诱导方式及基因型对小黑麦单倍体形成的影响

为探索小黑麦单倍体胚诱导方式及小黑麦基因型与玉米类型对小黑麦单倍体胚产生的影响,本文采用4种不同诱导方式、3个小黑麦基因型与3个不同类型的玉米分别对其在小黑麦单倍体胚诱导中的效果进行了研究。结果表明:以玉米花粉授粉后再辅以100mg/L 2,4-D+30ml/L二甲基亚砜对小黑麦单倍体胚的诱导效果最好,其单倍体诱导率为6.65%。不同小黑麦基因型在玉米花粉诱导小黑麦单倍体中的诱导效果是不同的,本研究中以基因型H09-4为最高;不同玉米类型远缘杂交的得胚率总趋势表现为:爆裂玉米ZPA 82/9(4.71%)>甜玉米新自31162(2.94%)>普通玉米103A(1.76%)。可见,除诱导方式外,小黑麦基因型及玉米类型对小黑麦单倍体胚的诱导效果具有重要影响。     

玉米单倍体胚性愈伤的诱导与鉴定

为建立一套适合玉米单倍体胚性愈伤培养和快速筛选体系,以单倍体诱导系MT-1为父本,18-599红为母本进行单倍体诱导,设置暗培养、全光照培养和光暗周期培养3种光照培养方式,均分别培养0、1、5、10、20、40 h后,观察幼胚形态和颜色。结果表明,自交系18-599红的单倍体和二倍体幼胚均能正常诱导形成胚性愈伤组织;不同光照培养方式对紫色(二倍体)愈伤率的检出效果依次为光培养>光暗周期培养>暗培养。通过光照筛选的方法可在早期鉴定愈伤组织,其二倍体愈伤的筛选率在培养20 h时可达68%,40 h时为71%,剔除了大部分非单倍体愈伤,综合分析确定光照强度为2 000 lx、20℃处理20 h为最适光照筛选处理。染色体压片技术获得的拟单倍体愈伤中有二倍体愈伤的检出,但经流式细胞仪检出获得的拟单倍体愈伤再经染色体压片检测,无二倍体愈伤,表明流式细胞仪检测单倍体愈伤的准确性高于染色体压片技术。通过光照初步筛选结合流式细胞仪的精确鉴定,迅速从3 000个单倍体愈伤中获得110个单倍体愈伤,单倍体愈伤率3.67%。本研究结果为以玉米单倍体愈伤为转基因受体,快速获得转基因植株提供了一定的技术支撑和理论参考。     

基于机器视觉的多个玉米籽粒胚部特征检测

为了利用机器视觉进行多个玉米种子品种的自动识别,该文提出了一种针对多个玉米籽粒进行胚部检测的方法。该方法基于阈值分割和形态学,在RGB空间,采用自动屏蔽0值像素的大津法（Otsu法）,根据B分量值对多粒玉米籽粒扫描图像进行分割,并采用改进的开闭运算对分割后的图像进行修整,最终得到多个玉米籽粒胚部区域。以4个黄玉米品种各45个籽粒为实验对象,以此方法进行胚部检测,为了验证所得胚部区域有效,提取胚部区域面积、周长分别与手工测量的面积、周长进行线性回归分析,R2的均值分别达到0.9834、0.9578;进一步提取所得胚部区域的形状参数,进行聚类识别,不同品种间的差距值反映了不同品种胚部视觉效果上的差异大小,4个品种中1种识别率为97.8%,其余3种均为100%;多个玉米胚部检测较每个籽粒单独处理的效率提高了29.59%。试验结果表明本文提出的多个玉米籽粒胚部检测方法可行。此研究结果为进一步研究玉米籽粒的胚部特征提供了有利条件,也为实现玉米品种的快速准确分类提供了参考。     

玉米单倍体种子胚部特征提取及动态识别方法

为了实现基于机器视觉方法的玉米单倍体种子识别,该文研究了一种玉米单倍体种子胚部特征提取及动态识别方法。采用一种基于B通道平均像素值的胚部特征提取方法,提取了具有Navajo标记的玉米种子的胚部图像,基于此在RGB颜色空间内提取了样本的Navajo标记图像,从而得到一套玉米单倍体种子快速识别RGB组合算法。在玉米分选试验台上进行了动态分选试验。试验结果表明,该算法对LC09124-UH400品种玉米单倍体的识别正确率为98.04%,对杂合体的识别正确率为94.44%。该文提出的玉米单倍体种子RGB组合快速识别算法与玉米分选试验台结合形成的动态分选系统,有助于实现玉米单倍体种子的自动化分选。     

