水稻资源开花期耐热性的全基因组关联分析

水稻在开花期对高温非常敏感,挖掘耐热种质并解析耐热性的遗传机制,有助于水稻的耐热性遗传改良。本研究选取205份国内外种质资源,在抽穗开花期对遇高温的稻穗进行标记,以高温下标记穗的结实率作为耐热指标,结合高密度SNP标记进行全基因组关联分析并初步预测候选基因。结果表明:不同水稻种质的耐热性差异明显,高温下的结实率最低为19.0%,平均值为64.0%,中位值为65.9%,最高值为86.6%,其中06-32、剪刀齐、娄早籼5号等17份种质的耐热性较强;全基因组关联分析共筛选到130个与耐热性显著关联的SNP标记,并鉴定到18个耐热QTL,其中6个QTL与已报道的耐热相关QTL共定位;qHT4-6与耐热性的关联度最高,根据该区间lead SNP的单倍型分类,G单倍型材料的开花期耐热性显著强于A单倍型材料,该区间附近有7个基因可能受高温调控。     

外源海藻糖对高温胁迫下穗分化期水稻叶片生理特性及产量的影响

该研究以耐热型水稻品种Nagina22和热敏型水稻品种YR343为供试材料,采用盆栽试验,设置喷施清水+常温处理(NT0)、喷施清水+穗分化期高温胁迫(HT0),以及分别喷施5、10、15、20 mmol·L^-1外源海藻糖+高温胁迫(分别记为HT1、HT2、HT3、HT4)共6个处理,分析外源海藻糖对高温胁迫下穗分化期水稻叶片叶绿素含量、光合气体交换参数、抗氧化酶活性、渗透调节物质含量、活性氧含量等生理特性,以及籽粒产量及其构成因素的影响,为水稻抗热栽培和耐热品种的选育提供理论依据。结果表明:(1)在高温胁迫下水稻穗分化期,2个水稻品种叶片的叶绿素含量、光合气体交换参数及渗透调节物质含量均降低,叶片MDA和H₂O₂含量以及■的产生速率均上升,叶片抗氧化酶活性呈先增后降的趋势,最终显示水稻籽粒产量及其构成因素显著下降。(2)喷施外源海藻糖能显著增加高温胁迫下穗分化期水稻的每穗粒数、千粒重和结实率,从而提高籽粒产量,其中弱势粒千粒重和结实率的增幅高于强势粒,外源海藻糖最适喷施浓度为15 mmol·L^-1...     

脱落酸对水稻抽穗开花期高温胁迫的诱抗效应

为探究脱落酸(ABA)对水稻(Oryza sativa)抽穗开花期高温胁迫的诱抗效应, 以江西省主推水稻品种黄华占为材料, 于孕穗期用蒸馏水、ABA溶液(10、50和100 µmol∙L^-1)、氟啶酮(FLU)和原花青素(PC) 6种溶液进行叶面喷施, 然后移入对照(CK)和高温胁迫(HS)环境处理8天, 考查籽粒活性氧(ROS)积累、抗氧化防御能力、产量构成及相关基因的表达。结果表明, 高温胁迫下, 水稻的穗长、穗重、结实率、千粒重和产量与超氧阴离子和过氧化氢含量呈显著负相关。高温胁迫下, 喷施ABA显著上调了ABA应答和抗氧化防御基因的表达, 籽粒中活性氧含量下降了8.24%-31.35%; 喷施ABA显著增加了水稻的穗长、穗重、结实率和千粒重, 显著上调了产量形成基因的表达, 增产12.73%-20.77%。高温胁迫下, 喷施FLU可抑制ABA的生物合成, 导致ROS过量积累和水稻减产; 喷施抗氧化剂PC则抑制ROS过量积累, 使产量增加。以上结果表明, 高温胁迫下, 孕穗期喷施ABA不仅能够激发ABA信号通路, 而且上调抗氧化防御能力和产量形成基因的表达, 进而提高水稻在抽穗开花期的耐热性, 达到增产目的。     

