The theropod ancestry of birds: new evidence from the late cretaceous of madagascar     

CA Forster  SD Sampson  LM Chiappe  DW Krause 《Science (New York, N.Y.)》1998,279(5358):1915-1919

A partial skeleton of a primitive bird, Rahona ostromi, gen. et sp. nov., has been discovered from the Late Cretaceous of Madagascar. This specimen, although exhibiting avian features such as a reversed hallux and ulnar papillae, retains characteristics that indicate a theropod ancestry, including a pubic foot and hyposphene-hypantra vertebral articulations. Rahona has a robust, hyperextendible second digit on the hind foot that terminates in a sicklelike claw, a unique characteristic of the theropod groups Troodontidae and Dromaeosauridae. A phylogenetic analysis places Rahona with Archaeopteryx, making Rahona one of the most primitive birds yet discovered.  相似文献   

水稻大面积高产综合配套技术研究开发与示范1996年度课题攻关报告   总被引：1，自引：0，他引：1  

湖南省课题攻关协作组 《中国水稻科学》1998,12(Z1):1-3

总结了1996年水稻大面积高产综合配套技术研究开发与示范的进展。  相似文献   

带有黄绿叶色标记的香型籼稻不育系形态特征及开花习性   总被引：1，自引：0，他引：1  

刘国民  高必军  文绍山 《分子植物育种》2009,7(5):916-921

我们对3个含有黄绿叶色标记的香型籼稻不育系黄标1A、黄标2A、黄标3A和正常绿叶不育系Ⅱ-32A、G46A的形态特征及开花习性进行了调查分析。结果表明：黄标1A、黄标2A、黄标3A不育系同正常叶色不育系Ⅱ-32A、G46A的叶色差异显著,易肉眼识别,其外部形态特征为植株叶片及颖壳呈黄绿色,黄标A株系株高（41.5～56.5cm）比Ⅱ-32A（59.5cm）、G46A（60.4cm）要矮,以黄标3A的播始期85d比Ⅱ-32A短8d、比G46A长7d,穗长、穗平着粒与Ⅱ-32A、G46A相当,千粒重比Ⅱ-32A、G46A高出1.8g和1.47g,其中颖尖、叶鞘、叶耳及叶片边缘呈紫红色。黄标1A、黄标2A、黄标3A不育系的柱头外露率、张颖角度都高于Ⅱ-32A和G46A,柱头生活力供试不育系间存在着生理功能的差异。包颈长度Ⅱ-32A最长,黄标1A、黄标2A、黄标3A与G46A相当;半包颈长度黄标1A、黄标2A和黄标3A相当（3.0～3.5cm）、而Ⅱ-32A最长（5.0cm）、G46A次之（4.5cm）。黄标1A、黄标2A、黄标3A不育系的开花动态相似,曲线呈双峰型,开花高峰为开花后的第2～5天,与Ⅱ-32A的开花动态相似,但Ⅱ-32A有明显的低谷,而G46A曲线呈单峰型。不同不育系所开的颖花数并不一样,以开花第8天统计开花数以黄标2A最多,其次是黄标3A,黄标1A和对照Ⅱ-32A开花数相同,而G46A到第8天开花结束。黄标1A、黄标2A的开花盛期与Ⅱ-32A一致,为开花后第5天,而黄标3A与G46A一致,为4d。参试不育系每天上午10：00时初花、11：00～12：30时为开花盛期,只有G46A表现出迟花特性。  相似文献   

Breeding of R8012,a Rice Restorer Line Resistant to Blast and Bacterial Blight Through Marker-Assisted Selection     

ZHAN Xiao-deng  ZHOU Hai-peng  CHAI Rong-yao  ZHUANG Jie-yun  CHENG Shi-hua  CAO Li-yong  Chinese National Center for Rice Improvement  State 《水稻科学》2012,19(1):29-35

Genetic improvement is one of the most effective strategies to prevent rice from blast and bacterial blight(BB) diseases,the two most prevalent diseases jeopardizing rice production.Rice hybrids with dural resistance to blast and BB are needed for sustainable production of food.An incomplete diallele design resulted in 25 crosses between five blast and five BB resistant germplasm accessions.Only one pair of parents,DH146 × TM487,showed polymorphism for all the markers to identify one blast resistance gene Pi25 and three BB resistance genes,Xa21,xa13 and xa5,thus it was used in the marker-assisted selection(MAS).F2 individuals of DH146 × TM487 were genotyped using flanking markers of RM3330 and sequence tagged site(STS) marker SA7 for Pi25.The resistant F2 plants with Pi25 were used for pyramiding BB resistance genes Xa21,xa13 and xa5 identified by the markers pTA248,RM264 and RM153,respectively in subsequent generations.Finally,after selection for agronomic traits and restoration ability among 12 pyramided lines,we acquired an elite restorer line,R8012 including all four target genes(Pi25+Xa21+xa13+xa5).Hybrid Zhong 9A/R8012 derived from the selected line showed stronger resistance to blast and BB,and higher grain yield than the commercial checks uniformally in experimental plots,2007 state-wide yield trial and 2008 nation-wide yield trial.This study provides a paradigmatic example to show that MAS is a practically feasible tool in effectively pyramiding multiple resistance genes.The resultant restoring line and its hybrid would play an important role in securing rice production in China.  相似文献   

Biotic and abiotic controls on body size during critical life history stages of a pelagic fish,Pacific herring (Clupea pallasii)     

Jonathan C. P. Reum  Timothy E. Essington  Correigh M. Greene  Casimir A. Rice  Patrick Polte  Kurt L. Fresh 《Fisheries Oceanography》2013,22(4):324-336

