Partiell resistens mot aksfusariose og mjøldogg i hvete

Both Fusarium head blight and powdery mildew are devastating diseases in wheat growing areas around the world. Breeding for resistance has been undergoing for many decades and mostly depends on phenotypic selection. Marker assisted selection (MAS) provides potential to accelerate the gain of selection. To exploit new resistance loci with closely linked makers is a key step to realize it. Our studies have mapped the resistance loci of promising sources of resistance and looked into the associations between FHB and morphological traits (plant height and anther extrusion). The first two studies (paper I and II) confirmed that Rht-D1b and Rht-B1b both compromised FHB resistance after spawn/spray inoculation. In a DH population of Avle x Line685, the negative impact of Rht-D1b could be counteracted with a combination of Fhb1 and the QTL on 5A, two frequently used resistance loci in breeding. In a RIL population from SHA3/CBRD x Naxos, Rht-B1b had less negative impact compared to Rht-D1b in DH population. The FHB resistance in SHA3/CBRD was found controlled by a major QTL on 2DLc and some minor QTL. The high anther extrusion (AE) alleles were always associated with FHB resistance after spawn/spray inoculation and considered as an escape of FHB at flowering time. We suggested that high AE could be used as visual assessment to screen large breeding populations at the early stage for FHB resistance. In paper III, we worked on PM resistance and analyzed the genetic basis of a promising partial resistance cultivar Naxos in the same RIL population as paper II. This high level of partial resistance is controlled by two major QTL on 1AS and 2DL, and two minor ones on 2BL and 7DS. The QTL on 1AS coincided with Pm3 and was effective in all environments, but Naxos doesn’t have any known Pm3 haplotype. Therefore, it is a racenon-specific QTL. We also looked into the relation between Pm3 and Pm8, but the suppression of Pm8 by Pm3 was not observed at the adult plant stage. Closely linked markers to the major QTL detected in our study could have potential for use in MAS. The closely linked markers near two coincident QTL on 2BL and 2DLc could improve both FHB and PM resistance.Aksfusariose og mjøldogg er to alvorlige sykdommer som angriper hvete og gjør skade i mange hvetedyrkingsområder rundt omkring i verden. Resistensforedling har foregått over mange tiår og er i stor grad basert på fenotypisk seleksjon. Markør-assistert seleksjon (MAS) gir muligheter til økt genetisk framgang. Å finne nye resistensgener og identifisere nært koblede markører er en viktig forutsetning for å nå dette potensialet. Våre studier har kartlagt resistensgenene til viktige resistenskilder og undersøkt sammenhenger mellom aksfusariose og morfologiske egenskaper som strålengde og støvknappfelling. De to første studiene (Paper I og II) bekreftet at dverggenene Rht-D1b og Rht-B1b begge hadde negativ innvirkning på fusariumresistens etter kornsmitte eller dusjsmitting. I en dobbel haploid (DH)-populasjon av Avle x Line685, kunne den negative virkningen av Rht-D1b bli oppveid ved å kombinere Fhb1 med resistens-QTL-et på 5A, to av de mest brukte resistensgenene i foredling. I en populasjon av rekombinante linjer (RIL) fra SHA3/CBRD x Naxos var den negative effekten av Rht-B1b mindre enn for Rht-D1b i DH-populasjonen. Fusariumresistensen i SHA3/CBRD viste seg å være kontrollert av et hoved-QTL på 2DLc og noen mindre QTL. Allelene for høy støvknappfelling (AE) var alltid assosiert med fusariumresistens etter kornsmitte eller dusjsmitting og kan betraktes som en mekanisme for å unngå fusarumangrep ved blomstring. Vi foreslår at visuell bedømming av støvknappfelling kan brukes som seleksjonskriterium til testing av store foredlingsmaterialer for fusariumresistens på tidlig stadium. I den tredje studien (Paper III) analyserte vi det genetiske grunnlaget for mjøldoggresistens i den lovende resistenskilden Naxos ved bruk av samme RIL populasjon som i paper II. Den høye graden av partiell resistens var kontrollert av to hoved-QTL på kromosomene 1AS og 2DL, og to mindre QTL på 2BL og 7DS. QTL-et på 1AS var lokalisert i samme område som det rasespesifikke genet Pm3 og viste effekt i alle miljø, men Naxos hadde ingen Pm3-haplotype. Dette er derfor et QTL for raseuspesifikk resistens. Vi undersøkte også et mulig samspill mellom Pm3 og Pm8, men fant ingen indikasjoner på at Pm3-allelet i SHA3/CBRD undertrykte resistensen til Pm8 på voksenplantestadiet. Nært koblede markører til de viktigste QTL-ene som er avdekket i denne avhandlingen kan ha potensial til bruk i MAS. De nært koblede markørene til to QTL sammenfallende QTL på 2BL og 2DLc kan brukes til å øke resistensen mot både aksfusariose og mjøldogg