水稻孕穗期耐热种质资源的初步筛选

在人工气候室设定极端高温条件下,对来源于不同国家和地区的58份处于温度敏感期的水稻品种耐热性进行鉴定,以结实率下降的百分率为指标,通过方差分析,对水稻种质资源的耐热性进行评价。结果表明,种质间的耐热性存在显著差异,筛选出极端耐热品种2份（IRAT118和冷水白）。     

干旱对东北春玉米生长发育和产量的影响

选取玉米品种丹玉39为供试材料,利用大型农田水分控制试验场,采用大田池栽方式,在玉米三叶-拔节期、拔节-吐丝期、吐丝-乳熟期分别开展中度干旱胁迫及复水控制对比试验,分析3个关键生育时期干旱胁迫对春玉米生长发育和产量的影响.结果表明:与水分适宜对照(CK)相比,三叶-拔节期遭受干旱胁迫后,全生育期推迟13 d,至拔节普遍期,株高偏低29.8％,叶面积偏小41.2％,复水后,株高和产量得到较大程度恢复,果穗性状和最终产量差异不大;拔节-吐丝期遭受干旱胁迫后,全生育期缩短7d,至吐丝普遍期,株高偏低18.6％,叶面积偏小14.1％,果穗长、穗粒数、果穗干质量、穗粒质量分别下降6.9％、19.1％、28.1％和29.4％,空秆率增加13.3％;吐丝-乳熟期遭受干旱胁迫后,全生育期缩短15 d,生长至乳熟普遍期,株高偏低2.3％,叶面积偏小37.3％,果穗长、穗粒数、果穗干质量、穗粒质量分别下降9.2％、24.1％、30.8％和27.9％,空秆率增加24.5％.拔节-吐丝期、吐丝-乳熟期干旱胁迫处理并复水后,玉米株高恢复不明显,产量降幅显著.     

干旱对东北春玉米生长发育和产量的影响

选取玉米品种丹玉39为供试材料,利用大型农田水分控制试验场,采用大田池栽方式,在玉米三叶-拔节期、拔节-吐丝期、吐丝-乳熟期分别开展中度干旱胁迫及复水控制对比试验,分析3个关键生育时期干旱胁迫对春玉米生长发育和产量的影响.结果表明：与水分适宜对照（CK）相比,三叶-拔节期遭受干旱胁迫后,全生育期推迟13 d,至拔节普遍期,株高偏低29.8%,叶面积偏小41.2%,复水后,株高和产量得到较大程度恢复,果穗性状和最终产量差异不大;拔节-吐丝期遭受干旱胁迫后,全生育期缩短7 d,至吐丝普遍期,株高偏低18.6%,叶面积偏小14.1%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降6.9%、19.1%、28.1%和29.4%,空秆率增加13.3%;吐丝-乳熟期遭受干旱胁迫后,全生育期缩短15 d,生长至乳熟普遍期,株高偏低2.3%,叶面积偏小37.3%,果穗长、穗粒数、果穗干质量、穗粒质量分别下降9.2%、24.1%、30.8%和27.9%,空秆率增加24.5%.拔节-吐丝期、吐丝-乳熟期干旱胁迫处理并复水后,玉米株高恢复不明显,产量降幅显著.     

我国玉米自交系茎秆性状多样性分析

研究我国玉米自交系茎秆性状特征及其多样性,是培育宜机收玉米品种的重要前提。本研究以兰卡斯特、PB、四平头、旅大红骨和瑞德五大主要类群70份主要玉米自交系为材料,调查12个茎秆相关性状(茎高、穗位高、穗位系数、茎节数、穗位节、穗节系数、穗茎长、穗茎粗、茎鲜重、茎干重、含糖量和含水量),分析性状相关性和类群多样性。结果表明,我国地方种质四平头和旅大红骨茎秆性状表型变异丰富;灌浆期玉米茎秆含水量比较稳定;玉米植株高度与茎节长度显著相关;玉米雌、雄穗节之间的节间数比较恒定;玉米茎秆含糖量与茎节长度、茎粗、果穗着生位置有关;有效降低穗位高度应从降低果穗着生节入手;类群茎秆特征鲜明:兰卡斯特茎节较少,瑞德茎秆较粗,PB茎秆较细,旅大红骨茎秆较粗、茎节较短,四平头植株较矮、茎秆含糖量较低、干物质含量较低;兰卡斯特×四平头和兰卡斯特×PB类群间存在较强的生物量及籽粒产量杂种优势;挖掘和利用茎节较长、穗位较低的玉米地方种质是我国宜机收玉米育种的技术途径。本研究结果对玉米育种具有重要指导意义。     

