Pleiotropic effects on the ml-o mildew resistance gene in barley in different genetical backgrounds

Summary The effects on quantitative characters of the ml-o5 allele has been investigated by means of doubled haploid lines produced by the Hordeum bulbosum method. In one series of experiments the genetic background in each cross was found significantly to modify the negative pleiotropic effects. Doubled haploids were also produced from a F1 cross and tested in the field during two years, one with strong and one with weak mildew infections. In the first year only an insignificant reduction in grain yield was detected in the mlo lines, in the second it was significantly reduced with 5.9%. Thousand grain weights were, however, higher in the resistant lines. In both series of experiments the possibility to extract very high yielding mlo genotypes was demonstrated. The nature of the genetic background effect is discussed.     

The evaluation of superior Hordeum bulbosum L. genotypes for use in a doubled haploid barley breeding programme

Summary Eight Hordeum bulbosum selections were produced from a cross between Cb 2920/4 and Cb 2929/1, two genotypes widely used in doubled haploid breeding programmes. The selections were hybridized with barley to evaluate their ability to produce high proportions of well-differentiated haploid embryos compared with Cb 2929/1 as control. We report here an initial small-scale investigation followed by a larger-scale test in two different environments to assess seed setting, haploid embryo differentiation rates and VB hybrid formation. These VB embryos contain both parental sets of chromosomes and occur more frequently in the glasshouse during the winter. Two of the eight selections were identified as combining the desirable characteristics of both parents, namely high seed setting on cv. Vada which is partially incompatible with H. bulbosum, large numbers of well-differentiated haploid embryos and a low incidence of VB hybrids. The selections are available for release to interested research workers and plant breedersAbbreviations DH doubled haploid - VB a hybrid from H. vulgare x H. bulbosum which contains both parental sets of chromosomes     

Production of Haploid Sugar Beet (Beta vulgaris L.) by Culturing Unpollinated Ovules

The culture of unpollinated ovules is shown to be a suitable system for the production of haploid sugar beet (Beta vulgaris L.). The yield of haploids depended upon the genotype and varied between 0 and 13 % with a mean of 1.0 %. Haploid plants could be produced from approximately 50 % of all genotypes examined. The majority of the haploids isolated (about 90%) maintained the haploid genome level during the in vitro culture and propagation; 10% of the haploid clones showed a spontaneous doubling to the diploid genome level.     

Studies on Low Crossabilities Encountered with the Hordeum bulbosum Method for Haploid Production of Barley, Hordeum vulgare L.

Crosses were made between four spring barley (Hordeum vulgare L.) cultivars and five F₁, hybrids with one genotype of Hordeum bulbosum L. in two locations to investigate further previous low crossabilities which had been found in the barley cultivar ‘Apex’ with H. bulbosum. Data at all the main steps of the H. bulbosum technique were recorded and statistically analyzed. Significant differences between barley genotypes were demonstrated for all characters. It was confirmed that ‘Apex’ has poor crossability with H. bulbosum. Out of the three F₁ hybrids having ‘Apex’ as one parent, two exhibited low crossability similarly to ‘Apex’ but one showed significantly higher seed setting than ‘Apex’. The effect of the location was only significant on seed setting, while genotype X location interactions were significant on seed setting, seed quality and rate of haploid plants in relation 10 florets pollinated. Another problem which has influenced the success rate of the H. bulbosum method was found in the cultivar ‘Havilla’. Although seed setting and seed quality were high for this cultivar, embryo differentiation was low. However, this latter problem was found to influence less the overall success rate than poor crossability. Mahalanobis's distances were calculated and the dendrite of the shortest distances between barley genotypes was plotted.     

Quantity production of anther-derived haploids from a multiple disease resistant tobacco hybrid. I. Frequency of plants with resistance or susceptibility to tobacco mosaic virus (TMV), potato virus Y (PVY), and root knot (RK)

Summary Methods are described for producing large numbers of haploid plantlets from anthers of a flue-cured tobacco hybrid with monogenic resistance to tobacco mosaic virus, (TMV), potato virus Y (PVY) and root knot (RK), respectively. Additional details are given on colchicine treatment for converting haploids to doubled haploids (DH's) and on the frequency of spontaneous DH's among untreated plantlets. Disparate genetic ratios of TMV-resistant to TMV-susceptible plants were obtained among colchicine-treated haploid plantlets, induced DH's and untreated haploids when compared with F₂ and BC₁ progenies. Haploids (gametes) with the gene for TMV resistance occurred more frequently than expected and plantlets with the gene for RK resistance occurred less frequenctly than expected. Transmission of the gene for PVY resistance differed only slightly from Mendelian expectations. These unexpected ratios, in addition to the frequent occurrence of plastid chimeras among anther-derived plantlets, strengthened our conviction that haploidy is somehow associated with mutation.Joint contribution from the Departments of Genetics, Crop Science and Plant Pathology, North Carolina State University, and the Tobacco Research Laboratory, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Oxford, North Carolina. Paper No. 5576 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina.     

