小麦苗期耐盐相关性状的QTL分析

以小麦敏盐品种太空6号和耐盐品种德抗961杂交形成的F2和F2:3家系为试验材料,选取小麦8条染色体上的321对SSR引物进行亲本间多态性的筛选,在太空6号和德抗961之间表现多态性的SSR引物为52个,位点为54个,其中barc172和cfa2121两个引物分别有两个多态性位点。对这54个位点进行连锁分析,构建了包含42个SSR标记、覆盖小麦基因组8条染色体的遗传连锁图,共704.5cM,标记间平均间距为16.8 cM。采用复合区间法进行耐盐QTL分析。对于4个性状共定位到6个QTL,分别位于5A,5B,5D染色体。对于发芽率,检测到1个QTL,位于染色体5D上,在标记cfd40~gwm182之间,贡献率为7.68%,表现加性效应;对于苗高,检测到2个QTL,分别位于染色体5D和5A上,在标记gwm182~wmc215及barc141~wmc415之间,贡献率分别为9.3%和8.14%,分别表现为显性和部分显性;对于根长,检测到2个QTL,均位于染色体5B上,在标记gwm234与wmc326及barc140与barc142之间,贡献率分别为8.74%和8.40%,分别表现为部分显性和超显性;对于鲜重,检测到1个QTL,位于染色体5D上,在标记wmc215~cfd29之间,贡献率为12.60%,表现超显性。与所得的QTL位点距离较近的SSR标记,如barc141等,可望为耐盐小麦品种的分子标记辅助选择提供参考信息。     

野生稻渗入系颖壳颜色的简易测定及QTL定位分析

用Unispec光谱仪测定水稻颖壳反射光谱,筛选对水稻颖壳色素敏感的色素指数,用筛选出的最佳植被指数NDVI作为检测颖壳颜色的指标,测定106个家系的颖壳颜色用于QTL定位分析.共检测到12个与颖壳颜色相关的QTL,其中有4个来源于栽培稻特青,分别位于第1染色体RM243附近,贡献率为5％;第7染色体RM295、RM481和RM82附近,贡献率分别为4％、7％和4％.另外8个QTL位点来源于野生稻,分别位于第1染色体RM5和RM212附近,贡献率分别为5％和6％,第2染色体RM233A附近,贡献率为6％;第4染色体RM273附近,贡献率为38％;第6染色体RM204和RM3附近,贡献率分别为17％和5％;第8染色体RM38附近,贡献率为6％,以及位于第12染色体RM235附近,贡献率为5％.在检测到的12个QTL中,来源于野生稻的位于第4染色体RM273附近,以及位于第6染色体RM204附近的QTL的加性效应及贡献率较大,分析是主效QTL.     

水稻籼粳交DH群体耐热性的QTLs定位

耐热性是水稻(Oryza sativaL.)抗逆研究中最重要的性状之一.应用典型的籼(Oryza sativa L.spop.indica)、粳(Oryzasativa L.spp.japonica)交组合IR64×Azucena花药培养的DH群体及其已构建的分子连锁图谱,在田间及温室高温条件下对该DH群体的结实率性状进行考查.采用QTL mapper1.0软件检测控制结实率的加性和上位性效应的数量性状位点(QTL),在第1、3、4、8和11等5条染色体上,共检测到6个具有加性效应的QTLs.其中位于第1、3染色体的2个加性效应QTLs来自父本Azucena的等位基因,是耐热的QTL,能提高结实率9.50%和6.46%,其贡献率为19.15%和2.86%.位于其余3条染色体的4个加性效应的QTLs来自母本IR64的等位基因,能提高结实率4.33%～10.37%.在第1、2、3、4、5、7、8、11等8条染色体之间还检测到8对加性×加性上位性效应,其贡献率为2.27%～8.13%.讨论了应用分子标记辅助育种选育耐热性水稻的可能性.     

