水稻中胚轴伸长特性的遗传分析

以长中胚轴/短中胚轴杂交组合的两个亲本、F₁、B₁、B₂和F₂为试验材料，在小型人工气候箱黑暗条件下培养幼苗，对水稻中胚轴伸长特性的遗传规律进行了研究。结果表明，中胚轴伸长特性受两对隐性基因控制。F₂群体中长、短中胚轴植株在节间长度、穗长、株高和剑叶长等性状上均存在较明显的差异，而中胚轴伸长特性与节间粗、剑叶宽、单株穗数、每穗总粒数、结实率、千粒重和单株产量等性状关系不明显。还对水稻中胚轴伸长特性的遗传改良以及长中胚轴材料在直播稻育种上的利用进行了探讨。     

外源激素对水稻中胚轴伸长的影响

国际水稻研究所的研究表明,水稻直播法优于栽培法,直播法不仅省工、省水,而且免除了稻农弯腰躬背之累,减轻劳动强度,还使水稻幼苗未遭拔秧引起的损伤,前期生长条件好,营养生长快,比移栽稻成熟早,即使在缺水情况下,其单产也高于移栽稻[1].但出苗难是目前制约直播稻发展的国际性难题之一.直播大田出苗率与中胚轴长度密切相关[2].目前所用的一些半矮秆品种,直播时由于中胚轴较短,苗难于出土[3,4],中胚轴长的品种适于直播,其种子发芽后,中胚轴明显伸长,顶土能力强,且直播后能通过较长时间淹水以控制杂草萌发,保持较高出苗率;另外在大干旱年份(如1994年夏),可深播以利于种子吸取必要的水分[9],其中胚轴伸长使苗出土,仍保持较高出苗率.过去,对于这个问题的解决是从栽培方法着手,而关于外源激素对品种中胚轴伸长的影响研究甚少.激素在植物的生长和发育过程中起着重要的调控作用,它能诱导种子休眠,抑制种子萌发和胚芽鞘的伸长,促进幼胚合成蛋白并且能对多种环境胁迫做出反应等[5～8].本文探究外源激素对水稻中胚轴伸长的影响,将有利于水稻直播技术在我国的进一步发展.     

高粱出苗能力的遗传研究

本文利用4个不育系和4个恢复系、两组亲本及其16个杂种、两个杂交组合的F_2为材料研究了高粱胚轴伸长潜力、出苗日数和出苗率的遗传规律及其相互关系.结果表明,高粱胚轴伸长潜力和出苗日数具有较高的遗传力,其基因系统的加性效应占主导地位;品种胚轴伸长潜力大小是出苗率高低的决定因素;出苗日数与胚轴伸长潜力呈高度负相关.     

多胺氧化酶(PAO)调控光诱导玉米中胚轴伸长的生理机制

以长中胚轴玉米自交系PH4CV为材料,在黑暗和光照两种处理条件下研究了玉米中胚轴长度与多胺氧化酶(Polyamine Oxidase, PAO)活性、H₂O₂含量、过氧化物酶(peroxidase, POD)活性及木质素含量的关系。通过添加5 mmolL^-1 PAO抑制剂2-羟乙基肼(2-hydroxyethylhydrazine, 2-HEH)和5 mmolL^-1 H₂O₂清除剂N,N’-二甲基硫脲(N,N’-Dimethylthiourea, DMTU)及组织化学染色,研究了影响中胚轴伸长的H₂O₂来源及其积累部位。采用实时荧光定量PCR(qRT-PCR)方法,探究了光对ZmPAO基因表达的影响。结果表明,光照处理显著抑制了玉米中胚轴的伸长,同时显著增加该部位的PAO活性、H₂O₂含量、POD活性及木质素含量。相关性分析表明,玉米中胚轴长度与PAO活性、H₂O₂含量和木质素含量呈极显著负相关,与POD活性呈显著负相关;PAO活性与H₂O₂含量、POD活性和木质素含量均呈正相关。外源PAO抑制剂和H₂O₂清除剂处理试验,玉米中胚轴表皮纵切面细胞长度显微观察及中胚轴H₂O₂组织化学染色表明,PAO氧化分解多胺(Polyamines, PAs)产生的H₂O₂参与了中胚轴细胞伸长的生理调控,从而抑制了中胚轴的伸长。表达分析表明,ZmPAO基因在黑暗环境下的表达量相对稳定,光刺激0.5 h后表达量迅速升高,3 h后达到最大值,随后逐渐下降,10 h后趋于稳定。本研究表明,PAO在接受光刺激后活性升高,氧化分解PAs产生H₂O₂,从而诱导POD氧化胞壁的单木质醇并聚合为木质素,使细胞壁硬化,造成细胞伸长受阻。研究结果为进一步探讨PAO活性调控光诱导玉米中胚轴伸长的生理机制和阐明玉米中胚轴对光逆境的响应机理提供了理论依据。     

