Dr. Brian Steffenson

Persistent link for this collectionhttps://hdl.handle.net/11299/184255

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Infection of gramineous species by Barley Yellow Dwarf Viruses in California
(Crop Science, 1990) Steffenson, Brian; Griesbach, J.A.; Brown, M.P.; Falk, B.W.; Webster, R.K.
Barley yellow dwarf viruses (BYDVs) continue to cause losses California cereal production. In some parts of the USA, native grasses have been implicated as reservoirs of BYDVs. This study examines the potential of native and irrigated pasture grasses as sources of BYDV inoculum in California. Theffects of both natural and natural plus supplemental inoculum were examined in field trials over two growing seasons using a completely randomized design. Results were assessed by enzyme-linked immunosorbent assay (ELISA) and verified with controlled greenhouse vector transmission trials. Thirty-seven of 56 species of cool-season grasses were infected by either PAV, MAV, or RPV isolates of the BYDVs. Of the BYDV-infected grasses, only 38% displayed symptoms typically seen in infected oat (Avena sativa L.) and barley (Hordeum vulgare L.), while the others were asymptomatic. None of the plants from seven species of Leymus, nor plants from the majority of Elymus and Elytrigia species, had detectable BYDV infections, even though they supported aphid vector populations. A survey of common grasses from irrigated pastures showed that plants from 6 of 10 species were infected by either the PAV, MAV, or RPV isolates of BYDVs. The incidence of MAV, PAV, and RPV BYDVs were roughly equivalent for the cool-season grasses, but were highly skewed toward PAV in the irrigated pasture survey. Both cool-season and irrigated warm-season pasture grasses have the potential to serve as BYDV reservoirs in California.
Linkage between the Rpg1 gene for stem rust resistance and the f5 locus on barley chromosome
(Crop Science, 1993) Steffenson, Brian; Jin, Yue; Franckowiak, Jerome D
Linkage studies can expedite the transfer of agronomically important genes in breeding programs. A study was conducted to determine the linkage relationship between loci segregating for stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) resistance (Rpg1) and a chlorina mutant (f5), and to confirm the linkage among Rpg1, br1 (brachytic) and fc (chlorina seedling). ‘Bowman’ barley (Hordeum vulgare L.) was crossed to genetic stocks possessing br1, fc, and f5, respectively. Estimates of linkage distances were 9.6 ± 1.4% between Rpg1 and br1, 13.6 ± 1.8% between Rpg1 and fc, and 25.9 ± 2.6% between Rpg1 and f5. The linkage between Rpg1 and f5 was established.
Sources of resistance to pathotype QCC of Puccinia graminis f. sp. tritici in barley
(Crop Science, 1994) Steffenson, Brian; Jin, Yue; Fetch, Thomas G.
The occurrence of a wheat stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) pathotype (Pgt-QCC) with virulence for the Rpg1 gene in barley (Hordeum vulgare L.) necessitated the search for resistant barley germplasm. From preliminary screenings of over 18 000 barley accessions, 13 lines were identified as possessing resistance to pathotype QCC: ‘Diamond’, ‘Hietpas 5’, Q21861, PC 11, PC 84, PC 249, PC 250, CI 5541, PI 452406, PI 452421, PI 477843, PI 477854, and PI 477860. This study was conducted to further characterize the reaction of the selected lines to pathotype QCC. The reaction was assessed by evaluating infection types at the seedling stage and infection responses at the adult plant stage in the greenhouse, and by evaluating disease severity and infection responses at the adult plant stage in the field compared to susceptible cultivars. Most lines exhibited low to intermediate infection types at the seedlings stage and moderately resistant to moderately susceptible infection responses at the adult plant stage in the greenhouse experiments. Among the selected lines, Q21861 exhibited the highest level of resistance at both the seedling and adult plant stages. These lines may provide an adequate level of resistance to pathotype QCC for cultivar development.
