Detection and verification of malting quality QTLs using wild barley introgression lines

A malting quality quantitative trait locus (QTL) study was conducted using a set of 39 wild barley introgression lines (hereafter abbreviated with S42ILs). Each S42IL harbors a single marker-defined chromosomal segment from the wild barley accession ‘ISR 42-8’ (Hordeum vulgare ssp. spontaneum) within the genetic background of the elite spring barley cultivar ‘Scarlett’ (Hordeum vulgare ssp. vulgare). The aim of the study was (1) to verify genetic effects previously identified in the advanced backcross population S42, (2) to detect new QTLs, and (3) to identify S42ILs exhibiting multiple QTL effects. For this, grain samples from field tests in three different environments were subjected to micro malting. Subsequently, a line × phenotype association study was performed with the S42ILs in order to localize putative QTL effects. A QTL was accepted if the trait value of a particular S42IL was significantly (P < 0.05) different from the recurrent parent as a control, either across all tested environments or in a particular environment. For eight malting quality traits, altogether 40 QTLs were localized, among which 35 QTLs (87.5%) were stable across all environments. Six QTLs (15.0%) revealed a trait improving wild barley effect. Out of 36 QTLs detected in a previous advanced backcross QTL study with the parent BC₂DH population S42, 18 QTLs (50.0%) could be verified with the S42IL set. For the quality parameters α-amylase activity and Hartong 45°C, all QTLs assessed in population S42 were verified by S42ILs. In addition, eight new QTL effects and 17 QTLs affecting two newly investigated traits were localized. Two QTL clusters harboring simultaneous effects on eight and six traits, respectively, were mapped to chromosomes 1H and 4H. In future, fine-mapping of these QTL regions will be conducted in order to shed further light on the genetic basis of the most interesting QTLs.     

AB-QTL analysis in spring barley: III. Identification of exotic alleles for the improvement of malting quality in spring barley (<Emphasis Type="Italic">H. vulgare</Emphasis> ssp. <Emphasis Type="Italic">spontaneum</Emphasis>)

Malting quality is genetically determined by the complex interaction of numerous traits which are expressed prior to and, in particular, during the malting process. Here, we applied the advanced backcross quantitative trait locus (AB-QTL) strategy (Tanksley and Nelson, Theor Appl Genet 92:191–203, 1996), to detect QTLs for malting quality traits and, in addition, to identify favourable exotic alleles for the improvement of malting quality. For this, the BC₂DH population S42 was generated from a cross between the spring barley cultivar Scarlett and the wild barley accession ISR42-8 (Hordeum vulgare ssp. spontaneum). A QTL analysis in S42 for seven malting parameters measured in two different environments yielded 48 QTLs. The exotic genotype improved the trait performance at 18 (37.5%) of 48 QTLs. These favourable exotic alleles were detected, in particular, on the chromosome arms 3HL, 4HS, 4HL and 6HL. The exotic allele on 4HL, for example, improved α-amylase activity by 16.3%, fermentability by 0.8% and reduced raw protein by 2.4%. On chromosome 6HL, the exotic allele increased α-amylase by 16.0%, fermentability by 1.3%, friability by 7.3% and reduced viscosity by 2.9%. Favourable transgressive segregation, i.e. S42 lines exhibiting significantly better performance than the recurrent parent Scarlett, was recorded for four traits. For α-amylase, fermentability, fine-grind extract and VZ45 20, 16, 2 and 26 S42 lines, respectively, surpassed the recurrent parent Scarlett. The present study hence demonstrates that wild barley does harbour valuable alleles, which can enrich the genetic basis of cultivated barley and improve malting quality traits.     