不同高粱种质幼苗器官形态与出苗能力关系的研究

高粱是世界上重要的禾谷类作物,具有抗旱、耐盐碱和耐贫瘠等多重抗性。种子出苗率低一直是高粱种植的制约因素之一,给高梁的机械化种植造成很大影响。本研究于2014年选用不同高梁种质进行室内发芽试验,通过设置不同播种深度研究高粱种质出苗率、中胚轴和胚芽鞘长度与覆土深度的关系。结果表明,杂交种发芽率和发芽势均表现出一定程度的正向中亲优势,变幅分别为5.45%~10.18%和9.59%~13.69%;随着播种深度增加,出苗率逐渐下降;播种深度越深中胚轴越长,但对胚芽鞘影响不显著;供试高粱材料不同播深(2cm和6cm)处理的中胚轴长度差与出苗率变化呈显著负相关(R2=一0.7065*),表明中胚轴的伸长能力是不同播种深度处理出苗率变化的重要因素。     

水稻已克隆中胚轴伸长基因效应解析及优异单倍型鉴定

旱直播是未来水稻生产的重要发展方向,在南亚和东南亚籼稻种植区已有较大面积,然而热带和亚热带地区粳稻种植多采用传统育苗移栽。中胚轴长度(Mesocotyl length,ML)是影响水稻旱直播出苗和幼苗活力的重要因素。基于分子标记辅助选择(Molecular marker assisted selection,MAS)育种,培育长中胚轴种质是促进水稻旱直播推广最为经济、高效的方式。迄今,已有4个水稻中胚轴伸长基因报道,即OsGSK2、GY1、OsPAO5和OsSMAX1。笔者选择3K重测序项目中TROP和TEMP粳稻亚群开展分析,测定中胚轴长度并鉴定OsGSK2、GY1、OsPAO5和OsSMAX1基因的优异单倍型。结果表明,TROP和TEMP亚群中胚轴长度呈典型的连续正态分布。OsGSK2、GY1、OsPAO5和OsSMAX1分别包括3、3、3和6种单倍型;同一基因在TROP和TEMP亚群中单倍型分布频率也存在差异。TROP亚群中OsGSK2-Hap1、GY1-Hap2、OsPAO5-Hap3、OsSMAX1-Hap2和OsSMAX1-Hap3为优异单倍型;TEMP亚群优异单倍型为Os...     

长根茎高粱种质资源的筛选

为了筛选不同血缘的长根茎高粱种质资源,选育高出苗率高粱杂交种,本试验选用36份中国高粱材料,26份美国高粱材料,12份印度高粱材料,共74份高粱材料为研究对象,测量黑暗发芽后胚轴和胚芽鞘长度。试验结果表明:所有参试材料中中国高粱的胚轴长度和胚芽鞘长度均显著高于美国和印度的高粱材料,而且不同来源的材料胚轴长度变异系数均显著大于胚芽鞘长度变异系数;通过胚轴长度聚类分析选出12份不同来源的长胚轴材料,其中中国的材料9份(‘24517’、‘晋五/Hc356·Sc499’、‘HM65/LE83472’、‘国窖红1号’、‘锦Y11’、‘1383-2’、‘赤7788’、‘沈院0-01’、‘三尺三’)、美国材料2份(‘Hc378B’、‘LR287-2’)、印度的材料1份(‘E565’)。为后续选育长胚轴杂交种提供了依据。     

南北方不同类型高粱的酿酒品质差异

对南北方不同类型高粱酿酒品质的差异进行了分析，南北方高粱的蛋白质和总淀粉含量都比较接近，差异在于：北方高粱绝大多数属于粳型品种，直链淀粉含量高，单宁含量低，角质含量高，其平均含量分别为２７．３５％、０．２８％和７５％；而南方高粱９０％以上属于糯型品种，直链淀粉含量低，单宁含量高，角质含量低，平均含量分别为５．２１％、１．４９％和３５％。     

