Relationships among the chalkiness,kernel size and endosperm cell morphology of rice kernels at different spikelet positions within a panicle

The occurrence of chalky kernels in rice is causally related to kernel size and endosperm morphology. This study aimed to investigate the occurrence of chalky kernels by analyzing kernel size, and the number and area of endosperm cells. Spikelets were sampled from upper and middle primary branches and lower secondary branches in a panicle, and divided into four categories: upper, middle, and lower perfect (PF) kernels and lower milky-white (MW) kernels. On the lower secondary branches, there was a higher percentage of chalky kernels, with smaller kernel lengths, widths and thicknesses, than the kernels on the upper and middle primary branches. MW kernels were smaller in size than PF kernels even on the same lower secondary branches. Regardless of grain appearance quality traits, the total areas of endosperm cross sections in lower kernels were significantly smaller than in upper kernels owing to the decreased cell area, and there was a significant negative correlation between the number of cells and average cell area. When the numbers and the areas of cells were analyzed using angular 30° intervals from the line connecting the center point and the dorsal vascular bundle, the MW kernels had significantly less cells than PF kernels near the ventral side at 120–180°. Thus, the decrease in the number of cells near the ventral side was a main causal factor in the decrease in MW kernel widths compared with PF kernel widths, and this suggested that cell division in MW kernels was inhibited at the early grain-filling stage.     

香稻胚乳的垩白性状研究及扫描电镜观察

【目的】研究不同香稻品种垩白性状与胚乳细胞和淀粉粒的形状结构、排列方式及发育情况的关系,为进一步研究香稻垩白性状的形成机理及培育优良品质的香稻新品种打下基础。【方法】通过田间试验,调查11个香稻品种的垩白粒率、垩白面积和垩白度,并对香稻品种胚乳细胞及淀粉粒进行电镜观察。【结果】供试11个香稻品种间差异最明显的垩白性状为垩白粒率,其次是垩白面积,最小的是垩白度,垩白粒率和垩白度成正比,垩白粒率越高则垩白度越高。不同香稻品种稻米胚乳细胞的排列方式、形态及其横断面淀粉粒的分布存在明显差异,其与垩白性状的形成存在一定关联,根据稻米胚乳中垩白形成的位置不同,可将垩白性状分为腹白、心白和背白3种垩白亚类。同一香稻品种,垩白米与无垩白米在淀粉粒形状结构及排列方式等方面也存在明显差异,但垩白米的透明部位和无垩白米的淀粉粒间无明显差异,且垩白度低的部位淀粉粒发育良好。【结论】香稻稻米的垩白性状与胚乳细胞和淀粉粒的形状结构、排列方式及发育情况密切相关,可用于香稻稻米品质鉴定。     

Transition from vitreous to floury endosperm in maize (Zea mays L.) kernels is related to protein and starch gradients

Relationships between kernel vitreousness and proteins and starch partitioning to the floury and vitreous regions of the endosperm were monitored in a set of 13 maize inbred lines. Decrease of protein contents from the vitreous to the floury endosperms were mainly assigned to α-zeins. Using Raman microspectroscopy, we observed a protein gradient from the periphery to the center of endosperms that well fitted with the inverse relationships between vitreousness and protein content of the vitreous and floury regions. In addition, Raman microspectroscopy highlighted an increase of starch crystallinity from the periphery to the center of the maize endosperms. This agrees with the higher amylose and associated lipid contents within starches of vitreous than in those of floury endosperms. Finally, starch granules from vitreous regions displayed more channels than the floury ones. These channels contain proteins that might favor adhesion of proteins to starch granules or granule–granule contacts to form the close packing of the vitreous endosperm. Therefore transition from vitreous to floury endosperm is at least the result of both protein and starch gradients. These gradients are probably associated with metabolic gradients that have been observed during endosperm development.     