基于X-rayμCT技术的玉米籽粒结构特征的粒位效应分析

玉米籽粒因其在果穗上着生位置不同存在较大差异,明确籽粒结构特征的粒位效应为玉米的消费、加工和播种质量等玉米产量和品质性状的评价提供参考。该研究以3个不同籽粒类型的玉米品种登海618(DH618)、KX3564和先玉335(XY335)为材料,利用X射线计算机断层(X-ray micro-computed tomography,X-ray μCT)技术扫描测试样本,通过图像滤波、阈值分割等图像分析方法重建籽粒3维结构,获取玉米果穗不同粒位籽粒的胚、胚乳、皮下空腔、胚空腔、硬质胚乳、粉质胚乳、胚乳空腔等结构参数。数据分析表明,籽粒不同结构指标在果穗上呈现不同的变化规律,从基部到顶部(不考虑果穗两端的极端籽粒),胚、胚乳及硬质胚乳体积线性下降,各指标在果穗上的变化范围分别为15.82～33.36、180.15～296.50及87.13～166.00 mm~3;胚乳空腔皮下空腔胚空腔,果穗中部籽粒的空腔较小且稳定,3个品种表现一致;胚与胚乳的比值在粒位间基本稳定,粉质胚乳体积、硬质胚乳与粉质胚乳的比值从基部至顶部逐渐减小,但不同指标的变化斜率存在差异。3个供试品种的籽粒结构参数不同:DH618果穗不同部位籽粒胚与胚乳的比值大于KX3564和XY335,XY335籽粒硬质胚乳与粉质胚乳的比值大于DH618和KX3564。在籽粒空腔方面,KX3564皮下空腔的比例较高,而XY335胚乳空腔的比例较高。3个品种胚、胚乳、皮下空腔体积在玉米籽粒中的比例平均分别为9.27%、89.87%、0.86%。X-ray μCT扫描技术为玉米籽粒性状的研究提供新的方法与思路,明确果穗籽粒结构的粒位效应有利于全面地掌握玉米果穗上籽粒的性状特征,为玉米的生产、加工及品种改良等提供借鉴。     

小麦×玉米诱导小麦单倍体的形态学及细胞学鉴定

为了鉴定小麦(Triticum aestivum L.)×玉米(Zeamays L.)产生的杂种子代的单倍性,采用形态学和细胞学鉴定相结合的方法对杂种幼胚及胚拯救产生的植株进行表型分析与染色体记数。结果表明,小麦×玉米诱导的杂种子房内均无胚乳,仅在少数子房内观察到1个游离的球形幼胚,这些幼胚发育成植株后在花期花药退化或花粉败育,这一特征可作为小麦×玉米杂交后代单倍性的形态学标记。研究同时表明,杂种子代植株体细胞染色体数目为2n=21,在整个染色体组中无可同源配对的成对染色体,并且未发现玉米染色体,结合麦族植物染色体基数x=7的特点,确定该杂种子代为小麦单倍体(三元单倍体),这是小麦×玉米杂交后代单倍体鉴定最重要的细胞学标记。文中同时对小麦×玉米杂交后代单倍体鉴定的重要性,及与以前相关研究结果的差异进行了讨论。     

花药组织培养和小麦×玉米杂交技术应用于产生小麦单倍体的比较研究

两个春小麦品种意塔和帕旺的花药组织培养和小麦×玉米杂交技术产生单倍体的效果不同。不同基因型花药诱导愈伤组织的诱导率从 9 4%到 1 9 7%不等 ,不同基因型所产生的再生株数量亦不同 ,两个小麦品种都有绿苗和白化苗产生 ,绿苗诱导率自 1 3%到 5 0 %。分别利用小麦×玉米杂交技术能有效诱导两个春小麦品种单倍体 ,杂交结实率为 80 2 %～95 1 % ,但只有 1 0 9%～ 1 4 6%的籽粒含有幼胚 ,其中 95 %以上的幼胚可发育成绿苗。每 1 0 0个杂交小花中平均可生成 1 0 5个到 1 4 0个绿苗 ,不产生白化苗 ,染色体亦不自然加倍。     

