Genotype by environment interactions and combining ability for strawberry families grown in diverse environments

Ten seedlings from 36 crosses representing eastern and western North American short day and remontant genotypes were evaluated in 2011 and 2012 in California, Michigan, New Hampshire and Oregon, for phenology, flower related traits, plant characteristics, fruit characteristics and fruit chemistry traits. There was significant variability among genotypes, locations and evaluation year for most of the characteristics; however, few genotype × location and genotype × year interactions were detected. General combining ability variance components were significant for all traits and greater than SCA variance components for peduncle length, total flowering weeks, flowering cycles, truss size, growing degree days for harvest data, remontancy, achene position, ease of capping, fruit weight, percent soluble solids, titratable acidity and soluble solids/titratable acidity. ‘Sarian’ was identified as the best contributing parent for remontancy. Narrow-sense heritability estimates were moderate to high (0.33–0.78) for total flowering weeks, flowering cycle, truss size, remontancy, number of runners, fruit weight, pH, and titratable acidity. Having a better understanding of these attributes will provide breeders guidance on the most effective breeding strategies for incorporating superior traits from this germplasm into their programs.     

不同氮素利用效率型小麦品种的生理差异分析

以不同氮素利用效率型小麦品种（2个氮高效、2个氮低效和2个中间型）为材料,分别在灌溉及雨养条件下测定其花后旗叶氮素同化及转运相关酶等生理性状的动态变化,同时在开花期和成熟期测定氮素积累及转运相关性状。结果表明,氮高效型品种晋麦54和晋麦66具有更高的植株氮素积累总量、氮素籽粒生产效率、氮素干物质生产效率、花后氮素转运量、花后氮素转运效率和单株产量,以及更低的花前氮素转运量和花前对籽粒氮积累的贡献率。同时,氮高效型品种的各酶活性及可溶性蛋白质含量高于其他4个品种,而中间型品种晋麦73和泰麦269又高于氮低效型品种晋麦61和泰农18。相关性分析结果显示,参试小麦品种多数关键酶活性与氮素籽粒生产效率、氮素干物质生产效率、花后氮素转运量、花后氮素转运效率、花后对籽粒氮积累的贡献率和单株产量呈显著正相关;与花前对籽粒氮积累的贡献率和花前氮素转运量呈显著负相关。     

Genetic control of yield and yield components in winter oilseed rape (Brassica napus L.) grown under nitrogen limitation

Despite its high nitrogen absorption capacity, oilseed rape (OSR) has a low apparent nitrogen use efficiency (NUE), which makes its production highly dependent on nitrogen fertilization. Improving NUE in OSR is therefore a main target in breeding. The objectives of the present work were to determine the genomic regions (QTLs) associated with yield and to assess their stability under contrasted nitrogen nutrition regimes. One mapping population, AM, was tested in a French location for three growing seasons (2011, 2012 and 2013), under two nitrogen conditions (optimal and low). Eight yield-related traits were scored and nitrogen-responsive traits were calculated. A total of 104 QTLs were detected of which 28 controlled flowering time and 76 were related to yield and yield components. Very few genotype × nitrogen interactions were detected and the QTLs were highly stable between the nitrogen conditions. In contrast, only a few QTLs were stable across the years of the trial, suggesting a strong QTL × year interaction. Finally, eleven critical genomic regions that were stable across nitrogen conditions and/or trial years were identified. One particular region located on the A5 linkage group appears to be a promising candidate for marker assisted selection programs. The different strategies for OSR breeding using the QTLs found in the present study are discussed.     

Quantitative trait locus analysis of nitrogen use efficiency in barley (Hordeum vulgare L.)

