Nutritional benefits of cultivated oat (Avena sativa L., 2n = 6x = 42, AACCDD) are well recognized; however, seed protein levels are modest and resources for genetic improvement are scarce. The wild tetraploid, A. magna Murphy et Terrell (syn A. maroccana Gdgr., 2n = 4x = 28, CCDD), which contains approximately 31% seed protein, was hybridized with cultivated oat to produce a domesticated A. magna. Wild and cultivated accessions were crossed to generate a recombinant inbred line (RIL) population. Although these materials could be used to develop domesticated, high-protein oat, mapping and quantitative trait loci introgression is hindered by a near absence of genetic markers. Objectives of this study were to develop high-throughput, A. magna-specific markers; generate a genetic linkage map based on the A. magna RIL population; and map genes controlling oat domestication. A Diversity Arrays Technology (DArT) array derived from 10 A. magna genotypes was used to generate 2,688 genome-specific probes. These, with 12,672 additional oat clones, produced 2,349 polymorphic markers, including 498 (21.2%) from A. magna arrays and 1,851 (78.8%) from other Avena libraries. Linkage analysis included 974 DArT markers, 26 microsatellites, 13 SNPs, and 4 phenotypic markers, and resulted in a 14-linkage-group map. Marker-to-marker correlation coefficient analysis allowed classification of shared markers as unique or redundant, and putative linkage-group-to-genome anchoring. Results of this study provide for the first time a collection of high-throughput tetraploid oat markers and a comprehensive map of the genome, providing insights to the genome ancestry of oat and affording a resource for study of oat domestication, gene transfer, and comparative genomics.

Although microsatellites are an efficient and reliable genetic marker system, availability is limited in cultivated oat (Avena sativa L.). Previous research has suggested that microsatellites from related species may be adapted to oat. This study investigated the stability of existing oat microsatellites, sequenced polymorphic oat amplicons derived from wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) primers, and redesigned primers to develop oat-based markers. We evaluated 161 published oat microsatellites and identified 9 with polymorphism between mapping parents Ogle1040 and TAM O-301 (OT). We also studied 30 wheat, 1 Aegilops tauschii Coss., and 9 barley primers with reported oat polymorphism. Sixteen primers (1 A. tauschii, 10 wheat, 5 barley) amplified random oat sequences and were used to generate 28 new oat STS markers. Eight primers, 4 each from wheat and barley, amplified oat repetitive motifs, generating 10 new oat SSRs. Four additional SSRs were developed from characterization of thaumatin-like pathogenesis-related protein sequences formerly utilized as the Rast1-4 oat marker. These new markers, along with 9 existing oat SSRs and 6 previously identified disease resistance loci, were mapped in the OT population, joining 3 pairs of linkage groups. Map locations of multiallelic SSRs and disease-resistance QTL interactions suggested possible homoeologous relationships among the oat chromosomes.

Durum wheat (Triticum turgidum L. subsp. durum) production in North America in recent years has been seriously threatened by epidemics of Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schw.) Petch]. Deployment of FHB‐resistant cultivars has been considered the most effective and cost‐efficient strategy to combat this disease; however, progress in developing FHB‐resistant durum wheat cultivars has been hindered by a lack of effective sources of resistance. The objective of this study is to identify tetraploid wheat germplasm that could be used to enhance FHB resistance in durum wheat. We evaluated FHB reactions in 376 accessions of five cultivated subspecies of T. turgidum, including Persian wheat [T. turgidum subsp. carthlicum (Nevski) Á. Löve and D. Löve], cultivated emmer wheat [T. turgidum subsp. dicoccum (Schrank ex Schübler) Thell.], Polish wheat [T. turgidum subsp. polonicum (L.) Thell.], Oriental wheat [T. turgidum subsp. turanicum (Jakubz.) Á. Löve and D. Löve], and Poulard wheat (T. turgidum L. subsp. turgidum). We used point inoculation to evaluate resistance to the spread of infection over three greenhouse seasons and used the grain inoculum method of inoculation to evaluate putatively resistant accessions in two field locations. Preliminary evaluation data showed that 16 T. turgidum subsp. carthlicum and 4 T. turgidum subsp. dicoccum accessions consistently exhibited resistance or moderate resistance to FHB. These accessions likely carry genetic resistance to FHB and could be used directly in breeding programs to enhance FHB resistance in durum wheat.

Tan spot (caused by Pyrenophora tritici-repentis) and Stagonospora nodorum blotch (SNB) (caused by Stagonospora nodorum) are destructive fungal diseases of wheat (Triticum aestivum) throughout the world. Host plant resistance is thought to be an efficient and economical method of control. The objective of the present study was to identify novel sources of tan spot and SNB resistance in wheat genotypes derived from the crosses between wheat and alien species. Evaluations were conducted at the seedling stage in a growth chamber with 100% relative humidity. For each genotype, three replications were used for each disease. Among the 199 wheat-alien species derivatives evaluated, 65 exhibited resistance to tan spot and 30 showed resistance to SNB similar to BR34, a Brazilian wheat line used as the resistant control. Eleven derivatives were resistant to both diseases. Reactions of the derivatives and their respective wheat parents to tan spot and SNB suggest that resistance genes in the derivatives are derived from alien species. These derivatives can serve as desirable bridges for introgression of resistance genes from alien species to cultivated wheat, and could contribute novel and effective tan spot and SNB resistance to wheat breeding.

