玉米产量-密度关系年代演化趋势的Meta分析

为明确中国玉米产量-密度试验结果的年代演化趋势,进一步探索提高玉米产量的突破方向和理论依据,汇集从1950s到2000s中国玉米产量-密度的文献结果,拟合产量-密度抛物线模型,剔除异常后进行直方图、相关、通径等Meta分析。结果表明,1950s和1960s玉米产量明显低于1970s和1980s,1990s以来产量持续增加,2000s最大,为10.5 t hm^-2,1960s以来年均增益150 kg hm^-2。最佳密度年代均值在4.5~6.8株 m^-2之间,呈现1950s 和1960s<1970s 和1980s<1990s,但是, 2000s却小于1990s。单株产量年代均值在0.08~0.17 kg之间,呈现1950s>1960s和1970s<1980s,且1990s以来持续上升,2000s上升幅度更为明显。1990s以来密度偏离最佳值引起的减产幅度呈现上升趋势。在持续增加密度的同时,通过育种和栽培途径提高单株产量,是玉米更高产的努力方向。     

Carbon assimilation,leaf area dynamics,and grain yield in contemporary earlier- and later-senescing maize hybrids

Maize breeding during the past 50 years has been associated with a delay of leaf senescence, but it is not clear whether this trait is likewise associated with higher grain yield in modern hybrids. Post-silking growth, leaf area dynamics, photosynthetic parameters and yield were compared in modern maize hybrids differing in canopy senescence rate. In the first two experiments, four hybrids were grown in the field at Balcarce, Argentina (37°45′ S, 58°18 W). In spite of differences in chlorophyll retention and photosynthesis of the ear leaf, post-silking growth and grain yield were very similar in all four hybrids while kernel N concentration was lower in the later-senescing hybrids. In a third experiment, a later-senescing (NK870) and an earlier-senescing (DK682) hybrid were grown to analyze the potential photosynthetic contribution of delayed leaf senescence. Leaf area and chlorophyll content were larger in NK870, especially at the lower canopy level (0.75 m above the ground). However, hybrids did not differ for canopy light interception. Because photosynthetic photon flux density below 1 m above the ground was less than 10% of incident radiation and photosynthesis quantum yield did not change during senescence, the potential photosynthetic output of lower leaves below 1 m was very low. Lower leaves of NK870 had N concentrations higher than those needed to sustain photosynthesis at the light conditions below 1 m. Therefore, we show that delayed senescence does not necessarily improve post-silking C accumulation because: (i) canopy light interception is not reduced by senescence except at very late stages of grain filling; (ii) contrasting hybrids show more pronounced senescence differences at canopy levels receiving less than 10% of incident radiation; (iii) delayed senescing hybrids present lower kernel N concentrations while extra N is retained in leaves exposed to a light limiting micro-environment. Delayed senescence at lower canopy levels may be unproductive, at least under non-stressing conditions.     

Trends of grain yield and plant traits in Chinese maize cultivars from the 1950s to the 2000s

Retrospective analyses may provide an understanding of unexploited genetic potential and indicate possible pathways for future yield improvement. The objectives of this study were to present maize(Zea mays L.)yield trends and plant traits changes for maize cultivars from the 1950s to the 2000s in China. Trials were conducted at three locations in 2007 and 2008, and at four locations in 2009. Twenty-seven single hybrids, four double-cross hybrids, and four open-pollinated varieties, were grown at three densities at each location each year. 56% of total yield gain was contributed to breeding from 1950 to 2000. New hybrids had more resistance to compound stress. Levels of response of all hybrids to higher-yielding environments were similar, and greater than that of OPVs. All maize cultivars showed morphological changes for all characteristics tested in a volatile manner from 1950 to 2000, except for relatively stable leaf number. ASI decreased and tolerance to root lodging improved, which were enhanced at higher plant densities. There were no trends for other characteristics at higher densities. Shorter maturity, smaller plant size and more tolerance to root and stalk lodging will be required for further yield improvement. Chinese maize yield improvement can benefit from agronomic strategies at higher plant densities.     