小麦淀粉品质性状配合力效应及遗传分析

选用9个冬小麦品种,按NCⅡ不完全双列杂交设计,对淀粉主要品质性状进行了配合力及相关分析。结果表明：淀粉品质性状一般配合力和特殊配合力方差均达显著或者极显著水平,综合考虑亲本各性状一般配合力相对效应,中优9507、济麦20、偃展4110适合做面条和馒头小麦品质育种优良亲本;藁麦6/偃展4110和扬麦16/偃展4110,一般配合力效应和特殊配合力效应表现优秀,总的配合力效应表现也最好,利用价值大,为优良组合。直链淀粉的遗传主要是基因的累加效应,粘度性状、总淀粉、蛋白质品质性状的遗传以加性效应为主,非加性效应为辅;峰值粘度、低谷粘度、最终粘度狭义遗传力达74.47%以上,宜在早代进行选择;直链淀粉、膨胀势在50%以下,高世代选择效果较好。峰值粘度、低谷粘度、最终粘度与支链淀粉、总淀粉、膨胀势呈极显著的遗传负相关,而与直链淀粉、降落数值均呈显著或极显著遗传正相关,可以完全同向选择。     

水稻DH群体(CJ06×TN1)稻米品质相关QTL分析

对于不同品种和不同种植环境中的稻米品质进行数量性状位点(quantitative trait locus,QTL)检测分析,可为分子遗传育种提供实验数据。本研究以粳稻(Oryza sativa ssp.japonica)春江06(CJ06)和籼稻(Oryza sativa ssp.indica)台中本地1号(TN1)杂交衍生的加倍单倍体群体(double haploid,DH)为试材,在西南地区种植并检测与稻米品质相关的特征值,进行QTL定位与分析,以期了解该生态环境对稻米品质的影响,为水稻品质的分子改良育种提供理论依据。经检测分析,共获得13个与稻米粒型、直链淀粉含量以及淀粉RVA(rapid viscosity analysis)谱特征值相关的QTLs,其中5个与粒型相关、7个与RVA谱相关、1个与直链淀粉相关。上述QTLs分别分布在第1、2、3、6、7、8、10染色体,即q HPV-6、q CPV-6、q BDV-6、q CSV-6、q SBV-1、q SBV-6、q SBV-7、q RL-2、q RLW-2、q RLW-3、q RLW-8-1、q RLW-10、q AC-6;分别调控热浆黏度、冷胶黏度、崩解值、回复值、消减值、稻米粒长、稻米长宽比和直链淀粉含量。其中7个与RVA相关的QTLs,似然函数比值对数值(logarithm of odds,LOD)在2.55~13.18之间,单个QTL贡献率在7.03%~49.05%之间,除q SBV-1和q SBV-7贡献率较低,其余单个QTL位点的贡献率均在25%以上,属于主效QTLs。此外,与RVA相关的5个QTLs—q HPV-6、q CPV-6、q BDV-6、q CSV-6及q SBV-6均定位于6号染色体同一区间,在该区间内还检测到1个与直链淀粉含量相关的主效QTL(q AC-6),其贡献率达到45.21%;生物信息学分析发现,该区间包含已被克隆的直链淀粉合成相关的Waxy(Wx)基因。粒型方面共检测到5个具有加性效应的QTL位点,LOD值在3.16~8.47之间,单个QTL贡献率在8.95%~27.23%之间,其中q RL-2、q RLW-3、q RLW-8等3个区间内包含了3个已被克隆的主效QTLs—GW2、GS3以及GW8。本研究通过QTL检测分析,为水稻品质的分子改良育种提供了基础资料。     