大米小包装储藏过程中脂类及微观结构的变化

【目的】由于胚乳失去保护,大米在储藏过程中易发生陈化、霉变等问题,致使其品质劣变甚至丧失食用价值。通过测定储藏过程中大米游离脂肪酸、总酸含量、脂肪酸组成和含量,观察大米横断面胚乳细胞、淀粉颗粒微观结构,探讨大米品质劣变原因,为大米储藏技术提供参考。【方法】以粳稻99号大米为对象,进行人工模拟储藏试验：采用编织袋、自然密闭缺氧、抽真空3种包装方式,置于温度为15、25和30℃（60%湿度）的人工气候箱中储藏180 d,每个月进行一次品质指标测定;测定大米储藏过程中脂肪酸值、总酸值的变化,利用气相色谱分析脂肪酸组成及含量变化,利用扫描电镜观察大米横断面胚乳细胞形态,探索脂类及横断面胚乳结构导致大米品质陈化的机理及品质劣变后淀粉颗粒微观形态的变化规律。【结果】①储藏过程中,编织袋及自然密闭缺氧包装的大米游离脂肪酸及总酸含量皆呈现急剧上升趋势,当品质劣变严重时两者含量反而下降;抽真空包装的大米游离脂肪酸及总酸含量均保持在较稳定的水平,且储藏温度对其含量影响不显著;②脂肪酸组成中含量最多的是亚油酸、油酸和棕榈酸,这3种脂肪酸含量占总脂肪90%以上。包装方式及储藏温度对各脂肪酸组成影响不同。除了花生酸（C20:0）及二十二烯酸（C22:1）外,其余脂肪酸受包装方式影响较大;而储藏温度仅与豆蔻酸（C14:0）和山嵛酸（C22:0）有显著性关系,对其余脂肪酸影响不大。脂肪酸变化规律符合：高不饱和脂肪酸含量随温度升高而降低,多不饱和脂肪酸与饱和脂肪酸及单不饱和脂肪酸间呈现显著负相关,具体表现为硬脂酸（C18:0）与亚油酸（C18:2）、亚麻酸（C18:3）;油酸（C18:1）与亚油酸、亚麻酸皆呈现明显的“此消彼长”现象。③新鲜大米淀粉粒以复粒形式存在,形状较大,表面有较厚的膜,排列整齐有序,两侧以片状的细胞间断面居多,放射状结构清晰可见。陈化加剧的大米胚乳细胞横断面结构松散无序,细胞内断面多于细胞间断面,横断面上可观测到“小孔”及一些分散在淀粉体周围的蛋白体和脂肪滴;细胞壁的完整性受到破坏致使复粒崩解并可见大量单粒细胞,一部分单淀粉粒形状近圆型,棱角较钝;细胞间的棱角模糊,放射状结构变得模糊甚至消失。【结论】编织袋及自然密闭缺氧包装的大米陈化劣变较为严重,储藏过程中其脂肪酸值、总酸值急剧上升后下降,胚乳表面光滑度变差、小孔数量及表面蛋白质膜的翘起变多,辐射状趋势渐渐消失。抽真空包装可以有效延缓大米品质劣变进程。     

Effects of Shading at Different Stages After Anthesis on Maize Grain Weight and Quality at Cytology Level

The objective of the current study is to investigate the effects of different stages of shading after anthesis on grain weight and quality of maize at cytology level.The shading experiments were conducted in the field from 2005 to 2006,with a common maize cultivar(TY2)as the experimental material.Plants were given stress using horizontal shading net and the light intensity was reduced by 55%.Field-grown maize plants were shaded at 1-14 d(S1),15-28 d(S2),and 29-42 d(S3)after pollination,respectively.Control plants(S0)were grown under natural light.Grain weight,quality,endosperm cell proliferation,cob sugar content,and grain pedicel vascular bundle cross section area were measured.The ultrastructural changes of endosperm cells and endosperm transfer cells were observed after pollination.The result indicated that the grain weight,starch content,endosperm cell number,and volume were declined after shading.On the contrary,the proportion of embryo and endosperm,protein content,and fat content in grain increased.Shading treatments significantly delayed the development of the starch granules and remarkably reduced the endosperm filling status.Among the three treatments.the number of the grain endosperm was the least under shading stress at 1-14 d after pollination.However,the volume of starch granules and the substantiation of endosperm under shading treatment at 15-28 d after pollination were the worst.Compared with the control(natural sunlight without shading),the soluble sugar of maize cob increased significantly,while there was no obvious change in vascular structure of small cluster stalk.The number of protein body in maize endosperm was influenced markedly by low light at different stages after pollination.Low light decreased the volume of the grain endosperm transfer and the cell wall extensions of the basal transfer cells became thinner and shorter under shading treatment than those of the control.Furthermore,the degree of connection and the capacity of the nutrient transport were decreased and the mitochondrion number of the transfer cell was reduced after shading.The change in grain quality after shading was observed due to increase in the proportion of embryo and endosperm.The morphology and functions in endosperm transfer cell and the shortage of energy restricted the nutrient transport greatly with shading at different stages,suggesting that an impeded flux may be one of the important reasons for the reduction of maize grain weight of maize grain at later growth stage under low light condition.     

