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 website: http://www.tandfonline.com/loi/tcjp20To 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

Receptivity of barley to Puccinia graminis f. sp. tritici

Canadian Journal of Plant Pathology website: http://www.tandfonline.com/loi/tcjp20The receptivity of barley genotypes {Hordeum vulgare) was studied in seedlings and adult plants in the greenhouse and in adult plants in the field to races I13-RTQ and 151-QSH of Puccinia graminis f. sp. tritici. In the greenhouse, significant differences in number of uredia/cm2 of leaf were detected due to the effects of races, host genotypes, and their interaction. The cultivar Hiproly was most receptive (had the most uredia) and 80-TT-29 was least receptive (had the fewest uredia) to both races at both growth stages. With race 151-QSH, genotypes with the T-gene, 80-TT-29 and Manker had low weighted infection types (seedling stage), moderately resistant host responses (adult stage), and lower receptivity (both growth stages) than cultivars lacking this gene. With race 113-RTQ, the T-gene was associated with low receptivity only in 80-TT-29. The data suggest that gene(s) other than the T-gene may confer receptivity to P. graminis f. sp. tritici. The ranking of genotypes and the relative differences in receptivity were similar in seedling and adult plants. In the field, genotypes with the T-gene had mostly moderately resistant reactions and fewer uredia than those without the gene. The significant race x host genotype interaction in this study suggests that receptivity in barley varies due to the specific host-parasite combination

Identification of Cochliobolus sativus isolates expressing differential virulence on two-rowed barley genotypes from North Dakota

Canadian Journal of Plant Pathology website: http://www.tandfonline.com/loi/tcjp20Severe spot blotch infection was observed in 1990 on several two-row barley breeding lines previously regarded as resistant to Cochliobolus sativus. Studies were conducted to compare the virulence pattern of a C. sativus isolate (ND90Pr) obtained from this two-row breeding nursery with one (ND85F) used in previous disease screening evaluations. Greenhouse and field experiments were performed in 1991 and 1992 at Fargo, ND, using a split plot design with isolate as the main effect. Isolates ND90Pr and ND85F exhibited distinct differential virulence patterns on barley genotypes ND 5883, ND 12437, ND 12720, ND 12721, and Bowman. Isolate ND90Pr displayed high virulence on ND 12720, ND 12721, and Bowman, and low virulence on ND 5883 and ND 12437. In contrast, isolate ND85F was highly virulent on ND 5883 and ND 12437 and weakly virulent on ND 12720, ND 12721, and Bowman. Both isolates expressed low virulence on genotype ND Bl 12, the primary source of resistance to C. sativus in commercial six-row barley germplasm. To incorporate adequate levels of resistance into future two-row barley cultivars, disease evaluations should be made with C. sativus isolates that express the full spectrum of virulence found in North Dakota

Puccinia coronata var. hordei var. nov. morphology and pathogenicity

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

Genome-wide association mapping of fusarium head blight resistance and agromorphological traits in barley landraces from Ethiopia and Eritrea

Fusarium head blight (FHB), caused primarily by Fusarium graminearum, is an important disease of barley (Hordeum vulgare L.), and other cereals. In barley, the genetic basis of FHB resistance has been intensively studied through linkage mapping that identified several quantitative trait loci (QTL). However, our understanding and application of these QTL in breeding is still limited due to the complex nature and low-to-moderate heritability of FHB resistance. Previous studies used either breeding lines, unimproved varieties, or germplasm selections. Here, we used association mapping in barley landraces to identify QTL associated with FHB severity, deoxynivalenol (DON) concentration and correlated agromorphological traits. Diverse barley landraces (n = 298) from Ethiopia and Eritrea were evaluated for the traits under field conditions for 2 yr (2011–2012) in Crookston, MN, and genotyped with 7842 single nucleotide polymorphism (SNP) markers. Association mapping analysis using a mixed model corrected for pairwise relatedness between individuals identified one common resistance QTL on barley chromosome 2HL significantly associated with both FHB severity and DON concentration and another one on 4HL associated with DON concentration. The QTL identified on 2HL is associated with the row-type locus Vrs1. Both of these QTL were not significantly associated with heading date or plant height unlike other QTL reported in previous studies. Thus, the resistant accessions carrying these QTL may be used in breeding programs without the confounding effects from these agromorphological traits. Importantly, these QTL could be new alleles preserved in this unique germplasm, and the linked SNP markers found may be useful in marker-assisted introgression of resistance

The rpg4/Rpg5 stem rust resistance locus in barley; resistance genes and cytoskeleton dynamics

