The distinctness and diversity of Ethiopian barleys

 The relative diversity and distinctness of Ethiopian barleys has been investigated using (1) morphology/isozyme/hordein polymorphisms and (2) RFLP markers. In the former a set of 51 landraces from over the whole of Ethiopia was compared with Iranian landraces based on data from previous studies and new hordein data. The two sets of landraces were found to have a comparable diversity. The Ethiopian ones are more diverse morphologically (5 traits), are similar in numbers of alleles per protein locus (17 loci) and in genetic differentiation, but are less diverse in average heterozygosity per locus and degree of polymorphism. However, on the basis of the hordein data the two sources of germplasm are very distinct. The correlation between morphological and protein diversity is very low. In the RFLP study 28 probes evenly distributed across the genome were used to analyse 43 Ethiopian landraces (represented by one single genotype) and to compare them with modern cultivars from North America, Europe and Japan, as well as 3 landraces from Iran, 1 from Nepal, and 1 accession of H. spontaneum from Afghanistan. The major finding was that the Ethiopian germplasm appears to be significantly less diverse than the modern germplasm but that it is genotypically very distinct. The apparent contradiction between a high diversity of useful genes coming from Ethiopia and an apparently low diversity at the DNA level is discussed. Received: 22 July 1996 / Accepted: 26 July 1996     

Improvement of anther culture methods for doubled haploid production in barley breeding

There is potential to accelerate cultivar development with a doubled haploid system for breeding line production. Anther culture methodology was evaluated for U.S.A. spring barley (Hordeum vulgare L.) breeding applications. Gelrite was found to be an acceptable replacement for ficoll in the induction medium to reduce costs while maintaining embryoid and plant production levels. Beneficial effects of 28 d cold pretreatment of donor spikes for anther culture were confirmed with Pacific Northwest USA barley genotypes. A 3 d mannitol solution pretreatment of fresh anthers was shown to be less effective for green plant production compared to 28 d cold pretreatment of donor spikes. Extended donor spike cold pretreatment from 28 to 42 d did not reduce anther culture productivity. Based on this research, anther culture techniques show promise for economical and convenient application in spring barley breeding.Abbreviations DH doubled haploid - LS Linsmaier and Skoog basal medium - BAP benzylaminopurine - GLM Generalized Linear Model - SAS Statistical Analysis System     

Genetic and physical mapping of a high recombination region on chromosome 7H(1) in barley

Approaches utilizing microlinearity between related species allow for the identification of syntenous regions and orthologous genes. Within the barley Chromosome 7H(1) is a region of high recombination flanked by molecular markers cMWG703 and MWG836. We present the constructed physical contigs linked to molecular markers across this region using bacterial artificial chromosomes (BAC) from the cultivar Morex. Barley expressed sequence tags (EST), identified by homology to rice chromosome 6 between the rice molecular markers C425A and S1434, corresponded to the barley syntenous region of Chromosome 7H(1) Bins 2–5 between molecular markers cMWG703-MWG836. Two hundred and thirteen ESTs were genetically mapped yielding 267 loci of which 101 were within the target high recombination region while 166 loci mapped elsewhere. The 101 loci were joined by 43 other genetic markers resulting in a highly saturated genetic map. In order to develop a physical map of the region, ESTs and all other molecular markers were used to identify Morex BAC clones. Seventy-four BAC contigs were formed containing 2–102 clones each with an average of 19 and a median of 13 BAC clones per contig. Comparison of the BAC contigs, generated here, with the Barley Physical Mapping Database contigs, resulted in additional overlaps and a reduction of the contig number to 56. Within cMWG703-MWG836 are 24 agriculturally important traits including the seedling spot blotch resistance locus, Rcs5. Genetic and physical analysis of this region and comparison to rice indicated an inversion distal of the Rcs5 locus. Three BAC clone contigs spanning the Rcs5 locus were identified. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