Quantitative trait locus (QTL) analysis of nitrogen use efficiency (NUE) of barley (Hordeum vulgare L.) was conducted on data generated from two pot experiments carried out in 2005 (using four nitrogen rates) and 2008 (with three rates) with AFLP markers and 94 recombinant inbred lines (RILs) of the Prisma × Apex mapping population. In total 41 QTLs were detected on 6 chromosomes and for 18 traits in both trials. About 95 % of the detected QTLs were with major additive effects. The percentage of variance accounted for by individual QTLs in the multiple QTL mapping model ranged from 8.4 to 54.4 % across all mapped traits in both years. Fifteen QTLs were related to NUE and its components; most of these QTLs were detected at lower nitrogen rates and none at the highest rate in both trials. These QTLs were found on Chromosomes 3(3H) and 7(5H) in 2005 and Chromosome 2(2H) in 2008. Except for the QTLs of plant height and NUE based on grain yield, none of the QTLs which were detected for a given trait in 2005, expressed themselves in 2008 irrespective of the nitrogen levels. QTLs controlling some traits were co-located in each year, and QTLs for many traits were detected on the same chromosome and close to the denso locus. Further research is needed to investigate the possibility to reduce nitrogen fertilizer requirements through breeding while maintaining high yield of barley.     

Variability and Correlations in Grain Sorghum Genotypes (Sorghum bicolor [L.] Moench) Under Drought Conditions at Different Stages of Growth

Twenty-two genotypes of grain sorghum were grown under drought conditions by omitting one irrigation during stages of before flowering period, kernel filling period, and physiological maturity period at Assiut Univ. Farm in 1987 and 1988 seasons. The results obtained revealed that considerable variation existed among genotypes for all the studied traits. The most effective moisture stress treatment in reducing grain yield, panicle weight and plant height was during flowering stage. While 1000-kernel weight was much affected by moisture stress during grain filling period. The genotype x year interaction (σ²_gy) was large compared to genotype x irrigation treatment (σ²_gl) indicated that genotypes responded differently when they were grown from year to year. The genotypic variance (σ²_g) for all traits were large reflecting the importance of genetic variability. Both phenotypic and genotypic correlations among traits showed that plant height and 1000-kernel weight were highly correlated with grain yield, while leaf area index was low associated with plant height.     

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.     

Genome-wide association study of differences in 14 agronomic traits under low- and high-density planting models based on the 660k SNP array for common wheat

One hundred and ninety-seven wheat accessions from Yellow and Huai Winter Wheat Region (YHW) were evaluated for differences of 14 agronomic traits under low- and high-density plantings. Compared with the high-density plantings, plant height, neck length, uppermost internode length, flag leaf angle and number of sterile spikelets under the low-density plantings reduced, while heading date, flowering date, flag leaf length and width, spike length, number of fertile spikelets, grain number per spike, thousand-kernel weight and grain weight per spike increased. A total of 1,118 markers were detected based on GWAS, and seven QTLs were confirmed. One QTL on chromosomes 5BL and two other QTLs on 5Dl were all tightly associated with flowering date difference. Bioinformatics analysis revealed that two haploblocks in 5Dl were involved, and the Vrn-D1 locus was located in this interval. A region on chromosome 5B at around 531.5 Mb was significantly associated with plant height difference. Two QTLs including AX-94840438 (7BL) and AX-94563647 (7DS) were responsible for neck length or uppermost internode length difference.     

Drought and heat stress reduce yield and alter carbon rhizodeposition of different wheat genotypes

Drought and high temperature are major environmental stress factors threatening wheat production during grain filling stage resulting in substantial yield losses. Four wheat genotypes (Suntop, IAW2013, Scout and 249) were planted under two temperature levels (25 and 30°C) and two water levels (15% and 25% soil moisture content). Wheat yield, leaf δ¹³C, plant rhizodeposition, shoot biomass and root traits were examined. Low moisture (drought stress) and high temperature (heat stress) decreased the grain yield of all wheat genotypes, in particular 249, while combined drought and temperature stresses had the most pronounced negative effect on plant biomass and grain yield. Decreasing soil water availability decreased the allocation of plant‐derived C to soil organic carbon (SOC) and to microbial biomass through rhizodeposition. Leaf δ¹³C decreased with increased yield, suggesting that higher yielding genotypes were less water stressed and allocated less C to SOC and microbial biomass through rhizodeposition. Wheat genotypes with lower root/shoot ratios and thinner roots were more efficient at assimilating C to the grain, while genotypes with higher root/shoot ratios and thicker roots allocated more C belowground through rhizodeposition at the expense of producing higher yield. Therefore, improving these traits for enhanced C allocation to wheat grain under variable environmental conditions needs to be considered.     