Identification and verification of QTLs for agronomic traits using wild barley introgression lines

A set of 39 wild barley introgression lines (hereafter abbreviated with S42ILs) was subjected to a QTL study to verify genetic effects for agronomic traits, previously detected in the BC₂DH population S42 (von Korff et al. 2006 in Theor Appl Genet 112:1221–1231) and, in addition, to identify new QTLs and favorable wild barley alleles. Each line within the S42IL set contains a single marker-defined chromosomal introgression from wild barley (Hordeum vulgare ssp. spontaneum), whereas the remaining part of the genome is exclusively derived from elite spring barley (H. vulgare ssp. vulgare). Agronomic field data of the S42ILs were collected for seven traits from three different environments during the 2007 growing season. For detection of putative QTLs, a two-factorial mixed model ANOVA and, subsequently, a Dunnett test with the recurrent parent as a control were conducted. The presence of a QTL effect on a wild barley introgression was accepted, if the trait value of a particular S42IL was significantly (P < 0.05) different from the control, either across all environments and/or in a particular environment. A total of 47 QTLs were localized in the S42IL set, among which 39 QTLs were significant across all tested environments. For 19 QTLs (40.4%), the wild barley introgression was associated with a favorable effect on trait performance. Von Korff et al. (2006 in Theor Appl Genet 112:1221–1231) mapped altogether 44 QTLs for six agronomic traits to genomic regions, which are represented by wild barley introgressions of the S42IL set. Here, 18 QTLs (40.9%) revealed a favorable wild barley effect on the trait performance. By means of the S42ILs, 20 out of the 44 QTLs (45.5%) and ten out of the 18 favorable effects (55.6%) were verified. Most QTL effects were confirmed for the traits days until heading and plant height. For the six corresponding traits, a total of 17 new QTLs were identified, where at six QTLs (35.3%) the exotic introgression caused an improved trait performance. In addition, eight QTLs for the newly studied trait grains per ear were detected. Here, no QTL from wild barley exhibited a favorable effect. The introgression line S42IL-107, which carries an introgression on chromosome 2H, 17–42 cM is an example for S42ILs carrying several QTL effects simultaneously. This line exhibited improved performance across all tested environments for the traits days until heading, plant height and thousand grain weight. The line can be directly used to transfer valuable Hsp alleles into modern elite cultivars, and, thus, for breeding of improved varieties.     

High-resolution linkage mapping for the non-brittle rachis locus btr1 in cultivated × wild barley (Hordeum vulgare)

Brittle rachis is an important trait to elucidate the domestication process in barley. Brittle rachis in wild barley (Hordeum vulgare ssp. spontaneum (C. Koch.) Thell) is controlled by two dominant complementary genes, Btr1 and Btr2. Cultivated barley (H. vulgare L. ssp. vulgare) lost the brittle rachis character during domestication as a result of mutation at the Btr1 or Btr2 locus. In this study, a high-resolution map of the btr1 locus was constructed using an F₂ population of cultivar (cv. ‘Kanto Nakate Gold’) × wild barley (line OUH602). We cloned and sequenced 26 AFLP markers linked with the btr1 and btr2 loci. Ten converted STS markers were located on the short arm of chromosome 3H only, and at least 9 of the 10 STS markers were allelic with their original AFLPs. Efficient conversion of co-dominant STS markers using BAC clones was successful. No suppression of recombination was observed in the btr1 region even though wild barley was used as one of the parents. Initial results of BAC screening confirmed the resolution power of the developed high resolution map.     

Features of Crossability, Haploidy and Polyembryony in Hybrid Combinations between Cultivated Barley Hordeum vulgare L. (2n = 14) and Wheat-Rye Substitution Lines Triticum aestivum L., Cultivar Saratovskaya 29/Secale cereale L., Cultivar Onokhoiskaya