小孢子培养获得松花型花椰菜DH再生植株

对5个松花型花椰菜(Brassica oleraceavar.botrytisL.)杂种一代的小孢子培养研究表明,小孢子胎胚发生主要依赖于基因型,庆农65天的每花蕾胚状体产量最高,平均达15.5个。松花菜的胚状体萌发率一般在30%左右,并有效地获得了大量的DH再生植株。冷激预处理能显著地影响花椰菜小孢子的胚胎发生,但供体材料间存在不同的结果。结球期和开花结角期再生植株的生育期与育性出现较大分离,可育且能正常结角的比例约占全部小孢子再生植株的50%以上,因而不再需要加倍处理。     

Regeneration of fertile doubled haploid plants from colchicine-supplemented media in wheat anther culture

The effect of colchicine added to induction medium for the production of fertile doubled haploid plants after in‐vitro anther culture was studied in wheat, Triticum aestivum L. For this, one winter and two spring wheat varieties were used. Anther cultures of the three genotypes were treated with 0.03% colchicine for 3 days at the beginning of microspore induction. Colchicine had no significant effect on anther response and embryoid production of the genotypes examined. However, in the winter wheat genotype ‘Mv Szigma’, colchicine caused a significant reduction in microspore‐derived structures. A significant decrease was also observed in plant regeneration ability of two genotypes (‘Vergina’ and ‘Acheloos’) after colchicine treatment. In addition, a significant reduction of the albinos produced was observed in all genotypes after olchicine treatment. In contrast, the regenerants obtained from the colchicine‐supplemented induction media produced significantly higher percentages of fertile plants in all genotypes. However, the level of fertility, was significantly different among the fertile plants obtained. This, together with the observation that in the case of the winter wheat variety the colchicine treatment resulted in 100% completely fertile plants with a high seed‐setting ability indicate that there is space for further improvement of the method when it is applied to spring cultivars. Finally, the increased number of seeds per 100 plated anthers obtained from all three genotypes after colchicine treatment, clearly demonstrates that the addition of colchicine to induction medium was superior to the conventional anther culture method and it could therefore be introduced into wheat breeding programmes.     

Comparison of doubled haploid lines and F2 bulks for the improvement of barley in the dry areas of North Syria

Drought stress is the main factor limiting barley yields in West Asia and North Africa. This study compares the utility of doubled haploid lines (DHLs) and conventional F₂ plant-derived bulks (F₂Bs) in improving barley in stress environments. Double crosses were made, DHLs were developed by anther culture from double-cross F₁ plants, and F₂Bs were produced by bulking the offspring of F₂ plants. Field tests were conducted in three drought-stressed environments. No major differences were observed in the mean performance of DHLs and F₂Bs. For most traits, both the genotypic and the genotype × location interaction variances were higher in the DHL group, whereas heritabilities were similar. Higher gains from selection were predicted for the DHL group. Regression analysis of yield stability indicated a lower predictability of the DHL performance. The haploid technique can improve breeding populations from which varieties with stable yields can be developed. The costs involved are determined by the DHL production rate, which needs to be improved in many developing countries.     

Genetics of multiple disease resistance in a doubled-haploid population of barley

The barley accession Q21861 possesses resistance to the stem-rust (Puccinia graminis f.sp. tritici), leaf-rust (P. hordei), and powdery-mildew (Blumeria graminis f.sp. hordei) pathogens. An anther-culture-derived doubled-haploid population was produced from F₁ plants from a cross of this accession and the susceptible breeding line SM89010 as a means of rapidly and efficiently determining the genetics of multiple disease resistance. The doubled-haploid population segregated 1:1 (resistant:susceptible) for resistance to the stem rust pathotype QCC indicating the involvement of a single resistance gene, rpg4. Two-gene (3:1) and one-gene (1:1) segregation ratios were observed for resistance to the stem-rust pathotype MCC at low (23–25°c) and high (27–29°C) temperature, respectively. These different segregation patterns were due to a pathotype × temperature interaction exhibited by rpg4 and Rpg1. another stem-rust-resistance gene present in Q21861. One-gene and two-gene segregation ratios were observed in reaction to the leaf rust and powdery mildew pathogens. These data demonstrate the utility of doubled haploid populations for determining the genetics of multiple disease resistance in barley.     

基于最小平方误差的单倍体和二倍体分类方法研究

基于玉米油分的花粉直感效应,采用核磁共振鉴别单倍体,快速、准确、低成本地确定单倍体与二倍体之间的含油率阈值,是实现大批量自动鉴别的前提和关键。提出一种基于最小平方误差的单倍体和二倍体分类方法,通过少量籽粒确定含油率阈值的研究,对单倍体和二倍体进行识别。以10个玉米组合为研究对象,利用核磁共振分析仪测定各组合一定数量单倍体和二倍体籽粒的含油率,依据最小平方误差方法确定各组合油分阈值,并通过逐级递增训练集样本数量的方法,确定油分阈值所需训练集规模,获得含油率阈值,能够满足单倍体正确识别率及对二倍体正确拒识率的均值达到90%以上的要求,为核磁共振全自动单倍体鉴别系统的后期大规模分类提供参数指导,提高分选效率。同时因单倍体生产效率低,运用最小平方误差的方法,通过少量的单倍体及二倍体籽粒来构建油分鉴别单倍体模型,以较小的投入获得更优的分类效果在玉米单倍体自动化分选中具有非常重要的现实意义,将该分类方法应用到全自动核磁分选单倍体系统中,可以达到较好的效果,为加快单倍体工程化育种提供保障。