水稻氮高效基因型及其评价指标的筛选

以48份不同水稻基因型为供试材料，研究了它们的氮素吸收和利用率，及其与主要农艺性状之间的关系。结果表明，水稻基因型在氮素吸收利用率方面间存在明显差异，从现有的材料中可筛选出氮高效基因型。长伦占不论在低氮处理还是高氮处理均表现出氮高效利用特性，为典型的氮高效基因型。此外，还筛选了适于低氮条件种植的广恢128和茉莉占选；适于高氮条件种植的97香、2466和银花占。低氮高效型适合在贫瘠地区种植，而高氮高效型适合在肥沃地区种植。结果表明，水稻氮素利用率与抽穗期及乳熟期倒2、倒3叶的叶绿素含量呈显著或极显著负相关；与收获指数、稻谷产量和穗数之间均呈极显著正相关，它们可作为水稻氮素利用效率的评价指标。但是水稻氮素吸收率与利用率之间存在极显著负相关，因此，如何协调二者关系，既能提高稻谷产量和氮素利用率，又减少施氮量是急需解决的问题。     

Wheat grain yield and stability assessed through regional trials in the Eastern Gangetic Plains of South Asia

Improving the level and stability of grain yield is the primary objective of wheat breeding programs in the Eastern Gangetic Plains (EGP) of South Asia. A regional wheat trial, the Eastern Gangetic Plains Yield Trial (EGPYT), was initiated by CIMMYT in collaboration with national wheat research programs in Bangladesh, Nepal, and India in 1999–2000 to identify wheat genotypes with high and stable grain yield, disease resistance, and superior agronomic traits for the EGP region. A set of 21 wheat experimental genotypes selected from a regional wheat screening nursery in South Asia, three improved widely grown cultivars (Kanchan, PBW343 and Bhrikuti), and one long-term cultivar (Sonalika) were tested at 9–11 sites in six wheat growing seasons (2000–2005) in the EGP. The 21 experimental genotypes were different in each year, whereas the four check cultivars were common. In each year, one or more of the experimental genotypes showed high and stable grain yield and acceptable maturity, plant height, and disease resistance compared to the check cultivars. Three improved cultivars have already been commercially released in the region through EGPYT and many germplasm lines have been used in the breeding programs as parents. Identification of wheat genotypes with high-grain yield in individual sites and high and stable yield across the EGP region underlines their value for regional wheat breeding programs attempting to improve grain yield and agronomic performance.     

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

Improved winter wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in Central and West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite winter wheat breeding lines developed by the International Winter Wheat Improvement Program (IWWIP), to analyze their stability across diverse environments, and to identify superior genotypes that could be valuable for winter wheat improvement or varietal release. One hundred and one advanced winter wheat breeding lines and four check cultivars were tested over a 5-year period (2004–2008). Grain yield and agronomic traits were analyzed. Stability and genotypic superiority for grain yield were determined using genotype and genotype × environment (GGE) biplot analysis. The experimental genotypes showed high levels of grain yield in each year, with mean values ranging from 3.9 to 6.7 t ha⁻¹. A set of 25 experimental genotypes was identified. These were either equal or superior to the best check based on their high mean yield and stability across environments as assessed by the GGE biplot analysis. The more stable high yielding genotypes were ID800994.W/Falke, Agri/Nac//Attila, ID800994W/Vee//F900K/3/Pony/Opata, AU//YT542/N10B/3/II8260/4/JI/Hys/5/Yunnat Esskiy/6/KS82W409/Spn and F130-L-1-12/MV12. The superior genotypes also had acceptable maturity, plant height and 1,000-kernel weight. Among the superior lines, Agri/Nac//Attila and Shark/F4105W2.1 have already been proposed for release in Kyrgyzstan and Georgia, respectively. The findings provide information on wide adaptation of the internationally important winter wheat genotypes, and demonstrate that the IWWIP program is enriching the germplasm base in the region with superior winter wheat genotypes to the benefit of national and international winter wheat improvement programs.     