Performance stability of maize genotypes across diverse hill environments in Nepal

The national maize improvement program in Nepal regularly receives elite maize (Zea mays L.) genotypes from CIMMYT and other countries and tests them for their performance stability in highly diverse environments. Studies were conducted on research stations and farmers’ fields at five sites in three years to determine performance stability of exotic maize genotypes. Replicated on-station and on-farm studies were conducted using 25 and 10 genotypes, respectively, including a local check and an improved check (Manakamana-3), in 2004–2006. We analyzed grain yield, days to flowering, plant and ear height, plant population, husk cover, and plant and ear aspect. Stability and genotype superiority for grain yield was determined using genotype and genotype × environment (GGE) biplot analysis that compares among a set of genotypes with a reference ‘ideal’ genotype, which has the highest average value of all genotypes and is absolutely stable. Several genotypes produced significantly higher grain yield than the local check. Four genotypes (‘Across9942 × Across9944’, ‘Open Ended White Hill Population’, ‘Population 44C10’ and ‘ZM621’), that produced significantly higher grain yield than the improved check, also had other agronomic traits (days to flowering, plant and ear height, number of ears, resistance to leaf blight, plant and ear aspect and husk cover tightness) equal to or better than the improved check. GGE-biplot analysis showed that Across9942 × Across9944 and ZM621 were the most superior genotypes in the on-station and on-farm trials, respectively. The findings from this study provide new information on the stability of the maize genotypes that are also adapted to other regions of the world. Such information could be useful for maize improvement program for the highlands in Nepal and other similar environments.     

玉米雌雄穗开花间隔与产量关系研究

以2个热带玉米群体Pool 16、 Pool 18的不同世代种质为材料, 分别种植在开花期充足灌水、中度水分胁迫和严重水分胁迫3种水分梯度条件下, 研究玉米的雌雄穗开花间隔(ASI)与产量及其其它性状间的关系. 研究表明, 随水分胁迫程度的加强, 产量与ASI间的相关性增强. 在严重胁迫条件下, 二者的相关系数r=-0.529**; 在胁迫条件下,     

20年来我国冬油菜新品种产量和抗病性状分析

根据近20年来我国冬油菜区域试验的结果,对长江上、中、下游及黄淮4组油菜新品种产量性状及抗病性状进行分析,结果表明,冬油菜新品种平均产量整体呈上升趋势,各组平均单株有效角果数变化不明显,而平均每果粒数和千粒重呈上升趋势,但长江流域各组每角粒数增量比黄淮组大,而黄淮组千粒重增量比长江流域各组高;新品种菌核病和病毒病发病率下降明显。今后一段时间内增加新品种每角粒数和千粒重是冬油菜遗传改良的重点,预计我国冬油菜新品种区域试验各组新品种产量水平仍将继续提高。     

不同基因型甘薯品种产量与地上部农艺性状及主要气象因子关联度分析

研究了北方甘薯主产区泰安市栽培的不同基因型的主要甘薯品种鲜薯、薯干产量与13个地上部主要农艺性状及生长期间主要气象因子间关联度。根据关联度的大小研究得出各个影响因子的关联序,影响鲜薯产量因子的关联序为：分枝叶柄鲜重>分枝叶片数>地上部总鲜重>分枝鲜重>分枝条数>分枝叶片鲜重>主茎叶柄鲜重>主茎长度>分枝长度>主茎粗度>主茎叶片数>主茎叶片鲜重>主茎鲜重;影响薯干产量因子的关联序为：分枝叶片鲜重>分枝长度>分枝叶柄鲜重>分枝条数>分枝叶片数>主茎鲜重>主茎长度>分枝叶片鲜重>分枝鲜重>主茎粗度>主茎叶片数>地上部总鲜重>主茎叶柄鲜重;气象因子对鲜薯产量影响的关联序依次为：最高气温>相对湿度>最低气温>平均气温>14时湿度>10cm低温>5cm低温>0cm低温>日照时数>降水量;对薯干产量影响关联序依次为平均气温>最高气温>最低气温>5cm低温>10cm低温>14时湿度>0cm低温>日照时数>相对湿度>降水量。     

利用单片段代换系测交群体定位玉米产量相关性状的杂种优势位点

杂种优势利用是提高农作物产量与品质的一种重要途径, 而明确杂种优势的遗传机制将促进优良玉米新品种的选育, 但是截至目前其遗传机制仍然不清楚。本研究以玉米自交系lx9801背景的昌7-2的单片段代换系为基础材料, 利用与自交系T7296的测交群体, 对昌7-2和lx9801对应染色体片段与T7296之间存在差异的杂种优势位点进行了分析, 共检测出64个不同穗部性状和产量的杂种优势位点(HL), 其中23个在2个环境中同时被检测到, 包括4个穗长的HL, 4个穗粗的HL, 4个穗行数的HL, 7个行粒数的HL和4个产量的HL, 并在多个染色体片段上鉴定出同时包含产量及其构成因子的杂种优势位点, 该研究为进一步解析玉米产量杂种优势形成的遗传机制奠定了材料基础。     

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.     