半矮秆基因brh1在大麦中的精细定位

选用从大麦、小麦和水稻中分离的RFLP标记 ,构建了大麦半矮秆基因brh1精细图谱。以快中子处理六棱大麦品种Steptoe的种子 ,从M2 代中选择出brh1突变体FN5 3。brh1是一个极易鉴别的形态学标记 ,通过对FN5 3×Morex的F2 代群体进行鉴定表明 ,brh1基因为隐性 ,前人通过BSA法将其初步定位在大麦第 1染色体 (7H)短臂上 ,靠近端粒区。这一区间还有一个控制秆锈病抗性的显性基因Rpg1。所以 ,brh1的精细定位不仅对研究其本身具有重要意义 ,同时 ,也为Rpg1的图位克隆和功能研究提供了更大的重组配子群体。定位实验全部以F2 中具有brh1特征的个体为对象完成 ,鉴定工作在苗期进行。在该精细图上 ,brh1区间长15 .2cM ,各标记间的平均距离为 0 .8cM。其中 ,大麦的cDNA克隆MWG2 0 74B与brh1共分离。 2 0 74A在靠近着丝点一侧 ,与brh1相距 0 .8cM。BCD12 9和R3139在定位群体内呈现与MWG2 0 74A共分离。CDO5 4 5位于端粒一侧 ,距离brh1为 0 .8cM。根据禾谷类作物基因组的共线性原理 ,CDO5 4 5成功定位在水稻的同源染色体即第 6染色体短臂brh1区间内。然而 ,由于在定位亲本间缺乏多态性 ,BCD12 9和MWG2 0 74的 2条主带A和B均未能定位在水稻的共线性区段内。推测MWG2 0 74的其他各带可能被定位在水稻的目标区间内 ,从而有     

QTL analysis of agronomic traits in barley based on the doubled haploid progeny of two elite North American varieties representing different germplasm groups

A better understanding of the genetics of complex traits, such as yield, may be achieved by using molecular tools. This study was conducted to estimate the number, genome location, effect and allele phase of QTLs determining agronomic traits in the two North American malting barley (Hordeum vulgare L.) quality variety standards. Using a doubled haploid population of 140 lines from the cross of two-rowed Harrington×six-rowed Morex, agronomic phenotypic data sets from nine environments, and a 107-marker linkage map, we performed QTL analyses using simple interval mapping and simplified composite interval mapping procedures. Thirty-five QTLs were associated, either across environments or in individual environments, with five grain and agronomic traits (yield, kernel plumpness, test weight, heading date, and plant height). Significant QTL×environment interaction was detected for all traits. These interactions resulted from both changes in the magnitude of response and changes in the sign of the allelic effect. QTLs for multiple traits were coincident. The vrs1 locus on chromosome 2 (2H), which determines inflorescence row type, was coincident with the largest-effect QTL determining four traits (yield, kernel plumpness, test weight, and plant height). QTL analyses were also conducted separately for each sub-population (six-rowed and two-rowed). Seven new QTLs were detected in the sub-populations. Positive transgressive segregants were found for all traits, but they were more prevalent in the six-rowed sub-population.QTL analysis should be useful for identifying candidate genes and introgressing favorable alleles between germplasm groups. Received: 18 August 2000 / Accepted: 15 December 2000     

Cultivar-related differences in the distribution of cell-wall-bound thionins in compatible and incompatible interactions between barley and powdery mildew

Leaf-specific thionins of barley (Hordeum vulgare L.) have been identified as a novel class of cell-wall proteins toxic to plant-pathogenic fungi and possibly involved in the defence mechanism of plants. The distribution of these polypeptides has been studied in the host-pathogen system of barley and Erisyphe graminis DC.f.sp. hordei Marchal (powdery mildew). Immunogold-labelling of thionins in several barley cultivars indicates that resistance or susceptibility may be attributed to the presence or absence of thionins at the penetration site in walls and papillae of epidermal leaf cells.All of the leaf-specific thionin genes are confined to the distal end of the short arm of chromosome 6 of barley. None of the genes for cultivarspecific resistance to powdery mildew which have previously been mapped on barley chromosomes are found close to this locus.     

QTL analysis of malting quality in barley based on the doubled-haploid progeny of two elite North American varieties representing different germplasm groups