Over one thousand accessions of wheat relatives at different ploidy levels and wheat-alien species derivatives with varied chromosome constitutions were evaluated for Fusarium head blight (FHB) resistance. FHB resistance identified from the relatives and derivatives were introgressed into adapted bread and durum wheat backgrounds using several strategies. A number of resistant introgression lines that contain minimal alien chromatin and do not have obvious linkage drag were developed. Some of the introgression lines exhibited resistance to other fungal diseases in addition to FHB. The biggest challenges of alien introgression for FHB resistance are linkage drag associated with alien chromatin and the epistatic effects of alien resistance genes with genetic backgrounds. Thus, efficient manipulation of alien chromatin and selection of proper recipient genotypes play a central role in the success of alien introgression for FHB resistance.

ABSTRACTFusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe, is a serious disease of wheat (Triticum spp.) worldwide. Host resistance has proven the most effective method of controlling FHB in common wheat (T. aestivum L., 2n = 6x = 42, genomes AABBDD). Progress in breeding for FHB resistance in durum wheat (T. turgidum L. ssp. durum, 2n = 4x = 28, genomes AABB), however, has been limited by a lack of resistance sources. Fortunately, durum wheat has a large number of tetraploid relatives, which represent a gene pool for improvement of FHB resistance in durum. The objective of this study was to search for sources of FHB resistance in wild emmer wheat [T. turgidum L. ssp. dicoccoides (Körn. ex Asch. & Graebner) Thell., 2n = 4x = 28, genomes AABB] (TDIC). We evaluated 416 accessions of wild emmer wheat for reaction to FHB using the point inoculation method in a greenhouse environment. Accessions exhibiting a low FHB disease rating in preliminary evaluations were retested in fully replicated experiments. Among the 416 accessions tested, there was wide variation in response to FHB, ranging from highly resistant to highly susceptible. Several accessions showed minimal disease development across two or more seasons and represent potential new sources to enhance resistance of durum wheat to FHB.

Four wheat (Triticum aestivum L.)-Thinopyrum ponticum derivatives SS5 (PI604926), SS156 (PI604947), SS363 (PI604970), and SS660 (PI604879), were identified as resistant to Fusarium head blight (FHB), a serious fungal disease of wheat worldwide. Seedling reactions to tan spot and Stagonospora nodorum blotch (SNB), two important foliar diseases of wheat, suggest that these four derivatives are resistant to tan spot and two of them (SS5 and SS156) are resistant to SNB. Fluorescent genomic in situ hybridization (FGISH) patterns of mitotic chromosomes indicate that these four derivatives are partial wheat-Th. ponticum amphiploids, each with a total of 56 chromosomes, though with different amounts of Th. ponticum chromatin. These four amphiploids were hybridized with each other to determine homology between the Th. ponticum genomes in each of the amphiploids. Analysis of chromosome pairing in the F1 hybrids using FGISH suggests that each amphiploid carries a similar set of Th. ponticum chromosomes. These wheat-Th. ponticum amphiploids represent a potential novel source of resistance to FHB, tan spot, and SNB for wheat breeding.

Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe, is a destructive disease of wheat (Triticum spp.) in humid growth conditions throughout the world. Genetic resistance of the host plant is considered the most effective and sustainable method of defense against FHB; however, only limited sources of resistance are available in wheat. Relatives of wheat have proven to be an invaluable gene pool for wheat improvement. The objective of this study was to explore relatives of wheat for FHB resistance. We evaluated 293 lines derived from the crosses of wheat with its relatives for resistance to spread of FHB infection over two greenhouse seasons. Of these 293 derivatives, 66 were susceptible, 153 appeared moderately resistant, and 74 lines exhibited a level of resistance comparable with T. aestivum L. `Sumai 3', the most widely used source of resistance to FHB. Alien species involved in development of these derivatives include T. tauschii (Coss.) Schmal., Roegneria kamoji C. Koch, R. ciliaris (Trin.) Nevski, Leymus racemosus Lam., Thinopyrum ponticum (Podp.) Barkworth & D.R. Dewey, Th. elongatum (Host) D.R. Dewey, Th. junceum (L.) Love, Th. intermedium (Host) Barkworth & D.R. Dewey, Dasypyrum villosa L., Secale cereale L., and oat (Avena saliva L.). The wheat-alien species derivatives identified as resistant to FHB include wheat-alien species amphiploids, synthetic hexaploid wheat lines, and wheat-alien species substitution and translocation lines. These derivatives could serve as novel sources to enhance resistance of wheat to FHB.

Fusarium head blight (FHB) is a destructive disease of wheat worldwide. Sources of resistance to FHB are limited in wheat. Search for novel sources of effective resistance to this disease has been an urgent need in wheat breeding. Fusarium head blight resistance has been identified in relatives of wheat. Alien chromatin carrying FHB resistance genes has been incorporated into wheat through chromosome addition, substitution, and translocation. Relatives of wheat demonstrate a great potential to enhance resistance of wheat to FHB.