Rice-barley synteny and its applications to saturation mapping of the barley Rpg1 region
(Nucleic Acids Research, 1995-07-25) Steffenson, Brian; Kilian, Andrzej; Kudrna, David A.; Kleinhofs, Andris; Yano, Masahiro; Kurata, Nori; Sasaki, Takuji
In order to facilitate the map-based cloning of the barley stem rust resistance gene Rpg1, we have demonstrated a high degree of synteny at a micro level between the telomeric region of barley chromosome 1P and rice chromosome 6. We have also developed and applied a simple and efficient method for selecting useful probes from large insert genomic YAC and cosmid clones. The gene order within the most terminal 6.5 cM of barley chromosome 1P was compared with the most terminal 2.7 cM of rice chromosome 6. Nine rice probes, previously mapped in rice or isolated from YAC or cosmid clones from this region, were mapped in barley. All, except one, were in synteny with the rice gene order. The exception, probe Y617R, was duplicated in barley. One copy was located on a different chromosome and the other in a non-syntenic position on barley chromosome 1P. The barley probes from this region could not be mapped to rice, but two of them were inferred to be in a syntenic location based on their position on a rice YAC. This work demonstrates the utility of applying the results of genetic and physical mapping of the small genome cereal rice to map-based cloning of interesting genes from large genome relatives.
Regions of the genome that affect agronomic performance in two-row barley
(Crop Science, 1996) Steffenson, Brian; Tinker, N.A.; Mather, D.E.; Rossnagel, B.G.; Kasha, K.J.; Kleinhofs, A.; Hayes, P.M.; Falk, D.E.; Ferguson, T.; Shugar, L.P.; Legge, W.G.; Irvine, R.B.; Choo, T.M.; Briggs, K.G.; Ullrich, S.E.; Franckowiak, J.D.; Blake, T.K.; Graf, R.J.; Dofing, S.M.; Saghai Maroof, M.A.; Scoles, G.J.; Hoffman, D.; Dahleen, L.S.; Kilian, A.; Chen, F.; Biyashev, R.M.; Kudrna, D.A.
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.
Identification and mapping of a leaf rust resistance gene in barley line Q21861
(Genome, 1997) Steffenson, Brian; Borovkova, I.G.; Jin, Y.; Kilian, A.; Blake, T.K.; Kleinhofs, A.
Barley line Q21861 possesses an incompletely dominant gene (RphQ) for resistance to leaf rust caused by Puccinia hordei. To investigate the allelic and linkage relations between RphQ and other known Rph genes, F2 populations from crosses between Q21861 and donors of Rph1 to Rph14 (except for Rph8) were evaluated for leaf rust reaction at the seedling stage. Results indicate that RphQ is either allelic with or closely linked to the Rph2 locus. A doubled haploid population derived from a cross between Q21861 and SM89010 (a leaf rust susceptible line) was used for molecular mapping of the resistance locus. Bulked segregant analysis was used to identify markers linked to RphQ, using random amplified polymorphic DNAs (RAPDs), restriction fragment length polymorphisms (RFLPs), and sequence tagged sites (STSs). Of 600 decamer primers screened, amplified fragments generated by 9 primers were found to be linked to the RphQ locus; however, only 4 of them were within 10 cM of the target. The RphQ locus was mapped to the centromeric region of chromosome 7, with a linkage distance of 3.5 cM from the RFLP marker CDO749. Rrn2, an RFLP clone from the ribosomal RNA intergenic spacer region, was found to be very closely linked with RphQ, based on bulked segregant analysis. An STS marker, ITS1, derived from Rrn2, was also closely linked (1.6 cM) to RphQ.
Registration of ‘Foster’ barley
(Crop Science, 1997) Steffenson, Brian; Horsley, R.D.; Franckowiak, J.D.; Schwarz, P.B.
Effect of incubation time and temperature on the phenotypic expression of rpg4 to Puccinia graminis f. sp. tritici in barley
(Canadian Journal of Plant Pathology, 1997-03-01) Sun, Yonglian; Steffenson, Brian
To study the effect of incubation time and temperature on the phenotypic expression of rpg4, five barley genotypes with this resistance gene were infected with pathotype QCCJ of Puccinia graminis f. sp. tritici at the seedling stage, then subjected to various times of incubation at either 18-19°C or 27~28°C. Genotypes with rpg4 exhibited low (0, 0;, and 1), mesothetic (e.g. 3-210;, 120;3), and high (3,3) infection types at 18-19°C after initial incubation at 27-28°C for 0-28, 40-76, and 88 or more hours, respectively. A period of 88 or more hours of initial incubation at high temperature rendered the rpg4 resistance completely ineffective against this pathotype of P. g. f. sp. tritici. In contrast, high, mesothetic, and low infection types were found for the same genotypes at 27-28°C after initial incubation at 18-19°C for 0-40, 52-100, and 112 or more hours, respectively. The resistant infection types conferred by rpg4 are apparently established within the first 112 hours after the end of the infection period since subsequent shifts to higher temperature did not result in marked changes in the resistance response. These data indicate the critical importance of maintaining precise temperature control when assessing the infection phenotypes of barley genotypes carrying the stem rust resistance gene rpg4.