Characterization of the determinants of economically important phenotypes showing complex inheritance should lead to the more effective use of genetic resources. This study was conducted to determine the number, genome location and effects of QTLs determining malting quality in the two North American barley quality standards. Using a doubled-haploid population of 140 lines from the cross of Harrington×Morex, malting quality phenotype data sets from eight environments, and a 107-marker linkage map, QTL analyses were performed using simple interval mapping and simplified composite interval mapping procedures. Seventeen QTLs were associated with seven grain and malting quality traits (percentage of plump kernels, test weight, grain protein percentage, soluble/total protein ratio, α-amylase activity, diastatic power and malt-extract percentage). QTLs for multiple traits were coincident. The loci controlling inflorescence type [vrs1 on chromosome 2(2H) and int-c on chromosome 4(4H)] were coincident with QTLs affecting all traits except malt-extract percentage. The largest effect QTLs, for the percentage of plump kernels, test weight protein percentage, S/T ratio and diastatic power, were coincident with the vrs1 locus. QTL analyses were conducted separately for each sub-population (six-rowed and two-rowed). Eleven new QTLs were detected in the subpopulations. There were significant interactions between the vrs1 and int-c loci for grain-protein percentage and S/T protein ratio. Results suggest that this mating of two different germplasm groups caused a disruption of the balance of traits. Information on the number, position and effects of QTLs determining components of malting quality may be useful for maintaining specific allele configurations that determine target quality profiles. Received: 28 May 1999 / Accepted: 9 November 1999     

Molecular marker assisted genetic analysis of head shattering in six-rowed barley

Head shattering in barley (Hordeum vulgare L.) has two forms; brittle rachis and weak rachis. Brittle rachis is not observed in cultivated barley since all cultivars carry non-brittle alleles at one of the two complementary brittle rachis loci (Btr1;Btr2). Weak rachis causes head shattering in barley cultivars and may be confused with brittle rachis. Brittle rachis has been mapped to the chromosome 3 (3H) short arm while map position(s) of the weak rachis is unknown. Two major and a putative minor QTL for head shattering were mapped using the Steptoe × Morex doubled haploid line population. The largest QTL, designated Hst-3, located on the chromosome 3 (3H) centromeric region, is associated with a major yield QTL. The Steptoe Hst-3 region, when transferred into Morex, resulted in a substantial decrease in head shattering. High-resolution mapping of Hst-3 was achieved using isogenic lines. Brittle rachis was mapped with molecular markers and shown to be located in a different position from that of Hst-3. The second major QTL, designated Hst-2 S, is located on chromosome 2 S. This locus is associated with an environmentally sensitive yield QTL.     

Fine mapping of a malting-quality QTL complex near the chromosome 4H S telomere in barley

Malting quality has long been an active objective in barley (Hordeum vulgare L.) breeding programs. However, it is difficult for breeders to manipulate malting-quality traits because of inheritance complexity and difficulty in evaluation of these quantitative traits. Quantitative trait locus (QTL) mapping provides breeders a promising basis with which to manipulate quantitative trait genes. A malting-quality QTL complex, QTL2, was mapped previously to a 30-cM interval in the short-arm telomere region of barley chromosome 4H in a Steptoe/Morex doubled haploid population by the North American Barley Genome Project, using an interval mapping method with a relatively low-resolution genetic map. The QTL2 complex has moderate effects on several malting-quality traits, including malt extract percentage (ME), -amylase activity (AA), diastatic power (DP), malt -glucan content (BG), and seed dormancy, which makes it a promising candidate gene source in malting barley-cultivar development. Fine mapping QTL2 is desirable for precisely studying barley malting-quality trait inheritance and for efficiently manipulating QTL2 in breeding. A reciprocal-substitution mapping method was employed to fine map QTL2. Molecular marker-assisted backcrossing was used to facilitate the generation of isolines. Fourteen different types of Steptoe isolines, including regenerated Steptoe and 13 different types of Morex isolines, including regenerated Morex, were made within a 41.5-cM interval between MWG634 and BCD265B on chromosome 4H. Duplicates were identified for 12 Steptoe and 12 Morex isoline types. The isolines together with Steptoe and Morex were grown variously at three locations in 2 years for a total of five field environments. Four malting-quality traits were measured: ME, DP, AA, and BG. Few significant differences were found between duplicate isolines for these traits. A total of 15 putative QTLs were mapped; three for ME, four for DP, six for AA, and two for BG. Background genotype seemed to make a difference in expression/detection of QTLs. Of the 15 QTLs identified, ten were from the Morex and only five from the Steptoe background. By combining the results from different years, field environments, and genetic backgrounds and taking into account overlapping QTL segments, six QTLs can be conservatively estimated: two each for ME and AA and one each for DP and BG with chromosome segments ranging from 0.7 cM to 27.9 cM. A segment of 15.8 cM from the telomere (MWG634–CDO669) includes all or a portion of all QTLs identified. Further study and marker-assisted breeding should focus on this 15.8-cM chromosome region.