Two closely linked resistance genes, rpg4 and Rpg5, conferring resistance to several races of Puccinia graminis, were cloned and characterized. The Rpg5 gene confers resistance to an isolate of Puccinia graminis f. sp. secalis (Pgs), while rpg4 confers resistance to Puccinia graminis f. sp. tritici (Pgt). Rpg5 is a novel gene containing nucleotide binding site-leucine rich repeat domains in combination with a serine threonine protein kinase domain. High-resolution mapping plus allele and recombinant sequencing identified the rpg4 gene, which encodes an actin depolymerizing factor-like protein (ADF2). Resistance against the Pgt races QCCJ, MCCF, TTKSK (aka Ug99) and RCRS requires both Rpg5 and rpg4, while Rpg5 alone confers resistance to Pgs isolate 92-MN-90. The dependency on the actin modifying protein ADF2 indicates cytoskeleton reorganization or redirection plays a role in pathogen-host interactions. Rpg5 may interact with ADF2 to activate or deactivate its function in the resistance response. Alternatively, Rpg5 could initiate signal transduction leading to resistance in response to detecting ADF2 protein modification. Pgt may redirect the actin cytoskeleton by inducing modifications of ADF2. The redirection of actin could possibly enable the pathogen to develop a haustoria-plant cell cytoskeleton interface for acquisition of nutrients

Agronomic Characteristics, Malt Quality, and Disease Resistance of Barley Germplasm Lines with Partial Fusarium Head Blight Resistance

Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe, has caused devastating losses in both yield and quality of barley (Hordeum vulgare L.) produced in the northern Great Plains from 1993 to 2003. Thirty-five barley germplasmlines with partial resistance to FHB have been identified in exotic and unadapted germplasm lines. Little is known about their agronomic characteristics, malt quality, and reaction to other diseases as compared to adapted cultivars. This information is needed so barley breeders can make informed decisions when planning crosses involving the resistant germplasm lines. The objective of this study was to compare the agronomic performance, malt quality, and disease reaction of barley germplasm lines with partial FHB resistance to cultivars grown in the northern Great Plains. Agronomic and malting data were collected on the 35 germplasm lines and five check cultivars grown in five environments in North Dakota from 1998 to 2000. Data for FHB severity and deoxynivalenol (DON, a mycotoxin produced by F. graminearum) accumulation were obtained for the same 40 entries grown in FHB-epidemic nurseries in North Dakota from 1997 to 1999. Seedling responses to foliar pathogens common in the northern Great Plains were determined in the greenhouse during fall 1997. None of the FHB-resistant barley germplasm lines had acceptable malt quality for all traits. Kernel plumpness, grain protein concentration, and malt extract were the traits impacted most severely. The FHB-resistant barley germplasm lines headed significantly later than the adapted barley cultivars. Most FHB-resistant germplasm lines were susceptible to the common foliar diseases of the northern Great Plains. At least four cycles of breeding will probably be necessary to develop FHB-resistant germplasm lines acceptable to producers and the malting and brewing industry

Predicting agronomic performance of barley using canopy reflectance data

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

A resistance gene to Ustilago nuda in barley is located on chromosome 3H

Canadian Journal of Plant Pathology website: http://www.tandfonline.com/loi/tcjp20Loose smut of barley is a common disease which can be controlled using resistant varieties. Information on the chromosome location of loci controlling loose smut resistance and the development of molecular markers to aid in selection for these genes can be beneficial in the resistant variety development process. The objectives of this work were to determine the resistance or susceptibility of doubled haploid barley lines arising from a cross of the varieties ‘Steptoe’ and ‘Morex’ to Ustilago nuda, the causal agent of loose smut of barley, and map the chromosome location of the loose smut resistance locus in ‘Morex’. The reaction to Ustilago nuda of the doubled-haploid barley plants was determined by inoculating spikelets of each line at anthesis by injection of a teliospore suspension using a needle inoculation method. Mature seeds from the inoculated spikelets were grown to determine the percentage of plants that developed with smutted heads. The lines were classified as susceptible if greater than 10% of the plants were smutted. The loose smut resistance locus from the resistant source ‘Morex’ was mapped using an existing DNA marker map of the ‘Steptoe’/‘Morex’ population. The distribution of the resistant and susceptible progeny from the loose smut testing fit a single gene model. The resistance gene was mapped to chromosome 3 (3H)

Analysis of ergosterol in single kernel and ground grain by gas chromatography-mass spectrometry

A method for analyzing ergosterol in a single kernel and ground barley and wheat was developed using gas chromatography−mass spectrometry (GC-MS). Samples were saponified in methanolic KOH. Ergosterol was extracted by “one step” hexane extraction and subsequently silylated by N-trimethylsilylimidazole/trimethylchlorosilane (TMSI/TMCS) reagent at room temperature. The recoveries of ergosterol from ground barley were 96.6, 97.1, 97.1, 88.5, and 90.3% at the levels of 0.2, 1, 5, 10, and 20 μg/g (ppm), respectively. The recoveries from a single kernel were between 93.0 and 95.9%. The precision (coefficient of variance) of the method was in the range 0.8−12.3%. The method detection limit (MDL) and the method quantification limit (MQL) were 18.5 and 55.6 ng/g (ppb), respectively. The ergosterol analysis method developed can be used to handle 80 samples daily by one person, making it suitable for screening cereal cultivars for resistance to fungal infection. The ability for detecting low levels of ergosterol in a single kernel provides a tool to investigate early fungal invasion and to study mechanisms of resistance to fungal diseases