小麦候选骨干亲本科农9204遗传构成及其传递率

科农9204是一个兼具高产和氮高效的候选小麦骨干亲本,其遗传背景复杂,携带冀麦38、小偃5号、绵阳75-18、小偃693和矮丰3号的遗传成分。利用221个PCR标记和89个DAr T标记,绘制了科农9204的全基因组基因型图谱。在2DL上,Xmag3596–Xmag4089区段与增加千粒重和籽粒含氮量的QTL紧密连锁;在4BL上,Xcnl10与增加穗粒数、降低株高和穗茎长的QTL紧密连锁;在6BS上,Xcnl113和Xwmc756均与降低株高、穗茎长和穗下节间长的QTL紧密连锁。这些标记在科农9204衍生后代的传递率均为100.0%。利用已报道的关联性标记检测科农9204基因型在衍生后代的传递情况,与增加穗粒数相关的1个优异等位基因位点在衍生后代中的传递率为71.6%;与增加千粒重相关的4个优异等位基因位点的传递率均为100.0%;与根部性状相关的4个基因位点中,3个传递率为100.0%。这些与重要农艺性状相关位点,科农9204基因型在其衍生后代中有很高的传递率,在很大程度上与其对应的优异的农艺性状密不可分。科农9204染色体区段上存在的重要QTL可能是其成为候选骨干亲本的遗传基础。     

Genetic diversity for nitrogen use efficiency in spinach (Spinacia oleracea L.) cultivars using the Ingestad model on hydroponics

Spinach is a leafy vegetable that requires a high N fertilization to have a satisfactory yield and quality, in part because it has poor nitrogen use efficiency (NUE). Therefore, there is a need to breed for cultivars with an excellent NUE. To this end the genetic diversity for NUE-related traits was studied in a diverse set of commercial cultivars. This set was evaluated in a hydroponic system using the Ingestad model; the system was set at a relative growth rate of 0.14 and 0.18 g g^?1 day^?1 (low and high N, respectively). Experiments were performed at low and high plant density. Traits monitored for single plants included fresh and dry weight, leaf area, specific leaf area, dry weight ratio between root and shoot, and chlorophyll content. The high density experiment showed more genotypic variation for the observed traits than the low density one. Biomass production was considerably lower at low than at high N. Path analysis revealed that leaf area had the highest direct effect on NUE, while specific leaf area was an important trait determining variation in NUE at low N. Slow and fast growing genotypes were shown to use different strategies to utilize N, and these strategies are expressed differently at high and low N availability. This indicates that improving spinach for NUE is feasible using the analysed genotypes as source material, and different strategies can be targeted for adaptation of spinach cultivars to low N conditions.     

Intraspecific Variation in Nitrogen Uptake and Nitrogen Utilization Efficiency in Wheat (Triticum aestivum L.)

Twenty wheat ( Triticum aestivum L.) varieties differing in plant height were grown in soil culture and evaluated for differences in nitrogen uptake and nitrogen utilization efficiency (NUE) at limited (40 kg N ha⁻¹) and normal (120 kg N ha⁻¹) nitrogen supply. Nitrogen uptake showed 1.4- and 1.5-fold varietal variation at harvest for limited and normal N supply, respectively. NUE for dry matter production (NE1) exhibited 1.28- and 1.38-fold genotypic variation while NUE for grain production (NE2) varied by 1.25- and 1.21-fold at limited and normal N supply, respectively. Tall varieties were found to have higher N uptake and NUE for dry matter production, while dwarf cultivars had greater NUE for grain production. Nitrogen uptake was found to be strongly positively associated with dry matter production (r=0.85 and r =0.77 at limited and normal N supply, respectively), indicating an important effect of growth rate on N uptake. NUE for biomass production, as well as for grain production, was reduced as the supply of nitrogen was increased.     