The role of individual chromosomes of rye in the manifestation of crossability and seedling development in hybrid combinations between cultivated barley Hordeum vulgare L., cultivar Nepolegayushchii (2n = 14) and five wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya (2n = 40 wheat + 2 rye chromosomes). Crossability, which was measured by two parameters—frequency of set grains and frequency of grains with embryos—was shown to be significantly affected by each of the five rye chromosomes examined: 1R, 2R, 3R, 5R, and 6R; the development of barley haploids was affected by rye chromosomes 1R, 3R, and 5R. We were the first to demonstrate that polyembryony could be induced by mutual effects of barley cytoplasm and rye chromosome 1R. Possible mechanisms controlling the development of haploids and twins in hybrid combinations H. vulgare × T. aestivum/S. cereale are discussed. The conclusion is drawn that hybrid combinations between cultivated barley and wheat-rye substitution lines can serve as new models for studying incompatibility mechanisms in distant crosses and genetic control of parthenogenesis.__________Translated from Genetika, Vol. 41, No. 6, 2005, pp. 784–792.Original Russian Text Copyright © 2005 by Pershina, Belova, Devyatkina, Rakovtseva, Kravtsova, Shchapova.     

Plastid genome characterisation in Brassica and Brassicaceae using a new set of nine SSRs

The objective of the present study was to identify favourable exotic Quantitative Trait Locus (QTL) alleles for the improvement of agronomic traits in the BC₂DH population S42 derived from a cross between the spring barley cultivar Scarlett and the wild barley accession ISR42-8 (Hordeum vulgare ssp. spontaneum). QTLs were detected as a marker main effect and/or a marker × environment interaction effect (M × E) in a three-factorial ANOVA. Using field data of up to eight environments and genotype data of 98 SSR loci, we detected 86 QTLs for nine agronomic traits. At 60 QTLs the marker main effect, at five QTLs the M × E interaction effect, and at 21 QTLs both the effects were significant. The majority of the M × E interaction effects were due to changes in magnitude and are, therefore, still valuable for marker assisted selection across environments. The exotic alleles improved performance in 31 (36.0%) of 86 QTLs detected for agronomic traits. The exotic alleles had favourable effects on all analysed quantitative traits. These favourable exotic alleles were detected, in particular on the short arm of chromosome 2H and the long arm of chromosome 4H. The exotic allele on 4HL, for example, improved yield by 7.1%. Furthermore, the presence of the exotic allele on 2HS increased the yield component traits ears per m² and thousand grain weight by 16.4% and 3.2%, respectively. The present study, hence, demonstrated that wild barley does harbour valuable alleles, which can enrich the genetic basis of cultivated barley and improve quantitative agronomic traits.     

Physiological and yield responses of recombinant chromosome substitution lines of barley to terminal drought in a Mediterranean‐type environment

Physiological traits and productivity of the recombinant chromosome substitution lines (RCSLs) of barley, developed through the cross of Hordeum vulgare ssp. vulgare cv. Harrington and the wild ancestor Hordeum vulgare ssp. spontaneum, were measured in plants growing in microplots (with and without irrigation) and in field conditions in two Mediterranean‐type environments, Cauquenes (rainfed) and Santa Rosa (irrigated). The objectives were to assess the degree of phenotypic variability in response to terminal drought stress and to test whether the introgression of the wild ancestor into cv. Harrington can increase the terminal drought tolerance of RCSLs of barley. Days from emergence to anthesis and from anthesis to maturity of the 80 RCSLs were reduced in only 2–4 days under water stress, in microplots. Specific leaf area (SLA) and stomatal conductance (gs) of 80 RCSLs and cv. Harrington decreased greatly under water stress in plants growing in microplots and field conditions (in 2004/05 growing season). No G × E interaction was detected except for SLA in the microplot experiment. The principal component analysis provided a clear distinction between RCSLs. Along the first principal component, it was possible to identify 24 RCSLs which represent the whole range of grain yield (GY), gs and SLA observed in the 80 RCSLs. The selected 24 RCSLs were evaluated in field conditions at Cauquenes and Santa Rosa, during two growing seasons (2007/08 and 2008/09). The gs and carbon isotope discrimination in grains (Δ¹³C) were significantly (P < 0.001) lower in the rainfed condition (Cauquenes), but the water‐soluble carbohydrates (WSC) in stems at anthesis and maturity was significantly (P < 0.001) higher than in well‐irrigated condition (Santa Rosa). Grain yield was reduced by 63% under drought conditions. Differences between RCSLs in gs, WSC and GY were significant (P < 0.001) in 2007/08. The stress tolerance index (STI) was highly (P < 0.01) correlated with GY in all environments (rainfed and irrigated conditions and the two growing seasons). The relationship between STI and Δ¹³C under rainfed condition allowed identifying drought tolerant and susceptible RCSLs; the former were high yielding lines under rainfed and irrigated conditions (and higher STI values), but with similar GY to cv. Harrington, but presented higher grain Δ¹³C values than cv. Harrington. The drought susceptible lines presented lower GY, STI and Δ¹³C values than cv. Harrington. These results suggest that H. spontaneum has contributed alleles that increase terminal drought tolerance to some of the RCSLs.     