分子标记辅助选择聚合水稻暗胚乳突变基因Wx-mq和抗条纹叶枯病基因Stv-b~i

以江苏高产粳稻品种武运粳7号为母本,具有条纹叶枯病抗性基因Stv-bi和暗胚乳突变基因Wx-mq的日本粳稻品种关东194作父本配制杂交组合进行聚合育种。利用与Stv-bi基因共分离的SCAR标记及与暗胚乳突变基因Wx-mq紧密连锁的CAPS功能标记对其分离世代进行标记位点的检测,结合田间多代选育、抗性鉴定和籽粒胚乳外观鉴定,将条纹叶枯病抗性基因Stv-bi和暗胚乳突变基因Wx-mq同时转育到高产品种中,筛选、培育出优质、抗病、高产且农艺性状优良的水稻新品系宁9108。利用与水稻优质及抗病基因紧密连锁的分子标记,不仅初步建立了优质、抗病育种的分子标记辅助选择体系,也为水稻优质、抗病、高产育种提供了一种简单、快捷的选择方法和重要的中间材料。     

柱花草内珠被、胚柄及胚乳细胞的程序性死亡

利用石蜡切片技术对柱花草胚胎发育过程中内珠被、胚柄及胚乳细胞进行显微观察。结果表明：上述胚珠和胚体的结构成分在胚胎发育进程中相继发育然后程序性地死亡。胚珠受精作用发生后，内珠被的内表皮细胞发育形成珠被绒毡层。原胚时期，珠被绒毡层外侧的内珠被细胞退化。球形胚时期，珠被绒毡层退化。鱼雷形胚时期，胚柄退化。扩大生长胚时期，胚乳细胞退化。内珠被、胚柄及胚乳细胞的发育和程序性死亡均与不同发育时期胚的营养物质供应和形态建成相关。     

胚乳性状测定方法对QTL遗传效应估计的影响

从理论上分析了不正确地基于胚乳性状测定方法的QTL定位方法造成遗传效应估计偏差的原因,并通过计算机模拟验证;同时探讨了胚乳性状测定方法对胚乳性状QTL的遗传效应估计结果的影响,并指出今后胚乳性状QTL定位的研究方向.     

水稻胚胎和胚乳双缺陷突变体eed1的表型与遗传分析

从由化学诱变剂甲基磺酸乙酯(ethylmethane sulfonate,EMS)处理的粳稻品种中花11突变体库中,筛选到一个可稳定遗传的胚胎和胚乳发育缺陷的突变体,命名为embryo and endosperm defective 1 (eed1)。eed1籽粒千粒重、颖果的粒长、粒宽、粒厚、萌发率、总淀粉、直链淀粉和贮藏蛋白系列指标较野生型均显著降低。eed1颖果严重皱缩,且胚乳呈粉质。利用扫描电镜观察发现,与中花11相比, eed1胚乳中淀粉粒排列疏松,多以单一、分散的淀粉粒存在,且呈近似球形。eed1胚胎结构异常,部分颖果未见有胚胎分化的痕迹。qRT-PCR发现, eed1胚乳中参与淀粉和贮藏蛋白合成的大部分基因表达下调。利用eed1与籼稻南京6号杂交得到的F2分离群体进行基因定位分析,将EED1定位于9号染色体长臂672kb的范围内,包含114个开放读码框。本研究为进一步解析EED1基因调控水稻胚胎和胚乳发育的机制奠定了基础。