水稻中胚轴长度QTL分析

为分析水稻中胚轴伸长与赤霉素的关系及其遗传基础,以沈农265(长中胚轴)和丽江新团黑谷(短中胚轴)的RIL群体为材料,结合其连锁图谱,对水和赤霉素溶液两种培养条件下的中胚轴长度进行QTL定位。结果表明,浓度为1.50μmolL~(-1)的赤霉素可显著促进中胚轴的伸长。两种培养条件下,共检测到控制中胚轴长度的5个QTL,分布在第1、第2、第3、第6和第11号染色体上,LOD值在3.65～15.52范围内,单个QTL对表型贡献率在7%～33%之间。其中qML3、qML6和qML11在2种处理条件下均被检测到,qML1和qML2仅在水培条件下被检测到。与其他研究比较发现,主效基因qML3可以在不同群体和不同环境下稳定表达。     

高粱与苏丹草杂种优势利用的研究

高粱与苏丹草杂种优势明显,F1单株生物产量性状高于双亲平均值,甚至超过或接近高亲。影响高粱-苏丹草杂交种单株茎叶鲜重的主要因素是主茎粗、叶长;决定单位面积鲜草产量的主要是密度、叶长和单株茎叶鲜重。多年随机区组试验结果表明,杂交种单位面积鲜草产量显著超过苏丹草,并以30万株/hm2为最适种植密度。杂交种营养品     

Combining ability and heterosis as influenced by male-sterility inducing cytoplasms in sorghum [Sorghum bicolor (L.) Moench]

An investigation was carried out to assess the efficiency of A₂ cytoplasmic-nuclear male-sterility (CMS) system in comparison to the widely used A₁ cytoplasm in terms of general combining ability (gca) effects of male-sterile (A-) lines and mean performance, specific combining ability (sca) effects and mid-parent heterosis of hybrids for days to 50% flowering, plant height and grain yield at International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India in 2001 and 2002 rainy seasons. The material for the study consisted of six pairs of iso-nuclear, allo-plasmic (A₁ and A₂) A-lines and 36 iso-nuclear hybrids produced by crossing these A-lines with three dual restorer (R-) lines. The results revealed that cytoplasm and its first-order interaction with year, R- and A-lines did not appear to contribute to variation in iso-nuclear hybrids for plant height and grain yield. Cytoplasm had limited effect on gca effects of A-lines and on sca effects and mid-parent heterosis of iso-nuclear hybrids for days to 50% flowering, plant height and grain yield. The mean days to 50% flowering, plant height and grain yield of A₂ cytoplasm-based hybrids were comparable with those of widely used A₁ cytoplasm-based hybrids. The relative frequency of the occurrence of the A₁- and A₂-based hybrids with significant sca effects and mid-parent heterosis indicated that A₂ CMS system is as efficient as A₁ with a slight edge over A₁ for commercial exploitation. The implications of these results are discussed in relation to opportunities for broadening not only cytoplasm base but also nuclear genetic base of both the hybrid parents.     

Genetic analysis of threshability in grain sorghum [Sorghum bicolor (L.) Moench]

The ease with which seeds are detached from panicles is one of the early domestication traits. Genotypes with sticky panicles are hard to thresh, and whenever threshed, the grain tends to remain attached to the glume which reduces market value and processability. This study was conducted to determine the genetic mechanisms underlying the threshability trait in sorghum. Four seed parents and eleven pollinators differing for threshability were intercrossed in Design II mating scheme and the resulting hybrids and the parents were grown in four environments. Threshability was estimated as the ratio of seed yield to panicle weight (TW) and proportion of seeds without sticky glumes (TG). Variation was significant among the entries, inbreds and hybrids with GCA for TG and TW varying markedly. Mean TG for inbred and hybrids of low threshable genotypes was not markedly different indicating that threshability trait is under the control of additive genes with dominant or partially dominant effects. Segregation analysis indicates that the TG trait may be under the control of few major genes with approximately one to three loci affecting the trait.     

Isozyme Analysis of Some Male Sterile Lines in Sorghum bicolor (L.) Moench

A comparative study of peroxidase and acid phosphatase of anthers was carried out on sorghum to characterize five male steriles and their maímainers. Differences in presence/absence and intensity of bands were observed for the isozyme patterns of all the male steriles and their corresponding maintainers. The better expression of enzymes in sterile anthers emphasized the role they play in breaking down various metabolites that are otherwise important for formation of fertile anthers.     