Identification of Hordeum spontaneum QTL alleles improving field performance of barley grown under rainfed conditions

Advanced backcross QTL (AB-QTL) analysis was deployed to identify allelic variation in wild barley (Hordeum vulgare ssp. spontaneum) of value in the improvement of grain yield and other agronomically important traits in barley (Hordeum vulgare ssp. vulgare) grown under conditions of water deficit in Mediterranean countries. A population of 123 double haploid (DH) lines obtained from BC₁F₂ plants derived from a cross between Barke (European two-row cultivar) and HOR11508 (wild barley accession) were tested in replicated field trials, under varying conditions of water availability in Italy, Morocco and Tunisia, for seven quantitative traits. Significant QTL effects at one (P 0.001) or more trial sites (P 0.01) were identified for all traits. At 42 (52%) of the 80 putative QTLs identified, the allele increasing a “traits' value” was contributed by H. spontaneum. For example, though the majority (67%) of QTL alleles increasing grain yield were contributed by H. vulgare, H. spontaneum contributed the alleles increasing grain yield at six regions on chromosomes 2H, 3H, 5H and 7H. Among them, two QTLs (associated to Bmac0093 on chromosome 2H and to Bmac0684 on chromosome 5H) were identified in all three locations and had the highest additive effects. The present study shows the validity of deploying AB-QTL analysis for identifying favourable QTL alleles from wild germplasm and indicates its potential as an enhancement strategy for the genetic improvement of cultivars better adapted to drought-prone environments.     

Localisation of genes for resistance against Blumeria graminis f.sp. hordei and Puccinia graminis in a cross between a barley cultivar and a wild barley (Hordeum vulgare ssp. spontaneum) line

The aims of this investigation have been to map new (quantitative) resistance genes against powdery mildew, caused by Blumeria graminis f.sp. hordei L., and leaf rust, caused by Puccinia hordei L., in a cross between the barley ( Hordeum vulgare ssp. vulgare) cultivar "Vada" and the wild barley ( Hordeum vulgare ssp. spontaneum) line "1B-87" originating from Israel. The population consisted of 121 recombinant inbred lines. Resistance against leaf rust and powdery mildew was tested on detached leaves. The leaf rust isolate "I-80" and the powdery mildew isolate "Va-4", respectively, were used for the infection in this experiment. Moreover, powdery mildew disease severity was observed in the field at two different epidemic stages. In addition to other DNA markers, the map included 13 RGA (resistance gene analog) loci. The structure of the data demanded a non-parametric QTL-analysis. For each of the four observations, two QTLs with very high significance were localised. QTLs for resistance against powdery mildew were detected on chromosome 1H, 2H, 3H, 4H and 7H. QTLs for resistance against leaf rust were localised on 2H and 6H. Only one QTL was common for two of the powdery mildew related traits. Three of the seven QTLs were localised at the positions of the RGA-loci. Three of the five powdery mildew related QTLs are sharing their chromosomal position with known qualitative resistance genes. All detected QTLs behaved additively. Possible sources of the distorted segregation observed, the differences between the results for the different powdery mildew related traits and the relation between qualitative and quantitative resistance are discussed.     