Changes in morphological and physiological traits associated with recurrent selection for grain yield in maize

Summary Experiments were conducted during the growing seasons of 1975 and 1976 to determine changes in morphological and physiological traits associated with recurrent selection for grain yield in maize (Zea mays L.). Four variety hybrids, BSSS(R)CO x BSCB1(R)CO, BSSS(R)C7 x BSCB1(R)C7 [from a reciprocal recurrent selection program involving Iowa Stiff Stalk Synthetic (BSSS) and Iowa Corn Borer Synthetic #1 (BSCB1)], BS12CO x B14A, and BS12C6 x B14A [from a half-sib selection program involving the open-pollinated variety Alph (BS12) and the inbred tester B14A] were grown at 59 300 and 98 800 plants/ha near Ames, Iowa We obtained data on CO₂-exchange rate (an estimate of photosynthetic rate), grain yield, grain-yield components, flowering dates, maturity traits, light interception and use, shelling percentage, harvest index, and various other plant traits.CO₂-exchange rate did not change appreciably with recurrent selection for yield. Grain yield per hectare and per plant were larger for the improved than unimproved hybrids. Grain-yield components did not change significantly with recurrent selection. Kernel weight of BSSS(R)C7 x BSCB1 (R)C7, however, was larger than that of BSSS(R)C0 x BSCB1(R)C0. Pollen-shed-to-silking interval was shorter for the improved than the unimproved hybrids, and grain-filling duration was longer in C7 x C7 than in C₀ x C₀ of the reciprocal recurrent selection program. Furthermore, improved hybrids were characterized by smaller tassels and more upright canopies. Usually, plant traits and leaf-area-related traits were similar for all hybiids.Although dry-matter productivity was similar for all hybrids, those that were improved by recurrent selection produced more grain per unit leaf area and per unit light interception. Also, BS12C6 x B14A was characterized by a higher harvest index than BS12CO x B14A.We concluded that the source (i.e., photosynthetic capacity) was not limiting grain yield in BSSS(R) x BSCB1(R) and BS12. Increased grain yields that resulted from recurrent selection were consequences of longer grain-filling duration for BSSS(R) x BSCB1(R) and increased translocation of photosynthate from source to sink for both BSSS(R) x BSCB1(R) and BS12.Journal Paper J-8953 of the Iowa Agriculture and Home Economics Exp. Stn., Ames, Iowa. Project No. 2152.     

Ridge-furrow mulching system in semiarid Kenya: A promising solution to improve soil water availability and maize productivity

In semiarid Kenya, field productivity of maize has been at a low integrity level due to insufficient use of rainwater use. From 2012 to 2013, an innovative ridge-furrow mulching system (RFMs) was tested using local maize (Zea mays L.) hybrid, KCB in KARI-Katumani Farm, Kenya in long and short rainy seasons. Field experiments were conducted in a randomized complete block design with four treatments: 1) RFMs with transparent polyethylene film (RFT), 2) RFMs with black polyethylene film (RFB), 3) RFMs with grass straw mulching (RFS), and 4) RFMs without mulching (CK). Soil moisture & temperature, grain yield, water use and economic benefit were determined and analyzed. The results indicated that both RFT and RFB treatments significantly increased soil water storage amount in the depth of 0–60 cm. Grain yield and water use efficiency (WUE) in both treatments were increased by 66.5–349.9% and 72.9–382% respectively, compared with those of CK over two growing seasons. In addition, grain yield and WUE in RFS treatment were only increased by from 4.2–127.1% compared with those of CK. Particularly, two types of plastic films displayed different effects on modifying topsoil temperature. Transparent film mulching significantly increased topsoil temperature by 1.3 °C (p < 0.05) higher than CK, to facilitate growth and grain formation in long (but cool) growing season. In contrast, black film mulching lowered soil temperature by 0.3 °C lower than CK in short (but warm) growing season, which led to better soil thermal balance. Overall, RFMs with film mulching could serve as an effective solution to increase maize productivity, and hence a promising strategy to cope with food security under climate change in semiarid Kenya.     