Sorghum [Sorghum bicolor (L.) Moench] landrace variation and classification in North Shewa and South Welo, Ethiopia

Fourteen phenotypic characters were chosen for the purpose of obtaining taxonomic evidence on the resemblances of 177 accessions of sorghum from North Shewa and South Welo regions of Ethiopia. Canonical Discriminant Analysis (CDA) and Modeclus cluster analysis were conducted to see if the 177 accessions could form clusters based on their morphological characters, and to test the consistency of farmers’ naming of the five most common Sorghum landraces represented by 44 accessions. Multivariate analyses grouped the 177 accessions into three clusters linked by a few phenotypic intermediate landraces. A botanical key was established for easy classification of the Sorghum crop plants grown in the study area. The number of accessions of the five most common landraces named by the farmers formed dissimilar groups, suggesting that farmers’ naming of these Sorghum landraces are consistent. Midrib color, grain color, grain size, glume color, glume hairiness, and grain shape were the leading morphological characters used by the farmers in naming these Sorghum landraces. This revised version was published online in July 2006 with corrections to the Cover Date.     

高粱微卫星分析中遗传完整性样本量的确定

采用微卫星分析高粱不同样本量对遗传多样性指数的影响,从而确定最佳样本量,为遗传完整性研究奠定基础。试验设置了10个样本量梯度,对群体的等位基因数目、有效等位基因数目、香农指数、观察杂合度、预期杂合度、多态位点百分数和稀有等位基因频率的变化趋势进行了分析。结果表明,10～40个样本量范围内,等位基因数目、有效等位基因数目、香农指数、多态位点百分数随着样本量的增大而增大;在40个样本量时,等位基因数目、有效等位基因数目和香农指数达到较高值,分别代表了100个群体98.5%的等位基因数、99.1%的有效等位基因数和98.5%的香农指数,之后样本量继续增加,各指标变化不显著。稀有等位基因频率在40个样本量以上,随着样本量的增加数值变化很小。以稀有等位基因频率、等位基因数、有效等位基因数和香农指数为多样性指标,在高粱遗传完整性研究中样本量大小的确定上达到一致性。因此,建议在用SSR技术对高粱进行遗传完整性分析时,样本量要选择40个单株以上。     

Variability for Salt Tolerance in Sorghum bicolor (L.) Moench. under Hydroponic Conditions

The response of seedlings of 51 Sorghum bicolor accessions to 0, 50, 100, 150, 175, and 200 mM NaCl in solution culture was examined. Plant growth was measured as longest root lengths, maximum shoot lengths, and total plant dry weights after 14 days. Increasing NaCl concentration caused significant reductions in all three characters. Accession response to increasing NaCl also varied. The data suggest that increase in NaCl tolerance in this species through recurrent selection may be possible.     

A genetic study of popping quality in Sorghum (Sorghum bicolor (L.) Moench)

Summary Two crosses of sorghum, Sorghum bicolor (L.) Moench (IS 1054 × ICSV-1, and IS 5604 × IS 1054) were evaluated in parental, F1, F2, and backcross generations for the variation in their popping quality as measured by pop volume (ml). Dominance was in the direction of low pop volume. Dominance and additive gene effects, in that order, governed most of the variation, while significant dominance x dominance type of interaction effects could also be detected. There was no evidence for higher order gene interactions.Approved as Journal Article 630 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, P.O. 502 324, Andhra Pradesh, India.     

Mapping of QTLs underlying flowering time in sorghum [Sorghum bicolor (L.) Moench]

Due to its critical importance in crop yield, the photoperiodic regulation of flowering time is considered an important trait in sorghum breeding programs. In this study, quantitative trait loci for flowering time were detected using an F₂ population derived from a cross between Kikuchi Zairai, a late-flowering cultivar originating from Japan and SC112, an early-flowering cultivar originating from Ethiopia. F₂ plants were grown with their parents under a natural day length and a 12 h day length. Two linkage maps were constructed using 213 simple sequence repeats markers. Nine quantitative trait loci controlling flowering time were identified in F₂ plants grown under a natural day length, whereas 7 QTLs were identified under a 12 h day length. Five QTLs controlling flowering time were shared under both of the day length conditions.