玉米改良单交种选育方法的研究

用30个遗传差异不大的Mo17改良系作用与Mo17组成姊妹种（A1×A2），再以30个姊妹种以及30个Mo17改良系作母本，与父本自交系E28，5003配成改良单交种和普通单交种，试验表明：改良单交种的产量、农艺性状和整齐度与相应的普通单交种基本一致，而姊妹种的产量明显地高于任一亲本自交系，故改良单交种具有制种产量高的优点。姊     

玉米改良单交种效应的研究──自交系48-2不同世代姊妹系配制姊妹种及改良单交种的比较

在48-2的众多姊妹系中，选出不同世代的姊妹系10个，配成姊妹种和改良单交种进行比较研究结果表明，从S_3分离形成的姊妹系配成的姊妹种，有一定的优势，有利于提高制种产量，用它们配成的改良单交种，其经济产量和主要的农艺性状与对应的正常单交种基本一致；同时还表明：一个自交系的同一姊妹种，对其所配的各改良单交种，具有不同的特殊配合力效应。     

试析玉米自交系与其姊妹种及其配制的单交种与改良单交种

该文通过对部分改良单交种与相应的常规单交种、姊妹种与相应的自交系配合力的诸多试验、对比调查资料的分析表明：其一,一些改良单交种能保持相应常规单交种的产量、抗性以及农艺性状;其二,任何一个姊妹种不能完全取代相应的自交系所配制的所有组合。     

玉米改良单交种选育方法的研究：Ⅱ.姊妹系和姊妹种的配合力研究

以ＧｒｉｆｉｎｇＩＩ双列杂交试验和ＮＣＩＩ遗传交配试验，测定玉米８个姊妹系及其２８个姊妹种的一般配合惫，结果两者基本一致。玉米妹系的一般配合力是一种遗传特性，它既可遗传给其组成的姊妹种，又能通过姊妹和种遗传给其组成的改良单交种；姊妹种的一般配合力与其双亲姊妹系一般配合力均值之间没有显著差异，并呈密切相关，这阐明了改良单交种与其对应的普通单交种相似的原因，并为改进和简化改良单交种选育程序提供理论依据     

利用种子醇溶蛋白选育玉米姊妹系和姊妹种的研究

不同分离世代产生的姊妹系配制的早晚代姊妹种在农艺性状、产量和种子蛋白图谱上存在很大的差别。大多数早代姊妹种种子蛋白谱带具有双亲的互补带，并表现出较强的优势，晚代姊妹种的种子蛋白图谱基本上与亲本相同，优势不及早代姊妹种明显。     

甘蓝型油菜隐性核不育系ZWAB临保三交种

利用甘蓝型油菜隐性核不育系ZWAB及临保系和恢复系分别配制了临保三交种、单交种进行组合的杂种优势比较。结果表明：临保三变种在抗性方面优于单交种，在经济性状及产量上与单交种相当。临保三交种完全可以替代单交种，从而节省了两系制种过程中初花期拔除50％可育株的环节，降低了劳动强度和成本，提高了制种产量和种子纯度。     

甘蓝型油菜隐性核不育系ZWAB临保三交种与单交种的比较

利用甘蓝型油菜隐性核不育系ZWAB及临保系和恢复系分别配制了临保三交种、单交种进行组合的杂种优势比较,结果表明:临保三交种在抗性方面优于单交种,在经济性状及产量上与单交种相当。临保三交种完全可以替代单交种,从而节省了两系制种过程中初花期拔除50%可育株的环节,降低了劳动强度和成本,提高了制种产量和种子纯度。     

冬小麦姊妹系间若干性状的对比研究

本试验对来自于同一株系群的14个姊妹系009、245、330、125、146、020、048、243、219、124、034、283、003、407，从产量和农艺性状等方面进行了比较研究，并以鲁麦14作为对照品种。研究发现：14个姊妹系的产量均高于对照品种鲁麦14，且增产幅度差异显著，其中以009品系增产幅度最大，产量最高，比对照品种增产达到极显著水平；各品系虽互为姊妹系，但在丰产性、农艺性状及抗逆性等方面仍存在着一定的差异；通过比较研究，上述各品系尤以009、245、330、125表现为最好，可推荐参加省或国家级区试。     