Variation in growth and body size during critical life history stages can have important implications for life history schedules and survivorship. For Pacific herring (Clupea pallasii), there is still debate as to whether juvenile body size is governed by density‐dependent or ‐independent processes and few have evaluated whether the relative importance of either process shifts over the course of early ontogeny. We used a unique data set consisting of seasonal measurements of abundance, body size, and spatial distribution within a semi‐enclosed basin of Puget Sound (Washington State, U.S.A.) to measure the relative importance of temperature and cohort abundance on body size at distinct time periods, and evaluated whether density‐dependent habitat shifts might be responsible for density‐dependent growth. Over the 9 years of sampling (2001–2010) midsummer body size was positively related to temperatures experienced during the egg/yolk sac and larval stages and unrelated to cohort abundance. However, fall body size was negatively correlated with abundance and uncorrelated with both midsummer body size and temperature, indicating a shift from density‐independent to density‐dependent control over the course of the growing season. Thus, density‐dependent effects may supplant density‐independent effects exhibited early in herring life history. Our data on spatial distributions of herring and their zooplankton prey indicate that density‐dependent reductions in growth may be explained by density‐dependent habitat shifts that lead to reduce overlap of herring with zooplankton. Evidence of density‐dependent growth in marine fish populations is often attributed to exploitative competition, but our results suggest that these patterns may partly be mediated by density‐dependent distribution expansions in to prey‐poor habitat.  相似文献   

两系不育系P88S育性转换的积温模型构建(英文)     

王志伟  吉达维  张芹  华泽田 《（《农业科学与技术》）编辑部》2011,(8)

[目的]构建两系不育系水稻P88S育性转换的积温模型。[方法]对2005年和2006年P88S在海南育性转换的试验数据进行分析。[结果]发现P88S在气温在26～28℃之间的可育性是由温度的绝对值和温度的累积效应决定的,并得到了1个基于双稳态的温度累积效应模型。[结论]利用积温模型可以有效地说明两系不育系春秋季育性转换温度的不对称性,即从可育转换为不育需要更高的温度,从不育转换为可育则需要更低的温度,并说明影响水稻育性的因素可能存在累加效应。  相似文献   

Spotted-Leaf Mutants of Rice(Oryza sativa)     

HUANG Qi-na  #  YANG Yang  SHI Yong-feng  CHEN Jie  WU Jian-li State Key Laboratory of Rice Biology/Chinese National Center for Rice Improvement  China National Rice Research Institute  Hangzhou  China  College of Life  Environmental Sciences  Hangzhou Normal University  Hangzhou 《水稻科学》2010,17(4):247-256

Many rice spotted-leaf(spl) mutants are ideal sources for understanding the mechanisms involved in blast resistance,bacterial blight resistance and programmed cell death in plants.The genetic controls of 50 spotted-leaf mutants in rice have been characterized and a few spotted-leaf genes have been isolated as well.This article reviews the origin,genetic modes,isolation and characterization of spotted-leaf genes responsible for their phenotypes,and their resistance responses to main rice diseases.  相似文献   

Australian Oryza: Utility and Conservation     

Robert J. Henry  Nicole Rice  Daniel L. E. Waters  Shabana Kasem  Ryuji Ishikawa  Yin Hao  Sally Dillon  Darren Crayn  Rod Wing  Duncan Vaughan 《Rice》2010,3(4):235-241

Australian Oryza are an understudied and underexploited genetic resource for rice improvement. Four species are indigenous: Oryza rufipogon, Oryza meridionalis, Oryza australiensis are widespread across northern Australia, whereas Oryza officinalis is known from two localities only. Molecular analysis of these wild populations is required to better define the distinctness of the taxa and the extent of any gene flow between them and rice. Limited collections of these wild populations are held in seed and DNA banks. These species have potential for domestication in some cases but also have many traits of potential value in the improvement of domesticated rice. Stress tolerance (biotic and abiotic) and grain quality characteristics in these populations may be useful.  相似文献   

Molecular Mechanism of Rice in Response to Salt Stress     

E Zhi-guo  ZHANG Li-jing  WANG Lei  .China National Rice Research Institute  Hangzhou  ;  .State 《农业科学与技术》2011,(6):785-788

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Roles of bootstrap resampling,measure of central tendency,and method for calculating thermal units when developing phenology models for pest management     

DE Legg  SM Van Vleet  DW Ragsdale  RW Hansen  LC Skinner  TR Collier 《国际虫害防治杂志》2013,59(4):319-325

The successful development of phenology models from field studies depends on many factors, some of which are entirely under the control of pest managers. For example, one such factor is the choice of method for calculating thermal units. In this study, we have demonstrated that four methods for calculating thermal units provided for acceptable predictions of one phenological event of one insect species, while another method for calculating thermal units did not. The measure of central tendency (mean or median) that is used to estimate lower developmental temperatures and required thermal summations is another factor that pest managers can control when developing phenology models from field studies. Here, we show that predictions that were made when using phenology models based on median lower developmental temperatures and median required thermal summations were superior to predictions that were made when using phenology models based on mean lower developmental temperatures and mean required thermal summations. The use of bootstrap vs. non-bootstrap estimates of lower developmental temperatures and required thermal summations is yet another factor that pest managers can control when developing phenology models from field studies. In this study, we found that calculating and using bootstrap estimates of lower developmental temperatures and required thermal summations in phenology models did not improve the predictions of one phenological event for one insect species. The implications of these and other findings are discussed.  相似文献