Genetic basis of grain filling rate in wheat (Triticum aestivum L. emend. Thell.)

Summary Grain filling rate in wheat (Triticum aestivum L. emend. Thell.) positively influences grain yield under a wide range of conditions. The effective utilization of this trait in breeding depends on an understanding of its genetic control. A study was, therefore, conducted to determine the genetic basis of grain filling rate in six crosses of wheat. Higher order genic interactions and/or linkage were important in the genetic regulation of grain filling rate (GFR) in the majority of crosses. Additive ([d]) and dominance ([h]) gene effects were important in the control of GFR in main ears (ME) and whole plant ears (WPE). Additive and additive × additive epistatic effects were the most important in the genetic control of GFR in last ears (LE). Location effects on genetic effects for GFR were significant (P < 0.05) in all ear types of some crosses except in ME. Genotype × environment interaction effects were important (P < 0.001) in LE and WPE.It was concluded that the inheritance of GFR is complex and is dependent on ear type. Breeding procedures that facilitate the exploitation of non-additive and additive gene effects were recommended for the genetic improvement of grain filling rate of wheat.     

Selection for brown stripe downy mildew resistance in maize

Summary The maize (Zea mays L.) cultivar Makki Safed 1 (MS1) with susceptibility to brown stripe downy mildew (BSDM) caused by Sclerophthora rayssiae var. zeae Payak & Renfro, was subjected to two cycles of mass selection and one cycle of full-sib family selection. Selection was carried out primarily for BSDM resistance.The mass selection was practised under artificial epiphytotic conditions in a disease nursery. Full-sib progenies and performance trials on MS1 and its improved versions were grown in diseased and disease free environments.Mass selection resulted in a significant improvement for resistance to BSDM. A cycle of full-sib selection resulted in an additional improvement for resistance to the disease. The disease rating of the improved version was 1.5 against 4.5 for the original population (scale: 1, highly resistant to 5, highly susceptible). The yield of the improved populations of MS1 was significantly greater than that of MS1 in the disease nursery. In disease free experiments, the improved populations showed almost no yield advantage over MS1. There were also no significant differences between the original population and the improved population after three selection cycles for ear length, ear girth, number of kernel rows per ear, number of kernels per row, 1000-kernel weight, plant height, ear height and days to silk.     

5个玉米新组合产量与主要农艺性状的灰色关联度分析

为了揭示玉米主要农艺性状对产量的影响,以‘盛农玉6号’、‘LCBB18-12’、‘百隆玉303’、‘惠农单5号’和‘西抗18’5个玉米新组合为材料,用Excel和SPSSPRO在线统计分析平台对包括生育期、株高、穗位高、穗长、穗粗、穗行数、行粒数、秃尖、单穗粒重、百粒重和产量的11个农艺性状进行灰色关联度分析。结果表明,所考察的性状对产量的影响依次为穗行数(0.85)、穗粗(0.846)、百粒重(0.845)、株高(0.843)、单穗粒重(0.839)、生育期(0.827)、穗长(0.817)、行粒数(0.812)、穗位高(0.812)、秃尖(0.59)。除秃尖以外的9个性状与产量的关联度均较大,关联系数在0.8以上,秃尖这一性状与产量的关联度相对较小,关联系数为0.59。由此可推断,穗行数、穗粗、百粒重、株高、单穗粒重、生育期、穗长、行粒数、穗位高是产量构成的主要因子。该结果为高产育种实践提供理论参考。     

Why SR52 is such a great maize hybrid? II. Heritability,correlation and path-coefficient analyses

Although exceptional heterosis for yield in the world’s first commercial single cross maize (Zea mays L.) hybrid SR52 has been confirmed, the role of secondary traits hasn’t been established. Objectives of this study were to establish relationship between grain yield and secondary traits, while assessing heritability and genotypic variation in SR52’s segregating populations. Knowledge on associations between yield and secondary traits would be crucial in extracting productive inbred lines from the population. Traits were subjected to correlation and path-coefficient analyses. Path analysis model accounted for over 70% of variation (R²) in all populations. Consistently high positive correlations with grain yield were observed for ear length and number of kernel rows on ear. Ear girth (0.19), and number of kernels per row (0.48) showed high direct effects on yield in the F₂ population and the trend was consistent in the backcrosses. Positive indirect effects of most traits on grain yield were negligible with the exception of kernel per row via total number of kernels on ear, which was above 0.40 in the F₂ and BCP1. Ear length can be exploited for indirect selection for yield in SR52’s segregating generations. 100-kernel weight and number of kernel rows on ear can, to a lesser extent, be targeted in selecting for grain yield. High to medium phenotypic variability in segregating generations of SR52 for traits such as ear length, number kernel rows on ear and grain yield should give impetus to selection of productive inbred lines from SR52 hybrid because of presence of diversity in the gene pool.     