小麦磷素利用效率的基因位点及其交互作用

利用小麦W7984和Opata85作亲本 ,通过一粒传而获得F7重组近交系 (RIL)群体。对该群体的 114个株系分别在正常供磷和低磷胁迫下探讨小麦地上部磷素利用效率 (SPUE)和全株磷素利用效率 (WPUE) ;并根据该群体而构建的遗传图谱包括覆盖整个染色体组的 918个RFLP标记 ,研究 2种供磷情况下小麦磷素利用效率的基因位点及基因间互作。结果表明 ,正常供磷 ,有 2个与SPUE有关的QTL ,分别位于染色体 1B和 5A上 ,变异解释率分别为 6.55 %和 1 1.61 % ;与WPUE有关的QTL有位于染色体 2B、5A和 7A上的 3个 ;SPUE和WPUE还分别受一对互作位点的影响。在磷胁迫下 ,有 3个QTL与SPUE有关 ,分别位于染色体 2D、3B和6D上 ,变异解释率分别为 14.2 %、7.73%和 6.58% ;与WPUE相关的 2个QTL分别位于染色体 2D、7A上 ,变异解释率分别为 18.01 %和 10.73 % ;SPUE受上位效应的影响。 7A染色体对于小麦的磷素利用效率有着重要的作用 ,位于该染色体上的片段Xfba354 Xfba69在 2种供磷情况下都显著影响WPUE ,同时此片段在正常供磷下还与其它基因互作而影响WPUE。此外 ,5A染色体在正常供磷、2D染色体在低磷胁迫下分别对磷素利用效率 (PUE)有较强的作用。     

小麦淀粉RVA特性的QTL定位及效应分析

小麦淀粉糊化(RVA)特性是评价小麦加工品质重要指标之一。为进一步挖掘优质小麦淀粉糊化特性相关数量性状位点(QTL)及位点间效应差异，以周麦23/郑麦366的F₈代重组自交系(RIL)群体的237个家系及其亲本为试验材料，利用55K核苷酸多态性(SNP)芯片构建高密度遗传图谱，根据2年3点5个环境下的数据对小麦淀粉RVA参数进行QTL定位分析。结果表明，共检测到96个QTL位点，位于21条染色体上，稳定位点共有8个，其中调控峰值黏度的Qpv. hau-4A. 1和Qpv. hau-6A. 1以及调控崩解值的Qbd. hau-4A. 1和Qbd. hau-6A. 1能够同时在2个以上的环境中检测到，分别解释了2.55%～24.23%、2.60%～6.00%、11.50%～48.30%和3.86%～8.09%的表型变异，调控峰值黏度的Qpv. hau-6A. 1可能为新的QTL位点，其增效等位基因来源于优质强筋小麦品种郑麦366，对峰值黏度具有显著的增效作用，与面条的弹性和韧性有关。QTL聚合效应分析结果发现，Qpv. hau-4A. 1和Qpv. hau-6A. 1...     

小麦萌发期幼苗相关性状耐旱系数的QTL定位

为了检测与小麦幼苗耐旱性相关的数量性状位点,用3个关联重组自交系(RIL)群体,对小麦萌发期幼苗的胚芽鞘长、苗高、最大根长、根数、苗鲜重、茎叶鲜重、根鲜重、根冠鲜重比、苗干重、茎叶干重、根干重、根冠干重比等12个表型性状的耐旱系数进行QTL定位。结果显示,共检测到28个耐旱相关位点,分布在小麦的1BL、1D、2B、3A、3B、3D、4A、6A、6B、6D、7A、7B等12条染色体上,可分别解释表型变异的5.61%~64.22%,其中,6个位点通过同一群体不同性状的耐旱系数检测到,2个位点通过2个群体不同性状的耐旱系数检测到,分别位于4A染色体的Xbarc61~wpt-9675标记区间和6A染色体的wpt-9679~wpt-8177标记区间内,这2个位点实现了在不同群体间的相互验证,可靠性大大提高。这些位点的发现对于小麦萌发期耐旱性的精细定位、图位克隆和分子标记辅助选择具有重要的意义。     

