Showing papers on "Rust published in 1994"

Characterisation and origin of rust and powdery mildew resistance genes in VPM1 wheat

Abstract: The expression of rust resistances conferred by closely linked genes derived from VPM1 varied with environmental conditions and with genetic backgrounds. Under low light and low temperature conditions seedlings carrying Yr17 showed susceptible responses. Stem rust and leaf rust resistance genes Sr38 and Lr37 tended to confer more resistance at 17±2° C than at normal temperatures above > 20° C. These studies supported the hypothesis that Yr17, Lr37 and Sr38 were derived from Aegilops ventricosa, whereas Pm4b was probably derived from T. persicum. Studies on certain addition lines and parental stocks indicated that wheat cytoplasm may enhance the expression of Sr38.

Compensation indices of radiation-induced wheat-Agropyron elongatum translocations conferring resistance to leaf rust and stem rust

Abstract: Species belonging to the genus Agropyron are an important source of disease resistance for bread wheat. Several resistance genes have been transferred. C-banding and in situ hybridization are the methods of choice for analyzing introgressed alien chromatin. Using these methods, we characterized radiation-induced wheat-Agropyron elongatum chromosome translocation lines carrying the rust resistance genes Sr26 and Sr25/Lr19. Data show that Sr26 is located on the translocation chromosome T6AS.6AL-6Ae#1L

Yield losses in winter barley resulting from a new race of Puccinia hordei in North America

Abstract: Leaf rust resistance, derived from the barley cultivar Cebada Capa, has been effective in the southeastern United States since 1950, when it was first used in the Virginia barley breeding program. In 1990, races of Puccinia hordei virulent to barleys that possess the resistance gene Rph7 were identified for the first time in North America. This research assessed the potential impact of Rph7-virulent races of leaf rust on grain yield and quality in winter barley. Natural epidemics of leaf rust occurred in cultivar trials at Painter and Warsaw, Virginia, in 1991 and 1992. Mean leaf rust severities for barley lines observed over three environments ranged from 10% for the moderately resistant line VA 90-42-45 to 76% for the susceptible cultivar Barsoy

Resistance to wheat leaf rust and stem rust in Triticum tauschii and inheritance in hexaploid wheat of resistance transferred from T. tauschii.

Abstract: Twelve accessions of Triticum tauschii (Coss.) Schmal. were genetically analyzed for resistance to leaf rust (Puccinia recondita Rob. ex Desm.) and stem rust (Puccinia graminis Pers. f.sp. tritici Eriks. and E. Henn.) of common wheat (Triticum aestivum L.). Four genes conferring seedling resistance to leaf rust, one gene conferring seedling resistance to stem rust, and one gene conferring adult-plant resistance to stem rust were identified. These genes were genetically distinct from genes previously transferred to common wheat from T. tauschii and conferred resistance to a broad spectrum of pathogen races. Two of the four seedling leaf rust resistance genes were not expressed in synthetic hexaploids, produced by combining tetraploid wheat with the resistant T. tauschii accessions, probably owing to the action of one or more intergenomic suppressor loci on the A or B genome. The other two seedling leaf rust resistance genes were expressed at the hexaploid level as effectively as in the source diploids. One...

Structure of Rust on Weathering Steel in Rural and Industrial Environments

Abstract: Rust on weathering steels exposed for up to 11 y in industrial and rural environments exhibited a spotty, nonuniform appearance as a result of contrast between light and dark areas on the surface. The area of the lighter regions increased with exposure time, as well as with increasing alloy content. Microscopic examination of cross sections revealed the dark regions had a porous appearance. The lighter regions were similar except for the presence of a relatively thin, smooth outer-surface layer. Raman spectroscopy indicated the dark, porous rust was comprised of goethite and lepidocrocite, while the smooth outer layer on the light areas was composed of hematite (α-Fe2O3) and magnetite (Fe3O4). Electrochemical potential measurements indicated the lighter areas were more passive. Results suggested formation of the thin outer layer of α-Fe2O3 and Fe3O4 is an important part of the mechanism of protective rust formation on weathering steels in the environments studied.

The relationship between wheat yield and stripe rust as affected by length of epidemic and temperature at the grain development stage of crop growth

Abstract: Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici. was associated with mean losses of up to 84% in the yield of wheat in southern New South Wales, Australia, between 1984 and 1987. Yield loss became smaller in cultivars with increasing levels of resistance in adult plant reaction and did not appear in cultivars with seedling susceptibility and moderate or better adult plant reaction levels in the 3 years when epidemics began after emergence of the flag leaf. However, in 1984 the stripe rust epidemic began during stem elongation, and yield losses of up to 21% occurred in cultivars with seedling susceptibility and a moderate or better adult plant reaction. Yield was significantly negatively correlated with the proportion of leaf area affected by stripe rust at stages of crop development from the end of heading to late milk. The correlation was greatest at the early milk stage of growth where the relationship was logarithmic. Two factors significantly influenced this relationship. Yield loss increased as the length of the epidemic increased, and decreased as temperature increased during grain development. The relationship that was developed for predicting yield loss accounted for 80-5% of the variance across all experiments, and was: y= 100(1-e10-4×(393+165 L-141T)) where y= yield loss (%); X= stripe rust (leaf area affected, range 0-99%) at early milk; L= time from 1% disease to early milk (range 0-70 days); and T= mean daily maximum temperature from 7 days before to 14 days after early milk (range 198-27.5°C).