玉米杂交种农艺性状与籽粒产量的相关和通径分析

玉米杂交种主要农艺性状遗传相关与通径分析结果表明，行粒数、穗行数、百粒重、果穗长在影响籽粒产量诸因素中占主导地位。认为单株籽粒产量改良应在稳定穗数的基础上，着重提高行粒数；适当增加穗行数以利提高百粒重；协调好穗行数、行粒数、百粒重三者关系，实现单株产量的较大幅度增长。     

灌浆初期低温对春玉米产量构成的影响研究

旨在研究东北地区低温冷害对春玉米灌浆的影响,确定春玉米灌浆期间冷害影响农业气象指标。用人工气候室通过模拟自然低温（平均15℃、17℃、19℃）方法,对灌浆初期盆栽春玉米进行（3、5、7天）胁迫处理。结果表明：春玉米在灌浆初期经不同天数的低温处理后,穗粒数减少,穗粒重、百粒重和叶绿素降低,成熟期延迟,果穗秃尖长度和籽粒含水量增加,作物产量呈不同程度的下降。温度越低,持续时间越长,对玉米产量的影响越严重。其中在15℃低温下处理7天后,玉米产量下降最大,较对照穗粒重减少了32.4%,百粒重减少9.2%。可见,灌浆初期低温对春玉米产量结构影响最大的因素是结实率和籽粒干物质含量的双重降低。     

春玉米农艺性状及养分积累动态对水溶肥管理的响应

探索东北半干旱区春玉米的最佳水溶肥管理措施是实现节肥增产的有效途径。试验在覆膜滴灌大田条件下,以‘迪卡159’为试验对象,研究吉林省西部半干旱区春玉米农艺性状及养分积累动态对水溶肥管理的响应。相关性和通径分析表明,产量(Y)与各农艺性状的相关关系由强到弱依次为行粒数(X₄)>穗粗(X₁)>穗行数(X₃)>穗长(X₂)>百粒重(X₅)。产量与穗行数和行粒数的最优回归方程为Y=-14878.79+465.886X₄+855.646X₃(R²=0.863,F=18.92)。同时,氮、磷、钾肥均追施4次不仅有利于春玉米穗粗、穗长、穗行数、行粒数和百粒重的增加,还能促进出苗63天后氮、磷、钾养分的积累与分配。在水溶肥用量与施肥方式相同的基础上,分次追施氮、磷、钾肥对春玉米产量的提高至关重要。     

玉米产量及产量相关性状QTL的图谱整合

利用生物信息学方法,借助高密度分子标记遗传图谱IBM2 2008 neighbors,利用图谱映射和元分析的方法,对不同试验中定位的400个玉米产量及产量相关性状QTL进行了图谱整合,构建了玉米产量及产量相关性状QTL的综合图谱和一致性图谱。结果表明,玉米产量及产量相关性状QTL在10条染色体上呈非均匀分布,第1染色体上最多,第10染色体上最少;发掘出96个玉米产量及产量相关性状的“一致性”QTL;关联性较强的产量性状的QTL常集中在相同或相近的座位上。     

The drought response of landraces of wheat from the northern Negev Desert in Israel

