Hexaploid Oat Research Articles

Regeneration of oat androgenic plants in relation to induction media and culture conditions of embryo-like structures

The effect of C17 and W14 induction media on the formation of embryo-like structures (ELS) from F3 generation of nine hexaploid oat hybrids was investigated in the study. In all genotypes, the highest number of ELS (0.6 - 12.1/100 anthers) was obtained on C17 medium. The efficiency of plant regeneration on medium 190-2 was tested, in relation to different ELS culture conditions. The highest rate of green plants per 100 ELS (3.3 - 42.4) was produced by incubation at 22<sup>o</sup>C in the dark for the first two weeks. Among 36 green regenerants, 28 (77.8%) were haploid and 8 (22.2%) were spontaneous doubled haploids, fully fertile. After colchicine treatment of haploid plants, 19 were partially fertile and set from 1 to 15 seed per panicle.

Additional Sources of Broad-Spectrum Resistance to Puccinia coronata f. sp. avenae from Canadian Accessions of Avena barbata.

Crown rust (Puccinia coronata f. sp. avenae) is considered the most damaging disease of oat and the use of race-specific seedling (Pc) genes for resistance has been the primary means of control. As these resistance genes from cultivated oat, Avena sativa, and the wild hexaploid animated oat, A. sterilis, were deployed in oat cultivars, corresponding virulence in the U.S. crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar in the United States is now 5 years or less. Introgression of resistance from diploid and tetraploid Avena spp. into hexaploid oat has been difficult due to the difference in ploidy levels and the lack of pairing of homeologous chromosomes between species. The wild tetraploid slender oat, A. barbata, has been a source of powdery mildew and stem rust resistance in cultivated oat but has largely been unexploited for crown rust resistance. A relatively high percentage of A. barbata accessions from the United States Department of Agriculture (USDA) National Small Grains Collection were resistant to a highly diverse crown rust population in recent tests. Tests of 1,099 A. barbata accessions from the Canadian Plant Gene Resources Center not represented in the USDA collection revealed that a similar percentage (11.4%) were at least moderately resistant at the seedling and adult plant stage when tested with a highly diverse bulk inoculum derived from the St. Paul buckthorn nursery. Eighteen accessions were rated as highly resistant or a mix of highly resistant and resistant plants in both seedling and adult plant tests. Three accessions (CN21531 from Italy and CN26271 and CN26305 from Spain) displayed a unique "blotchy" resistant reaction as adult plants. Resistant accessions were found from throughout much of the natural range of A. barbata but the Western Mediterranean and Lebanon had the highest frequency of accessions with broad-spectrum resistance.

Genetic control of agronomic traits in an oat population of recombinant lines

Understanding the genetic control of phenotypic traits is essential to increase the efficiency of selection for adapted, high-yielding genotypes. The purpose of this study was to determine the genetic control of nine traits of hexaploid oat. Phenotypic data were collected from a population of 162 recombinant lines derived from the cross 'UFRGS17 x UFRGS 930598-6'. For the traits plant growth habit, hairs on leaf edges and panicle type, monogenic genetic control was observed. A quantitative and/or polygenic genetic control was stated for the traits panicle weight, panicle length, vegetative cycle, plant height, test weight and grain yield. High heritability was estimated for the traits vegetative cycle (h² = 0.89) and plant height (h² = 0.79), while moderate heritability was determined for test weight (h² = 0.51) and grain yield (h² = 0.48).