同源姊妹种与其双亲的配合力测定

被测的两个同源自交系和相配的两个姊妹种．系与系之间、系与姊妹种之间、姊妹种之间（正反交）产量差异都不显著、而产量之间的差异主要是由于测验种之间的差异造成的。配合力测定结果．两个同源自交系和两个姊妹种中,系与系之间,系与姊妹种之间,两个姊妹种之间一般配合力差异不显著，说明利用配合力差异不显著的姊妹种替代自交系是可以作为杂交亲本生产种子的。     

利用姊妹种提高毕单系列玉米杂交种制种产量的研究

本研究利用玉米姊妹交技术，克服自交衰退，提高种子生产效益。用以研究的５个毕单系列玉米杂交种，通过用姊妹种配制出了相应的改良单交种，显著提高了杂交种制产量，且改良单交的Ｆ１杂种优势不下降，生产力与原单交Ｆ１持平或略增。     

Effect of Ogura male-sterile cytoplasm on the performance of cabbage hybrid variety

Summary Cabbage hybrid seeds are commercially produced by means of self-incompatibility. This system may show some instability mainly under tropical conditions, where cytoplasmic male sterility can be an alternative approach for hybrid seeds production. However, cabbage hybrids holding Ogura male-sterile cytoplasm show some irregularities during development. By assessing some characteristics during the growing cycle of male-sterile cabbage hybrids and comparing them to genomic similar male-fertile ones and to the most common cabbage hybrid cultivated in Brazil, it was observed that the male-sterile hybrids had the same vigour, uniformity, number of leaves, resistance to Xanthomonas campestris pv. campestris, and earliness as their male-fertile counterparts and performed better than the commercial check hybrid for some of these characteristics. Although male-sterile hybrids showed yellowing of leaves, some parental combinations succeeded in overcoming or strongly reducing this cytoplasmic effect.Abbreviations dat days after transplanting - CMS Cytoplasmic Male Sterility - CNPH National Centre for Vegetable Crops Research     

Cytology and digoxin production in hybrids between Digitalis lanata and D. grandiflora

Summary Digitalis lanata is the only commercial source of the cardiac glycoside digoxin. It is an outbreeder and displays considerable variation. An attempt to increase uniformity was made by making D. lanata × D. grandiflora diploid hybrids and from these produce allotetraploid hybrids using colchicine treatment. Such tetraploid plants would be homozygous. Tetraploid hybrids were shown to contain digoxin but at lower levels than in D. lanata. Progeny of selfed tetraploid hybrids were significantly more uniform than D. lanata grown from commercial seed, but were considerably less vigorous.     

The potential use of heterosis in Beta vulgaris L. II. Yield performance of pure lines and their hybrids

Summary The yield performance is described of pure lines obtained from doubled monoploids and their corresponding polycross and pair-cross hybrids. The total dry matter yields of fifteen pure lines averaged 60–90% of the yields of the progenitor and control varieties. Seven of the resultant polycross hybrids gave dry matter yields similar to or higher than the progenitor varieties, whilst the remaining hybrids were less productive than their parental lines. In pair-cross hybrids significant reciprocal differences were found in some cases. This was attributed to differences in self-fertility and the degree of self-fertilization in reciprocal crosses. Based on the frequency of offspring with white or coloured roots, self-fertilization frequencies ranging from 14% to 92% were found. It is estimated that in the event of complete cross-fertilization, the yields of certain pair-cross hybrids would have exceeded those of the control varieties by 9–29%.     