玉米籽粒重金属铅(Pb2+)含量的QTL定位

铅(Pb²⁺)是现存环境最大量的有毒重金属污染元素,在我国特别是西南地区种植的玉米受重金属Pb²⁺污染日益严重,已严重影响到食物安全。文章利用玉米籽粒Pb²⁺低富集自交系178和籽粒Pb²⁺高富集自交系9782杂交衍生的重组自交系群体为作图群体,利用165对SSR多态性标记,构建了总长度为1499.85 cM、标记间平均距离为9.07 cM的分子遗传图谱,对玉米籽粒Pb²⁺含量性状进行了QTL定位分析,以期为选育籽粒低富集Pb²⁺的玉米新品种提供参考。结果表明,在Pb²⁺浓度为333.32 mg/kg胁迫下,共检测到2个与籽粒Pb²⁺含量相关的QTL,分别位于玉米第1、第4号染色体,其中qPC1位于标记区间umc1661~phi002h之间,表型贡献率为11.13%,加性效应为0.062;qPC4位于umc1117~nc005之间,表型贡献率为5.55%,加性效应为-0.044。性状相关分析结果表明,籽粒中Pb²⁺含量与穗长、穗粗、行粒数、穗重和百粒重等产量性状间均未达到显著水平,表明选育玉米籽粒Pb²⁺低富集的新自交系或杂交种不一定会影响到产量性状,而且籽粒Pb²⁺含量是一个相对独立的遗传性状。     

弱光胁迫对不同耐荫型玉米果穗发育及内源激素含量的影响

2010—2011年以耐荫性较弱的玉米杂交种豫玉22和耐荫性较强的玉米杂交种郑单958为材料,在抽雄前3 d开始进行弱光胁迫处理,吐丝后10 d恢复自然光照,研究弱光胁迫及光恢复对不同耐荫型玉米果穗生长发育及其内源激素含量的影响。结果表明:弱光胁迫下,玉米果穗生长发育明显减缓,穗长、穗粗和果穗干物质积累显著减小,秃尖度变大;穗行数、穗粒数和籽粒库容显著降低;吐丝期果穗顶部小穗子房发育停滞,已有败育迹象的籽粒在恢复自然光照后无明显改善;豫玉22果穗和籽粒性状在处理间的差异程度均大于郑单958。弱光胁迫下,两玉米杂交种果穗的ABA和ZR含量均升高,而GA含量和GA/ABA比值均降低;IAA含量和IAA/ABA比值在郑单958果穗中表现为升高,而豫玉22则表现为下降。     

240份玉米自交系纹枯病抗性鉴定与评价

在人工接种条件下,连续3年对240份玉米自交系纹枯病抗性进行鉴定和评价,分析了玉米纹枯病抗性与主要农艺性状的相关性。结果表明,玉米纹枯病抗性资源较为缺乏,240份自交系中无免疫或高抗的材料,有中抗自交系4份、感病自交系18份、高感自交系218份。旅大红骨、Reid、PA和塘四平头类群自交系中未发现玉米纹枯病抗源,PB类群和Lancaster类群自交系纹枯病抗性相对较好,今后应主要从这两类种质中寻找玉米纹枯病抗源。玉米纹枯病病情指数与株高、穗位高、穗位高/株高、穗下节间数和穗下平均节间长均呈极显著负相关,这些表型可以作为非接种条件下筛选抗玉米纹枯病种质的参考指标。     