A new chromosome nomenclature system for oat (Avena sativa L. and A. byzantina C. Koch) based on FISH analysis of monosomic lines

Fluorescent in situ hybridization (FISH) with multiple probes was used to analyze mitotic and meiotic chromosome spreads of Avena sativa cv 'Sun II' monosomic lines, and of A. byzantina cv 'Kanota' monosomic lines from spontaneous haploids. The probes used were A. strigosa pAs120a (a repetitive sequence abundant in A-genome chromatin), A. murphyi pAm1 (a repetitive sequence abundant in C-genome chromatin), A. strigosa pITS (internal transcribed spacer of rDNA) and the wheat rDNA probes pTa71 (nucleolus organizer region or NOR) and pTa794 (5S). Simultaneous and sequential FISH employing pairs of these probes allowed the identification and genome assignation of all chromosomes. FISH mapping using mitotic and meiotic metaphases facilitated the genomic and chromosomal identification of the monosome in each line. Of the 17 'Sun II' lines analyzed, 13 distinct monosomic lines were found, corresponding to four monosomes of the A-genome, five of the C-genome and four of the D-genome. In addition, 12 distinct monosomic lines were detected among the 20 'Kanota' lines examined, corresponding to six monosomes of the A-genome, three of the C-genome and three of the D-genome. The results show that 19 chromosomes out of 21 of the complement are represented by monosomes between the two genetic backgrounds. The identity of the remaining chromosomes can be deduced either from one intergenomic translocation detected on both 'Sun II' and 'Kanota' lines, or from the single reciprocal, intergenomic translocation detected among the 'Sun II' lines. These results permit a new system to be proposed for numbering the 21 chromosome pairs of the hexaploid oat complement. Accordingly, the A-genome contains chromosomes 8A, 11A, 13A, 15A, 16A, 17A and 19A; the C-genome contains chromosomes 1C, 2C, 3C, 4C, 5C, 6C and 7C; and the D-genome consists of chromosomes 9D, 10D, 12D, 14D, 18D, 20D and 21D. Moreover, the FISH patterns of 16 chromosomes in 'Sun II' and 15 in 'Kanota' suggest that these chromosomes could be involved in intergenomic translocations. By comparing the identities of individually translocated chromosomes in the two hexaploid species with those of other hexaploids, we detected different types of intergenomic translocations.

Hybrids of Avena sativa with two diploid wild oats (CIav6956) and (CIav7233) resistant to crown rust

Two diploid accessions of wild oat, CIav6956 and CIav7233, were identified as carrying seedling resistance to oat crown rust (caused by Puccinia coronata f. sp. avenae; Pca). Two vigorous interploidy F1 hybrids were generated from crosses involving the hexaploid oat cultivar Wintaroo and the diploid oat Avena strigosa Schreb. accession CIav6956. An additional interploidy F1 hybrid, designated “F1-Aa1”, was produced from a cross of Wintaroo and the diploid oat accession CIav7233. All three hybrids were more vigorous and taller than the cultivated parent Wintaroo. The three F1 hybrids contained full chromosome complements from both parents (2n = 4x = 28), but no seeds were obtained when the three F1 hybrids were selfed. Meiotic analyses of the hybrids indicated that they exhibited a high degree of inter-genome and intra-genome pairing. Trivalent configurations were detected in 95–96% of meiotic cells and a minimum of three bivalents was present in all cells. An average chiasma frequency of 7.2–7.9 per cell was observed for the three F1 hybrids. A fourth F1 hybrid was subsequently generated from a cross between the diploid oat accession CIav7233 and Wintaroo. One octaploid (2n = 8x = 56) was generated from this hybrid and progeny were resistant to two Pca races. The chromosome number of the octaploid progeny varied between 51 and 54 chromosomes. Development of a chromosome addition line(s) with the crown rust resistance should be possible from these partial-octaploids.

Broad-Spectrum Resistance to Crown Rust, Puccinia coronata f. sp. avenae, in Accessions of the Tetraploid Slender Oat, Avena barbata.