Summary Diverse landraces of wheat, collected from the semi-arid (150 to 250 mm of total annual rainfall) Northern Negev desert in Israel were considered as a potential genetic resource of drought resistance for wheat breeding. These materials were therefore evaluated for their reponses to drought stress in agronomical and physiological terms. Up to 68 landraces, comprising of Triticum durum, T. aestivum, and T. compactum were tested in two field drought environments, in one favourable field environment, under post-anthesis chemical plant desiccation which revealed the capacity for grain filling from mobilized stem reserves, under a controlled drought stress in a rainout shelter and in the growth chamber under polyethylene glycol (PEG)-induced water stress. Biomass, grain yield and its components, harvest index, plant phenology, canopy temperatures, kernel weight loss by chemical plant desiccation, growth reduction by PEG-induced drought stress and osmotic adjustment were evaluated in the various experiments.Landraces varied significantly for all parameters of drought response as measured in the different experiments, which was in accordance to their documented large morphological diversity. Variation in grain yield among landraces under an increasing drought stress after tillering was largely affected by spike number per unit area. Kernel weight contributed very little to yield variation among landraces under stress, probably because these tall (average of 131 cm) landraces generally excelled in their capacity to support kernel growth by stem reserve mobilization under stress. Yield under stress was reduced with a longer growth duration of landraces only under early planting but not under late planting. Landraces were generally late flowering but they were still considered well adapted phenologically to their native region where they were always planted late.Landraces differed significantly in canopy temperature under drought stress. Canopy temperature under stress in the rainout shelter was negatively correlated across landraces with grain yield (r=0.67^**) and biomass (r=0.64^**) under stress. Canopy temperature under stress in the rainout shelter was also positively correlated across landraces (r=0.50^**) with canopy temperature in one stress field environment. Osmotic adjustment in PEG-stressed plants was negatively correlated (r=–0.60^**) with percent growth reduction by PEG-induced water stress. It was not correlated with yield under stress in any of the experiments. In terms of yield under stress, canopy temperatures and stem reserve utilization for grain filling, the most drought resistant landrace was the Juljuli population of T.durum.     

普×爆F3家系穗粒性状及其与膨化倍数的相关分析

在春播和夏播两种环境条件下,对一个普通与爆裂玉米自交系杂交组合的259个F3家系的穗粒性状及其与膨化倍数的相关分析结果表明：F3代分离出优于爆裂亲本穗粒性状的家系较多;穗粒性状是由微效多基因控制的数量性状;百粒重、穗粒重对膨化倍数直接或间接作用为较大负效应,行粒数、轴粗、穗长对膨化倍数的直接作用为正效应,其它性状通过行粒数和穗长对膨化倍数的间接作用多为正效应。因此,可以直接对穗长和行粒数进行正向选择,提高普×爆后代选系的产量。     

高产栽培条件下夏玉米穗部性状研究

本文采用灰色关联分析理论,对16个玉米杂交种穗部性状与产量的关系进行研究。结果表明,在高产栽培条件下,玉米产量与穗部性状的关联度排序为：粒数/m2＞千粒重＞穗粒数＞出籽率＞穗行数＞行粒数＞穗粗＞穗数/hm2＞穗长＞秃尖长。进一步分析表明与高产栽培条件相适应的杂交种是单位面积粒数较多、穗粒数和千粒重较高的中大穗耐密型玉米杂交种,出籽率较高;从玉米的形态性状来看,穗行数和穗粗对产量的影响大于行粒数和穗长对产量的影响。     

Yield Components of Apical and Subapical Ear Contributing to the Grain Yield Responses of Prolific Maize at High and Low Plant Populations

Subapical ears are largely responsible for grain yield variations in prolific maize (Zea mays L.) grown under conditions favourable for the expression of prolificacy trait, but limited information exists on yield components contributing to yield responses. A field experiment was conducted to determine the yield components of apical and subapical ear in prolific maize after various pollination treatments at two plant populations. Hybrid Pioneer 3733 was grown in the perfect stands of 71 428 and 35 714 plants ha^?1. Three pollination treatments were carried out: (i) free pollination; (ii) subapical earshoots were covered to prevent pollination; and (iii) apical earshoots were covered to prevent pollination. Grain yields of free pollinated plants were by 50.1 % larger at low plant population (265 g per plant) than at high plant population (177 g per plant) due to a 45.3 % increase in kernels per plant, whereas 1000‐kernel weight slightly increased by 3.3 %. These increased kernels per plant at low plant population were, in part, the result of kernel increments on apical ear (10.1 %), and mainly associated with kernels from subapical ears that did not occur at high plant population. At low plant population, the total grain yield per plant was reduced by 94 g (35.5 %) after the apical ear was bagged to prevent pollination, but only 52 g (19.6 %) when the subapical ear was bagged. When subapical ear development was stopped at low plant population, grain yield on apical ears increased by only 3.9 % as a result of heavier 1000‐kernel weights, clearly demonstrating limitations in kernel set and size. After grain development on apical ear was prevented, subapical ear enlarged to 80.3 % of maximum apical ear yield because the former had, on average, 2.5 % lighter 1000‐kernel weight and 17.5 % fewer kernels than the latter. Ears did not differ in row number when only apical or subapical ear was developed on plant, whereas subapical ears tended to have fewer rows than apical ears when both were present on the same plant. Our results showed that: (i) plant population affected all yield components on both apical and subapical ear except row number; (ii) the occurrence of subapical ear is triggered by achieving maximum potential kernel set on apical ear; and (iii) subapical ear is inferior in potential grain yield to apical one even when the latter was prevented from pollination.     