小麦成熟期产量及钾效率相关性状的全基因组关联分析

  【目的】  探明不同钾供应条件下控制产量及钾效率相关性状的稳定的显著关联分子标记位点，为小麦产量及钾效率相关性状的遗传控制机理研究及相关基因的克隆提供参考。  【方法】  利用134个小麦品种 (系) 组成的群体为试验材料，设置正常供钾 (T1) 和不施钾 (T2) 两个处理，进行了2年田间试验 (E1、E2)。对小麦成熟期株高、穗长、穗粒数及钾吸收、利用效率等23个性状进行了表型鉴定，分别定义了同年同一处理和同一处理两年平均共6个环境平均值。采用GLM+Q一般线性模型和MLM+K+Q混合线性模型相结合的方法，利用群体差异SNP分子标记 (90K SNP芯片) 对小麦产量和钾效率相关性状进行全基因组关联分析。  【结果】  与正常钾处理相比，不施钾处理条件下籽粒钾利用效率显著升高，单株钾累积量、单株钾含量及总小穗数等性状显著降低。供试小麦各性状的群体变异系数为6.98%～350.38%，有14个性状的遗传力在50%以上，以株高的遗传力最高 (92.03%)。利用保留的7485个多态性好的群体差异 (SNP) 进行了全基因组关联分析，共检测到1420个分子标记位点与供试23个性状在P ≤ 0.001水平存在显著关联，分布在21条染色体上。有1097个 (77.25%) 分子标记位点仅在一个关联分析环境中被检测到；能在至少两个关联分析环境中被检测到的相对稳定分子标记位点有323个，其中113个位点与钾效率相关性状有关，Tdurum_contig26281_139、Kukri_c307_2053等分子标记位点可以提高钾吸收效率，Ex_c19038_571、BS00039148_51等分子标记位点能够提高钾利用效率。在至少4个关联分析环境中被检测到的位点有22个，分别与株高、千粒重、穗粒数等5个性状相关。与株高和千粒重显著关联的分子标记位点RFL_Contig4069_2628和BS00003632_51可同时在全部6个关联分析环境中检测到，平均贡献率为9.59%和13.66%，环境稳定性非常好，与株高的降低和千粒重的提高显著关联。  【结论】  不同钾供应水平下与产量及钾效率相关性状显著关联的分子标记位点存在显著差异，77.25%的分子标记位点仅在特定环境下被检测到。但也有22个显著关联分子标记位点 (涉及9个产量及钾效率相关性状) 在至少4个关联分析环境 (共6个环境) 下被检测到，形成高频表达分子标记位点。其中与株高和千粒重分别显著关联的两个分子标记位点在所有6个关联分析环境中均稳定被检测到，能显著降低株高和提高千粒重。这些分子标记位点的相关基因对相关性状的调控效应受钾处理环境影响小，具有较高的理论和应用价值，值得深入研究。     

小麦光温敏核雄性不育系BS20育性的QTL分析

以小麦(Triticum aestivum L.)光温敏不育系BS20×Fu3 DH群体的289个系为材料,于2005-2006年度种植于北京海淀和安徽阜阳,进行了育性(结实率和结实小穗率)的调查.利用SSR标记和分离群体分组分析法(BSA)分析该群体中与育性相关的分子标记,用128对SSR引物,初步构建BS20×Fu3群体的分子标记遗传连锁框架图.BSA的结果表明,与育性连锁的3个标记是Xgwm294、Xgwm374和Xgwm44,分别位于染色体2AL、2BS和7DS;采用混合线性复合区间作图法对小麦育性进行QTL分析,检测到6个QTL,分布在1AS、2BS、2DL、6AL、6BL和7DS染色体,贡献率为1.1%～12.5%,其中7DS上的QTL与2BS、6AL和6BL上的QTL存在显著的互作效应.综合BSA和QTL分析结果,确定染色体7DS和2BS上的QTL重复性较好、贡献率和互作效应较大,为小麦光温敏核雄性不育性状的重要QTL,标记区间分别为Xgum44-Xcfd14和Xgwm148-Xgwm374,贡献率分别为7.2%～12.5%和2.1%～2.5%.     