The Horn of Africa as a centre of barley diversification and a potential domestication site

According to a widely accepted theory on barley domestication, wild barley (Hordeum vulgare ssp. spontaneum) from the Fertile Crescent is the progenitor of all cultivated barley (H. vulgare ssp. vulgare). To determine whether barley has undergone one or more domestication events, barley accessions from three continents have been studied (a) using 38 nuclear SSR (nuSSRs) markers, (b) using five chloroplast SSR (cpSSR) markers yielding 5 polymorphic loci and (c) by detecting the differences in a 468 bp fragment from the non-coding region of chloroplast DNA. A clear separation was found between Eritrean/Ethiopian barley and barley from West Asia and North Africa (WANA) as well as from Europe. The data from chloroplast DNA clearly indicate that the wild barley (H. vulgare ssp. spontaneum) as it is found today in the “Fertile Crescent” might not be the progenitor of the barley cultivated in Eritrea (and Ethiopia). Consequently, an independent domestication might have taken place at the Horn of Africa. Jihad Orabi and Gunter Backes have contributed equally to this work.     

Selecting a set of wild barley introgression lines and verification of QTL effects for resistance to powdery mildew and leaf rust

A set of 59 spring barley introgression lines (ILs) was developed from the advanced backcross population S42. The ILs were generated by three rounds of backcrossing, two to four subsequent selfings, and, in parallel, marker-assisted selection. Each line includes a single marker-defined chromosomal segment of the wild barley accession ISR42-8 (Hordeum vulgare ssp. spontaneum), whereas the remaining part of the genome is derived from the elite barley cultivar Scarlett (H. vulgare ssp. vulgare). Based on a map containing 98 SSR markers, the IL set covers so far 86.6% (1041.5 cM) of the donor genome. Each single line contains an average exotic introgression of 39.2 cM, representing 3.2% of the exotic genome. The utility of the developed IL set is illustrated by verification of QTLs controlling resistance to powdery mildew (Blumeria graminis f. sp. hordei L.) and leaf rust (Puccinia hordei L.) which were previously identified in the advanced backcross population S42. Altogether 57.1 and 75.0% of QTLs conferring resistance to powdery mildew and leaf rust, respectively, were verified by ILs. The strongest favorable effects were mapped to regions 1H, 0–85 cM and 4H, 125–170 cM, where susceptibility to powdery mildew and leaf rust was decreased by 66.1 and 34.7%, respectively, compared to the recurrent parent. In addition, three and one new QTLs were localized, respectively. A co-localization of two favorable QTLs was identified for line S42IL-138, which holds an introgressed segment in region 7H, 166–181. Here, a reduction effect was revealed for powdery mildew as well as for leaf rust severity. This line might be a valuable resource for transferring new resistance alleles into elite cultivars. In future, we aim to cover the complete exotic genome by selecting additional ILs. We intend to conduct further phenotype studies with the IL set in regard to the trait complexes agronomic performance, malting quality, biotic stress, and abiotic stress.     

Mapping of powdery mildew resistance genes in a newly determined accession of Hordeum vulgare ssp. spontaneum

