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。     

玉米穗期水分胁迫对产量和水分利用效率的影响

在盆栽条件下,以6个玉米杂交种为试验材料,研究了玉米穗期正常供水、轻度和中度水分胁迫下产量和水分利用效率(Water Use Efficiency,简称WUE)的变化.结果表明,6个玉米品种的产量和耗水量的水分胁迫效应均显著,随胁迫程度加大,产量和耗水量均明显降低,但不同品种对水分胁迫的反应存在差异.轻度水分胁迫下,供试品种中有两个品种表现出产量下降幅度不大、且比耗水量下降幅度小、WUE有所提高的优良特性;中度水分胁迫下,6个品种均表现为产量大幅度下降,且远高于耗水量的下降幅度,导致WUE明显降低.相关分析表明,3种供水条件下,WUE与产量均呈显著正相关,与耗水量的相关性均不显著.     

不同供肥条件下水分分配对旱地玉米产量的影响

以盆栽试验和田间试验研究了不同供肥条件下不同生育期水分状况对玉米产量的影响。结果表明，任何生育期的土壤干旱胁迫均会导致玉米减产，肥料供应充足时减产幅度较小；干旱胁迫越严重，肥料的这一作用越显著。无论正常供肥还是低肥，玉米对抽雄期土壤水分最敏感，防止这一时期干旱胁迫对保证玉米产量具有重要意义。拔节期是旱地玉米有限灌溉的另一个关键时期，水分的增产潜力很大，低肥时增加拔节期土壤水分供应效果更显著。玉米苗期并不耐旱，尤其是低肥时苗期干旱显著影响玉米的籽粒产量。在相对含水量45%~90%范围内，玉米产量随土壤含水量的增加而增加，但增加幅度与肥料供应和生育期有关。玉米获得最高产量的土壤水分条件与肥料供应密切相关，与正常供肥相比，低肥时所需土壤含水量较低。玉米增产的肥效大于水效，产量随肥料投入的增加显著提高，水分胁迫条件下增加肥料供应同样具有增产作用。肥料供应不足时水分的增产作用会受到限制。在现有的水资源条件下，提高肥料供应水平是旱地玉米增产的主要途径。     

广东甜玉米不同品种耐旱性鉴定试验

采用塑料大棚遮挡自然降水的方法研究了不同水分胁迫下8个甜玉米品种散粉至吐丝间隔期（ASI）、营养器官和产量构成因素性状指标的变化。结果表明，在干旱胁迫下，各品种的散粉至吐丝间隔期（ASI）受到不同程度的延迟，营养器官和产量构成因素性状指标呈下降趋势。轻度干旱对各甜玉米品种上述性状的影响较小，中度干旱对其影响比较大，与正常水分条件相比部分品种受到的影响达到显著或极显著的差异。以散粉至吐丝间隔期（ASI）、产量及产量的耐旱系数为主并结合营养器官形态性状和产量构成因素进行耐旱性综合评价较为可行。粤甜13号和正甜38号耐旱性相对较好，在生产中可作为耐旱节水型的品种加以应用。     

常用玉米自交系抗旱性及抗旱性鉴定指标研究

采用人工水分胁迫处理,通过植物生理学方法,对10个常用玉米自交系进行了抗旱性研究。结果表明,不同玉米自交系存在明显差异,沈136、齐319、丹598和沈137耐旱性较好,可以作为玉米耐旱育种的基础材料。干旱胁迫下,玉米植株叶片相对含水量、丙二醛含量、电导率和ASI与玉米子粒产量极显著相关,能够比较准确地评价玉米自交系抗旱性的强弱,和抗旱系数、抗旱指数一样可以作为玉米育种耐旱自交系筛选的鉴定指标。     

PEG处理幼苗和盆栽水分胁迫不同玉米自交系抗旱性研究

用高渗溶液PEG-6000模拟干旱胁迫,对10个玉米自交系进行发芽和幼苗培养试验,同时进行室外盆栽控制水分,在苗期和开花期进行中度水分胁迫试验测定籽粒产量.结果表明,PEG处理后,所测定的指标与田间水分胁迫一样具有相同的趋势,都表现电导率上升、丙二醛含量增加、叶片水势增大,说明利用PEG处理模拟水分胁迫,能够达到与田间水分胁迫相似的效果.进一步的相关性分析结果表明,所测定抗旱鉴定指标与水分胁迫下的籽粒产量表现极显著相关.因此可以利用PEG模拟干旱胁迫代替盆栽、田间水分胁迫对玉米种质进行抗旱性研究.     