水氮耦合对强筋冬小麦子粒蛋白质和淀粉品质的影响

在高肥力条件下,研究水氮耦合对小麦子粒产量、蛋白质含量及组成、蛋白质质量、淀粉含量及组成和淀粉品质的影响。结果表明,无论施氮与否,灌水均显著提高小麦子粒产量,同时显著降低子粒粗蛋白、单体蛋白及湿面筋含量;但不同灌水量间(W1、W2、W3)差异不显著。在低灌水频次(W0、W1)条件下,施氮具有明显的增产效应;而高灌水频次(W2、W3),施氮的增产效应不显著。随着灌水次数增加,谷蛋白总量保持稳定,而谷蛋白组分产生了显著的变化,其中可溶性谷蛋白含量呈上升趋势,不溶性谷蛋白含量和谷蛋白聚合指数呈下降趋势,粉质仪参数(形成时间和稳定时间)也呈下降趋势。小麦子粒蛋白质含量及组分和子粒品质均因施氮(N.168.kg/hm2)而有不同程度的提高,其中非面筋蛋白(清蛋白和球蛋白)的增加幅度高于面筋蛋白(醇溶蛋白和谷蛋白),可溶性谷蛋白增加幅度高于不溶性谷蛋白,即降低了谷蛋白聚合指数。水氮对子粒的淀粉含量及其组成的影响存在明显的交互效应。在不施氮肥条件下,随灌水次数增加,支链淀粉和总淀粉含量呈上升趋势;施氮条件下,各灌水处理(W1、W2、W3)的总淀粉和支链淀粉含量均显著高于不灌水处理(W0),但各灌水处理间差异不显著。随灌水次数增加,直链淀粉含量和直/支比均呈下降趋势,黏度仪指标(峰值黏度、稀值、最终黏度和反弹值)均呈上升趋势。施氮在低灌水频次(W0、W1)条件下促进支链淀粉的合成,同时降低直链淀粉含量和直/支比;高灌水频次(W2、W3)条件下则相反。     

Processing of novel elevated amylose wheats: functional properties and starch digestibility of extruded products

Different types of novel wheat lines with different starch contents and amylose/amylopectin ratios, relating to defined alterations in the number and activity of starch synthase IIa genes, were processed by pilot-plant extrusion. Two types of products were produced: pure wholemeal products and breakfast cereals made from wholemeal/maize blends. Lower apparent shear viscosity was obtained in the extruder with lower starch content and higher amylose/amylopectin ratio flours (SSIIa-deficient line). The bulk density of the products decreased with increasing extrusion temperature and was always higher for the triple-null line. The bulk density was not completely explained by the melt shear viscosity, suggesting the importance of the fillers (fibers, brans) in the process of expansion and structure acquisition. The different mechanical properties were explained by the density and by the material constituting the cell walls. Enzyme-resistant starch (RS) content and hydrolysis index (HI) were not correlated to the extrusion temperature, but RS was higher in pure wholemeal products and in the SSIIa-deficient line. These results are discussed in terms of starch molecular architecture and product microstructure.     

Structural and molecular basis of starch viscosity in hexaploid wheat

Wheat starch is considered to have a low paste viscosity relative to other starches. Consequently, wheat starch is not preferred for many applications as compared to other high paste viscosity starches. Increasing the viscosity of wheat starch is expected to increase the functionality of a range of wheat flour-based products in which the texture is an important aspect of consumer acceptance (e.g., pasta, and instant and yellow alkaline noodles). To understand the molecular basis of starch viscosity, we have undertaken a comprehensive structural and rheological analysis of starches from a genetically diverse set of wheat genotypes, which revealed significant variation in starch traits including starch granule protein content, starch-associated lipid content and composition, phosphate content, and the structures of the amylose and amylopectin fractions. Statistical analysis highlighted the association between amylopectin chains of 18-25 glucose residues and starch pasting properties. Principal component analysis also identified an association between monoesterified phosphate and starch pasting properties in wheat despite the low starch-phosphate level in wheat as compared to tuber starches. We also found a strong negative correlation between the phosphate ester content and the starch content in flour. Previously observed associations between internal starch granule fatty acids and the swelling peak time and pasting temperature have been confirmed. This study has highlighted a range of parameters associated with increased starch viscosity that could be used in prebreeding/breeding programs to modify wheat starch pasting properties.     