Host specificity testing and assessment of the pathogenicity of the rust, Puccinia abrupta var. partheniicola, as a biological control agent of Parthenium weed (Parthenium hysterophorus)

Abstract: Parthenium hysterophorus, a native of Central America, is a problem weed of Australian rangeland, particularly in Queensland. Following field surveys in Mexico, the rust fungus Puccinia abrupta var. partheniicola was selected as a potential biological control agent. One isolate was chosen for further investigation after infection studies with one Kenyan and five Mexican isolates. Assessment of inoculation conditions showed that temperatures of less than 20° C and dew periods of more than 6 hours were required for abundant pustule production. Infection with the rust hastened leaf senescence, significantly decreased the life span and dry weight of Parthenium plants, and reduced flower production 10-fold. Subsequent host-range studies against 120 species and varieties, with further screening against a limited number of species conducted under a range of environmental regimes, indicated the rust to be sufficiently host-specific to be considered for introduction. Additional host-range tests against sunflowers demonstrated that resistance to P. abrupta var. partheniicola was not modified by prior inoculation with P. helianthi.

The effect of an insect herbivore and a rust fungus individually, and combined in sequence, on the growth of two Rumex species.

Abstract: The chrysomelid beetle Gastrophysa viridula and the rust fungus Urmnyces rumicis both occur on leaves of Rumex crispus and R. obtusifolius. We investigated the effect of beetle grazing or rust infection individually and when combined in sequence on the growth of their hosts in the field. Singly, beetle or rust reduced leaf area and plant biomass; the effect was greater on R. crispus, and rust caused greater damage than the beetle. Beetle grazing with subsequent rust infection caused damage no greater than that caused by rust alone, although on R. obtusifolius damage was greater than that from beetle grazing alone. Rust infection of R. obtusifolius with subsequent beetle grazing produced damage similar to that from other treatments; involving rust infection. In R. crispus this treatment produced the greatest reduction in biomass, The reductions in root and total plant weight from rust infection with subsequent beetle grazing were accurately predicted by a model including the damage produced by beetle and rust alone and the length of time each was present on the plant. This model also predicted accurately the damage to R. obtusifolius from the beetle followed by rust treatment, but over-estimated by up to 40% the damage to R. crispus. This can be explained mainly by an inhibition of rust infection by beetle grazing.

Stabilizing Process of Rust Layer Formed on Weathering Steels by Atmospheric Corrosion for a Long Period

Abstract: The rust layers formed on weathering low-alloy steels, which resist atmospheric corrosion, exposed for various periods have been examined. It is elucidated that the inner stable and protective rust layer which covers the surface of a weathering low-alloy steel exposed for 26 years mainly consists of small particles of ƒ¿-FeOOH and ƒ¿(Fe1 _X, CrX) OOH (X=0.03) containing a considerable amount of Cr. The variation in the amount of rust constituents against the exposure period supports well a newly proposed schematic

Mortality among hybrid poplar clones in a stool bed following leaf rust caused by Melampsoramedusae f.sp. deltoidae

Abstract: Melampsoramedusae Thuem. f.sp. deltoidae was found to be the primary cause of leaf rust in a stool bed, in Westport, Oregon, on 41 hybrid poplar clones. Each clone was represented by approximately 1000 ramets planted in a block in spring of 1992. Rust severity was rated, using the Schreiner scale (0–100), on three dates in the fall of 1992: August 28, September 18, and October 28, 1992. Of the 41 clones, 1, 12, and 21 scored 100 (i.e., maximal rust) on the three rating dates, respectively. Percent mortality the following spring was estimated for each clone on May 19. Correlation coefficients for rust severity versus mortality on the three rating dates were 0.89 (p < 0.0001), 0.85 (p < 0.0001), and 0.63 (p < 0.0001), respectively. Thus, rust severity and subsequent mortality were highly correlated, especially on the first rating date characterized by maximal infection of the most susceptible clone.

