New sources of scald (Rhynchosporium secalis Davis) resistance for western Canadian barley

Non-Peer ReviewedScald, caused by Rhynchosporium secalis Davis, is an important fungal foliar disease of barley which can cause significant losses of yield and quality in western Canada. Scald can be controlled by fungicides and/or cultural methods, however, the use of genetic resistance is most desirable control strategy. The objectives of this study were to evaluate scald resistance in two New Zealand barley genotypes; to study the inheritance of that resistance and to test its novelty relative to a number of existing resistance sources available to Canadian breeding programs. New Zealand genotypes 145L2 and 4176/n, which showed scald resistance in NZ nurseries and in Alberta scald screening nurseries in 1998, were evaluated in 1999 and 2000 Alberta nurseries. To determine the genetic control of resistance, these resistant lines were each crossed with scald susceptible CDC McGwire; and resistant versus susceptible progeny ratios from F2 populations and F5 recombinant inbred lines (RILs) were tested for chi-square goodness of fit for one or two gene control. To determine the source of the resistance, ‘known’ H. vulgare parents of these NZ lines were evaluated in the Alberta scald nurseries. In addition, 145L2 was crossed with 4176/n and four local resistant lines to determine allelic relationships between ‘145L2’ resistance and the resistance in the local lines. In 1999 and 2000, both NZ lines expressed good scald resistance. Inheritance studies indicated that resistance in both NZ lines is governed by a single dominant gene. ‘145L2’ resistance is different from resistance in 4176/n and the other barley lines tested. All ‘known’ progenitors of these lines were susceptible suggesting that resistance is a result of mutation and/or introgression(s) from what is described as an ‘unknown’ parent in their pedigrees. The NZ lines provide new sources of scald resistance that can be incorporated into local breeding lines

Low-lignin hull in oat

Non-Peer ReviewedThe use of whole oat in feed rations is restricted due to low digestibility of the hull. AC Assiniboia hulls have decreased acid detergent lignin (ADL) content. AC Assiniboia was crossed with OT 775 and the resulting lines were measured for ADL content. The ratio of F4:5 lines with low to normal ADL concentration fit a 1:1 genetic ratio. Indicating that the low-lignin trait is controlled by a single major gene. ADL concentration was correlated with hull colour and acid detergent fiber concentration. ADL concentration was not correlated with the protein or fat concentration of the groat. Simple inheritance of the low-lignin trait indicates that it can be incorporated into the oat breeding program. Furthermore, ADL concentration is not correlated with groat fat so a cultivar with a low lignin hull and high fat groat can be developed

Molecular marker assisted introgression of loose and covered smut resistance into CDC McGwire hulless barley

Non-Peer ReviewedCDC McGwire is a high yielding hulless barley cultivar from the Crop Development Centre (CDC), University of Saskatchewan which is susceptible to both true loose and covered smut. Screening for these diseases is time, labour and space consuming and escapes are very frequent making it necessary to screen putative resistant lines several times to confirm resistance. In addition, both the diseases are expressed in the inflorescence, simultaneous screening for them is not possible. Molecular Marker Assisted Selection (MAS) is a good alternative to combine the resistance to both diseases in the same line. Sequence characterized amplified region (SCAR) markers linked to the loose smut resistance gene Run8 (Eckstein et al. 2002) and covered smut resistance gene Ruhq (Ardiel et al. 2002, Grewal et al. 2004) have been developed at the CDC and a program was initiated to introgress loose smut resistance (Run8) and covered smut resistance (Ruhq) into CDC McGwire using MAS. Loose smut resistance was transferred from TR251 (Run8) and covered smut resistance from either Q21861 or TR640 (Ruhq). Two strategies (doubled haploidy and marker-assisted backcrossing) were used to introgress both resistance genes. Screening 35 microspore culture derived doubled haploid (DH) lines against covered and loose smut in the field and greenhouse showed that in most lines, the phenotype defined by disease reactions and genotype defined by the SCAR markers agreed. Screening putative resistant lines three times for covered and loose smut identified 12 DH lines resistant to both smuts and positive to molecular markers of both the diseases. In the marker-assisted backcross program, plants were genotyped in each generation and plants positive for both markers were backcrossed to CDC McGwire. The genotyping of BC1F1, BC2F1 and BC3F1 plants with SCAR markers (UhR450 and Un8700R) showed a 1:2:2:1 segregation indicating the presence of two major genes. Twenty BC3F3 lines (10 lines selected with the covered smut resistance from Q21861 and 10 lines selected with the covered smut resistance from TR640) were evaluated for covered smut reaction in the field in 2004 and in the greenhouse in the fall of 2004. All lines showed resistance to covered smut. BC3F3 lines were inoculated with loose smut in the field in 2004 and evaluated in the greenhouse. Eighteen of 20 lines showed loose smut resistance. These putative double resistant lines will be phenotyped in BC3F5 generations to confirm disease reactions. These results confirm that molecular markers can assist in rapid introgression of simply inherited disease resistance genes into elite lines with considerable savings in time and cost