不同磷、钾处理小麦苗期氮营养性状的QTL分析

【目的】 对不同浓度磷、钾处理下小麦苗期氮养分效率相关性状进行QTL分析,以深入理解磷、钾与氮养分效率的相互关系,为氮营养相关性状的图位克隆及分子标记辅助选择育种奠定基础。 【方法】 采用苗期液培试验,以“川35050 ×山农483”组合衍生的小麦重组自交系群体(131个株系)为研究材料,设置了中磷中钾(MPMK)、高磷(HP)、低磷1 (LP1)、低磷2 (LP2)、低磷3 (LP3),高钾(HK)、低钾1 (LK1)、低钾2 (LK2)、低钾3 (LK3)共9个处理,对不同磷、钾处理下的氮养分效率相关性状进行研究,并结合分子标记遗传图谱,从整个基因组水平对与小麦苗期氮养分效率相关的10个性状进行QTL定位及遗传分析。 【结果】 不同处理下的10个性状共检测到137个QTL,位于除3D外的20条染色体上,大部分QTL (89.05%)仅在单一处理下被定位到,有3个QTL (QRnue-1A.2、QSnue-1A.1和QTnue-1A.1)可在至少4个处理中被检测到,有5个QTL (QRnue-1A.1、QTnue-1A.1、QSnc-4A、QRnc-6A.3和QSnue-6B)可同时在低磷和低钾环境中被检测到。本研究还检测到至少包含3个以上QTL的QTL簇17个,分别位于1A、1B、2B、2D、3A、3B、4A、4B、5D、6A、6B、6D和7A染色体上,共涉及66个QTL,占QTL总数的48.18%。其中,有5个QTL簇仅与特定磷、钾处理有关,大多数QTL簇均同时定位了不同磷、钾处理的不同性状,许多QTL簇位点还与前人定位的生物量、产量及其他养分有关。 【结论】 磷、钾的供应能够显著影响小麦苗期对氮素的吸收利用及其相关QTL的表达。影响苗期小麦氮养分效率相关性状的QTL大多数仅在特定处理下被检测到,但大多数QTL会形成QTL簇,构成了控制氮养分效率的QTL热点,许多热点区域也与前人定位的许多成株期性状如生物量、产量及其他养分效率有关,这些QTL/基因密集区域及其特点的发现,为我们深入理解小麦氮养分效率的遗传控制特点及其与磷、钾养分供应的关系提供了新的视角,也为这些重要位点的克隆及其应用提供数据支持。     

Soft Wheat Starch Pasting Behavior in Relation to A‐ and B‐type Granule Content and Composition

Flours of two soft wheat cultivars were fractionated into native, prime, tailing, A‐, and B‐type starch fractions. Starch fractions of each cultivar were characterized with respect to A/B‐type granule ratio, amylose content, phosphorus level (lysophospholipid), and pasting properties to investigate factors related to wheat starch pasting behavior. While both cultivars exhibited similar starch characteristics, a range of A‐type (5.7– 97.9%, db) and B‐type granule (2.1–94.3%, db) contents were observed across the five starch fractions. Though starch fractions displayed only subtle mean differences (<1%) in total amylose, they exhibited a range of mean phosphorus (446–540 μg/g), apparent amylose (18.7–23%), and lipid‐complexed amylose (2.8–7.5%) values, which were significantly correlated with their respective A‐ and B‐type granule contents. A‐type (compared with B‐type) granules exhibited lower levels of phosphorus, lipid‐complexed amylose, and apparent amylose, though variability for the latter was primarily attributed to starch lipid content. While starch phosphorus and lipid‐complexed amylose contents exhibited negative correlation with fraction pasting attributes, they did not adequately account for starch fraction pasting behavior, which was best explained by the A/B‐type granule ratio. Fraction A‐type granule content was positively correlated with starch pasting attributes, which might suggest that granule size itself could contribute to wheat starch pasting behavior.     