Heat tolerance for yield and its components in different wheat cultivars

Summary Twenty one diverse, standard and experimental cultivars of common spring wheat (Triticum aestivum L.) were tested for the effect of heat stress on phenology, yield and its components by growing the materials for 2 years under full irrigation during the hot summer (offseason), and the cool winter (normal) conditions. Heat tolerance was estimated for each variable by the heat susceptibility index (S) which scales the reduction in cultivar performance from cool to hot conditions relative to the respective mean reduction over all cultivars.Genotypes differed significantly in S for yield and its components. The ranking of cultivars in S over the 2 years was consistent for yield, kernels per spike and kernel weight, but not for spike number. Of the three yield components, the greatest genotypic variation in S was expressed for kernels per spike. However, S for yield could not be simply attributed to S in a unique component across all cultivars. On the other hand, a general linear model regression of summer yield on its components revealed that the most important yield component affecting yield variation among cultivars under heat stress was kernel number per spike. Kernel number per spike was positively associated across cultivars with longer duration and greater stabilty of thermal time requirement from emergence to double ridge. It is therefore concluded that kernel number per spike under heat stress is a reasonable estimate of heat tolerance in yield of wheat and that this tolerance is operative already during the first 2 to 3 weeks of growth.     

土壤含水量对玉米产量因素的影响研究

在旱作条件下研究了不同玉米品种的穗长、穗粗,行粒数,百粒重等产量因素和亩保苗株数、灌浆期土壤含水量等环境因素对产量的影响。结果表明：穗粗对产量有极显著的正相关和正向的直接效应,百粒重和穗长对产量呈微弱的正相关,行粒数对产量有微弱的负相关。土壤含水量与产量有较高的负相关和负向的直接效应,株高、功能叶数、亩保苗与产量有较低的正相关。灌浆期比较抗旱品种是丰禾7号、绥玉7号和丰禾332品系;先玉335表现中度抗旱,龙单13、四单19表现出抗旱性较差。     

黑龙江省中早熟玉米杂交种产量相关性状的分析

以2003年黑龙江省第六区区域试验的12个参试组合（含对照）为研究材料，运用灰色系统理论中杂交组合灰色评判原理与方法，对影响玉米产量的10个性状进行灰色关联分析，结果表明：各主要数量性状对黑龙江省中早熟玉米产量的关联度大小为叶片数、穗位高、秃尖、穗长、出籽率、穗粗、穗行数、株高、行粒数、百粒重。     

鲜食糯玉米农艺性状与鲜穗产量的灰色关联度分析

以正在参加黄淮海国家糯玉米区域试验的19个新品种为材料，利用灰色关联度分析方法，对11个农艺性状与鲜穗产量进行了关联度分析。结果表明，糯玉米农艺性状与产量关联度的大小依次为穗粗﹥穗行数﹥穗长﹥株高﹥收获期﹥行粒数﹥轴粗﹥穗位高﹥鲜百粒重﹥鲜出籽率﹥秃尖长。穗粗、穗行数、穗长、株高是影响糯玉米鲜穗产量的主要因素，而鲜穗百粒重、鲜出籽率、秃尖长度对产量影响则较小。但影响鲜穗产量的主要因素在不同产量水平品种中存在一定差异     

An evaluation for genetic variation within maize inbred lines maintained by sib-mating and self-pollination

