小鼠电融合胚胎发育影响因素的研究

电融合技术，是获得四倍体胚胎的主要手段．本试验研究了各种不同因素，对小鼠电融合胚发育的影响．结果表明，电刺激前后，使用不同的操作液对融合胚发育有影响．电刺激前使用Ｍ２液、电刺激后在Ｗｈｉｔｔｅｎ氏液中融合，然后转入ＣＺＢ液中培养，这一操作体系（Ｍ／Ｗ—ＣＺＢ）效果最好，融合胚的囊胚发育率为８０．５％，显著高于Ｍ／Ｗ—Ｗ，Ｗ／Ｗ—Ｗ，Ｗ／Ｗ—ＣＺＢ组，后者的囊胚发育率分别为０，０，５４．５％（Ｐ＜０．０５）．试验还发现，刺激强度为１．０ｋｖ／ｃｍ，８０μｓ；１．０ｋｖ／ｃｍ．４０μｓ和０．８ｋｙ／ｃｍ，８０μｓ时，融合囊胚的发育率分别为７９．０，８１．９和７１．１％．ＨＣＧ注射后４７ｈ、４８ｈ的２—细胞胚胎的融合胚发育率，显著高于（Ｐ＜０．０１）ＨＣＧ注射后４２ｈ、４４ｈ和４６ｈ的，囊胚发育率分别为８２．９，８０．６，０，０和２２．８％．     

罗非鱼染色体组操作研究现状与展望

罗非鱼属鲈形目(Perciformes),丽鱼科(Cichlidae),约有700种,主要分布于非洲。按照Trewavas[1]分类法,可把罗非鱼分为3个属,即Tilapia属、Sarotherodon属和Oreochromis属。目前,有生产应用价值的主要是Oreochromis属的尼罗罗非鱼(O.niloticus)、奥利亚罗非鱼(O.aureus)以及莫桑比克罗非鱼(O.mossambicus)[2]。罗非鱼具有生长快、食性杂、繁殖快、产量高和味道鲜美而少刺等优良特征,近年来,全球罗非鱼养殖产量逐年递增,现已成为世界性主要养殖鱼类之一。这就迫使人们不断对养殖罗非鱼进行遗传改良,以防其种质退化。当前,国内外除了人工选…     

葡萄二倍体与四倍体品种间杂交胚挽救取样时期的确定

 通过系统测定葡萄二倍体与四倍体品种间杂交胚珠的重量变化和解剖观察胚珠的发育情况，判断其败育发生时期和发生方式，并进一步通过胚珠培养试验确定取样时期。与无核品种不同，大多数有核品种与倍性不同的品种杂交后，胚珠的败育存在个体间差异。胚珠发生败育的时期与母本品种的成熟期相关，早熟品种从花后第5周开始出现败育胚珠，中熟品种开始败育时期比早熟品种晚1周，晚熟品种花后9周才开始败育。胚挽救的取样时期可以根据母本品种成熟期确定，早熟品种为授粉后6～9周，中熟品种为授粉后7～10周，晚熟品种为授粉后9～12周。     

四倍体百合体细胞形态发生中三种同工酶谱变化的研究

首次报道了四倍体龙牙百合体细胞形态发生的激素调控及不同形态发生类型中酯酶、淀粉酶与过氧化物酶同工酶谱动态变化的研究结果。ＭＳ培养基中分别添加６－ＢＡＩ～２ｍｇ／Ｌ和２，４－Ｄ２ｍｇ／Ｌ，四倍体龙牙百合鳞片叶外植体则分别按器官型和器官发生型两种途径进行形态发生；分析上述３种酶同工酶谱，发现它们分别反映出其形态发生的进程，但在两种不同途径中存在明显差异，主要表现器官发生型形态发生其细胞内同工酶经历了比器官型形态发生更为深刻的变化，表明这３种酶同工酶谱的变化与形态发生明显相关，可以作为形态发生进程及途径确定的重要生化指标。     

四倍体刺槐离体培养及其不定根发育和叶片解剖观察

 .通过茎段离体培养建立了四倍体刺槐无性系的微体繁殖体系。结果表明:基本培养基为MS或WPM培养基。BA、NAA影响芽的增殖生长,在一定的范围内,BA对芽的增殖影响比NAA大,而NAA对芽的高生长影响比BA大,二者的比例对芽的增殖生长也有影响,芽增殖生长的最适BA和NAA组合应为BA0.5mg·L-1+NAA0.1mg·L-1。四倍体刺槐无性系生根的最适生长调节物质配比为NAA0.25mg·L-1+IBA0.4mg·L-1。对试管苗不定根发育过程及分步炼苗叶片结构的变化进行了解剖观察,发现试管苗嫩梢无潜伏根原基,不定根由诱生根原基发育形成,诱生根原基源于髓射线细胞的分裂和分化,植株叶解剖观察,进一步证明了分步炼苗可提高移栽成活率。     

Geographic variation in tetraploid wheat (Triticum turgidum spp. turgidum convar. durum) landraces from two provinces in Ethiopia

There is considerable wealth of genetical and morphological variation in tetraploid wheat collected from Ethiopia by past expeditions. Several authors have speculated on the reasons for this concentration of diversity so far removed from the centre of origin of wheats in West Asia. The present study reports results of evaluation carried out on material collected in the early 1970's from Ethiopia. The landraces from the two provinces Shewa and Tigray were found to be distinctly different. This divergence was attributed to the differences in environmental conditions between them. Wide differentiation among landraces within each province was also present. The Ethiopian farmer's practice of growing composite cultivars in the field has resulted in bulk samples of Ethiopian landraces containing several agrotypes. The proportion of total variance due to differences among agrotypes within landraces was by far the greatest found in this study, followed in most cases by the variation among landrace populations within provinces which exceeded, in turn, the variation between province gene pools. The optimal strategy for further germplasm collections and implications for improvement and conservation in locally-based community gene banks are discussed.     