河南省南部组小麦品种主要农艺性状的演变

利用近二十年河南省南部组区域试验数据,对新育成品种的主要农艺性状演变规律进行了分析,结果表明：随着品种育成年份的延后,抽穗期和成熟期呈提前趋势;株高呈降低趋势;全生育期天数和每亩有效穗数呈减少趋势;灌浆时间、穗粒数、千粒重和亩产量呈增加趋势。相关性分析表明,产量与千粒重、穗粒数呈显著正相关,与成熟期呈极显著负相关,说明产量的提高主要是与穗粒数和千粒重增加有关。     

QTL mapping and analysis of epistatic interactions for grain yield and yield-related traits in <Emphasis Type="Italic">Triticum turgidum</Emphasis> L. var. <Emphasis Type="Italic">durum</Emphasis>

A quantitative trait loci (QTL) analysis of grain yield and yield-related traits was performed on 93 durum wheat recombinant inbred lines derived from the cross UC1113 × Kofa. The mapping population and parental lines were analyzed considering 19 traits assessed in different Argentine environments, namely grain yield, heading date, flowering time, plant height, biomass per plant, and spikelet number per ear, among others. A total of 224 QTL with logarithm of odds ratio (LOD) ≥ 3 and 47 additional QTL with LOD > 2.0 were detected. These QTL were clustered in 35 regions with overlapping QTL, and 12 genomic regions were associated with only one phenotypic trait. The regions with the highest number of multi-trait and stable QTL were 3BS.1, 3BS.2, 2BS.1, 1BL.1, 3AL.1, 1AS, and 4AL.3. The effects of epistatic QTL and QTL × environment interactions were also analyzed. QTL putatively located at major gene loci (Rht, Vrn, Eps, and Ppd) as well as additional major/minor QTL involved in the complex genetic basis of yield-related traits expressed in Argentine environments were identified. Interestingly, the 3AL.1 region was found to increase yield without altering grain quality or crop phenology.     

Genetic improvement of grain yield and associated traits in the southern China winter wheat region: 1949 to 2000

To understand the genetic gains of grain yield in the Southern China Winter Wheat Region (SCWWR), two yield potential trials, i.e., YPT 1 including 11 leading cultivars from the Middle and Low Yangtze Valley (Zone III) and YPT 2 including 15 leading cultivars from the Southwestern China Region (Zone IV) from 1949 to 2000, were conduced during the 2001–2003 cropping seasons. A completely randomized block design of three replicates was employed with controlled field environments. Molecular markers were used to detect the presence of dwarfing genes and the 1B/1R translocation. Results showed that average annual genetic gain was 0.31% (P < 0.05) or 13.96 kg/ha/year and 0.74% (P < 0.01) or 40.80 kg/ha/year in Zones III and IV, respectively. In YPT 1, changes of all other traits were not significant, but plant height was significantly reduced. In YPT 2, the genetic improvement of grain yield was primarily attributed to the increased thousand kernel weight (TKW) (0.65%, P < 0.01) and kernel weight/spike (0.87%, P < 0.01), reduced plant height and increased harvest index (HI). The dwarfing gene Rht 8 was most frequently present (46.1%), Rht-B1b was observed in three genotypes in Zone III, and Rht-D1b was present in only one genotype in Zone IV. The 1B/1R translocation was present in four genotypes. Utilization of Italian germplasm and development of landmark cultivar Fan 7 were the key factors for grain yield improvement in SCWWR. The future challenge of wheat breeding in this region is to continue improving grain yield and disease resistance, and to develop cultivars suitable for the reduced tillage of wheat/rice double cropping. Utilization of Mexican germplasm could provide opportunities for future yield improvement.     