Relationship between genetic markers and morphological traits in a maize inbred lines collection

Summary Genetic markers (isozymes), in addition to the traits recommended by the UPOV convention, have been used in France since 1989 to characterize the maize inbred lines submitted to registration. In the years 1989. 1990 and 1991, a total of 974 inbreds has been described according to this procedure. Relationships between genetic markers were investigated and underlined the occurrence of linkage disequilibria within the tested germplasm. These disequilibria appeared to depend strongly on the breeding history of the germplasm. In some cases, these disequilibria could be related to a major progenitor (foundation effect). Relationships between genetic markers and quantitative traits were also pointed out. High coefficients of determination (up to 60%) were in some cases observed at the within group level, and also appeared to be very dependent on the major progenitors of the group of interest. The consequences of these results for breeding and distinctiveness studies are discussed.     

不同年代中籼水稻品种的米质及其对氮肥的响应

旨在探明中籼水稻品种改良过程中米质变化特点以及施氮量对其产量和品质的影响。以江苏省近70年来生产上广泛应用的12个代表性中籼水稻品种(含杂交稻组合)为材料,依据应用年代将其分为20世纪40-50年代、60-70年代、80-90年代和2000年以后(超级稻)4个类型,设置零氮(0N,全生育期不施氮)、中氮(MN,全生育期施氮210 kg hm^-2)和高氮(HN,全生育期施氮300 kg hm^-2)3个施氮水平,测定了产量和稻米品质诸性状。结果表明,随品种的改良,中籼水稻品种的产量显著提高,整精米率、垩白度、长宽比、直链淀粉含量、胶稠度、蛋白质组分和淀粉黏滞特性等显著改善,但现代品种的垩白度仍然较高。在3种施氮水平下,超级稻以HN的产量最高,其他年代品种以MN产量最高或MN与HN的产量差异不显著。随施氮量增加,稻米的蛋白质含量和垩白度增加,崩解值降低,消减值增大,稻米的食味品质降低。在HN下稻米中K、P、S、Ca、Mg等营养元素含量也较0N或MN下降低。以上结果说明,中籼水稻品种改良显著提高了产量,改善了稻米品质。总体上,增施氮肥特别是高量施用氮肥会降低稻米品质。如何通过氮肥的优化运筹实现水稻高产优质的协调发展是亟待研究的问题。     

不同生态条件下玉米产量源库关系的研究

１９９３－１９９４年在新疆石河子、北京大兴、山东济南、江苏扬州对多花品种掖单１３和中花品种鲁玉１０进行春播试验，采用高产群体剪叶剪穗、不同密肥培植不大不同群体研究了玉米群体主要源库指标与产量的关系。结果表明：尽管玉米产量因试点经续度及生态条件的差异很大，但不同试点的玉米产量水平均随花后干物质积累量（源）、总粒数（库）的增加而增加，源库相互促进增产。但增源增产与增库产比，增库增产更为重要。这方面花数     

Phenotypic divergence for morphological and yield-related traits among landrace genotypes of durum wheat from Jordan

Summary Landrace genotypes of durum wheat, from 10 districts in Jordan, have been evaluated for 18 morphological and yield related traits. Results of multivariate analysis, including analysis of variance, cluster analysis and canonical discriminant analysis, indicate that the magnitude of phenotypic divergence in these landrace genotypes is large, especially when compared with a world collection of durum wheat. These results provide an experimental evidence for phenotypic differentiation as a result of variation in altitude and long-term average rainfall of collection sites, but not on the basis of district of collection. R²-values for fit to least squares model ranged from 67.0–78.0%, and from 18.5–30.0%, for the first and second cases, respectively. Landrace genotypes from different districts formed 5 clusters on the basis of altitude and long-term average rainfall of collection site. Three canonical factors accounted for 92% of total variance in these clusters. The first canonical factor accounted for 57% of total variance and was mainly correlated with spike length, awn length and spikelets/spike. The second canonical factor accounted for 22% of total variance and was positively correlated with peduncle length, seed weight per plant, kernel weight and ratio of peduncle length to plant height. However, it was negatively correlated with awn length. The phenotypic diversity found in these landrace genotypes could help identify genetically different genotypes for durum wheat improvement.     