The accession PI466197 of wild barley (Hordeum vulgare ssp. spontaneum) with a newly identified resistance to powdery mildew caused by Blumeria graminis f.sp. hordei was studied with the aim to localise the genes determining resistance on a barley genetic map using DNA markers. Molecular analysis was performed in the F₂ population of the cross between the winter variety ‘Tiffany’ and the resistant accession PI466197, consisting of 113 plants. DNA markers, 17 simple sequence repeats (SSRs), four sequence-tagged sites (STSs) and one cleaved amplified polymorphic sequence (CAPS) marker developed from the Mla locus sequence were used for genetic mapping and a two-locus model of resistance was shown. One of the resistance genes originating from H. vulgare ssp. spontaneum PI466197 was localised between the markers RGH1aE1 and Bmac0213 on the short arm of chromosome 1H, which is the position consistent with the Mla locus. The other gene was proven to be highly significantly linked with GBMS247, Bmac0134 and MWG878 on the short arm of chromosome 2H. The flanking markers were Bmac0134 and MWG878, assigned 4 and 8 cM from the resistance gene, respectively. Until now, no gene conferring powdery mildew resistance originating from H. vulgare has been located on the short arm of barley chromosome 2H.     

Monosomic and double monosomic substitutions of Hordeum bulbosum L. chromosomes into H. vulgare L.

Summary One of the aims of the interspecific crossing programme between Hordeum vulgare L. and H. bulbosum L. has been to introgress desirable genes into barley from the wild species. However, despite their close taxonomic relationship there have been few reports of achieving this objective using amphidiploid hybrids. In order to broaden the range of available hybrids, partially fertile triploids between H. vulgare (2n = 2x = 14) and H. bulbosum (2n = 4x = 28) were developed and crossed with H. vulgare as female parent. From 580 progeny which were screened, eight putative single monosomic chromosome substitution lines and one double monosomic substitution were identified by cytological analysis. These involved the substitution of H. vulgare chromosome 1 (two lines), 6 (four lines), 6L (one line), 7 (one line) and 1 + 4 (one line) by their respective H. bulbosum homoeologues. The H. bulbosum chromosome was frequently eliminated during plant development, but it was observed regularly in pollen mother cells of two lines. However, pairing between the H. bulbosum chromosome and its H. vulgare homoeologue was low. Several of the lines were more resistant than their H. vulgare parents to powdery mildew (Erysiphe graminis DC. f.sp. hordei Em. Marchai), net blotch (Drechslera teres Sacc.) and scald (Rhynchosporium secalis (Oudem.) Davis). Apart from their use in studying genome relationships, their value to plant breeders will depend on the ease of inducing translocations between the parental chromosomes.     

Comparative AB-QTL analysis in barley using a single exotic donor of Hordeum vulgare ssp. spontaneum.

This paper reports on the first comparative advanced backcross quantitative trait locus (AB-QTL) study in barley. The BC₂F₂ population H×101 was generated from crossing var. Harry [H; Hordeum vulgare ssp. vulgare (Hv)] with ISR101-23 [101; H. v. ssp. spontaneum (Hsp)]. The results of the AB-QTL analysis for 13 quantitative traits are presented and, subsequently, compared with the AB-QTL study of the barley cross Apex × ISR101-23 (A×101; Pillen et al., Theor Appl Genet 107:340–352). Both AB populations share the exotic Hsp donor accession ISR101-23. In H×101, 108 putative QTLs (17%) were identified among the 650 marker×trait combinations tested. Altogether 52 (48 %) favorable effects were identified from the exotic parent. At these marker loci, the homozygous Hsp genotype was associated with an improvement in the trait compared to the homozygous Hv genotype. The percentage of QTLs detected in H×101 was comparable to that in A×101 (17% vs. 15%), however more favorable exotic QTL alleles were located in H×101 than in A×101 (48% vs. 34%). In H×101, the Hsp QTL allele at EBmac0679_[4H] was associated with a yield increase of 5.9% averaged across the six environments tested. A comparison of putative QTLs between H×101 and A×101 was based on 26 shared SSR markers. In total, 26% of the putative QTLs could be detected simultaneously in both AB populations. This finding indicates that only a portion of the QTL effects of the donor allele can be transferred from one elite recipient to the next.Communicated by G. WenzelThis work is dedicated to the 65th birthday of Prof. Dr. H.H. Geiger, Department of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Germany.     

An APETALA1 ortholog affects plant architecture and seed yield component in oilseed rape (Brassica napus L.)