Phylogenetic relationships among natural populations of perennial buckwheat, Fagopyrum cymosum Meisn., revealed by allozyme variation

Twenty natural populations of F. cymosum, an insect-pollinated allogamous wild species of Fagopyrum, were investigated for their chromosome number and allozyme variation at 10 Ioci encoding 8 enzymes. Diploid populations were obtained in Sichuan, Yunnan and Tibet in China, whereas tetraploid populations were obtained in Tibet, the Himalayan hills, Thailand and southern China. Both diploid and tetraploid populations maintained a large amount of allozyme variation. The average heterozygosity, H_e, ranged from 0.045 to 0.389 (0.213 on average). Tetraploid populations showed higher H_e values than diploid populations. Natural populations of F. cymosum were locally well differentiated (G_ST = 0.322), probably due to reproductive isolation between the two ploidy levels and to distribution over wide areas from southern China to the Himalayan hills. The phylogenetic tree constructed by the neighbor-joining method based on allozyme variation clarified two distinct groups of diploid populations, the Sichuan and Yunnan groups. As for the tetraploid populations, polyploidization occurred twice independently, once in Yunnan and once in eastern Tibet. Tetraploid F. cymosum diffused to warmer areas such as southern Yunnan and Thailand as well as to cooler areas of Tibet and the high Himalayan hills and became the most widely distributed of the Fagopyrum species.     

Significance of allelic diversity and 2n gametes for approaching maximum heterozygosity in 4 x ppotatoes

Summary High level of heterozygosity is directly related to heterosis for yield in polysomic polyploids. Modern breeding schemes in potato (2n=4×=48) involve utilization of wild or cultivated 2 x relatives that provide a source of allelic diversity, and 2n gametes that transfer diversity to the 4 x level. Different levels of allelic diversity and different modes of 2 n egg formation were considered theoretically to determine their significance for the recovery of heterotic 4 x progeny from 2××4× crosses. The support from the experimental data is provided.Decline in parental allelic diversity in 2××4× crosses or 4××4× crosses resulted in significant yield reduction. The average level of homozygosity and loss of intra-locus interactions are equally adequate to predict the trend in yield changes in 4 x potatoes derived from parents of variable allelic diversity utilizing different modes of 2 n egg formation.The differences between the modes of 2 n gamete formation increase when the genetic diversity decreases. The more genetically diverse parents the less pronounced differences between 2 n gametes. Breeding of 4 x cultivars for polygenic traits where nonadditive effects are important should be oriented towards maximizing heterozygosity in terms of allelic diversity. Utilization of 2 n gametes to generate 4 x progeny following 2×–× or 2×–2× crosses upgrades the level of heterozygosity depending on diversity present in parents.     

Influence of genotype and culture conditions on the production of embryos from anthers of tetraploid wheat (Triticum turgidum)

Summary Anther culture of 10 tetraploid wheat (Triticum turgidum) genotypes and two backcross lines representing a wide range of genetic variation was studied in a randomized block design with three replications. Each replication consisted of 2 pots with 3 plants. The day length was 16h and temperature 25° C/15°C for day/night in a controlled greenhouse where the anther donor plants were grown. Two different treatments were used for anther culture. The first one was potato 2 medium (Chuang et al., 1978) modified by adding 0.5 mg/l glutamine and solidified by gelrite (4g/l) (Henry & De Buyser, 1981). Cultures were incubated in light (15 E m^–2 S^–1) at 26°C at 16h day length. The second medium was described by Fadel & Wenzel (1990), differing from the first by the nature of the sugar (maltose) and consistency of the medium (semiliquid by ficoll). Anther cultures were incubated in the dark at 28°C. The study of about 1300 anthers per genotype and treatment showed that both genotype and treatment affected embryo formation of tetraploid wheat. The backcross lines exhibited significant differences for androgenic abilities when compared to their common parent. Most of the genotypes were medium dependent for androgenesis and revealed significant interactions with the two treatments. Five green plantlets were regenerated and fertile doubled haploid plants were obtained from three out of the 12 studied genotypes.     

栽培措施对四倍体刺槐生物量的影响

为了探索根龄、栽培密度和刈割方法对四倍体刺槐饲料林生物量及再生能力的影响,确定合理的饲料林栽培模式,对不同根龄、不同密度、不同刈割周期及留茬高度和不同刈割工具及刈割部位的当年生林分从总质量、叶质量等生物量指标方面进行了测量分析.结果表明:四倍体刺槐饲料林生物量随根龄的增长而增加;其合理的栽培密度为0.4 m×0.8 m...