波兰小麦×普通小麦品系中13重组自交系(RIL)群体穗部性状的QTL分析

小麦穗部性状是与籽粒产量关系密切的重要农艺性状。本研究以一个由99个株系组成的来源于波兰小麦(Triticum polonicum L.)和普通小麦(Triticum aestivum L.)品系中13杂交后代的F8重组自交系(recombinant inbred lines,RIL)群体为实验材料,利用微卫星(simple sequence repeat,SSR)标记对穗长、穗粒数和有效小穗数进行数量性状基因座(quantitative trait locus,QTL)定位分析。所构建的A染色体组和B染色体组共14个连锁群的遗传连锁图谱由115个SSR标记位点组成,图谱全长822.9cM,标记间的平均遗传距离为7.16cM。采用复合区间作图法在两年的环境中检测到分布在2A、3A、3B、5B和7B染色体上的6个穗长QTL,5个穗粒数QTL和2个有效小穗数QTL,表型变异贡献率分别为9.21%～22.94%,9.18%～19.71%和11.48%～13.01%。两年中都在3A染色体上的Xbarc12～Xbarc310区间内检测到控制穗粒数的主效QTL,说明该QTL较少受环境条件的影响,是一个稳定可靠的穗粒数QTL。该QTL与最近标记的遗传距离为0.01cM,可用于小麦产量性状的分子标记辅助育种。     

Kernel and Starch Properties of U.S. and Imported Medium‐ and Short‐Grain Rice Cultivars

The production of medium‐ and short‐grain rice in the mid‐Southern U.S. rice‐growing region is increasing. This work aimed to identify the quality traits of importance to the markets for these grain types. Twenty‐five medium‐ and short‐grain milled rice samples were collected and analyzed for physical, gelatinization, pasting, and starch structural properties. Six samples were from Arkansas (AR), five from California (CA), and 14 imported (IM). Cluster and principal component analyses showed that the AR samples had greater gelatinization temperature, enthalpy, and percentages of amylopectin long chains (B2 and B3 chains) but lesser kernel whiteness, total setback viscosity, and percentage of amylopectin short chains (A chains) than the CA samples. With the exception of one sample from Taiwan, chemometrics indicated that the IM samples differed from the AR samples (cluster A) in some properties and were grouped into three clusters (clusters B, C, and D). Cluster B samples had properties that were similar to the CA samples; cluster C samples had lower gelatinization temperature and peak viscosity but greater percentages of amylose and A chains than the AR samples; and cluster D samples had lesser paste breakdown but greater final viscosity and percentage of B1 chains than the AR samples. Kernel width, color, and chalk were the primary sources of variation in milled rice appearance. In relation to structure and functionality, the percentages of amylopectin A and B3 chains and amylose content were the major sources of variation.     