The use of race-specific seedling genes for resistance has been the primary means of controlling crown rust of oat (Puccinia coronata). As resistance genes from hexaploid cultivated oat, Avena sativa and, later, the wild hexaploid animated oat, A. sterilis, were deployed in oat cultivars, corresponding virulence in the crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar in the United States is now 5 years or less. Introgression of resistance genes from diploid and tetraploid Avena spp. into hexaploid oat has been difficult due to differences in ploidy levels and the lack of homology of chromosomes between the two species. The wild tetraploid slender oat, A. barbata, has been a source of powdery mildew and stem rust resistance in cultivated oat but has largely been unexploited for crown rust resistance. In total, 359 accessions of A. barbata from the National Small Grains Collection were evaluated in seedling greenhouse tests. Of these accessions, 39% were at least moderately resistant when inoculated with a crown rust race with low virulence (DBBC). When tested further with a highly diverse bulk inoculum from the 2006 and 2007 St. Paul buckthorn nursery, 48 accessions (approximately 13%) were resistant. Many of these accessions were heterogeneous in reaction, but two accessions (PI320588 from Israel and PI337893 from Italy) were highly resistant (immune) and two others (PI337886 from Italy and PI367293 from Spain) consistently produced resistant reactions (chlorotic flecks) in all tests. Resistant accessions were found from throughout much of the natural range of A. barbata. Crosses of some of the better accessions have been made to cultivated oat.

The first doubled haploid linkage map for cultivated oat

To date, all linkage maps of hexaploid oat (Avena sativa L.) have been constructed using recombinant inbred lines (RILs). Doubled haploids (DHs), however, have the advantage over RILs of their comprehensive homozygosity. DHs have been used for mapping in several cereal species, but in oats the production of large DH populations has only recently become an option. A linkage map of hexaploid oat was constructed using an anther culture-derived DH population (137 individuals) from the F1 individuals of a cross between the Finnish cultivar 'Aslak' and the Swedish cultivar 'Matilda'. The map is composed of 28 linkage groups containing 625 DNA markers: 375 AFLPs (amplified fragment length polymorphisms), 3 IRAPs (inter-retrotransposon amplified polymorphisms), 12 ISSRs (inter simple sequence repeats), 12 microsatellites, 57 RAPDs (random amplified polymorphic DNAs), 59 REMAPs (retrotransposon-microsatellite amplified polymorphisms), 105 SRAPs (sequence-related amplified polymorphisms), and 2 SNPs (single-nucleotide polymorphisms). The total map size is 1526 cM. Over half of the markers in the map showed distorted segregation, with alleles from 'Aslak' usually prevailing. This is explained by the better performance of 'Aslak' in anther culture. Quantitative trait loci affecting some important quality and agronomic traits are being localized on the map.

The origin of the C-genome and cytoplasm of Avena polyploids

The contribution of C-genome diploid species to the evolution of polyploid oats was studied using C-genome ITS-specific primers. SCAR analysis among Avena accessions confirmed the presence of C-genome ITS1-5.8S-ITS2 sequences in the genome of AACC and AACCDD polyploids. In situ hybridization and screening of more than a thousand rRNA clones in Avena polyploid species containing the C-genome revealed substantial C-genome rRNA sequence elimination. C-genome clones sequenced and Maximum Likelihood Parsimony analysis revealed close proximity to Avena ventricosa ITS1-5.8S-ITS2 sequences, providing strong evidence of the latter's active role in the evolution of tetraploid and hexaploid oats. In addition, cloning and sequencing of the chloroplastic trnL intron among the most representative Avena species verified the maternal origin of A-genome for the AACC interspecific hybrid formation, which was the genetic bridge for the establishment of cultivated hexaploid oats.

Molecular diversity of the 5S rRNA gene and genomic relationships in the genus Avena (Poaceae: Aveneae)