Mapping of disease resistance loci in barley based on visual assessment of naturally occurring symptoms
(Crop Science, 1998) Steffenson, Brian; Spaner, D.; Shugar, L.P.; Choo, T.M.; Falak, I.; Briggs, K.G.; Legge, W.G.; Falk, D.E.; Ullrich, S.E.; Tinker, N.A.; Mather, D.E.
Using field-scored data of disease severity under natural infestation, we mapped loci affecting resistance to powdery mildew (Blumeria graminis DC f. sp. hordei Ém. Marchal), leaf rust (Puccinia hordei Otth.), stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.), scald [Rhynchosporium secalis (Oudem.) J.J. Davis], and net blotch (Pyrenophora teres Drechs.). The mapping population included parents and doubled-haploid progeny of the two-row barley cross Harrington/TR306. Resistance was affected by two to five loci, explaining 8 to 45% of the phenotypic variance, per disease. All chromosomes, except chromosome 5 (1H), contained regions with at least one disease resistance locus. One region on chromosome 4 (4H) contributed to resistance to stem rust, scald, and net blotch. This region has previously been reported to affect days to heading and maturity. Two known resistance genes in the population, Rpgl and M1g, were mapped to within 3 centimorgans (cM) of their previously estimated genomic locations by simple interval mapping of the field-scored data. This indicates that the genomic positions of disease resistance genes can be estimated accurately with simple interval mapping, even on the basis of field-scored data.
Sequence analysis of a rice BAC covering the syntenous barley Rpg1 region
(Genome, 1999) Steffenson, Brian; Han, F.; Kilian, A.; Chen, J.P.; Kudrna, D.; Yamamoto, K.; Matsumoto, T.; Sasaki, T.; Kleinhofs, A.
In the course of map-based cloning of the barley stem rust resistance gene Rpg1, we identified a rice bacterial artificial chromosome (BAC) containing the Rpg1 flanking markers. Based on the excellent gene order colinearity between barley and rice in this region, we expected that this rice BAC would contain the barley Rpg1 homologue. In order to identify the putative rice homologue, we sequenced ca. 35 kb of the rice BAC at random and then an additional 33 kb of contiguous sequence between the two most closely spaced Rpg1 flanking markers. Sequence analysis revealed a total of 15 putative genes, 5 within the 33-kb contiguous region. A rice Rpg1 homologue was not identified, although a gene encoding a hypothetical polypeptide with similarity to a membrane protein could not be eliminated as a candidate. Surprisingly, four of the genes identified in the 33-kb contiguous rice sequence showed a high degree of similarity with genes on Arabidopsis chromosome 4. The genome regions harboring these genes showed some relatedness, but many rearrangements were also evident. These data suggest that some genes have remained linked even over the long evolutionary separation of Arabidopsis and rice, as has also been reported for mammals and invertebrates.
Puccinia coronata var. hordei var. nov. morphology and pathogenicity
(Mycologia, 1999) Steffenson, Brian; Jin, Y.
A new variety of Puccinia coronata causing a disease on barley and other gramineous species is described. The fungus is different from other reported forms of P coronata in both morphology and pathogenicity. Its most prominent characters are the elongated teliospore appendages with dichotomous branching and wide pathogenicity on species in the tribe Triticeae, particularly the genus Hordeum. The name of P coronata var. hordei is proposed for the rust fungus. The common name 'crown rust of barley' is proposed for the disease of barley caused by this rust fungus. Results of inoculation indicated that P coronata var. hordei is pathogenic on species of Aegilops, Agropyron, Elymus, Elytrigia, Leymus, Pascopyrum, Psathyrostachys, Secale, and Triticum in the tribe Triticeae, and some species of Brachypodium, Bromus, Festuca, and Lolium in the tribe Poeae, and Phalaris in the tribe Aveneae. In the northern Great Plains of the USA, the following native and introduced gramineous species were found naturally infected by P coronata var. hordei: Bromus tectorum, Elymus canadensis, E. trachycaulus, E. virginicus, Elytrigia intermedia, E. repens, Hordeum jubatum, H. vulgare, Leymus angustus, L. cinerius, L. dahuricus, L. racemosus, Pascopyrum smithii, Psathyrostachys juncea, and Secale cer- eale.