小麦×玉米诱导小麦单倍体高效系统的建立

为建立一套高效的小麦×玉米单倍体诱导系统用于构建小麦DH群体,采用杂交后剪穗进行人工控制环境条件的室内离体培养法和田间常规杂交法诱导小麦×玉米单倍体,研究了不同培养环境、离体培养时环境温度、常规杂交法时T>10℃有效积温对单倍体成胚率和成苗率的影响。结果表明:就平均成胚率而言,离体培养法(23.6%)>常规杂交法(18.1%),获得最高成胚率的环境温度为21℃~23℃,T>10℃有效积温为188℃;就平均成苗率而言,离体培养法(18.7%)高于常规杂交法(15.1%),获得最高成苗率的环境温度为23℃,T>10℃有效积温为188℃。并在此基础上建立了一套高效、可靠、重复性好的小麦×玉米单倍体诱导系统。实验还表明大田条件下,授粉后12~14d的培养时间不宜作为小麦×玉米单倍体剥胚的时间标准,而应以授粉后外界环境提供的T>10℃有效积温作为剥胚的时间标准可能更准确。     

高油玉米综合杂交种含油特性的探讨

用6个高油玉米单交种组配5个综合杂交种，对各综合杂交种的含油特性进行了研究，结果表明：玉米的油分主要分布在胚中；含油率高且粒大的籽粒主要分布在果穗中部；不同综合杂交种的含油率与株高、穗位高的相关性不同；含油率与产量的相关关系不显著。     

提高小麦×玉米杂交产生单倍体胚频率的研究

为了提高小麦×玉米杂交单倍体胚的产生频率，采用了2,4-D中含有不同体积浓度的二甲基亚砜和不同的激素处理组合两种方法诱导小麦×玉米产生单倍体，研究其对得胚率的影响。结果表明，就平均得胚率而言，在二甲基亚砜激素浓度处理中，最佳的二甲基亚砜体积浓度为3.0%（得胚率为17.0%），而且各不同浓度的处理均高于对照（9.7%）；在不同激素配比试验中，2,4-D+3%二甲基亚砜单独处理的得胚率（7.3%）﹥2,4-D两次处理(6.9%)﹥2,4-D与2,4-D+3%二甲基亚砜配合处理(5.5%)﹥2,4-D一次处理(2.9%)。     

玉米单倍体核磁共振自动分拣系统的开发

摘要：为满足玉米单倍体育种与研究的大规模应用,本研究利用玉米油份花粉直感效应的生物学特性,开发了玉米孤雌生殖诱导单倍体核磁共振自动识别分拣系统。该系统由单籽粒自动进样模块、玉米油份自动测试模块和自动分拣模块三大模块组成。结果证实该玉米单倍体核磁共振自动分拣系统具有快速（平均速度为4秒/粒）、准确（平均为92.3%）、自动、智能分拣玉米单倍体的优良特性,同时,本系统也可应用于基于油份差异的其他样品的自动智能化筛选。     

Selecting and Sorting Waxy Wheat Kernels Using Near‐Infrared Spectroscopy

An automated single kernel near‐infrared (NIR) sorting system was used to separate single wheat (Triticum aestivum L.) kernels with amylose‐free (waxy) starch from reduced‐amylose (partial waxy) or wild‐type wheat kernels. Waxy kernels of hexaploid wheat are null for the granule‐bound starch synthase alleles at all three Wx gene loci; partial waxy kernels have at least one null and one functional allele. Wild‐type kernels have three functional alleles. Our results demonstrate that automated single kernel NIR technology can be used to select waxy kernels from segregating breeding lines or to purify advanced breeding lines for the low‐amylose kernel trait. Calibrations based on either amylose content or the waxy trait performed similarly. Also, a calibration developed using the amylose content of waxy, partial waxy, and wild‐type durum (T. turgidum L. var durum) wheat enabled adequate sorting for hard red winter and hard red spring wheat with no modifications. Regression coefficients indicated that absorption by starch in the NIR region contributed to the classification models. Single kernel NIR technology offers significant benefits to breeding programs that are developing wheat with amylose‐free starches.     

