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Showing papers on "Rust published in 2009"


Journal ArticleDOI
TL;DR: This research quantifies differences in aggressiveness among isolates representative of the pre-2000 and post-2000 populations to demonstrate that wheat rust fungi can adapt to warmer temperatures and cause severe disease in previously unfavorable environments.
Abstract: Milus, E. A., Kristensen, K., and Hovmoller, M. S. 2009. Evidence for increased aggressiveness in a recent widespread strain of Puccinia striiformis f. sp. tritici causing stripe rust of wheat. Phytopathology 99:89-94. Stripe rust (yellow rust) of wheat, caused by Puccinia striiformis f. sp. tritici, has become more severe in eastern United States, Australia, and elsewhere since 2000. Recent research has shown that this coincided with a global spread of two closely related strains that were similar based on virulence phenotype and amplified fragment length polymorphism. The objective of this research was to quantify differences in aggressiveness among isolates representative of the pre-2000 and post-2000 populations. Representative isolates were evaluated at low (10 to 18°C) and high (12 to 28°C) temperature regimes for latent period, lesion length, lesion width, lesion area, and spore production on adult plants of a susceptible wheat cultivar with no known genes for resistance to stripe rust. “New” isolates (since 2000) were significantly more aggressive than “old” isolates (before 2000) for all variables. At the low temperature regime, new isolates sporulated 2.1 days (16%) sooner, grew 0.3 mm per day (18%) faster, produced 999 (140%) more spores per inoculation site per day, and produced 6.5 (71%) more spores per mm 2 of lesion per day compared with old isolates. At the high temperature regime, new isolates sporulated 3 days (26%) sooner, grew 0.2 mm per day (18%) and 2.2 mm 2 per day (88%) faster, grew 1.2 mm (50%) wider, produced 774 (370%) more spores per inoculation site per day, and produced 6.2 (159%) more spores per mm2 of lesion per day than old isolates. New isolates showed significant adaptation to the warm temperature regime for all variables. Based on these results and previously published models for stripe rust epidemics, recent severe stripe rust epidemics were most likely enhanced by the pathogen’s increased aggressiveness, especially at higher temperature. Furthermore, these results demonstrate that wheat rust fungi can adapt to warmer temperatures and cause severe disease in previously unfavorable environments.

318 citations


Journal ArticleDOI
TL;DR: Ten, widely-used vegetation indices, based on mathematical combinations of narrow-band optical reflectance measurements in the visible/near infrared wavelength range were evaluated for their ability to discriminate leaves of 1 month old wheat plants infected with yellow (stripe), leaf and stem rust.
Abstract: Ten, widely-used vegetation indices (VIs), based on mathematical combinations of narrow-band optical reflectance measurements in the visible/near infrared wavelength range were evaluated for their ability to discriminate leaves of 1 month old wheat plants infected with yellow (stripe), leaf and stem rust. Narrow band indices representing changes in non-chlorophyll pigment concentration and the ratio of non-chlorophyll to chlorophyll pigments proved more reliable in discriminating rust infected leaves from healthy plant tissue. Yellow rust produced the strongest response in all the calculated indices when compared to healthy leaves. No single index was capable of discriminating all three rust species from each other. However the sequential application of the Anthocyanin Reflectance Index to separate healthy, yellow and mixed stem rust/leaf rust classes followed by the Transformed Chlorophyll Absorption and Reflectance Index to separate leaf and stem rust classes would provide for the required species discrimination under laboratory conditions and thus could form the basis of rust species discrimination in wheat under field conditions.

170 citations


Posted Content
TL;DR: In this article, the authors present a set of abbreviations and acronyms for nouns and acronyms, including the following terms: nouns, adjectives, and acronsyms.
Abstract: vii Abbreviations and Acronyms viii