干旱胁迫对土壤水分动态及玉米水分利用效率影响研究

为研究干旱胁迫效应下土壤的水分动态及玉米水分利用效率,设置干旱胁迫处理和正常灌水处理2种模式,比较不同处理下土壤的水分特征、耗水规律和水分利用效率。结果表明：作物进入拔节期以后,干旱胁迫效应明显,土壤水分开始显著低于正常灌水处理;灌溉后的作物耗水量显著高于干旱胁迫处理,灌溉是影响研究区域玉米生长水分条件的主要因素,玉米进入生殖生长阶段后灌水较不灌水处理的日耗水量增长幅度达到了1.4~7.0倍;干旱胁迫对玉米产量造成严重影响,产量下降54.6%,但是水分利用效率较正常灌水处理高27.3%。     

水分胁迫对甜玉米主要农艺性状及产量的影响

在大棚内采用人工供水的方法,研究不同水分胁迫下甜玉米品种主要农艺性状与产量的关系。结果表明,轻度干旱胁迫下可用株高、茎粗、散粉至吐丝间隔期(ASI)、穗粗、每穗粒数、千粒重等6个性状耐旱系数作为品种耐旱性鉴定的指标,而中度干旱胁迫下可用穗位叶面积、散粉至吐丝间隔期(ASI)、穗粗、每穗粒数、出籽率、千粒重这6个性状耐旱系数预测品种产量的耐旱系数。在不同程度水分胁迫下,散粉至吐丝间隔期(ASI)、穗粗、每穗粒数、千粒重等4个性状耐旱系数是不同品种耐旱性鉴定的重要指标,除此之外,株高、茎粗、穗位叶面积等决定植株形态的性状指标也对甜玉米耐旱性起一定作用。     

玉米抗旱育种的研究进展

干旱胁迫严重影响我国玉米的产量,抗旱育种是确保产量最有效的手段.在众多的二级目标性状中,根系的数量与重量、株高与叶卷曲、ASI、ABA等是抗旱育种研究的重点目标性状.     

水分胁迫对玉米光合速率和水分利用效率的影响

以7个玉米品种为试材,采用单株室外盆栽在开花期进行中度水分胁迫处理,研究了水分胁迫对玉米叶片净光合速率(Pn)、水分利用效率(WUE)、气孔导度(Gs)、胞间CO2浓度(Ci)等光合参数的影响.结果表明:水分胁迫使光反应中心受到抑制,非气孔限制是影响净光合速率增加的主要限制因子;WUE与Pn、Gs、Tr存在显著的正相关关系,与Cj存在显著的负相关关系,叶片在水分胁迫条件下主要通过降低蒸腾作用来提高水分利用效率.     

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.     