The Efficacy of Mixtures of Susceptible and Resistant Hosts to Two Wheat Rusts of Different Lesion Size: Controlled Condition Experiments and Computerized Simulations

Abstract: Controlled-environment experiments and computerized simulations on wheat yellow rust and wheat brown rust epidemics indicated that mixtures of resistant and susceptible hosts controlled parasites with small lesions more effectively than parasites with large lesions. Experiments were conducted on seedlings, during two parasitic cycles. Yellow rust lesions were about 200 times larger than those of brown rust. The measured efficacy of seedling mixtures in reducing disease spread was 22 % for yellow rust and 46 % for brown rust. Computerized simulations suggested that, for a given quantity of inoculum, mixture efficacy was limited for a large-lesion parasite because of fast host-plant saturation. Zusammenfassung Mit Versuchen unter kontrollierten Bedingungen und mit Computermodellen von Weizengelbrostund -braunrostepidemien konnte gezeigt werden, das Mischungen von resistenten und anfalligen Sorten die Erregerentwicklung effektvoll unterdruckten, wenn der Erreger kleine statt grose Verletzungen venirsachte. Versuche wurden an Samlingen wahrend zwei Etltwicklungskreislaufen durchgefuhrt. Gelbrostverletzungen waren ca. 200 mal groser als die des Braunrostes. Die ermittelte Wirksamkeit der Samlingsmischungen bei der Mmderung der Krankheitsverbreitung war 22 % bei Gelbrost bzw. 46 % bei Braunrost. Computermodelle deuteten darauf hin, das, bei einem vorgegebenen Inokulum, die Wirksamkeit der Mischungen bei Grosverletzungserregern dadtirch begrenzt wurde, Weil die Vf irtspflanze schnell besiedelt wurde.

Lodgepole pine stem diseases and management of stand density in the British Columbia interior

Abstract: The incidence of western gall rust, stalactiform blister rust, comandra blister rust and Atropellis canker was measured in 16 permanent sample plots in young lodgepole pine stands in the Interior of B.C. in 1980, shortly following juvenile spacing, and again in 1985 and 1992. The incidence (as percent of living trees with live rust infections) of the three rusts increased substantially between 1980 and 1985 in both treated and control plots, but declined from 1985 to 1992, partly because of infected tree mortality, but mostly because of a low rate of new infection and the death of all branch infections on many surviving trees. More than 85 percent of all stalactiform and comandra blister rust infections and 60 percent of all gall rust stem infections occurred within 2 m of the ground. The low incidence of new infection in these plots since 1985 is probably attributable to the loss of live branches due to crown closure and branch suppression in that 2 m zone as well as altered climatic conditions and reduc...

Rust, corrosion, and scale remover

Abstract: A rust, corrosion, and scale removing composition is provided. It comprises an additive concentrate and water. The additive concentrate preferably consists of, on a parts by weight basis, 1.5 to 5 parts glycolic acid, 0.2 to 1 parts tetrasodium salt of ethylenediaminetetraacetic acid, 2 to 6 parts citric acid, and 1 to 3 parts trisodium citrate dihydrate.

The transfer of leaf rust resistance from Triticum turgidum ssp. dicoccoides to hexaploid wheat

Abstract: Accession 8404 of Triticum turgidum ssp dicoccoides was shown to have excellent resistance to leaf rust Genetic analysis of the F3 of 8404 and RL6089, a leaf rust susceptible durum, indicated that 8404 had three genes for leaf rust resistance Two of these genes were transferred to hexaploid wheat (Thatcher) by a series of backcrosses One of the genes transferred was the same as Lr33 (RL6057) The second gene, which gives a fleck reaction to avirulent P recondita races, appears to be fully incorporated into the hexaploid where it segregated to fit a one-gene ratio Backcross lines with this gene give excellent resistance to leaf rust, although race MBG is virulent to this gene This may be a previously unidentified leaf rust resistance gene and should increase the genetic diversity available for wheat breeders Key words:Triticum aestivum, wheat, Triticum turgidum ssp dicoccoides, leaf rust resistance

Galvanized metal corrosion inhibitor

Abstract: A white rust inhibiting composition and method of inhibiting white rust for evaporative water coolers are disclosed. The composition includes, in combination, a blend of one or more organophosphorus compounds, one or more tannin compounds, and one or more water soluble metal compounds.

Relationships between temperature and latent periods of rust and leaf-spot diseases of groundnut

Abstract: The effect of temperature on the latent periods of rust, late leaf spot and early leaf spot diseases of groundnut caused by Puccinia arachidis, Phaeoisariopsis personata and Cercospora arachidicola. respectively, was studied. The latent periods (LP) of rust, late leaf spot and early leaf spot ranged from 12-49 days, 13-38 days and 13-39 days, respectively, between 12 C and 33 C An equation relating the rate of pathogen development (1/LP) to temperature was fitted using daily mean temperatures to provide three cardinal temperatures: the minimum (7"m,n), optimum (r^pc), and maximum (Tm,,). T^,^ was about I2°C for rust and about 10°C for the two leaf-spot diseases. Top, for all three diseases was close to 25 C. 7"max was Bl'C for early leaf spot, and extrapolated values for late leaf spot and rust were about 35 and 40°C, respectively.