Exploring the natural occurring genetic variation of the wild barley genepool has become a major target of barley crop breeding programmes aiming to increase crop productivity and sustainability in global climate change scenarios. However this diversity remains unexploited and effective approaches are required to investigate the benefits that unadapted genomes could bring to crop improved resilience. In the present study, a set of Recombinant Chromosome Substitution Lines (RCSLs) derived from an elite barley cultivar ‘Harrington’ as the recurrent parent, and a wild barley accession from the Fertile Crescent ‘Caesarea 26–24’, as the donor parent (Matus et al. Genome 46:1010–23, 2003) have been utilised in field and controlled conditions to examine the contribution of wild barley genome as a source of novel allelic variation for the cultivated barley genepool. Twenty-eight RCSLs which were selected to represent the entire genome of the wild barley accession, were genotyped using the 9 K iSelect SNP markers (Comadran et al. Nat Genet 44:1388–92, 2012) and phenotyped for a range of morphological, developmental and agronomic traits in 2 years using a rain-out shelter with four replicates and three water treatments. Data were analysed for marker traits associations using a mixed model approach. We identified lines that differ significantly from the elite parent for both qualitative and quantitative traits across growing seasons and water regimes. The detailed genotypic characterisation of the lines for over 1800 polymorphic SNP markers and the design of a mixed model analysis identified chromosomal regions associated with yield related traits where the wild barley allele had a positive response increasing grain weight and size. In addition, variation for qualitative characters, such as the presence of cuticle waxes on the developing spikes, was associated with the wild barley introgressions. Despite the coarse location of the QTLs, interesting candidate genes for the major marker-trait associations were identified using the recently released barley genome assembly. This study has highlighted the role of exotic germplasm to contribute novel allelic variation by using an optimised experimental approach focused on an exotic genetic library. The results obtained constitute a step forward to the development of more tolerant and resilient varieties.     

Genetic diversity among wild and cultivated barley as revealed by RFLP

Genetic variability of cultivated and wild barley, Hordeum vulgare ssp. vulgare and spontaneum, respectively, was assessed by RFLP analysis. The material consisted of 13 European varietes, single-plant offspring lines of eight land races from Ethiopia and Nepal, and five accessions of ssp. spontaneum from Israel, Iran and Turkey. Seventeen out of twenty-one studied cDNA and gDNA probes distributed across all seven barley chromosomes revealed polymorphism when DNA was digested with one of four restriction enzymes. A tree based on genetic distances using frequencies of RFLP banding patterns was estimated and the barley lines clustered into five groups reflecting geographical origin. The geographical groups of land-race lines showed less intragroup variation than the geographical groups of spontaneum lines. The group of European varieties, representing large variation in agronomic traits, showed an intermediate level. The proportion of gene diversity residing among geographical groups (F_ST) varied from 0.19 to 0.94 (average 0.54) per RFLP pattern, indicating large diversification between geographical groups.     

Genetic Diversity Analysis of Tibetan Wild Barley Using SSR Markers

One hundred and six accessions of wild barley collected from Tibet, China, including 50 entries of the two-rowed wild barley Hordeum vulgare ssp. spontaneum (HS), 29 entries of the six-rowed wild barley Hordeum vulgare ssp. agriocrithon (HA), and 27 entries of the six-rowed wild barley Hordeum vulgare ssp. agriocrithon var. lagunculiforme (HL), were analyzed using 30 SSR markers selected from the seven barley linkage groups for studying genetic diversity and evolutionary relationship of the three subspecies of Tibetan wild barley to cultivated barley in China. Over the 30 genetic loci that were studied, 229 alleles were identified among the 106 accessions, of which 70 were common alleles. H. vulgare ssp. spontaneum possesses about thrice more private alleles (2.83 alleles/locus) than HS (0.93 alleles/locus), whereas almost no private alleles were detected in HL. The genetic diversity among-subspecies is much higher than that within-subspecies. Generally, the genetic diversity among the three subspecies is of the order HS > HL > HA. Phylogenetic analysis of the 106 accessions showed that all the accessions of HS and HA was clustered in their own groups, whereas the 27 accessions of HL were separated into two groups (14 entries with group HS and the rest with group HA). This indicated that HL was an intermediate form between HS and HA. Based on this study and previous works, we suggested that Chinese cultivated barley might evolve from HS via HL to HA.     