Genetic and molecular characterization of mating type genes in Cochliobolus sativus
(Mycologia, 2001-09-01) Steffenson, Brian; Zhong, Shaobin
Genetic and molecular approaches were used to characterize the mating type (MAT) genes in Cochliobolus sativus. One hundred and four ascospore progeny derived from a cross of C. sativus isolates ND93-1 (MAT-1) X ND9OPr (MAT-2) were backcrossed with their parents to determine mating type, but only five progeny produced pseudothecia with asci and/or ascospores. When degenerate primers from the conserved high mobility group (HMG) protein domain encoded by the MAT-2 gene in Cochliobolus species were used in polymerase chain reaction (PCR) with genomic DNA of C. sativus as templates, an amplicon of predicted size was amplified only from MAT-2 isolates. The presence of a MAT-2 homolog in these MAT-2 isolates was confirmed by Southern hybridization with the HMG box as a probe. Additionally, the presence or absence of the HMG homolog in the progeny segregated in a 1:1 ratio, as expected for the single gene control of mating type. Using primers based on the conserved regions at the 5' and 3' flanks of the idiomorphs in the MAT genes of other Cochliobolus species, the full-length MAT-1 and MAT-2 idiomorphs were cloned by PCR from C. sativus isolates ND93-1 and ND9OPr, respectively. DNA sequence analysis indicated that these two idiomorphs are organized in a manner similar to their respective counterparts in other Cochliobolus species. DNA hybridization and PCR amplification analysis of 54 field isolates of C. sativus collected worldwide showed that both mating types exist in populations round the world. The low frequency of successful backcrosses of progeny to parents in the ND93-1 X ND9OPr cross, combined with the fact that many crosses between isolates of opposite mating type are unsuccessful, suggests that genetic factors other than MAT genes affect the fertility of the fungus.
Registration of ‘Drummond’ barley
(Crop Science, 2002) Steffenson, Brian; Horsley, R.D.; Franckowiak, J.D.; Schwarz, P.B.
Registration of 6NDRFG-1 six-rowed barley germplasm line with partial Fusarium head blight resistance
(Crop Science, 2002) Steffenson, Brian; Urrea, C.A.; Horsley, R.D.; Frankowiak, J.D.
The barley stem rust-resistance gene Rpg1 is a novel disease-resistance gene with homology to receptor kinases
(Proceedings of the National Academy of Sciences of the United States of America, 2002-07-09) Steffenson, Brian; Brueggeman, R.; Rostoks, N.; Kudrna, D.; Kilian, A.; Han, F.; Chen, J.; Druka, A.; Kleinhofs, A.
Stem rust caused by Puccinia graminis f. sp. tritici was among the most devastating diseases of barley in the northern Great Plains of the U.S. and Canada before the deployment of the stem rust-resistance gene Rpg1 in 1942. Since then, Rpg1 has provided durable protection against stem rust losses in widely grown barley cultivars (cvs.). Extensive efforts to clone Rpg1 by synteny with rice provided excellent flanking markers but failed to yield the gene because it does not seem to exist in rice. Here we report the map-based cloning and characterization of Rpg1. A high-resolution genetic map constructed with 8,518 gametes and a 330-kb bacterial artificial chromosome contig physical map positioned the gene between two crossovers ≈0.21 centimorgan and 110 kb apart. The region including Rpg1 was searched for potential candidate genes by sequencing low-copy probes. Two receptor kinase-like genes were identified. The candidate gene alleles were sequenced from resistant and susceptible cvs. Only one of the candidate genes showed a pattern of apparently functional gene structure in the resistant cvs. and defective gene structure in the susceptible cvs. identifying it as the Rpg1 gene. Rpg1 encodes a receptor kinase-like protein with two tandem protein kinase domains, a novel structure for a plant disease-resistance gene. Thus, it may represent a new class of plant resistance genes.
Molecular mapping of the leaf rust resistance gene Rph5 in barley
(Crop Science, 2003) Steffenson, Brian; Mammadov, J.A.; Zwonitzer, J.C.; Biyashev, R.M.; Griffey, C.A.; Jin, Y.; Saghai Maroof, M.A.
