Genetic Inactivation of Stinging Catfish (Heteropneustes fossilis) Sperm with UV Irradiation

To improve the efficiency of gynogenetic induction, the effect of UV light on sperm of Heteropneustes fossilis was optimized. The sperm suspension was diluted to 1 × 10⁷ sperm/ml^?1 in Hank's Balanced Salt Solution. Sperm suspension was irradiated under UV light for different exposure times ranging from 15 to 360 seconds (7500 ergs/mm^?2 for 60 seconds). Sperm motility and egg activation efficiency were assessed for the different exposure durations. Complete inactivation of sperm genetic material was recorded from 120 seconds onwards, and a good motility score was recorded until 240 seconds. A typical “Hertwig effect” in the yield of hatched larvae was observed with doses of UV exposure greater than 75 seconds. Larvae resulting from sperm UV irradiated above 120 seconds were 100% haploid. The genetic inactivation of paternal chromosomes was confirmed by chromosome counting (n = 29) from the resulting embryo, which also had a characteristic haploid syndrome. The resulting embryo (with 29 chromosomes) exhibited haploid syndrome and died after yolk sac absorption.     

棉花半配合材料 VSg-1的选育及其育种应用研究

从美国引入的海岛棉(Gossypium barbadense L.)半配合材料 VSg~(**),经过八年的选育和加倍,培育出适合我国气候的新品系 VSg-1。单倍体遗传频率达到69.9%。棉花半配合材料 VSg-1,已初步成功地应用于单倍体育种。已获得陆地棉(Gossypiumhirsutum L.)四个杂交组合育种初代材料的单倍体和少量加倍单培体种子。     

Influence of culture medium and in vitro conditions on shoot regeneration in Solanum phureja monoploids and fertility of regenerated doubled monoploids

Incorporation of monoploids in practical breeding requires an efficient method of producing homozygous diploids. This study investigated factors for efficient regeneration of doubled monoploid (DM) potato, crossability of DMs and their field performance. Incorporation of silver thiosulphate (STS) in propagation medium for in vitro monoploid plantlets of Solanum phureja did not affect the frequency of cells with diploid(2x) nuclei but increased those with monoploid (1x) and decreased those with 4x nuclei. Higher shoot regeneration was obtained from leaf explants compared with stem explants. Induction of shoots from calluswas affected neither by light during incubation nor by overnight treatment with a benzyl adenine pulse. Female fertility based on seed set after pollination of DMs with heterozygous diploid clones varied among DMs but encouraged their utilization in practical breeding.     

Doubled haploids of Coffea canephora: development,fertility and agronomic characteristics

Summary Doubled haploids (DH) of Coffea canephora Pierre were developed using haploid embryos which occur spontaneously in association with polyembryony. The frequencies of polyembryonic seeds and haploid embryos varied according to the parental genotypes. However, production of a large number of DH seemed possible from all genotypes. More than 750 DHs produced from various genotypes were grown under field conditions and evaluated for different characters of agronomic importance. Approximately half of DH genotypes did not survive, suggesting a strong, negative effect of homozygosity. Inbreeding depression is particularly severe on general vigor and reproductive aspects. For several characters studied such as leaf shape, leaf rust resistance and hundred bean weight, considerable genetic variations were observed within and between groups of DHs constituted by the DHs produced from the same clone. Despite their low vigor and reduced fertility, the DHs of C. canephora offer new possibilities in genetic research and coffee breeding.     

水稻叶鞘相关性状的遗传分析

本研究以典型釉粳交(春江06/台中本地1号)的F1代花药加倍的DH群体为材料,系统考察了DH群体及其双亲在抽穗期的叶鞘长、叶鞘重、叶鞘厚等性状上的分布情况.结果表明,叶鞘长度的遗传力较高,受环境的影响相对较小,叶鞘长与叶鞘厚及叶鞘干重间大多呈极显著的正相关.QTL分析共检测到31个与叶鞘有关的QTL,分布于水稻第1、第...     

Inheritance of resistance to wheat midge, Sitodiplosis mosellana, in spring wheat

Inheritance of resistance to a wheat midge, Sitodiplosis mosellana (Géhin), was investigated in spring wheats derived from nine resistant winter wheat cultivars. F₁ hybrids were obtained from crosses between resistant winter wheats and susceptible spring wheats, and used to generate doubled haploid populations. These populations segregated in a ratio of 1:1 resistant to susceptible, indicating that a single gene confers the resistance. The F₂ progeny from an intercross among spring wheats derived from the nine resistance sources did not segregate for resistance. Therefore, the same gene confers resistance in all nine sources of resistance, although other genes probably affect expression because the level of resistance varied among lines. Heterozygous plants from five crosses between diverse susceptible and resistant spring wheat parents all showed intermediate levels of response, indicating that resistance is partly dominant. Susceptible plants were reliably discriminated from heterozygous or homozygous resistant ones in laboratory tests, based on the survival and development of wheat midge larvae on one or two spikes. This powerful resistance gene, designated Sm1, is simply inherited and can be incorporated readily into breeding programmes for spring or winter wheat. However, the use of this gene by itself may lead to the evolution of a virulent population, once a resistant cultivar is widely grown.     