Inheritance of Rust Resistance in a Source of MC29 Sunflower Germplasm

Abstract: Sunflower rust, Incited by Puccinia helianthi Schw., is a significant disease problem in sunflower (Helianthus annuus L.) production areas of North America, Argentina, and Australia and has been identified on sunflower grown in all regions of the world. Five races of rust presently have been identified in the USA. Recently, a new rust isolate gave a previously unreported virulence reaction pattern and was designated North American Race 6. A genetic study was conducted to determine the inheritance of resistance to Race 6 found in MC29 (AUS), a germplasm line introduced from Australia. F-1, F-2, and testcross progeny were produced from two crosses following hand pollinations: HA89/MC29 (AUS) and MC29 (AUS)/MC69. A multiple race inoculation technique was utilized under greenhouse conditions to evaluate the resistance or susceptibility of each plant to North American Races 1, 3, and 6. Chi-square tests for goodness of fit and heterogeneity were utilized to test each Fz and testcross family. A single, dominant gene in MC29 (AUS) was found to confer resistance to North American Races 1, 3, and 6. The gene was independent and nonallelic to the genes R(1) and R(2), and was designated R(10). Identification of resistance to Race 6 has increased the genetic diversity of resistance to sunflower rust in North America.

Effect of Melampsora rust on the growth and development of Salix burjatica‘Korso’in Northern Ireland

Abstract: The impact of Melampsora rust on the growth of Salix burjatica‘Korso’was assessed. Comparisons were made between untreated plants and those where the disease had been partially controlled using fungicides. Fungicides delayed the onset of the disease and its effects on growth. Leaf loss was reduced whilst shoot growth and dry matter yields increased. The effect of secondary organisms was also reduced resulting in lower levels of shoot death in the following season.

Corrosion studies of iron and its alloys by means of 57 Fe Mössbauer spectroscopy

Abstract: Some of the advantages and limitations of Mossbauer spectroscopy when used in corrosion research are shown by using three examples taken from the work of the authors on (i) the passive layer of iron, (ii) the corrosion of weathering steels by SO2-polluted atmospheres and (iii) the performance of rust converters.

Epidemiology of bean rust in Ethiopia

Abstract: Field and greenhouse experiments were conducted to study the epidemiology of rust ( Uromyces appendiculatus ) on beans ( Phaseolus vulgaris L.) in Ethiopia. The experiments were conducted under low input conditions reflecting the traditional bean production practices. Surveys identified five major diseases. Bean rust, bacterial blight and anthracnose were widely distributed. Angular and floury leaf spots were prominent in the humid west. Disease severities depended on regions, cropping practices and seasons. Strong associations between sowing date and rust severity and between bacterial blight and weediness or plant density were found. Artificial differences in rust epidemics produced large differences in crop growth, yield and yield loss. Multiple regression models were developed to estimate yield and yield loss. Yield and yield loss were best estimated by leaf area index and rust severity during flowering and late pod setting stages. Differences were found in the velocity of focus expansion (3 to 16 cm day -1 ) when susceptible and resistant bean cultivars were mixed at different proportions. The velocity of focus expansion increased linearly with the logarithm of the fraction of susceptible in the mixture. Five components of partial resistance were evaluated in a bean rust pathosystem. Differences between cultivars were largest for infection efficiency and sporulation capacity. Correlations existed between latency period and infection efficiency, infection efficiency and pustule size, and sporulation capacity and pustule size. Latency period, infection efficiency and pustule size can be used in screening for partial resistance.

Role of partial resistance to Puccinia hordei in barley in the defence of barley to inappropriate rust fungi.

Abstract: The partial resistance (PR) of barley to Puccinia hordei and the non-host reaction to inappropriate rust fungi are both based on a pre-haustorial barrier. It has been suggested that genes for PR in barley also confer resistance to inappropriate rust fungi. This hypothesis was tested by determining the correlation between the level of PR to P. hordei and the level of resistance to two inappropriate rust species in barley seedlings. The latent period of P. hordei and infectibility by P. recondita f.sp. tritici and by P. hordei-murini showed continuous segregation among the F 8 lines derived from two crosses between barley lines. The significant correlation between these parameters suggests that genes for partial resistance to P. kordei jn barley play a role in the resistance to P. recondita f.sp. tritici . There is evidence, however, that a large part of the genetic variation between the lines for resistance to P. recondita f.sp. tritici and to P. hordei-murini is not associated with the determination of the latent period of P. hordei . Lines with relative susceptibility to P. recondita f.sp. tritici also tended to be relatively susceptible to P. hordei-murini . These results indicate that some of the genes for resistance segregating in the progenies studied in this work are effective against more than one rust fungal species.