The molecular diversity of the rDNA sequences (5S rDNA units) in 71 accessions from 26 taxa of Avena was evaluated. The analyses, based on 553 sequenced clones, indicated that there were 6 unit classes, named according to the haplomes (genomes) they putatively represent, namely the long A1, long B1, long M1, short C1, short D1, and short M1 unit classes. The long and short M1 unit classes were found in the tetraploid A. macrostachya, the only perennial species. The long M1 unit class was closely related to the short C1 unit class, while the short M1 unit class was closely related to the long A1 and long B1 unit classes. However, the short D1 unit class was more divergent from the other unit classes. There was only one unit class per haplome in Avena, whereas haplomes in the Triticeae often have two. Most of the sequences captured belonged to the long A1 unit class. Sequences identified as the long B1 unit class were found in the tetraploids A. abyssinica and A. vaviloviana and the diploids A. atlantica and A. longiglumis. The short C1 unit class was found in the diploid species carrying the C genome, i.e., A. clauda, A. eriantha, and A. ventricosa, and also in the diploid A. longiglumis, the tetraploids A. insularis and A. maroccana, and all the hexaploid species. The short D1 unit class was found in all the hexaploid species and two clones of A. clauda. It is noteworthy that in previous studies the B genome was found only in tetraploid species and the D genome only in hexaploid species. Unexpectedly, we found that various diploid Avena species contained the B1 and D1 units. The long B1 unit class was found in 3 accessions of the diploid A. atlantica (CN25849, CN25864, and CN25887) collected in Morocco and in 2 accessions of A. longiglumis (CIav9087 and CIav9089) collected in Algeria and Libya, respectively, whereas only 1 clone of A. clauda (CN21378) had the short D1 unit. Thus there might be a clue as to where to search for diploids carrying the B and D genomes. Avena longiglumis was found to be the most diverse species, possibly harboring the A, B, and C haplomes. The long M1 and short M1 are the unit classes typical of A. macrostachya. These results could explain the roles of A. clauda, A. longiglumis, and A. atlantica in the evolution of the genus Avena. Furthermore, one clone of the tetraploid A. murphyi was found to have sequences belonging to the short D1 unit class, which could indicate that A. murphyi might have been the progenitor of hexaploid oats and not, as postulated earlier, A. insularis. The evolution of Avena did not follow the molecular clock. The path inferred is that the C genome is more ancient than the A and B genomes and closer to the genome of A. macrostachya, the only existing perennial, which is presumed to be the most ancestral species in the genus.

An Intergenomic Reciprocal Translocation Associated with Oat Winter Hardiness Component Traits

The reciprocal intergenomic translocation between hexaploid oat (Avena sp.) chromosomes 7C and 17 (T7C‐17) has been associated with the division of cultivated oat into A. sativa L. and A. byzantina K. Koch species and differences in crown freezing tolerance and winter field survival. The objectives of this experiment were: (i) to validate the association of T7C‐17 with crown freezing tolerance and winter field survival in a population derived from a cross of the non‐winter‐hardy ‘Fulghum’ (non‐T7C‐17) with winter‐hardy ‘Norline’ (T7C‐17); (ii) to determine if preferential selection for T7C‐17 occurred during inbreeding; and (iii) to examine the association of T7C‐17 with the winter hardiness component traits heading date, plant height, and vernalization and photoperiod responses. Crown freezing tolerance and vernalization and photoperiod responses were evaluated in controlled environment studies. Heading date, plant height, and winter field survival were evaluated in field experiments during two seasons. The presence of the translocation was associated with greater crown freezing tolerance, winter field survival, and days to flowering. Translocation status was not associated with vernalization and photoperiod responses or plant height. The T7C‐17/non‐T7C‐17 segregation ratio was 2:1. These results confirmed the importance of T7C‐17 in conferring winter hardiness traits in winter oat and preferential selection for the translocation during inbreeding.

Assessments of genetic diversity within a world collection of cultivated hexaploid oat (Avena sativa L.) based on qualitative morphological characters

A characterization of 10,105 accessions of hexaploid cultivated oat (Avena sativa L. sensu lato) from 85 countries of the Plant Gene Resources of Canada (PGRC) collection was conducted at Saskatoon, Saskatchewan, Canada. Eight environmentally stable morphological characters (panicle type, panicle erectness, panicle density, lemma colour, dorsal awn of lemma, ligula, major infraspecific group), differentiated into 18 character states, were used to define genetically distinct morphological groups. Comparisons of oat diversity from different countries, among the major infraspecific groups and among Canadian oat cultivars registered between 1886 and 2002 were possible. The 10,105 accessions represented 118 different morphological groups. The number of accessions in each morphological group was unevenly distributed with the 13 most frequent morphological groups including 90% of the accessions. The most frequent morphological groups in the PGRC collection were identical with the most frequent types of Canadian oat cultivars. The greatest richness of diversity was found in oat from countries with temperate climates and intensive oat breeding programmes. The oat accessions comprised 8,754 accessions of common hulled oat, 183 accessions of hull-less oat and 1,168 accessions of red oat. For red oat (A. byzantina C. Koch), West Asia was richest in diversity. The USA could be considered a secondary centre of diversity for red oat and Canada a secondary centre of diversity for hull-less oat. Morphological diversity of oat cultivars released in Canada increased during the twentieth century. The morphological groups were related to formal taxonomical infraspecific classifications of A. sativa. Applications of the concept of defining morphological groups for phenotyping a large germplasm collection are demonstrated discussed.