Haplotype diversity and population structure in cultivated and wild barley evaluated for Fusarium head blight responses

Fusarium head blight (FHB) is a threat to barley (Hordeum vulgare L.) production in many parts of the world. A number of barley accessions with partial resistance have been reported and used in mapping experiments to identify quantitative trait loci (QTL) associated with FHB resistance. Here, we present a set of barley germplasm that exhibits FHB resistance identified through screening a global collection of 23,255 wild (Hordeum vulgare ssp. spontaneum) and cultivated (Hordeum vulgare ssp. vulgare) accessions. Seventy-eight accessions were classified as resistant or moderately resistant. The collection of FHB resistant accessions consists of 5, 27, 46 of winter, wild and spring barley, respectively. The population structure and genetic relationships of the germplasm were investigated with 1,727 Diversity Array Technology (DArT) markers. Multiple clustering analyses suggest the presence of four subpopulations. Within cultivated barley, substructure is largely centered on spike morphology and growth habit. Analysis of molecular variance indicated highly significant genetic variance among clusters and within clusters, suggesting that the FHB resistant sources have broad genetic diversity. The haplotype diversity was characterized with DArT markers associated with the four FHB QTLs on chromosome 2H bin8, 10 and 13 and 6H bin7. In general, the wild barley accessions had distinct haplotypes from those of cultivated barley. The haplotype of the resistant source Chevron was the most prevalent in all four QTL regions, followed by those of the resistant sources Fredrickson and CIho4196. These resistant QTL haplotypes were rare in the susceptible cultivars and accessions grown in the upper Midwest USA. Some two- and six-rowed accessions were identified with high FHB resistance, but contained distinct haplotypes at FHB QTLs from known resistance sources. These germplasm warrant further genetic studies and possible incorporation into barley breeding programs.     

Antigenicity of nitrate reductase-deficient mutants in Hordeum vulgare L.

Summary Ten nitrate reductase (NR)-deficient mutants have been characterized for their cross-reactivity against specific barley (Hordeum vulgare L.) nitrate reductase antibodies. The rabbit antibodies raised against the purified barley wild type (cv. Steptoe) enzyme quantitatively inactivate nitrate reductase in crude extracts. All nitrate-grown (induced) mutants show positive precipitin reaction against the antiserum by Ouchterlony double diffusion test and all have the ability to neutralize antisera in a NR protection assay. Under induced growth conditions, mutants Az 12, Az 23, Az 29 and Az 30 which have low NR associated catalytic activities also have the lowest level of antigenicity; mutants Az 13, Az 31, Az 33 and Az 34 have intermediate level of both NR associated catalytic activities and antigenicity, while mutants Az 28 and Az 32 have the highest level of both NR associated catalytic activities and antigenicity. Under noninduced growth conditions, all mutants except Az 12 contain detectable but very low levels of NR antigenicity. These results support the concept that these NR-deficient mutants with various levels of NR associated catalytic activities represent different mutation events at the loci coding the NR structural components.Abbreviations NR nitrate reductase - DTT dithiothreitol - FAD flavin adenine dinucleotide - BSA bovine serum albumin - NRCRM nitrate reductase cross-reacting materials Scientific Paper No. 5765. College of Agriculture Research Center, Washington State University, Pullman, Project Nos. 0233 and 0430. Supported in part by National Science Foundation Grant #PCM7807649, and U.S. Department of Agriculture CRGO Grant #7900536