes differing in their salt‐tolerance levels were grown in salt‐affected soil at two different locations and also under greenhouse conditions. Dry weight and leaf area of the upper and lower two leaves of the main stem and total dry weight at Zadoks scale 47 were measured in plants grown under field conditions. The concentrations of Cl^?, Na⁺, K⁺ and Ca²⁺ in the upper and lower two leaves of the main stem at Zadoks scale 47 and different yield components were measured in plants grown under both conditions. Our results indicate that measurements derived from the upper two leaves of the main stem were generally more effective as screening criteria than those from the lower two leaves. Correlation coefficients between grain yield and either dry weight or leaf area of the upper two leaves of the main stem indicated that dry weight is inferior to leaf area as a screening criterion under field conditions. Number of sterile spikelets per plant performed well under both conditions, whereas the number of spikelets per plant and 1000‐grain weight failed to distinguish the differences of salt‐tolerance levels among genotypes accurately. Weight and number of grains per plant and number of fertile spikes per plant were poor criteria under controlled conditions, but effective under field conditions. The maintenance of low Cl^? and Na⁺ concentrations in the upper two leaves offered the best guide to salt tolerance under both conditions. Potassium concentration was a poor criterion compared with the selectivity of K⁺ over Na⁺, which was useful under both field and controlled conditions. Calcium concentration and Ca²⁺ over Na⁺ selectivity in the upper and/or lower two leaves of the main stem were also effective in ranking genotypes according to their salt tolerance under both field and controlled conditions. Therefore, we conclude that simple measurements of the upper two leaves of the main stem including a straightforward measurement of leaf area, visually estimating the number of sterile spikelets, and a quick, practical determination of Na⁺ and Ca²⁺ concentration constitute effective criteria to screen wheat genotypes for salt tolerance under both field and controlled conditions.     

Further Evaluation of the Resistance of Black Barley to Water Stress: Preliminary Assessment for Selecting Drought Resistant Barley

Some parameters for screening drought resistance in barley were examined during various stages of plant development using two contrasting cultivars (local Iraqi cv. Black and Australian cv. Clipper). These parameters include leaf growth, tiller number, relative water content (RWC), proline accumulation and ionic composition. More pronounced drought resistance in Black was expressed by significantly lower reduction in leaf area, cell and tiller numbers compared with Clipper; proline concentration, RWC and ionic (N, P, K) concentration in expanded leaves, on the other hand, did not clearly distinguish the cultivars. Black was particularly drought tolerant at the post-flowering stage.     

Evaluation of Maize Germplasm for Tolerance to Low Temperature Stress under Field and Laboratory Conditions

Sixty-four inbred lines of maize ( Zea mays L.) were evaluated for their tolerance to low temperature stress in three experiments at Punjab Agricultural University, Ludhiana. All the 64 inbred lines were evaluated under laboratory conditions. Forty-four of these were also studied under field conditions. In the laboratory test the materials were exposed for four hours to 1, 0, −1, −2, −3 and −3.5°C on six successive nights. Significant genotypic differences were observed for freezing injury in laboratory test and for frost and non-freezing (yellowing) injuries in field evaluation. Expression of frost injury under field condition and freezing injury in laboratory test at −2, −3 and −3.5 °C showed positive correlation in one experiment. The range and mean square for freezing injury of inbred lines were the largest either at −3 or at −3.5°C. The correlation of yellowing with frost injury in field and freezing injury in laboratory at −3 and 3.5°C was not significant suggesting the lack of association between yellowing and frost/freezing injury.     

Screening Wheat (Triticum spp.) Genotypes for Root Length under Contrasting Water Regimes: Potential Sources of Variability for Drought Resistance Breeding

Screening for root traits has been one of the most difficult areas to practise over large number of genotypes. Hydroponic systems enable easy access to roots while high‐molecular weight polyethylene glycol (PEG) is used to induce water stress. A total of 838 genotypes were evaluated for root length in a hydroponic trial under PEG‐induced stress and non‐stress growing conditions. Augmented complete block design with seven blocks and six standard control varieties was used. Root length differences were highly significant (P < 0.01) under both stress and non‐stress growing conditions among genotypes. Osmotic stress has caused an average reduction of 54 % in root length. Among the genotypes, root length ranged from 1.4 to 13.3 cm under stress, and 4.4 to 23.3 cm under non‐stress conditions, respectively. The best control variety for drought resistance was significantly (P < 0.05) outperformed by four new entries namely Colotana 296‐52, Compare, Santa Elena and Tammarin Rock, while the shortest roots were measured on genotypes Aus 16356, Elia, Camm, Portugal 3, and Sentinel. Differences among ploidy levels, domesticated and wild forms were also significant (P < 0.05). Hexaploid wheat showed significantly longer roots in both growing conditions while wild tetraploids showed the shortest roots under stress. There was a change in the ranking of genotypes under the two water regimes, which indicates the difficulty of selecting drought resistant varieties under optimum environments.