Leaf rust caused by Puccinia hordei G. Otth is an important disease of barley (Hordeum vulgare L.) in many regions of the world. Yield losses up to 32% have been reported in susceptible cultivars. The Rph5 gene confers resistance to the most prevalent races (8 and 30) of barley leaf rust in the USA. Therefore, the molecular mapping of Rph5 is of great interest. The objectives of this study were to map Rph5 and identify closely linked molecular markers. Genetic studies were performed by analysis of 93 and 91 [F.sub.2] plants derived from the crosses `Bowman' (rph5) x `Magnif 102' (Rph5) and `Moore' (rph5) x Virginia 92-42-46 (Rph5), respectively. Bulk segregent analysis (BSA) using amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), and simple sequence repeat (SSR) markers was conducted. Linkage analysis positioned the Rph5 locus to the extreme telomeric region of the short arm of barley chromosome 3H at 0.2 centimorgans (cM) proximal to RFLP marker VT1 and 0.5 cM distal from RFLP marker C970 in the Bowman x Magnif 102 population. Map positions and the relative order of the markers were confirmed in the Moore x Virginia 92-42-46 population. RFLP analysis of the near isogenic line (NIL) Magnif 102/*8Bowman, the susceptible recurrent parent Bowman, and RpH5 donor Magnif 102, confirmed the close linkage of the markers VT1, BCD907, and CD0549 to Rph5. Results from this study will be useful for marker-assisted selection and gene pyramiding in programs breeding for leaf rust resistance and provide the basis for physical mapping and further cloning activities.
Genetically engineered stem rust resistance in barley using the Rpg1 gene
(Proceedings of the National Academy of Sciences of the United States of America, 2003-01-07) Steffenson, Brian; Horvath, Henriette; Rostoks, Nils; Brueggeman, Robert; Wettstein, Diter von; Kleinhofs, Andris
The stem-rust-susceptible barley cv. Golden Promise was transformed by Agrobacterium-mediated transformation of immature zygotic embryos with the Rpg1 genomic clone of cv. Morex containing a 520-bp 5′ promoter region, 4,919-bp gene region, and 547-bp 3′ nontranscribed sequence. Representatives of 42 transgenic barley lines obtained were characterized for their seedling infection response to pathotype Pgt-MCC of the stem rust fungus Puccinia graminis f. sp. tritici. Golden Promise was converted from a highly susceptible cultivar into a highly resistant one by transformation with the dominant Rpg1 gene. A single copy of the gene was sufficient to confer resistance against stem rust, and progenies from several transformants segregated in a 3:1 ratio for resistance/susceptibility as expected for Mendelian inheritance. These results unequivocally demonstrate that the DNA segment isolated by map-based cloning is the functional Rpg1 gene for stem rust, resistance. One of the remarkable aspects about the transformants is that they exhibit a higher level of resistance than the original sources of Rpg1 (cvs. Chevron and Peatland). In most cases, the Golden Promise transformants exhibited a highly resistant reaction where no visible sign of infection was evident. Hypersensitive necrotic “fleck” reactions were also observed, but less frequently. With both infection types, pathogen sporulation was prevented. Southern blot and RT-PCR analysis revealed that neither Rpg1 gene copy number nor expression levels could account for the increased resistance observed in Golden Promise transformants. Nevertheless, this research demonstrates that stem-rust-susceptible barley can be made resistant by transformation with the cloned Rpg1 gene.
Genetic variation for virulence and RFLP markers in Pyrenophora teres
(Canadian Journal of Plant Pathology, 2003-03-01) Wu, H.-L.; Steffenson, Brian; Zhong, S; Li, Y; Oleson, A.E.