Development and Mapping of PCR‐Based SCAR and CAPS Markers Linked to Oil QTLs in Oat

ABSTRACTOat cultivars (Avena sativa L.) are unusually diverse in groat oil content, and breeding for this trait can increase the value of oat in human and livestock diets. Seven random amplified polymorphic DNA (RAPD) fragments closely linked or tentatively linked to quantitative trait loci (QTLs) for oil content in the ‘Terra’ × ‘Marion’ (TM) or the ‘Kanota’ × ‘Ogle’ (KO) hexaploid oat mapping populations were used to develop more robust sequence characterized amplified region (SCAR) or cleaved amplified polymorphic sequence (CAPS) markers. Three SCAR and two CAPS markers mapped on the TM population to the same map locations as the corresponding RAPD markers. One SCAR marker mapped to a homeologous TM linkage group (LG). The last two SCAR markers were mapped to regions that are currently not known to be orthologous to the original RAPD locations. All SCAR and CAPS markers were also tested in two additional high × low oil content populations. These SCAR markers have potential utility for marker‐assisted selection (MAS) for high and low oil germplasm in oat breeding programs.

Transfer of new dwarfing genes from the weed species Avena fatua into cultivated oat A. byzantina

AbstractNew sources of dwarfing genes were identified from accessions of Avena fatua in Japan and Korea. The dwarfing genes were transferred from backcrossed and self‐pollinated relatives to the cultivated oat ‘Kanota’. In the cultivated form, the dominant dwarfing gene Dw8 showed a relatively lower transmission rate than recessive, semi‐dominant and nondwarfing genes and was characterized by a distinct link with wild gene cluster. This was also supported by the high transmission rate of wild specific SSR alleles. Four dwarf inbred lines (L153, L169a, L169b and L812) were identified as involving a single recessive dwarfing gene(s). The recessive dwarfing genes that showed normal and stable transmission rates in BC1F3 were first reported in hexaploid oats. The L169 segregated two different recessive dwarf lines in BC1, which were selected as semi‐ (L169a) and extreme‐ (L169b) dwarf lines. The L169a was a good genotype with a high grain yield. L288 is a semi‐dwarf line conditioned by a semi‐dominant dwarfing gene, with a unilateral panicle, large florets and good grain quality due to strong resistance to lodging. L342 had a short peduncle, making the panicle compact, and its phenotype was similar to the dwarfness controlled by Dw7, but the dwarfing genes were different.