优质小麦子粒淀粉组成与糊化特性对氮素水平的响应

在大田条件下,选用3个不同类型优质小麦品种: 豫麦47（强筋品种）、山农8355（中筋品种）和豫麦50（弱筋品种）,设置3个氮肥水平: 施N 0、15和30 g/m2,研究了小麦子粒淀粉的粒度分布、直支链淀粉组成、糊化特性及其对氮素水平的响应。结果表明,优质小麦子粒中淀粉粒的粒径分布范围为1～45 μm,其数目分布呈单峰或双峰曲线变化,体积和表面积分布均呈双峰曲线变化,峰谷位于10 μm处; 据此可将淀粉粒分为两种类型: A型大淀粉粒（10～45 μm）和B型小淀粉粒（1～10 μm）。优质小麦子粒淀粉粒组成存在显著的基因型差异。强筋品种豫麦47子粒中B型淀粉粒的比例较高,弱筋品种豫麦50子粒中A型淀粉粒的比例较高,中筋品种山农8355居中。施氮水平对优质小麦子粒中淀粉的粒度分布存在显著影响。在本试验条件下,随氮素水平的提高,强筋品种豫麦47子粒中A型淀粉粒的比例提高,而B型淀粉粒的比例下降; 增施氮肥后弱筋品种豫麦50和中筋品种山农8355子粒中B型淀粉粒的比例增大,而A型淀粉粒的比例降低,且前者变化的幅度较大。适量增施氮肥提高优质小麦子粒中的淀粉含量,氮肥用量进一步增大后,淀粉含量降低; 增施氮肥后优质小麦子粒中直链淀粉含量降低。增施氮肥对优质小麦子粒淀粉的糊化特性存在较大影响,且此影响的趋势因基因型和施氮量而异。其中强筋品种豫麦47表现为低谷粘度、最终粘度、反弹值、糊化温度和峰值时间提高,而高峰粘度和稀懈值降低; 当氮肥用量增大至30 g/m2时,糊化温度和峰值时间降低,而以粘度为单位的参数均提高。弱筋品种豫麦50表现为增施氮肥后,RVA参数呈下降趋势,与之相对应中筋品种山农8355的呈上升趋势。相关性分析表明,B型淀粉粒的数目、体积和表面积比例与高峰粘度和稀懈值存在显著正相关; 与低谷粘度、最终粘度和反弹值存在显著负相关。子粒中直链淀粉含量、支链淀粉含量和总淀粉含量与高峰粘度和稀懈值呈显著负相关,与低谷粘度、最终粘度、反弹值和峰值时间呈一定程度正相关; 直链淀粉相对含量与RVA特征参数之间的相关趋势与子粒中直链淀粉含量的趋势一致,但均未达显著水平。由此可以认为,氮肥通过调控小麦子粒中淀粉的直、支链组成和粒度分布而影响其糊化特性。     

Functional Characteristics of Bread Wheat (Triticum aestivum L.) Near‐Isogenic Lines Differing at the Waxy (Wx) Locus

The Waxy (Wx) gene in hexaploid wheat (Triticum aestivum L.) encodes granule‐bound starch synthase (GBSS1), which is involved in the synthesis of amylose, a mostly linear glucan polymer that makes up ∼25% of wheat starch. A null mutation of the Wx gene in each of the three genomes is associated with starch almost entirely consisting of the branched glucan polymer amylopectin (waxy starch), with corresponding changes in functionality. However, the rheological behavior of partially waxy starch remains unclear. The objective of this study was to characterize flour and baking quality in 16 near‐isogenic lines, null at the Wx locus on zero, one, two, or all three genomes, grown in four different environments. Across allelic groups, significant variations in amylose concentrations, flour paste viscosity, loaf structure and texture, dough stability, and proximate variables were observed. Because waxy wheat starch has greater water absorbance and resistance to retrogradation than normal starch, its inclusion in flour blends has been suggested as a means of improving the texture and appearance of bakery products and noodles. The results indicate that wheat encoding <3 functional homeologs of GBSS1 produces starch that has potential in the production of certain food items, such as Asian noodles. However, further research is necessary to determine the optimal amylose‐to‐amylopectin ratio to improve baking quality.     

Approaches for Modification of Starch Composition in Durum Wheat

Manipulation of starch composition in cereals and particularly in wheat is receiving increasing attention due to recognition of its important role in food and nonfood applications. The amylose/ amylopectin ratio influences the physicochemical properties of starches and nutritional value of derived end products. Identification of the key enzymes involved in the starch biosynthetic pathway has opened new avenues for altering the amylose and amylopectin content in durum and bread wheat. The granule bound starch synthases (GBSSI), or waxy proteins, are the enzymes responsible for amylose synthesis in storage tissues; amylopectin is produced by the concerted action of different enzymes, including starch synthases (SS), branching (SBE), and debranching enzymes (DBE). By altering the level of key enzymes involved in the regulation of starch synthesis, it is possible to generate novel starches with unique functional properties. In this respect, both low and high amylose starches are particularly interesting because they are associated with industrial and processing properties as well as with human health and nutrition. So far, major attention has addressed the manipulation of starch composition in bread wheat, whereas durum wheat has been investigated to a much lesser extent. Approaches currently available to alter amylose/amylopectin ratio and tailor starch composition in durum wheat are presented.