Pyrenophora teres f. teres (causing net blotch) and Pyrenophora teres f. maculata (causing "spot form" of the disease) are important foliar pathogens of barley. In breeding for resistance to disease, it is important to have a thorough knowledge of the degree of genetic variation in the pathogen. This study was undertaken to assess genetic variation in a small, but geographically diverse collection of P. teres isolates. Isolates derived from single conidia were evaluated for their virulence phenotypes on 25 differential barley genotypes. Fifteen pathotypes were identified from a collection of 23 P. t. f. teres isolates, and 4 pathotypes, from a collection of 8 P. t. f. maculata isolates. In general, the P. t. f. teres isolates exhibited a broader spectrum and a higher level of virulence on the host differentials than the P. t. f. maculata isolates. Eight barley genotypes were resistant to all 19 pathotypes identified and should be useful in breeding barley for resistance to both forms of P. teres. Genetic variation was also examined by restriction fragment length polymorphism (RFLP) analysis. A 0.46-kb DNA fragment (ND218) generated by the polymerase chain reaction from genomic DNA of a California isolate of P. t. f. teres was used as a probe. Every P. teres isolate tested with ND218 exhibited a unique RFLP pattern. Cluster analysis, based on both the virulence phenotypes and RFLP patterns, indicates that P. teres possesses a high degree of diversity at the species and subspecies levels. The high degree of polymorphism revealed by ND218 will make this probe a useful tool for the DNA fingerprinting of P. teres isolates.
Predicting agronomic performance of barley using canopy reflectance data
(Canadian Journal of Plant Pathology, 2004) Steffenson, Brian; Fetch, T.G.; Pederson, V.D.
The ability to accurately and rapidly predetermine agronomic performance would be desirable in most plant breeding programs. Remote sensing of canopy reflectance is a quick and nondestructive method that may be useful in the estimation of agronomic performance. Studies were conducted at Fargo and Langdon, North Dakota, to determine the effectiveness of a multispectral radiometer in estimating yield, kernel plumpness (KP), and 1000-kernel weight (TKW) in barley. Canopy reflectance was measured in eight (500–850 nm) discrete narrow-wavelength bands. Three types of reflectance models were evaluated: simple models using one to four wavelengths, simple ratio and normalized difference vegetation indices (NDVI) using green, red, and near-infrared wavelengths, and soil-adjusted vegetation indices (SAVI). The relationship between canopy reflectance and agronomic performance was significantly influenced by environment, growth stage, and plant genotype. Grain yield was best estimated near GS73 (0.84 < R2 < 0.92) at Fargo and at GS83 (0.55 < R2 < 0.81) at Langdon. In contrast, KP and TKW could be estimated at both late (GS83; 0.68 < R2 < 0.93) and early (GS24–GS47; 0.72 < R2 < 0.91) growth stages. The 550-nm and 800-nm wavelengths are critical for development of predictive models. A simple model using 550-nm, 600-nm, and 800-nm from GS47-GS73 gave significant (0.45 < R2 < 0.64) estimation of agronomic performance across all environments. In contrast, simple ratio, NDVI, and SAVI were less effective (0.05 < R2 < 0.77) in predicting agronomic performance. Remote sensing using canopy reflectance is a potential tool to estimate agronomic performance of barley, but genotypic and crop stage factors affect this method. Further studies are needed to improve the usefulness of multispectral radiometry in predicting agronomic performance.
Sources of resistance to septoria speckled leaf blotch caused by Septoria passernii in barley
(Canadian Journal of Plant Pathology, 2004-09-01) Toubia-Rahme, H; Steffenson, Brian
Septoria speckled leaf blotch (SSLB), incited by Septoria passerinii, has reemerged as one of the most serious foliar diseases of barley (Hordeum vulgare) in the Upper Midwest region of the United States over the last decade. The most cost-effective and environmentally safe method of preventing SSLB epidemics is through the use of resistant cultivars. Thus, the objective of this study was to investigate sources of resistance to S. passerinii in barley and to determine the reliability of greenhouse seedling tests for predicting the adult-plant reaction in the field. From a preliminary greenhouse screening of over 250 barley accessions, 78 lines were selected and subsequently evaluated at the seedling (greenhouse) and adult-plant (field) stages for reaction to S. passerinii. All of the major malting (H. vulgare ‘Drummond’, ‘Excel’, ‘Foster’, ‘Lacey’, ‘Legacy’, ‘Morex’, ‘Stander’, ‘Conlon’, and ‘Robust’) and feed (H. vulgare ‘Bowman’, ‘Logan’, and ‘Royal’) cultivars grown in or recommended for the Upper Midwest region of the United States were highly susceptible. Highly significant correlations were detected between the infection response of seedlings in the greenhouse and adult plants in the field. Twenty-nine accessions exhibited resistance at both the seedling and adult-plant stages. The resistant accessions identified in this study were from geographically diverse regions and will be valuable in developing barley cultivars with diverse and broad-based resistance to SSLB.

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