Combining ability of tropical maize lines for seed quality and agronomic traits

Studies of genetic effects of early selection of maize based on seed quality traits are rare, especially those that use materials from different heterotic groups. These studies are also useful in tropical environments and for the advancement of sustainable agriculture with cropping during seasons not commonly used for cultivation. We estimated, through diallel crosses, the predominant genetic effects on the expression of agronomic traits and seed quality and on the general combining ability of nine maize lines from commercial hybrids and the specific combining ability of hybrid combinations among them. In the evaluation of seed quality, seven tests were used: first count and final count of seed germination, seedling vigor classification, cold tolerance, seedling emergence rate in a sand seedbed, speed of emergence in a sand seedbed, and speed of emergence index. Plant height, first ear height and grain yield were the estimated agronomic traits. In the diallel analysis, method 3 (model I) proposed by Griffing was used. There was a greater significance of non-additive genetic effects in the genetic control of seed quality of the various lines. The Flash, Dekalb 350 and P 30F80 lines combined high seed quality and high grain yield. For growth during the normal planting season, the combinations CD 3121-1 x P 30F80, Speed x CD 3121-2, Dow 8330 x AG 8080 and Dekalb 350 x CD 3121-2 were the most promising for both seed quality and agronomic traits.     

我国不同年代玉米自交系茎秆性状演替规律

茎秆是玉米植株重要的组成部分,与植株倒伏、籽粒产量密切相关。研究我国玉米茎秆性状变化趋势,探讨不同年代茎秆性状演变规律,为我国玉米抗倒伏及高产品种选育提供参考。本研究以20世纪60-90年代65个代表性玉米自交系为材料,调查植株茎高、穗位高、茎节数、穗位节、茎粗、茎秆含水量、茎秆含糖量7个茎秆性状,及其衍生的穗位系数(穗位高/茎高)和穗节系数(穗位节/茎节数),基于最佳线性无偏估计值,开展性状相关性分析及不同年代自交系茎秆性状演变规律研究。结果显示,玉米自交系间茎秆性状差异显著;不同年代的茎秆性状时代特征不明显;随着年代的更替,玉米茎高、穗位高、茎节数、穗位节呈下降趋势;20世纪60-90年代穗位高改良效果显著;80年代左右玉米茎秆粗细育种目标由粗壮型调整为纤细型,可能与合理密植、提高单产的育种目标有关;90年代,玉米茎秆含水量降低3个百分点,下降显著。总之,抗倒伏研究一直是我国玉米育种的重要研究方向,且穗位高改良效果显著,玉米茎节数、穗位节将成为玉米抗倒伏及高产研究中新的重要关注点,研究结果对玉米抗倒伏及高产育种具有重要的指导意义。     

QTL analysis of shading sensitive related traits in maize under two shading treatments

During maize development and reproduction, shading stress is an important abiotic factor influencing grain yield. To elucidate the genetic basis of shading stress in maize, an F(2:3) population derived from two inbred lines, Zhong72 and 502, was used to evaluate the performance of six traits under shading treatment and full-light treatment at two locations. The results showed that shading treatment significantly decreased plant height and ear height, reduced stem diameter, delayed day-to-tassel (DTT) and day-to-silk (DTS), and increased anthesis-silking interval (ASI). Forty-three different QTLs were identified for the six measured traits under shading and full light treatment at two locations, including seven QTL for plant height, nine QTL for ear height, six QTL for stem diameter, seven QTL for day-to-tassel, six QTL for day-to-silk, and eight QTL for ASI. Interestingly, three QTLs, qPH4, qEH4a, and qDTT1b were detected under full sunlight and shading treatment at two locations simultaneously, these QTL could be used for selecting elite hybrids with high tolerance to shading and high plant density. And the two QTL, qPH10 and qDTS1a, were only detected under shading treatment at two locations, should be quit for selecting insensitive inbred line in maize breeding procedure by using MAS method.     