Genetic characterization of spontaneous diploid androgenetic wheat and triticale plants

The homozygosity of spontaneous hexaploid plants derived from anther culture was evaluated in wheat and triticale by means of 18 and 22 microsatellite markers, respectively. Most of the spontaneous hexaploid plants were homozygous for all the loci tested and had chromosomes recombining for parental alleles. Only 12% of the spontaneous hexaploid wheat plants, 11% of the artificially doubled wheat plants and 4.4% of the spontaneous hexaploid triticale plants were heterozygous at one to three of the loci studied. This showed that spontaneous hexaploid plants mostly came from normal haploid cells, obtained after meiosis, that underwent spontaneous chromosome doubling. However, first or second division restitution, producing unreduced gametes, cannot be completely excluded to explain the origin of the spontaneous hexaploid plants. Cytomixis, involving only one chromosome, or development of aneuploid trisomic gametes, followed by chromosome doubling for the spontaneous hexaploid plants, or transposition events could also explain some of the results obtained.     

Genetic analysis of total glucosinolate in crosses involving a high glucosinolate Indian variety and a low glucosinolate line of Brassica juncea

Analysis of the glucosinolate content and composition by high‐pressure liquid chromatography indicated that varieties of Brassica juncea bred and grown in India have a high glucosinolate content characterized by the presence of 2‐propenyl (allyl) and 3‐butenyl as the major and 4‐pentenyl as the minor fractions. In contrast, the B. juncea germplasm from other countries is characterized by the presence of 2‐propenyl as the major glucosinolate fraction, trace amounts of 3‐butenyl and a total lack of the 4‐pentenyl types. In order to transfer the low glucosinolate trait to Indian B. juncea, the inheritance of total glucosinolates was investigated using doubled haploid (DH) populations derived from F1 (DH₁) and BC₁ (BC₁DH) of a cross between ‘Varuna’ (the most widely cultivated high glucosinolate variety of India) and ‘Heera’ (a non‐allyl type low glucosinolate line). A total of 752 DH₁ and 1263 BC₁DH gave rise to seven and 11 low glucosinolate (containing less than 18 μmol/g seed) individuals, respectively. On the basis of the frequency of the low glucosinolate individuals, the total glucosinolate was found to be under the control of seven genes. There was presence of both allyl and non‐allyl types in DH₁ and BC₁DH low‐glucosinolate individuals and absence of 3‐butenyl glucosinolate in some of the BC1DH low glucosinolate individuals, indicating segregation for these fractions in the population. The size of the segregating DH population proved to be crucial for precise determination of the number of genes controlling the trait. Because of the large number of genes involved, incorporation of low glucosinolate trait in Indian B. juncea should be approached through doubled haploid (DH) breeding.     

烤烟6个农艺性状的QTL定位

由于烟草的分子标记开发和遗传图谱构建十分困难,迄今烟草中有关数量性状基因座(QTL)的定位研究仍非常有限。本研究利用一个由207个株系组成的烤烟DH群体及基于该群体所构建的含有24个连锁群、611个SSR标记,总长为1 882.1 cM的遗传图谱,采用复合区间作图方法,对株高(PH)、茎围(SG)、节距(IL)、叶片数(LN)、最大腰叶长(LWL)和最大腰叶宽(WWL) 6个与叶片产量有关的农艺性状进行QTL定位分析。共检测到69个QTL,大部分QTL的效应值较小,仅有4个具有较大的效应值,可解释大约15%~20%的表型变异。6个性状之间大多彼此相关。与此相符,在基因组中发现存在许多小区域,每个区域包含两个或两个以上紧密连锁的不同性状的QTL。     

Production of haploids of potato (Solanum tuberosum subsp. tuberosum) and their identification with electrophoretic analysis

Summary The frequency of haploid production following the interspecific pollination of eight tetraploid potato cultivars (Solanum tuberosum subsp. tuberosum) with Solanum phureja clone 1.22 was investigated. A total of 185 haploids were produced with an overall haploid frequency of 3.9 haploids/100 fruits. The haploid frequency was affected by the genotype of the maternal parent. Atlantic, ND860-2, Superior, Saginaw Gold, Spartan Pearl, Nooksack and Onaway had frequencies of 6.2, 5.1, 4.7, 3.9, 2.3 and 0.7 haploids/100 fruits, respectively. There were 60 and 57 haploids produced from Atlantic and Saginaw Gold, respectively, and no haploids were extracted from fruits of Lemhi Russet. Isozyme analysis and visual examination were performed independently to compare the efficiency of discriminating hybrids from haploids. Approximately 80% of total hybrids could be identified by electrophoretic analysis, while 77% were distinguished through visual examination. Pgm-2 ¹, which is unique in the clone 1.22 and absent from all seed parents, was found to be the most useful locus in hybrid identification and 50% of total hybrids could be distinguished by this allele. With similar rationale, Mdh-1 ¹ allozyme, which was absent in six of the eight parents, identified 37% of total hybrids. A combination of both visual and electrophoretic methods made hybrid identification even more efficient, with an average identification efficiency of 91%. A scheme was proposed to develop a new haploid inducer which would be homozygous for both Pgm-2 ¹ and embryo spot.