85 citations


Journal ArticleDOI
TL;DR: Soybean rust severity measured over time as area under the disease progress curve (AUDPC) was negatively correlated with yield and the effectiveness of any given treatment was often dependent on when rust was first detected and the intensity of its development.
Abstract: Mueller, T. A., Miles, M. R., Morel, W., Marois, J. J., Wright, D. L., Kemerait, R. C., Levy, C., and Hartman, G. L. 2009. Effect of fungicide and timing of application on soybean rust severity and yield. Plant Dis. 93:243-248. Soybean rust, caused by Phakopsora pachyrhizi, is a devastating foliar disease of soybean that may cause significant yield losses if not managed by well-timed fungicide applications. To determine the effect of fungicide timing on soybean rust severity and soybean yield, field trials were completed in Paraguay (four locations), the United States (two locations), and Zimbabwe (one location) from 2005 to 2006. Treatments at each location included applications of tebuconazole, pyraclostrobin, or a combination of azoxystrobin + propiconazole, and in some locations pyraclostrobin + tebuconazole at the following soybean growth stages (GS): (i) GS R1 (beginning flowering), (ii) GS R3 (beginning pod), (iii) GS R5 (beginning seed), (iv) GS R1 + R3, (v) GS R3 + R5, and (vi) GS R1 + R3 + R5. Soybean yields from plots treated with fungicides were 16 to 114% greater than yields from no fungicide control plots in four locations in Paraguay, 12 to 55% greater in two locations in the United States, and 31% greater in Zimbabwe. In all locations, rust severity measured over time as area under the disease progress curve (AUDPC) was negatively correlated (r = –0.3, P < 0.0001) to yield. The effectiveness of any given treatment (timing of application and product applied) was often dependent on when rust was first detected and the intensity of its development. For example, when soybean rust was first observed before GS R3 (two locations in Paraguay), the plants in plots treated with a fungicide at GS R1 had the lowest AUPDC values and highest yields. When soybean rust was first observed after GS R3, plants treated with a fungicide at GS R3 and/or GS R5 had the lowest AUDPC values and highest yields with a few exceptions.

84 citations


Journal ArticleDOI
TL;DR: An Agrobacterium-mediated genetic transformation procedure for the model flax rust fungus Melampsora lini, which infects flax (Linum usitatissimum), confirms that the cloned AvrL567 gene is responsible for flax Rust virulence phenotypes, and demonstrates the utility of this system to probe rust gene function.
Abstract: Rust fungi cause devastating diseases on many important food crops, with a damaging stem rust epidemic currently affecting wheat production in Africa and the Middle East. These parasitic fungi propagate exclusively on plants, precluding the use of many biotechnological tools available for other culturable fungi. In particular the lack of a stable transformation system has been an impediment to the genetic manipulation required for molecular analysis of rust pathogenicity. We have developed an Agrobacterium-mediated genetic transformation procedure for the model flax rust fungus Melampsora lini, which infects flax (Linum usitatissimum). Selection of transgenic rust lines is based on silencing of AvrL567, which encodes a rust effector protein that is recognised by the flax L6 immune receptor. The non-transgenic rust line is unable to infect flax plants expressing L6, while silenced transgenic lines are virulent on these plants, providing an effective selection system. This directly confirms that the cloned AvrL567 gene is responsible for flax rust virulence phenotypes, and demonstrates the utility of this system to probe rust gene function.

69 citations


Journal ArticleDOI
TL;DR: Isolate B157 is considered a potential bio-control agent for coffee rust for organic crop systems in Brazil and reduced rust intensity as effectively as copper hydroxide.

62 citations


Journal ArticleDOI
TL;DR: The preliminary results obtained from this laboratory-scale research demonstrated that this multispectral imaging method could quantitatively detect soybean rust and quantify severity in real time field scouting.
Abstract: Soybean rust, caused by Phakopsora pachyrhizi, is one of the most destructive diseases for soybean production. It often causes significant yield loss and may rapidly spread from field to field through airborne urediniospores. In order to implement timely fungicide treatments for the most effective control of the disease, it is essential to detect the infection and severity of soybean rust. This research explored feasible methods for detecting soybean rust and quantifying severity. In this study, images of soybean leaves with different rust severity were collected using both a portable spectroradiometer and a multispectral CDD camera. Different forms of vegetation indices were used to investigate the possibility of detecting rust infection. Results indicated that both leaf development stage and rust infection severity changed the surface reflectance within a wide band of spectrum. In general, old leaves with most severe rust infection resulted in lowest reflectance. A difference vegetation index (DVI) showed a positive correlation with reflectance differences. However, it lacks solid evidence to identify such reflectance change was solely caused by rust. As an alternative, three parameters, i.e. ratio of infected area (RIA), lesion color index (LCI) and rust severity index (RSI), were extracted from the multispectral images and used to detect leaf infection and severity of infection. The preliminary results obtained from this laboratory-scale research demonstrated that this multispectral imaging method could quantitatively detect soybean rust. Further tests of field scale are needed to verify the effectiveness and reliability of this sensing method to detect and quantify soybean rust infection in real time field scouting.