Summary Maintaining maize (Zea mays L.) inbred lines without genetic change is an important concern of maize breeders and seed producers. Long-time inbred lines, however, have been shown to be genetically unstable, and with selection pressure acting on the resulting genetic variation, these lines have evolved into different strains. The objective of this study was to compare maintenance of line integrity under reproduction by sib-mating and self-pollination in ear-to-row progenies. Ten lines, varying from 5 to 35 generations of previous ear-to-row selfing, were maintained for 11 successive generations under each method of reproduction. Alternate generations were compared by using a randomized complete-block design with each family of lines as a separate experiment. Data were collected for 10 plant and yield traits: pollen shed and silk emergence dates, plant and ear heights, tassel branch number, kernel row number, ear length and diameter, grain yield, and 300-kernel weight. Summarizing for F-tests over all traits and experiments, 30% were significant among sib-mated generations and 56% among selfed generations. Also, overall generation means of the two methods were different for 51% of the comparisons, and the selfed lines were less vigorous for 79% of the significant comparisons. It was concluded that sib-mating lessens the effect of genetic instability and that a reproduction system of sib-mating with intermittent generations of selfing may be more beneficial than continuous ear-to-row selfing for certain lines.Joint contribution: USDA-ARS, and Journal Paper No. J-11880 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project No. 2194.     

Identification of genetic factors affecting plant density response through QTL mapping of yield component traits in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.)

It is generally believed that grain yield per unit area of modern maize hybrids is related to their adaptability to high plant population density. In this study, the effects of two different plant densities (52,500 and 90,000 plants/hm²) on 12 traits associated with yield were evaluated using a set of 231 F_2:3 families derived from two elite inbred lines, Zheng58 and Chang7-2. Evaluation of the phenotypes expressed under the two plant density conditions showed that high plant density condition could decrease the value of 10 measured yield component traits, while the final grain yield per hectare and the rate of kernel production were increased. Twenty-seven quantitative trait loci (QTLs) for 10 traits were detected in both high and low plant density conditions; among them, some QTLs were shown to locate in five clusters. Thirty QTLs were only detected under high plant density. These results suggest that some of the yield component traits perhaps were controlled by a common set of genes, and that kernel number per row, ear length, row number per ear, cob diameter, cob weight, and ear diameter may be influenced by additional genetic mechanisms when grown under high plant density. The QTLs identified in this study provide useful information for marker-assisted selection of varieties targeting increased plant density.     

不同玉米种质材料植株与穗粒性状的灰色关联度分析

为了掌握生产上广泛使用的12个玉米单交种的主要农艺性状间的关系,对被测试材料的植株、穗粒、产量以及品质性状进行了灰色关联度分析。结果表明：与产量密切相关的植株与穗粒性状是出籽率、行粒数、穗粗、穗粒重、百粒重等,其关联度在0.4353~0.3327。与粗蛋白、粗脂肪、粗淀粉和赖氨酸含量等营养品质密切相关的植株与穗粒性状是出籽率、株高、穗长、轴粗、行粒数等,其关联度在0.5106~0.3929。综上所述,对于不同玉米种质材料进行遗传改良宜在保证正常生长的前提下,优先对出籽率、百粒重进行选择,还要注重对株高、穗长、轴粗、行粒数等性状的选择,进而提高育种效率。     

玉米果穗不同部位籽粒激素含量及其与胚乳发育和籽粒灌浆的关系

以玉米品种登海11为材料, 分别进行大田和温室试验, 观察灌浆期果穗不同部位籽粒玉米素(Z)+玉米素核苷(ZR)、吲哚-3-乙酸(IAA)、脱落酸(ABA)和赤霉素(GA₃)含量变化及其与胚乳发育和籽粒灌浆的关系。结果显示, 籽粒最大胚乳细胞数目、最大胚乳细胞增殖速率及平均速率、最大灌浆速率、平均灌浆速率和百粒重表现为果穗下部籽粒>中部籽粒>上部籽粒。在胚乳细胞活跃增殖期或活跃灌浆期, 籽粒Z+ZR、IAA和ABA含量以果穗下部籽粒最高, 中部籽粒其次, 上部籽粒最低。GA₃含量则为果穗上部籽粒>中部籽粒>下部籽粒。两个试验的结果趋势一致。胚乳细胞增殖速率和籽粒灌浆速率与籽粒Z+ZR、IAA和ABA含量呈极显著正相关, 与籽粒GA₃含量呈显著负相关。说明玉米果穗上部籽粒轻主要是由于这些籽粒的胚乳细胞增殖速率小, 导致其胚乳细胞数少, 这与其灌浆期较低的Z+ZR、IAA和ABA含量及较高的GA₃含量有密切关系。