Hybrid and N Fertilization Affect Corn Silage Yield and Quality

We determined the effect of N fertilization on dry matter (DM) yield, predicted milk yield, and forage quality of fresh (green chopped) and ensiled forage of two brown midrib (BMR) hybrids, a leafy hybrid, and a conventional silage hybrid. Increasing N rates from 0 to 200 kg ha^?1 increased corn grain, stover and whole plant DM yield and milk yield. The forage yield and quality response to N was similar for all hybrids. Nitrogen fertilization increased forage crude protein (CP) concentration but had little effect on other forage quality components. BMR hybrids, F377 and F657, had the lowest grain, stover and whole plant yield but had the highest digestibility and predicted milk yield Mg^?1 of forage. Predicted milk yield ha^?1 was similar for the BMR, leafy and conventional hybrids. Ensiling reduced starch concentration compared with green chopped forage, but effects on other forage quality variables were less consistent. Hybrid and N fertilization affects were similar for green chopped and ensiled corn forage.     

rDNA和端粒重复序列鉴定马铃薯和茄子体细胞杂种染色体丢失和融合

植物体细胞杂交是植物种质资源创制的重要方法。体细胞杂种在原生质体再生的过程中染色体会产生非常多的遗传变异。研究体细胞杂种的染色体行为为马铃薯体细胞杂种的创制和利用提供理论基础。本研究采用rDNA和端粒重复序列作为探针进行原位杂交(fluorescence in situ hybridization),并结合基因组原位杂交(genomic in situ hybridization),对马铃薯和茄子体细胞杂种染色体组成和变异进行了分析。原位杂交结果表明,体细胞杂种中存在马铃薯和茄子融合的染色体和双着丝粒染色体,并发现部分融合染色体是由马铃薯和茄子2号染色体末端对末端融合得到的。重排的双着丝粒染色体的着丝粒一个来源于马铃薯,一个来源于茄子。此外,体细胞杂种中来源于茄子的5S rDNA在体细胞杂种再生及稳定的过程中全部丢失。研究结果表明马铃薯与茄子在进行体细胞杂交的过程中,染色体是不稳定的,容易造成融合后代出现双着丝粒和染色体重排等现象。体细胞杂种的染色体会通过染色体重排、双着丝粒、rDNA均一化等多种形式使其染色体趋于稳定。     

Maize commercial hybrids compared to improved population hybrids for grain yield and agronomic performance

Improved maize (Zea mays L.) populations and population hybrids can both be profitable alternatives to commercial single-cross hybrids as well as good elite sources of diverse inbred lines. The objective of this research was to compare grain yield and agronomic performance between early maturing maize population hybrids and current early maturing commercial single-cross hybrids. This is a consequence of our research program targeted at identifying alternative heterotic patterns for the northern Corn Belt. Improved maize populations and population hybrids (S₀ generations) were evaluated in experiments arranged in randomized complete block and partially balanced lattice designs across 29 environments. Grain yield potential of population hybrids was optimally expressed under irrigated conditions. Data across environments showed that 20% of the population hybrids evaluated were not different (P 0.05) from at least one of the commercial single-cross hybrids for grain yield performance, root lodging, and stalk lodging percentages. The average mid-parent heterosis value across population hybrids from different geographic regions was 20.4% with negative estimates observed in only two population hybrids. Breeding efforts toward elite populations and population hybrids have demonstrated that germplasm improvement is extremely valuable and deserves public funding. These efforts should be supported in order to enable the development of elite sources of diverse inbred lines and the development of improved population hybrids for specific markets (e.g., organic) to increase producer options. Public maize breeding programs utilizing recurrent selection methods for germplasm improvement could address the need. These programs, however, should incorporate extensive testing of population hybrids.     