施氮对不同种植密度下夏玉米产量及子粒灌浆的影响

以夏玉米杂交种郑单958为材料,在不同种植密度(52500、67500、82500株/hm2)及不同供氮水平(0、120、240、360kg/hm2)下对玉米子粒产量、产量构成、植株地上部干物质积累、子粒灌浆动态及灌浆过程中的物质代谢状况进行了研究。结果表明,不同施氮水平及种植密度下子粒产量的差异主要是由穗粒数所决定。产量及穗粒数的形成与植株地上部干物质积累密切相关,施氮可明显促进植株地上部干物质积累量的增加。穗顶部与中下部子粒的灌浆动态及物质代谢具有明显的不同,授粉后5～20d,顶部子粒灌浆体积、干重、灌浆速率、总可溶性糖、蔗糖、淀粉含量均明显低于中下部子粒;同化物供应的差异是导致顶部与中下部子粒发育差异的一个重要原因。顶部子粒灌浆体积、干重、总糖、淀粉含量施氮处理高于不施氮处理;施氮可明显促进同化物的积累及向顶部子粒的供应,促进顶部子粒灌浆,减少败育,增加有效粒数,提高产量。     

DNA content in embryo and endosperm of maize kernel (Zea mays L.): impact on GMO quantification

PCR-based techniques are the most widely used methods for the quantification of genetically modified organisms (GMOs) through the determination of the ratio of transgenic DNA to total DNA. It is shown that the DNA content per mass unit is significantly different among 10 maize cultivars. The DNA contents of endosperms, embryos, and teguments of individual kernels from 10 maize cultivars were determined. According to our results, the tegument's DNA ratio reaches at maximum 3.5% of the total kernel's DNA, whereas the endosperm's and the embryo's DNA ratios are nearly equal to 50%. The embryo cells are diploid and made of one paternal and one maternal haploid genome, whereas the endosperm is constituted of triploid cells made of two maternal haploid genomes and one paternal haploid genome. Therefore, it is shown, in this study, that the accuracy of the GMO quantification depends on the reference material used as well as on the category of the transgenic kernels present in the mixture.     

玉米籽粒冲击破碎特性试验研究

农业物料的冲击破碎特性对运输、排种和粉碎等机械设备的工作参数设定具有重要参考意义。该研究以玉米籽粒为研究对象，设计并搭建了单颗粒物料冲击破碎试验装置，开展了5种不同含水率（10.86%±0.13%，13.87%±0.18%，17.24%±0.08%、20.23%±0.19%和23.46%±0.23%）玉米籽粒的冲击破碎试验，并以籽粒破碎模式、临界速度和破碎程度表征籽粒的破碎特性。试验结果表明，玉米籽粒的破碎模式可分为未破碎、破裂和破碎3种形式，其中破裂形式包括整体破裂和局部破裂；以碎粒中大颗粒质量与玉米籽粒质量间的比值W界定玉米籽粒的破碎模式，并建立了不同含水率玉米籽粒的W值与冲击速度间的回归模型，模型的决定系数均大于0.92，确定了5种不同含水率（含水率由低到高）玉米籽粒的临界破裂速度分别为11.45、15.54、19.84、30.49和34.28 m/s，临界破碎速度分别为19.55、23.75、28.68、42.07和46.79 m/s，表明玉米籽粒的临界破裂速度和破碎速度均随含水率的增加而增加；采用响应曲面法建立了破碎颗粒平均粒径与冲击速度和含水率之间的回归模型，模型的决定系数为0.96，方差分析结果表明冲击速度、含水率及其交互作用对玉米籽粒的破碎程度影响极显著（P<0.01），且破碎程度随冲击速度的提高而增加，随含水率的提高而降低。该研究可为玉米籽粒处理设备的工作参数设定提供参考，并为农业物料颗粒的冲击破碎特性研究提供理论依据和试验方法参考。     

An Automated Near‐Infrared System for Selecting Individual Kernels Based on Specific Quality Characteristics