Loci affecting flowering time in oat under short-day conditions

Flowering time (or days to heading) is an important characteristic in crop plants that affects adaptation to cropping cycles and growing seasons. The objectives of this study were to identify molecular markers associated with flowering time in 3 oat populations developed from Brazilian oat varieties, and to compare their map locations with those of other loci that might influence flowering time. Flowering time was studied in recombinant inbred lines from 3 hexaploid oat populations: UFRGS 8 x Pc68/5*Starter; UFRGS 881971 x Pc68/5*Starter; and UFRGS 8 x UFRGS 930605. Bulked segregant analysis, using amplified fragment length polymorphism, was followed by selective mapping in each population and in a reference population, 'Kanota' x 'Ogle' (KxO). One quantitative trait locus (QTL) with major effects on flowering time was identified in each cross. Comparative mapping showed that a major QTL, with earliness alleles originating from UFRGS 8 and UFRGS 881971, is in a region with close homology to KxO linkage group 17 and to a locus that reportedly confers day-length insensitivity in oat (Di1). This is the first report to identify the map location of the Di1 locus, and putatively confirm the presence of Di1 alleles in new germplasm. Further comparative mapping and the alignment of mapped oat markers with the sequenced rice genome suggest that this QTL and (or) Di1 is orthologous to the Hd1 locus in rice and the CONSTANS gene in Arabidopsis and other species. A different QTL with major effects segregated in the UFRGS 8 x UFRGS 930605 cross, where the early-flowering allele for Di1 was probably fixed. Two additional QTLs with smaller effects were identified in the UFRGS 8 x Pc68/5*Starter population. These results suggest that the Brazilian oat line UFRGS 8 contains an optimal set of alleles conditioning earliness under the short-day conditions of the Brazilian winter growing season, and that molecular selection could be used to introgress these alleles into other breeding material.

Identification of resistance gene analogs as markers of disease resistance loci in oats, using near-isogenic lines

Genomic sequences with features of the major class of disease resistance genes and which bear nucleotide-binding leucine-rich repeat sequences (resistance gene analogs; RGA) were tested as potential markers of crown rust resistance loci in hexaploid oats. Two collections of paired near-isogenic lines carrying resistance to different isolates of crown rust, Puccinia coronata were screened. Two out of the four RGAs assayed showed restriction fragment length polymorphism (RFLP) between one line of each collection and its recurrent parent. The paired lines X466 and D494 were polymorphic for RGA III2.2 and the pair of lines X470 and D504 were polymorphic for RGA III2.18. The III2.18 polymorphism was located in the hexaploid map Avena byzantina cv. ‘Kanota’ × A. sativa cv. ‘Ogle’ in linkage group KO17 in a region previously associated with crown rust resistance. In addition, 220 random primers were used for random amplified polymorphic DNA (RAPD) analysis to screen the two sets of NILs. Only one polymorphic band was obtained that differentiated the paired lines X470 and D504 from their parents. The RAPD band was used as a probe and the relevant RFLP that differentiated the NILs X470 and D504 was found at 1.7 cM from the III2.18 marker in KO17. RFLP analysis using probes previously mapped in KO17 confirmed differences for X470 and D504 in the region around the III2.18 marker. These results suggest that the resistance locus shared by this pair of NILs is probably linked to the markers revealed by RGA III2.18. The use of RGAs as RFLP probes in the screening of NILs with differences in crown rust resistance has proved to be more effective than RAPDs for finding polymorphic markers possibly linked to resistance loci.

Inheritance and mapping of a powdery mildew resistance gene introgressed from Avena macrostachya in cultivated oat

The powdery mildew resistance from Avena macrostachya was successfully introgressed into hexaploid oat (A. sativa). Genetic analysis of F(1), F(2), F(3) and BC(1) populations from two powdery-mildew resistant introgression lines revealed that the resistance is controlled by a dominant gene, tentatively designated Eg-5. Molecular marker analysis was conducted using bulked-segregant analysis in two segregating F(3) populations. One codominant simple sequence repeats (SSR) marker AM102 and four AFLP-derived PCR-based markers were successfully developed. The SSR marker AM102 and the STS marker ASE41M56 were linked to the gene Eg-5, with genetic distances of 2 and 0.4 cM, respectively, in both mapping populations. Three STS markers (ASE45M56, ASE41M61, ASE36M55) co-segregated with Eg-5 in one population while two (ASE45M56, ASE36M55) of them linked to Eg-5 with a genetic distance of 1 cM in another population. The gene was further mapped to be in a region corresponding to linkage group 22_44+18 in the Kanota x Ogle (KO) hexaploid oat map by comparative mapping. To our knowledge, this is the first report of mapping powdery-mildew resistance in hexaploid oat. The new resistance source of A. macrostachya, together with the tightly linked markers identified here, could be beneficial in oat breeding programmes.