利用回交导入系定位干旱环境下水稻植株水分状况相关QTL

日益严重的水资源危机使水稻的耐旱育种尤为迫切, 干旱环境下较高的植株水分含量有助于提高或维持作物产量的稳定性, 挖掘与耐旱性密切相关的分子标记有助于提高耐旱品种的选育效率。从供体Lemont (粳稻)导入到特青(籼稻)背景的254个高代回交导入系中筛选出覆盖供体全基因组的55个回交导入系, 采用PVC管栽培, 分析了干旱(胁迫)条件下水稻植株水分状况相关性状与籽粒产量、生物量的相关性并定位了相关QTL。研究表明, 植株水分相关性状(相对含水量、叶片水势、渗透势、卷叶度)均与籽粒产量显著相关。检测到7个相对含水量QTL, 7个叶片水势QTL, 5个渗透势QTL及5个卷叶QTL; 另检测到5个产量QTL, 7个生物量QTL。分析发现, 不仅QLwp5、QLr5、QRwc5和QY5同时分布在RM509~RM163区域, 且该区域还分布有对水分环境表现稳定的产量QTL(QGy5), 效应方向一致, 从遗传学角度解释了籽粒产量与水分相关性状之间的显著相关性。另外, QLr5、QRwc5、QY5、QLr2、QLr7、QLr8、QLr9、QRwc3、QRwc4a、QRwc12及QY7 等11个QTL曾在不同遗传背景群体中被检测到, 它们控制相同目标性状。研究认为RM509~RM163区域及QLr2、QLr7、QLr8、QLr9、QRwc3、QRwc4a、QRwc12和QY7所分布的染色体区域对水分环境或者遗传背景相对稳定, 在水稻分子标记辅助选择(MAS)耐旱育种实践中有较重要利用价值。     

Combining ability and testcross performance of drought‐tolerant maize inbred lines under stress and non‐stress environments in Kenya

Drought and poor soil fertility are among the major abiotic stresses affecting maize productivity in sub‐Saharan Africa. Maize breeding efforts at the International Maize and Wheat Improvement Center (CIMMYT) have focused on incorporating drought stress tolerance and nitrogen‐use efficiency (NUE) into tropical maize germplasm. The objectives of this study were to estimate the general combining ability (GCA) and specific combining ability (SCA) of selected maize inbred lines under drought stress (DS), low‐nitrogen (LN) and optimum moisture and nitrogen (optimum) conditions, and to assess the yield potential and stability of experimental hybrids under these management conditions. Forty‐nine experimental three‐way cross hybrids, generated from a 7 × 7 line by tester crosses, and six commercial checks were evaluated across 11 optimum, DS and LN sites in Kenya in 2014 using an alpha lattice design with two replicates per entry at each site. DS reduced both grain yield (GY) and plant height (PH), while anthesis–silking interval (ASI) increased under both DS and LN. Hybrids ‘L4/T2’ and ‘L4/T1’ were found to be superior and stable, while inbreds ‘L4’ and ‘L6’ were good combiners for GY and other secondary traits across sites. Additive variance played a greater role for most traits under the three management conditions, suggesting that further progress in the improvement of these traits should be possible. GY under optimum conditions was positively correlated with GY under both DS and LN conditions, but GY under DS and LN was not correlated. Our results suggest the feasibility for simultaneous improvement in grain yield performance of genotypes under optimum, DS and LN conditions.     

Modelling nitrogen stress with probe genotypes to assess genetic parameters and genetic determinism of winter wheat tolerance to nitrogen constraint

Environmental and economical constraints in Europe will favour low nitrogen (N) input systems and wheat varieties adapted to moderate N deficiency. In this context, we studied the dynamics of genetic parameters according to N stress intensity and characterized the genetic determinants for plant tolerance to N deficiency. Thus, we combined N stress modelling with a genetic approach. Two hundred and twenty-two doubled haploid lines were experimented in the field for a range of nitrogen conditions. Those conditions were characterized by the Nitrogen Nutrition Index (NNI) of Récital. Grain Yield (GY) and Kernel Number (KN) were assessed. For GY and KN, and for each line, factorial regressions using NNI of Récital as environmental index were performed. In addition, we assessed the sensitivity to N stress (slopes of the regression) and the performances under low N conditions (predicted values for a NNI of 0.5). QTL detection was performed on these parameters as well as on KN and GY measured in each environment. G × N variance increased with N stress intensity whereas heritability and genetic variance decreased. 11 QTL regions were detected: 3 were N supply-specific QTL (on linkage groups 2A2, 3A and 4B) while 4 contained QTL detected under N⁺ and under N⁻ (2D1, 4B and 5A1). Out of these four, 2 coincided with QTL for factorial regression parameters (2D1 and 4B). Finally, 4 QTL were specific for factorial regression parameters (3B, 5A2 and 7B2). The role of genes commonly used in breeding programs (rht-B1 on 4B, and Ppd1 on 2D1) in plant adaptation to nitrogen constraint was highlighted. Future studies should focus on grain protein yield, another target for low-N breeding scheme.     