An automated sorting system was developed that nondestructively measured quality characteristics of individual kernels using near‐infrared (NIR) spectra. This single‐kernel NIR system was applied to sorting wheat (Triticum aestivum L.) kernels by protein content and hardness, and proso millet (Panicum miliaceum L.) into amylose‐bearing and amylose‐free fractions. Single wheat kernels with high protein content could be sorted from pure lines so that the high‐protein content portion was 3.1 percentage points higher than the portion with the low‐protein kernels. Likewise, single wheat kernels with specific hardness indices could be removed from pure lines such that the hardness index in the sorted samples was 29.4 hardness units higher than the soft kernels. The system was able to increase the waxy, or amylose‐free, millet kernels in segregating samples from 94% in the unsorted samples to 98% in the sorted samples. The portion of waxy millet kernels in segregating samples was increased from 32% in the unsorted samples to 55% after sorting. Thus, this technology can be used to enrich the desirable class within segregating populations in breeding programs, to increase the purity of heterogeneous advanced or released lines, or to measure the distribution of quality within samples during the marketing process.     

Automated Single‐Kernel Sorting to Select for Quality Traits in Wheat Breeding Lines

An automated single kernel near‐infrared system was used to select kernels to enhance the end‐use quality of hard red wheat breeder samples. Twenty breeding populations and advanced lines were sorted for hardness index, protein content, and kernel color. To determine whether the phenotypic sorting was based upon genetic or environmental differences, the progeny of the unsorted control and sorted samples were planted at two locations two years later to determine whether differences in the sorted samples were transmitted to the progeny (e.g., based on genetic differences). The average hardness index of the harvested wheat samples for segregating populations improved significantly by seven hardness units. For the advanced lines, hardness index was not affected by sorting, indicating little genetic variation within these lines. When sorting by protein content, a significant increase from 12.1 to 12.6% was observed at one location. Purity of the red samples was improved from ≈78% (unsorted control) to ≈92% (sorted samples), while the purity of the white samples improved from 22% (control) to ≈62% (sorted samples). Similar positive results were found for sorting red and blue kernel samples. Sorting for kernel hardness, color, and protein content is effective and based upon genetic variation.     

Hydration Rates for Various Types of Mexican Maize Based on Single‐Kernel Measurements

Hydration kinetics for sound maize kernels in liquid water, determined by single‐kernel measurements for three different Mexican maize types, yielded water diffusion coefficients ordered as Celaya corn > Toluca corn > Palomero corn, at all temperatures examined. These diffusion coefficients are lower than those reported earlier for maize grains, possibly due to the fact that in the present study damaged kernels were rigorously excluded. The energies of activation determined from the Arrhenius plots were ordered as Palomero corn > Celaya corn = Toluca corn and were similar in value to those reported earlier for other maize types. Damage to the surface of the maize kernels during the hydration experiments occurs at a significant frequency. Even minor surface lacerations can strongly affect the rate of hydration of the kernels. Experiments with maize grains selectively varnished in various parts of their surface show that the entry of water into the kernels occurs predominantly through the pericarp, not through the tip cap, though the tip cap has a higher water inflow per unit area.     

Relationships Between the Microstructure,Physical Features,and Chemical Composition of Different Maize Accessions from Latin America

Chemical composition (moisture, total lipids, protein, and apparent amylose) and some physical features (1,000 kernel weight, hardness, and anatomical composition) were determined in 71 accessions representing races of maize from Latin America. Their microstructural characteristics (size and compaction of endosperm cell bodies, pericarp thickness, horny‐floury endosperm ratio, and morphology and size of starch granules) were also evaluated using environmental scanning electron microscopy (ESEM). Compaction was the most important microstructural feature of the maize kernels, representing kernel hardness. Highly compact kernels tended to be hard, with high protein, pericarp, and hard‐endosperm content and high pericarp thickness, but with low moisture, amylose content, and kernel weight and size. The opposite was observed in the least compact kernels. Highly compact kernels tended to have small, polygonal starch granules (<10 μm), while the least compact kernels contained large, spherical granules (>10 μm). These results suggest that microstructure is responsible for the physical features of maize kernels and that microstructure is related to chemical composition.