In vitro induction of hexaploid plants from triploid hybrids of Pennisetum purpureum and Pennisetum glaucum

This study describes an efficient in vitro method using colchicine-treated triploid seedlings of Napiergrass and Pearl millet hybrids to produce hexaploid hybrids and their subsequent identification with flow cytometry. It also describes chromosome count and stomatal morphology and their use to ploidy analysis. Four-hundred and eighty triploid seeds, representing 12 different hybrids were sterilized and transferred to MS media to induce chromosome doubling. Surviving plants were analysed by flow cytometry. From six triploid (control) and hexaploid plants, the stomata sizes and frequency were analysed. Chromosome count was performed only in the plants identified as hexaploid. Seventeen plants were identified as hexaploid by flow cytometry analysis. Further confirmation of the hexaploid condition was performed with stomatal morphology (stomatal frequency reduction and stomatal length increase) and chromosome count (2n = 6x = 42). Chromosome doubling has numerous applications in Pennisetum breeding. It can be used to restore the fertility of interspecific hybrids and to improve seed size.     

Risk assessment of outcrossing of transgenic rapessed to related species:

Summary The risk for a gene dispersal is reported for reciprocal crosses between a transgenic rapeseed variety resistant to the herbicide phosphinotricin and five related species. The first stages after pollination were cytologically observed and fertilized ovaries were established in in vitro culture for the production of interspecific hybrids. A similar classification was observed for the index of pollination compatibility and embryo yield. From the 243 embryos produced, 109 plantlets were obtained in a greenhouse. All the interspecific combinations tested were able to produce hybrid plants. A higher number of hybrids was obtained when rapeseed was used as the female parent. The hybrids had the expected triploid structure except for two amphidiploid, B. napus × B. oleracea, and one amphidiploid, B. napus × S. arvensis, plants with 56 chromosomes. The triploid hybrids were sterile or partially fertile but two of the amphidiploid plants, B. napus × B. oleracea, were fully fertile. The cytoplasm source did not seem to affect the fertility of the hybrids.     

A comparison of the growth and yield during a 20 year period of Amelonado and upper amazon hybrid cocoa in Ghana

Summary Progeny trials were planted at Tafo in 1952 and 1954 to compare 3 selfed local-Trinitarios, 1 outcrossed and 3 sibbed Upper Amazon progenies and 13 hybrids between Amelonado or local-Trinitarios and Upper Amazons; 1 trial included West African Amelonado. The Amazon hybrids and the outcrossed Amazon were particularly vigorous and precocious and maintained a yield advantage for 20 years. The 13 hybrids were similar in yield potential, but varied in net yield following differential losses from pod diseases, mainly caused by Phytophthora palmivora. Disease losses were lowest on one of the sibbed Amazons and the outcrossed Amazon and lower on Amelonado than on any of the 7 hybrids tested with it; in both trials losses were lower on Amelonado hybrids than on Trinitario hybrids.There was wide variation in both size and growth rates of mature trees and no consistent relationship between continued growth and crop. It seemed that later yields were not prejudiced by the precocity of Amazon hybrids, the yields from all types fluctuated together. Because the differences in disease losses are likely to be accentuated under farmer's conditions. Amelonado hybrids are preferable to local-Trinitario hybrids. The results also suggest that commercially acceptable pure Upper Amazon varieties could be developed.On secondment on technical assistance from the United Kingdom Ministry of Overseas Development.     

糯玉米诱导率遗传规律探索

以40份糯玉米杂交种作为母本(其中母本材料前20份为10对互为正反交的杂交种,其余20份分别为一父十母的10份杂交种以及一母十父的10份杂交种),以2份诱导系作为父本进行杂交诱导,以探求不同遗传背景的糯玉米杂交种的诱导率遗传关系.研究结果表明,同一份诱导系与不同遗传背景的糯玉米杂交种的诱导率大不相同,本试验认为诱导系的诱导率与糯玉米杂交种的母本有重要遗传关系.试验结果表明,以YD 1为诱导系诱导杂交种时,母本为Y88的BY 19杂交种的诱导率最高,为5.706％,而母本为F46白的BY 28杂交种的诱导率最低,为2.590％.以YD 2为诱导系诱导杂交种时,母本为F45的BY 27杂交种的诱导率最高,为11.875％,而母本为F8的BY 22杂交种的诱导率最低,为6.165％.