甘肃省近年来玉米品种主要性状的演化及育种方向分析

2000-2018年共搜集整理了309份甘肃省审定玉米品种信息,并选取其中245份普通玉米品种综合分析了其19个相关性状的变化情况及彼此间的关联性,以期为进一步了解品种更替对玉米品种相应性状的影响及为未来玉米育种方向提供参考。结果表明:(1)随年份更替,审定品种的株高、种植密度、千粒重、产量、粗淀粉积累量呈显著升高,其年均分别升高1.7 cm、772.5株/hm^2、1.92 g、232.2 kg/hm^2、1.35 g;穗位高、粗淀粉含量、粗脂肪积累量呈缓慢升高趋势;穗行数和行粒数基本维持不变,其年均分别为16.6行和39.78粒;穗长、穗粗、出籽率、粗蛋白含量呈显著降低,其年均分别降低0.21 cm、0.02 cm、0.13%、0.11%;生育期、粗脂肪、赖氨酸含量、粗蛋白及赖氨酸积累量呈缓慢降低趋势。(2)相关及热图聚类分析表明,玉米品种的这19个相关性状间彼此紧密关联,彼此间协同或抑制作用共同形成了品种的DUS特性。(3) PCA分析筛选出了对总体方差累计贡献率达72.565%的6个主成分,其中株高、穗长、穗粗、穗行数、行粒数、千粒重、赖氨酸含量及粗蛋白、粗脂肪、粗淀粉和赖氨酸积累量等是造成这些品种间差异的主要因素。(4)从审定品种的亲本间筛选出了20份适用于今后进行遗传改良的优良自交系。(5)今后在玉米理想株型育种方面,应适当降低其株高、以便进一步增加其种植密度、抗倒伏性及耐旱性;穗行数和千粒重是影响玉米高产最为重要的因素,在高产育种上应进一步改良增加其穗行数和千粒重;籽粒中粗淀粉含量和积累量较为快速的提高可能对其粗蛋白、粗脂肪及赖氨酸等品质性状的含量和积累量造成碳稀释效应,更好地协调玉米籽粒中各品质组分间关系是培育优质粮饲兼用或青贮玉米新品种的重要策略。     

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。     

Detection of epistatic and environmental interaction QTLs for leaf orientation‐related traits in maize

Leaf architecture traits in maize are quantitative and have been studied by quantitative trait loci (QTLs) mapping. However, additional QTLs for these traits require mapping and the interactions between mapped QTLs require studying because of the complicated genetic nature of these traits. To detect common QTLs and to find new ones, we investigated the maize traits of leaf angle, leaf flagging‐point length, leaf length and leaf orientation value using a set of recombinant inbred line populations and single nucleotide polymorphism markers. In total, 19 QTLs contributed 4.13–13.52% of the phenotypic effects to the corresponding traits that were mapped, and their candidate genes are provided. Common and major QTLs have also been detected. All of the QTLs showed significant additive effects and non‐significant additive × environment effects in combined environments. The majority showed additive × additive epistasis effects and non‐significant QTL × environment effects under single environments. Common and major QTLs provided information for fine mapping and gene cloning, and SNP markers can be used for marker‐assisted selection breeding.     

玉米叶片保绿度开花后衰减特性与产量性状相关性初步研究

摘要：采用Excel工作表及Origin7.0、DPS统计分析软件对不同基因型玉米开花后叶片保绿度衰减特性与产量性状相关性进行了初步研究,结果表明：叶片保绿度最大衰减速率出现时间、最大衰减速率对产量性状影响大于叶片保绿度衰减启动时间对产量性状影响,最大衰减速率出现时间越晚、最大衰减速率越低,越有利于获得较高的单穗粒重、百粒重、穗粒数、容重、出籽率。     

不同生育时期遮光对玉米籽粒灌浆特性及产量的影响

为探索不同时期遮光对玉米籽粒灌浆特性和产量的影响, 2012-2013年以玉米品种京科968与郑单958为试验材料, 在大田条件下用透光率50%的遮阳网分别于13叶全展期(T1)、吐丝期(T2)、吐丝后15 d (T3)遮光处理, 每期遮光7 d, 以自然光照为对照, 并利用Logistic方程y =A/(1+Be^–Cx)比较不同遮光处理玉米籽粒灌浆过程。结果表明,不同时期遮光均导致玉米穗粒数、千粒重和产量不同程度降低, 且遮光时期越晚降幅越大, 其中产量差异显著; 遮光导致灌浆高峰持续期与活跃灌浆天数(P)缩短, 最大灌浆速率(G_max)与平均灌浆速率均下降, 籽粒终极生长量(A)降低; 品种特性决定粒重、穗粒数与灌浆参数的关系, 同一品种的粒重与灌浆速率最大时的生长量(W_max)呈显著正相关, 品种间的粒重差异由活跃灌浆天数(P)决定, 同一品种的穗粒数与最大灌浆速率(Gmax)呈显著正相关, 品种间的穗粒数差异由灌浆速率最大时的生长量(W_max)决定。选择适宜品种, 提高籽粒灌浆速率最大时的生长量(W_max)与最大灌浆速率(G_max), 并延长活跃灌浆天数(P)是玉米在光胁迫环境下获得高产、稳产的重要途径。