Improving adaptation to drought stress in white pea bean (Phaseolus vulgaris L.): Genotypic effects on grain yield,yield components and pod harvest index

Common bean (Phaseolus vulgaris L.) is the most important food legume crop in Africa and Latin America where rainfall pattern is unpredictable. The objectives were to identify better yielding common bean lines with good canning quality under drought, and to identify traits that could be used as selection criteria for evaluating drought‐tolerant genotypes. In all, 35 advanced lines were developed through single seed descent and evaluated with a standard check under drought and irrigated conditions at two locations over 2 years in Ethiopia. Grain yield (GY), pod number per m², seed number per m² and seed weight decreased by 56%, 47%, 49% and 14%, respectively, under drought stress. Eight genotypes had better yield with good canning quality under drought compared to the check. Moderate to high proportion of genetic effects were observed under drought conditions for GY and yield components compared to genotype × environment effects. Significant positive correlations between GY and pod harvest index (PHI) in drought suggest that PHI could be used as an indirect selection criterion for common bean improvement.     

Increase in grain protein percentage in high-yielding common wheat breeding lines by genes from wild tetraploid wheat

Summary Forty-one breeding lines of common wheat, derived from crosses between the Israeli cultivars Miriam and Lakhish and high-protein lines of wild tetraploid wheat, Triticum turgidum var. dicoccoides, were tested for various protein and yield parameters in field trials, under typical agronomic conditions. All lines had a higher grain protein percentage (GPP) than the leading Israeli cultivar Deganit, which was grown as a control. Grain yield (GY) ranged in the breeding lines from a low of 2.44 t/ha to as high as that of Deganit (6.95 t/ha). Despite the weak negative correlation between GPP and GY, several lines excelled both in GPP and in GY. The grain protein yield (GPY) of some of these selected breeding lines was higher than that of Deganit; e.g., 1.19 t/ha in the best line vs. 1.02 t/ha in Deganit. The 16.7% increase in GPY in this line reflected a more efficient utilization of nitrogen.     

我国主要玉米自交系开花期耐旱性差异及改良

通过对37份我国主要玉米自交系两年的开花期耐旱性鉴定, 筛选出耐旱系12份(K22、 SH15、 X178、 P138、中自01、中自451、金黄96B、齐319、旱23、东91、临京11、 CA156). 在干旱胁迫下, 果穗吐丝延迟, 雌雄开花间隔增大, 结穗率下降, 籽粒产量严重降低; 雌雄开花间隔天数和结穗率与籽粒产量均呈极显著相关, 是可供耐旱性选择     

Kernel number as a positive target trait for prediction of hybrid performance under low-nitrogen stress as revealed by diallel analysis under contrasting nitrogen conditions

Environmental sustainability concerns make improving yield under lower N input a desirable breeding goal. To evaluate genetic variation and heterosis for low-N tolerance breeding, 28 F1 hybrids from a diallel scheme, along with their eight parental lines, were tested for agronomic traits including kernel number per ear (KNE) and grain yield per plant (GY), in replicated plots over two years under low-nitrogen (LN, without nitrogen application) and normal-nitrogen (NN, 220 kg N ha⁻¹) conditions. Taken together the heritability in this and our previous studies, the correlation with grain yield, and the sensitivity to the stress for target trait selection, KNE was a good secondary target trait for LN selection in maize breeding. KNE also showed much higher mid-parent heterosis than hundred-kernel weight under both nitrogen levels, particularly under LN, indicating that KNE contributed the majority of GY heterosis, particularly under LN. Therefore, KNE can be used as a positive target trait for hybrid performance prediction in LN tolerance breeding. Our results also suggest that breeding hybrids for LN tolerance largely relies on phenotypic evaluation of hybrids under LN condition and yield under LN might be improved more by selection for KNE than by direct selection for GY per se.