35份人工合成六倍体小麦的综合评价

为有效利用人工合成六倍体小麦种质资源,拓宽现有种质基础,从国际玉米小麦改良中心引进35份人工合成六倍体小麦,对其株高、穗下节长、穗下茎长、穗长、旗叶面积、分蘖数、穗粒数、生物量、收获系数、产量和千粒重11个主要农艺性状和产量性状,以及籽粒水分含量、蛋白含量、面筋含量、淀粉含量、纤维素含量、硬度、SDS沉降值和Zeleny沉降值8个品质指标进行综合评价。结果表明,这批材料的农艺和产量性状变异系数为7.46%~32.29%,平均为15.36%;多样性指数（H′）为1.85~2.04,平均为1.98。品质性状的变异系数为2.80%~17.55%,平均为10.19%;多样性指数的变化范围为1.87~2.04,平均为1.96。主成分分析表明,前5个主成分构成的信息量为总信息量的82.84%。聚类后方差分析可将材料分为4个类群,类群Ⅲ的产量等相关性状较高,类群Ⅳ的蛋白质含量、纤维含量、面筋含量、硬度和SDS沉降值最高。这批材料的农艺性状、产量和品质性状变异程度大,遗传类型丰富,可作为种质资源加以利用。     

Impact of grain morphology and the genotype by environment interactions on test weight of spring and winter wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Wheat (Triticum aestivum L.) market grades and prices are determined in part by test weight (TW). Millers value high TW because it is typically associated with higher flour extraction rates and better end-use quality. Test weight is expected to be influenced by other directly quantifiable grain attributes such as grain length (GL), grain width (GW), shape, single-grain-density (SGD), thousand-grain-weight (TGW), and packing efficiency (PE). The objectives of this study were to: (1) determine the primary morphological grain attributes that comprise TW measurements for winter and spring wheat classes; and (2) determine TW stability and genotype and genotype × environment interactions (GEIs) of the attributes that comprise TW. A market class representative group of 32 hard spring and 24 hard winter wheat cultivars was grown at several locations in South Dakota in 2011 and 2012. A regularized multiple regression algorithm was used to develop a TW model and determine what grain attribute reliably predicts TW. A GGE biplot was used for stability and GEI analyses whereas a linear mixed model was used for variance analyses. Data were collected on eight grain traits: TW, SGD, TGW, protein concentration, GW, GL, shape, size, and PE. Observations showed that in both spring and winter wheat, SGD accounted for over 90% of the phenotypic variation of TW. Cultivars with stable and high TW were identified in both wheat classes. Apart from TW; significant (p?<?0.0001) genotype, environment, and GEI variances were observed for GW and SGD, a more direct measure of which could help improve genetic gain for TW.     

陕西省不同年代玉米品种产量和氮效率性状的变化

明确陕西省不同年代玉米产量和氮效率性状响应氮肥的变化趋势,对西北旱区玉米高产氮高效品种选育具有重要的实践意义。本文以1981—2010年间陕西省12个玉米主栽品种为材料,于2011年和2012年在典型旱区陕西长武进行3个氮水平(0、120和240 kg hm–2)的田间试验,分析了不同年代玉米品种农艺和氮效率性状变化趋势。结果显示,不同年代玉米品种籽粒产量随氮水平增加而提高,在施氮0、120和240 kg hm–2处理下籽粒产量增益分别为每年46、65和83 kg hm–2。所有氮水平下2000—2010年间品种产量和生物量显著高于1980—1989年间品种,而秸秆产量变化不明显;现代玉米品种(2000—2010年)产量的增加归因于穗粒数、千粒重和生物量的提高。不同年代玉米品种消光系数随氮水平增加而降低,说明现代玉米品种(2000—2010年)较老品种(1980—1989年)叶片直立,截获更多的光能,致使产量和生物量高。随着年代的递进,玉米品种氮肥农学利用率呈递增趋势,在低氮水平下现代品种氮肥利用效率最高,且显著高于老品种。氮肥农学利用率与氮吸收效率(NUpE)和花后氮素积累量呈显著相关(r=0.75;r=0.72),而与氮生理效率(NUtE)和花前氮素积累量相关性不显著(r=0.42;r=0.39)。说明现代玉米品种氮肥农学利用率提高主要来自氮肥吸收效率和花后氮素积累量的增加。上述结果表明,陕西玉米育种应注重穗粒数、千粒重、氮吸收效率性状和株型结构改良,低氮环境压力选择将有助于旱区玉米高产氮高效新品种培育。