Regions of the genome that affect agronomic performance in two-row barley

Quantitative trait locus (QTL) main effects and QTL by environment (QTL × E) interactions for seven agronomic traits (grain yield, days to heading, days to maturity, plant height, lodging severity, kernel weight, and test weight) were investigated in a two-row barley (Hordeum vulgare L.) cross, Harrington/TR306. A 127-point base map was constructed from markers (mostly RFLP) scored in 146 random double-haploid (DH) lines from the Harrington/TR306 cross. Field experiments involving the two parents and 145 random DH lines were grown in 1992 and/or 1993 at 17 locations in North America. Analysis of QTL was based on simple and composite interval mapping. Primary QTL were declared at positions where both methods gave evidence for QTL. The number of primary QTL ranged from three to six per trait, collectively explaining 34 to 52% of the genetic variance. None of these primary QTL showed major effects, but many showed effects that were consistent across environments. The addition of secondary QTL gave models that explained 39 to 80% of the genetic variance. The QTL were dispersed throughout the barley genome and some were detected in regions where QTL have been found in previous studies. Eight chromosome regions contained pleiotropic loci and/or linked clusters of loci that affected multiple traits. One region on chromosome 7 affected all traits except days to heading. This study was an intensive effort to evaluate QTL in a narrow-base population grown in a large set of environments. The results reveal the types and distributions of QTL effects manipulated by plant breeders and provide opportunities for future testing of marker-assisted selection

Tracing the phylogeny of the Hexaploid oat with satellite DNAs

The genus Avena contains 30 different species from diploid through tetraploid to hexaploid with different genome compositions. Research regarding the origin of the different genomes in the polyploid species has been inconclusive. The objectives of this research were to investigate the phylogenetic relationships of the Avena species by means of polymorphisms in satellite, minisatellite, and microsatellite DNA. A satellite DNA sequence, ASS49, was isolated from a microsatellite-enriched library of the hexaploid oat Avena sativa L. Southern hybridization showed that ASS49 was a species-specific rather than a genome-specific satellite. ASS49 was able to distinguish species that may be the diploid and tetraploid progenitors of hexaploid oat. The phylogenetic relationship of Avena species was further investigated using 40 microsatellite and four minisatellite primers. These results appeared to support the findings with ASS49. It appears that the Ac-genome diploid species (A. canariensis Baum Raj. et Samp.) is the progenitor and A-genome donor of the hexaploid oat rather than the generally believed As-genome species (A. strigosa Schreber). Instead, A. strigosa appears to be a member of a separate lineage of diploid and tetraploid species including the tetraploid species A. abyssinica Hochst

Developing markers for canola seed quality – relationship of seedcoat colour and lignin content in Brassica carinata.

Non-Peer Reviewe

Targeted development of a microsatellite marker associated with a true loose smut resistance gene in barley (Hordeum vulgare L.)

Microsatellite markers have many of the properties of an ideal marker, but development of microsatellite markers is tedious, time-consuming and expensive. In the past few years, great efforts have been made to develop, map and utilize microsatellite markers in various crops. It is still a major challenge to find a microsatellite marker associated with an economically important trait. In the present study we report on the targeted development of a microsatellite marker to a barley disease resistance gene. The method includes the following steps: (1) pooling DNA samples from a segregating population based on the principle of bulked-segregant analysis; (2) digesting the pooled DNAs and ligating adaptors; (3) selectively amplifying and identifying polymorphic microsatellites; and (4) developing primers for the microsatellite associated with the targeted trait. Using this method, a microsatellite marker associated with the true loose smut resistance gene (Un8) in the Harrington × TR306 doubled-haploid population was identified. This marker showed polymorphism in four breeding populations segregating for true loose smut resistance. In three of these populations, genetic distance between the microsatellite and the true loose smut resistance gene varied from 8.6 to 10.3 cM. Polymorphism of the microsatellite was tested among three disease resistant lines and 21 susceptible cultivars. Fourteen to eighteen of the 21 susceptible cultivars exhibited a polymorphism for the microsatellite with respect to at least one of the disease-resistant lines. This method for the targeted development of microsatellite markers should have widespread applicability and should efficiently provide highly polymorphic markers for use in breeding programs

Genetic diversity in yardlongbean (Vigna unguiculata subspecies unguiculata cvgr sesquipedalis) as revealed by simple sequence repeat (SSR) markers

Genetic diversity was investigated among fifty accessions of yard-long-bean (Vigna unguiculatasubspecies unguiculatacultivar group sesquipedalis) using simple sequence repeat (SSR) markers. Sixteen SSR primers were used to amplify DNA of the 50 accessions. A total of 63 polymorphic bands were detected and these were used for cluster analysis. A dendrogram generated following unweighted pair group using mathematical average (UPGMA) cluster analysis isolated one of the accessions from the others at a similarity coefficient of 0.68. However, at 0.76 similarity coefficient, nine clusters were formed with the eighth and ninth clusters containing more than two-thirds of the total accessions used. There were four accessions that paired at 1.0 similarity coefficient. The members of each pair could not be separated from each other on the dendrogram suggesting very close relationships be-tween each pair. The distribution of the yard-long-bean accessions along the axes of the first two principal components showed to a very large extent similar grouping as were identified on the den-drogram. Accessions of yard-long-bean from India showed the highest level of genetic diversity, as revealed by SSR markers, compared with those from other countries thereby providing further evidence in support of the suggestion that India may be the center of diversity for the crop. Thus SSR markers are useful in assessing the genetic diversity among individuals of yard-long-bean