Molecular mapping of adult plant resistance to Parastagonospora nodorum leaf blotch in bread wheat lines ‘Shanghai-3/Catbird’ and ‘Naxos’

acceptedVersio

Analysis of barley mutants ert-c.1 and ert-d.7 reveals two loci with additive effect on plant architecture

Main conclusion: Both mutant ert-c.1 and ert-d.7 carry T2-T3 translocations in the Ert-c gene. Principal coordinate analyses revealed the translocation types and translocation breakpoints. Mutant ert-d.7 is an Ert-cErt-d double mutant. Abstract: Mutations in the Ert-c and Ert-d loci are among the most common barley mutations affecting plant architecture. The mutants have various degrees of erect and compact spikes, often accompanied with short and stiff culms. In the current study, complementation tests, linkage mapping, principal coordinate analyses and fine mapping were conducted. We conclude that the original ert-d.7 mutant does not only carry an ert-d mutation but also an ert-c mutation. Combined, mutations in Ert-c and Ert-d cause a pyramid-dense spike phenotype, whereas mutations in only Ert-c or Ert-d give a pyramid and dense phenotype, respectively. Associations between the Ert-c gene and T2-T3 translocations were detected in both mutant ert-c.1 and ert-d.7. Different genetic association patterns indicate different translocation breakpoints in these two mutants. Principal coordinate analysis based on genetic distance and screening of recombinants from all four ends of polymorphic regions was an efficient way to narrow down the region of interest in translocation-involved populations. The Ert-c gene was mapped to the marker interval of 2_0801to1_0224 on 3HL near the centromere. The results illuminate a complex connection between two single genes having additive effects on barley spike architecture and will facilitate the identification of the Ert-c and Ert-d genes

Anther extrusion and plant height are associated with Type I resistance to Fusarium head blight in bread wheat line ‘Shanghai-3/Catbird’

acceptedVersio

Genetic mapping of the barley lodging resistance locus Erectoides-k

The barley (Hordeum vulgare L.) mutant erectoides-k.32 (ert-k.32) was isolated in 1947 from an X-ray-mutant population of cultivar ‘Bonus’. The mutant was released as a cultivar in 1958 with the name ‘Pallas’ – one of the first cereal crop cultivars developed from induced mutants. ‘Pallas’ is a semi-dwarf barley cultivar known for its culm stability and resistance to lodging. In total, eight allelic ert-k mutants are known that show different phenotypic strength concerning culm length and spike architecture. They represent alternatives to the widely used, but pleiotropic ‘Green Revolution’ alleles of the Sdw1 (semidwarf1/denso) and Uzu1 (semi-brachytic1) genes in breeding of robust elite barley cultivars. In the present study, we locate Ert-k to a 15.7-cM region in the centromeric region of chromosome 6H. Although the interval is estimated to contain approximately 700 genes, the work provides a solid foundation for the identification of the underlying mutations causing the ert-k lodging-resistant phenotype. In addition, the linked markers could be used to follow the ert-k mutant genotype in marker-assisted selection of new lodging-resistant barley cultivars

Identification of a candidate dwarfing gene in Pallas, the first commercial barley cultivar generated through mutational breeding

Many induced mutants are available in barley (Hordeum vulgare L.). One of the largest groups of induced mutants is the Erectoides (ert) mutants, which is characterized by a compact and upright spike and a shortened culm. One isolated mutant, ert-k.32, generated by X-ray treatment and registered in 1958 under the named “Pallas”, was the first ever induced barley mutant to be released on the market. Its value was improved culm strength and enhanced lodging resistance. In this study, we aimed to identify the casual gene of the ert-k.32 mutant by whole genome sequencing of allelic ert-k mutants. The suggested Ert-k candidate gene, HORVU.MOREX.r3.6HG0574880, is located in the centromeric region of chromosome 6H. The gene product is an alpha/beta hydrolase with a catalytic triad in the active site composed of Ser-167, His-261 and Asp-232. In comparison to proteins derived from the Arabidopsis genome, ErtK is most similar to a thioesterase with de-S-acylation activity. This suggests that ErtK catalyzes post-translational modifications by removing fatty acids that are covalently attached to cysteine residues of target proteins involved in regulation of plant architecture and important commercial traits such as culm stability and lodging resistance