基于DUS测试性状的玉米自交系形态多样性分析

利用DUS测试中的47个性状对15份普通玉米自交系和13份糯玉米骨干自交系进行了形态多样性研究。结果表明:本研究所选用的普通玉米自交系较糯玉米自交系的形态变异更为丰富;47个性状的Shannon-Weaver多样性指数存在较大差异。聚类分析表明,糯玉米自交系紧密地聚在一起,与普通玉米自交系存在较大形态差别。DUS测试性状涵盖的信息量大且受环境影响相对较小,可应用于玉米自交系的形态多样性分析。     

Associations between quantitative traits and enzyme loci in the F2 population of a maize hybrid

Summary Univariate and multivariate analyses were used to identify associations between eight enzyme marker loci and 11 quantitative traits of maize (Zea mays L.). The material analyzed included inbred lines Wf9 and Pa405, single-cross hybrid Wf9 X Pa405, and the F2 generation of the selfed single-cross hybrid. Each enzyme locus assayed was associated with at least one quantitative trait, and all quantitative traits were associated with genotypes at particular enzyme loci. Significant associations also were found between the level of heterozygosity per individual and nine of 11 quantitative traits. The total contribution to heterosis, for seed yield per plant, of genes linked with the eight enzyme loci, was 27% of the F2 mean and 18% of the difference in mean between the F1 hybrid and the inbred parents. Genes linked with Glu1 accounted for nearly one third of the total dominance effect detected by the eight enzyme loci. The chromosome segments marked by loci with significant effects on seed yield were markedly overdominant. The large heterotic effects of chromosome segments marked by particular loci suggest that enzyme loci could be used to help transfer genes responsible for heterosis to inbred lines. We conclude that analyses of additional inbred lines, F1 hybrids, and F2 populations in more environments will halp identify specific associations between enzyme loci, or chromosome segments which they mark, and important agronomic traits.Cooperative investigations of the USDA, ARS and Dept. of Plant Sciences, South Dakota State Univ. (SDSU), Brookings, Journal Series No. 2039; and the Institute of Animal Resource Ecology, Univ. of British Columbia, Vancouver, B.C. V6T 1W5, Canada     

The Genetic Basis of Natural Variation in Kernel Size and Related Traits Using a Four-Way Cross Population in Maize

Kernel size is an important component of grain yield in maize breeding programs. To extend the understanding on the genetic basis of kernel size traits (i.e., kernel length, kernel width and kernel thickness), we developed a set of four-way cross mapping population derived from four maize inbred lines with varied kernel sizes. In the present study, we investigated the genetic basis of natural variation in seed size and other components of maize yield (e.g., hundred kernel weight, number of rows per ear, number of kernels per row). In total, ten QTL affecting kernel size were identified, three of which (two for kernel length and one for kernel width) had stable expression in other components of maize yield. The possible genetic mechanism behind the trade-off of kernel size and yield components was discussed.     

Analysis of genetic distance by SSR in waxy maize

We examined the genetic diversity of 80 inbred waxy maize lines using 22 SSR molecular markers that could be used to achieve heterosis in waxy maize. Eighty inbred waxy maize lines with different phenotypes, 40 yellow, 25 white, 13 black, and two red lines were analyzed by SSR molecular marker fingerprint and cluster analysis. Using a standard genetic distance of 0.55, the 80 waxy maize inbred lines were clustered into nine groups. Among them, group II, group V, groups VII and VIII, and group IX were divided into three subgroups at a genetic distance of 0.46, into two subgroups at 0.49, into two subgroups at 0.46, and into four subgroups at 0.493, respectively. All but one of the yellow waxy maize inbred lines were clustered in groups VI, VII, VIII, and IX. Group IX (30 lines) contained 28 yellow lines; the other 11 yellow lines were distributed among groups VI, VII and VIII. Among the 25 white lines, 21 were clustered in groups III, V, VI and the third subgroup of group II. The black line N72 was in a group of its own. The black lines N75, N76 and N78 were distributed in groups VII, VIII and IX, respectively. The other nine black lines were clustered in group II. The red lines were distributed in the second subgroup of group II and there was no difference in genetic distance between them. In conclusion, there were considerable genetic differences among waxy maize inbred lines of different colors. The mean genetic distance of inbred lines of the same color was significantly less than that of lines of different colors. Therefore, we concluded that it was more accurate to determine the difference between the populations using the highly stable DNA genetic markers.     