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

A Cytological Marker Associated with Winterhardiness in Oat

The intergenomic translocation T7C‐17 occurs at different frequencies in fall‐ versus spring‐sown hexaploid oat (Avena sp.) germplasm. The objectives of this experiment were to evaluate crown meristem freeze tolerance and winter field survival among 94 random F4–derived lines from the cross between the cultivars Wintok (T7C‐17, winterhardy) and Fulghum (non‐T7C‐17, less winterhardy) and to examine the association between these winterhardiness traits and T7C‐17. Crown meristem freeze tolerance was evaluated in a three‐replicate randomized complete block design in controlled environment growth cabinets. Field survival was evaluated in a three replicate randomized complete block design at Laurel Springs, NC during the 1999–2000 season. Greater crown meristem freeze tolerance and greater winter field survival were associated with the presence of T7C‐17. Lines heterogeneous for the translocation had similar levels of crown meristem freeze tolerance and field survival as lines homozygous for the translocation. Twenty‐two percent of the variation in crown meristem freeze tolerance and 27% of the variation in field survival was accounted for by translocation status. The observed frequencies of translocation homozygotes and heterozygotes did not fit the expected frequencies for single factor segregation in the F4 generation. There were almost threefold as many homozygotes with the translocation as homozygotes without the translocation which indicated preferential selection for T7C‐17 during inbreeding. Our results suggested that T7C‐17 might be isolating, in terms of recombination, either a dominant allele or a group of loci conditioning winterhardiness in our population.

Variation in the Ratio of Oat (Avena) Protein Fractions of Interest in Coeliac Grain Diets

The previously found wide range in the ratios of avenin or methanol-precipitated fractions to residual proteins was revisited by studying 75 oat varieties, mainly representing landraces from Finland, and included old varieties or selections, cv. Kyto, synthetic hexaploid oats and an Avena strigosa line (HA 71–87). The means of the fraction ratios ranged from 4.17 to 6.46 with significant differences. Samples of 10 narrow-ratio and 10 wide-ratio oats were compared more closely. The wide-ratio sample had significantly higher total protein content and significantly lower content of the methanol-precipitated protein fraction. Therefore, both fractions in general appear to contribute to the ratio of the protein fractions. The wide-ratio sample had significantly lower grain mass and husk-free karyopsis mass. Samples of the extreme ends in the ratios of the protein fractions showed different electrophoretic protein patterns, which was also seen in samples representing the same population of origin. It is evident that polymorphisms in the protein fractions would allow breeding of oat cultivars showing further lowering of proteins putatively toxic to coeliacs assuming oats contain these toxic proteins.

Patterns of AFLP variation in a core subset of cultivated hexaploid oat germplasm

Many core collections have been developed from large collections of crop germplasm, but most of these have not been characterized, particularly using molecular techniques, for germplasm management and utilization. We have attempted to characterize a structured sample representing a world collection of 11,622 cultivated hexaploid oat accessions in the hope of understanding the genetic structure of the world collection. The amplified fragment length polymorphism (AFLP) technique was applied to screen 670 accessions representing 79 countries and one group of uncertain origin. For each accession, 170 AFLP polymorphic bands detected by five AFLP primer pairs were scored. Analyses of the AFLP data showed the effectiveness of the stratified sampling applied in capturing country-wise AFLP variation. The frequencies of polymorphic bands ranged from 0.11 to 0.99, with an average of 0.72. The majority (89.9%) of the AFLP variation resided within accessions of each country, and only 6.2% of the AFLP differences existed among accessions of major geographic regions. Accessions from the Mediterranean region were the most distinct, while those from Russia and the USA were the most diverse. The two distinct groups that were observed were separated largely on the basis of common oat and red oat. Red oat was genetically more diverse than its common and hull-less counterparts, and hull-less oat was more related to common oat than red oat. Landrace and non-landrace accessions displayed similar AFLP variation patterns. These patterns are significant for understanding the domestication of cultivated oat and are useful in classifying the intraspecific diversity of oat germplasm, developing specific core subsets of the oat collection, and exploring new sources of genes for oat improvement.