EMS对三个玉米自交系的诱变效应分析

EMS诱变玉米花粉是玉米化学诱变的主要技术。该研究以生产上3个常用的玉米自交系K305、21-ES、R08为材料,对其花粉用不同浓度的EMS诱变处理,探讨其EMS诱变的最佳浓度范围,明确其诱变效应。结果表明：3个自交系经过不同浓度的EMS诱变后,其结实率随着浓度的增大表现出减小的趋势,从其半致死剂量来看,EMS诱变花粉的适宜浓度范围自交系K305和R08均为0.67~1.0 mL?L-1,21-ES在1.67 mL?L-1附近。 M1代不同性状其变异幅度和变异系数与对照相比主要表现出增大的趋势,其不同性状的生物学效应在材料间表现不一致,表明性状在不同材料间对EMS的敏感性不一样,生育期表现为21-ES>K305>R08;主要株型性状表现为R08>21-ES>K305;主要雄穗性状K305和21-ES比R08敏感;主要果穗性状表现为21-ES>K305>R08。 M2代整体表现为变异谱扩大,其株高、穗位高和叶面积以及主要果穗性状的变异表现复杂,主要雄穗性状中除K305的M2株系雄穗分枝数呈双向变异外,其余M2株系整体偏向于雄穗变短,雄穗分枝数减小。该研究结果为后续研究和应用打下了基础。     

Molecular characterization of endophytic strains of Fusarium verticillioides (= Fusarium moniliforme) from maize (Zea mays. L)

The species Fusarium verticillioides (= F. moniliforme) is often found in maize seeds, constituting an important source of inoculum in the field. Fusarium spp., associated with symptomatic and asymptomatic plants, may be a primary causal agent of disease, a secondary invader or an endophyte. In the present work, endophytic fungi were isolated from two populations of Zea mays (BR-105 and BR-106) and their respective inbred lines. Within different inbred lines of maize, Fusarium was found at a frequency of 0 to 100% relative to the number of total isolated fungi. The frequency with which the genus occurred was practically the same in the two field sites (around 60%). Twenty-one F. verticillioides strains were analysed using the random amplified polymorphic DNA (RAPD) technique, employing 10 random primers. Variability analysis of endophytic isolates via RAPD showed genome polymorphism taxa of species around 60%. Endophytic isolates were clustered by their sites of origin. RAPD analysis clustered the endophytic isolates by their maize inbred lines hosts (Mil-01 to Mil-06), whereas at site A they clustered into two major groups related to the maize gene pool (BR-105 or BR-106 population). All strains isolated from seeds collected in Site A, except strains L9 and L10, were sub-grouped according to maize inbred lines. The analysis showed a discrete sub-grouping at site B. Results obtained here could be explained by a co-evolution process involving endophytic isolates of F. verticillioides and maize inbred lines.     

Identification of quantitative trait loci for nitrogen use efficiency in maize

Intensively managed crop systems are normally dependent on nitrogen input to maximize yield potential. Improvements in nitrogen- use efficiency (NUE) in crop plants may support the development of cropping systems that are more economically efficient and environment friendly. The objective of this study was to map and characterize quantitative trait loci (QTL) for NUE in a maize population. In preliminary experiments, inbred lines contrasting for NUE were identified and were used to generate populations of F2:3 families for genetic study. A total of 214 F2:3 families were evaluated in replicated trials under high nitrogen (280 kg/ha) and low nitrogen (30 kg/ha) conditions in 1996 and 1997. Analysis of ear-leaf area, plant height, grain yield, ears per plant, kernels number per ear, and kernel weight indicated significant genetic variation among F2:3 families. The heritability of these traits was found to be high (h2=0.57–0.81). The mapping population were genotyped using a set of 99 restriction fragment length polymorphism (RFLP) markers. A linkage map of these markers was developed and used to identify QTL. Between two and six loci were found to be associated with each trait. The correspondence of several genomic regions with traits measured under nitrogen limited conditions suggests the presence of QTL associated with NUE. QTLs will help breeders to improve their maize ideotype of a low-nitrogen efficiency by identifying those constitutive and adaptive traits involved in the expression of traits significantly correlated with yield, such as ear leaf area and number of ears per plant. This revised version was published online in June 2006 with corrections to the Cover Date.