60 citations


Journal ArticleDOI
TL;DR: The results confirm that weather data can be successfully used in wheat disease prediction models and find statistically significant correlations between incidence and severity were found for LBDs, brown rust and eyespot, but not for yellow rust and powdery mildew.

59 citations


Journal ArticleDOI
TL;DR: Comparisons of the yields obtained from plots in which brown rust was controlled early versus late in the epidemic suggested that the impact of the disease is greatest from the middle to late epidemic period when stem elongation has begun.
Abstract: Brown rust, caused by Puccinia melanocephala, can cause severe epidemics in susceptible sugarcane cultivars during spring and early summer in Louisiana. The effect of the disease on yield was evaluated in field experiments conducted during three growing seasons. A mixture of three fungicides-azoxystrobin, propiconazole, and tebuconazole-applied biweekly during the spring epidemic period kept brown rust severity low (<5%), and plants protected by fungicide applications throughout the epidemic provided an estimate of attainable yield for comparison with plants naturally infected with rust. A combined analysis over three seasons estimated brown rust caused reductions of 16 and 14% in cane tonnage and total amount of sucrose produced, respectively, in cv. LCP 85-384. The greatest reduction in total sucrose yield of 22% resulted from the epidemic of longest duration, and stalk weight was negatively correlated with rust severity. Comparisons of the yields obtained from plots in which brown rust was controlled early versus late in the epidemic suggested that the impact of the disease is greatest from the middle to late epidemic period when stem elongation has begun.

53 citations


Journal ArticleDOI
TL;DR: Differences in phenolic metabolism were analyzed between inoculated and noninoculated plants using two susceptible and three resistant soybean genotypes with known resistance genes to understand the metabolic responses of the plant to a devastating foliar disease, soybean rust.
Abstract: Understanding the metabolic responses of the plant to a devastating foliar disease, soybean rust, caused by Phakopsora pachyrhizi, will assist in development of cultivars resistant to soybean rust. In this study, differences in phenolic metabolism were analyzed between inoculated and noninoculated plants using two susceptible and three resistant soybean genotypes with known resistance genes. Rust infection resulted in increased accumulation of isoflavonoids and flavonoids in leaves of all soybean genotypes tested. Although the soybean phytoalexin glyceollin was not detected in leaves of uninfected plants, accumulation of this compound at marked levels occurred in rust-infected leaves, being substantially higher in genotypes with a red-brown resistant reaction. In addition, there was inhibition of P. pachyrhizi spore germination by glyceollin, formononetin, quercetin, and kaempferol. However, there was no correlation between concentrations of flavonoids quercetin and kaempferol and rust-induced isoflavonoid formononetin in soybean leaves and rust resistance. Lignin synthesis also increased in all inoculated soybean genotypes whereas there was no significant difference in all noninoculated soybean genotypes. Cell wall lignification was markedly higher in inoculated resistant lines compared with inoculated susceptible lines, indicating a possible protective role of lignin in rust infection development.

49 citations


Journal ArticleDOI
TL;DR: It is suggested that fungicides can be used effectively in reducing stem rust severity and increasing yield of susceptible wheat cultivars in stem-rust-prone areas.
Abstract: The emergence of a new virulent race of stem rust (Puccinia graminis f. sp. tritici) of wheat (Triticum aestivum), TTKS (Ug99), calls for urgent measures to contain the disease, which is a serious threat to wheat production in Kenya. Nine commercial fungicides were evaluated for control of stem rust in the field in three locations in 2005 and 2006. Ten treatments, including untreated control, were applied on field plots in a randomized complete block design with four replications. Assessment of stem rust severity was done at growth stage (GS) 55 (heading), GS 65 (flowering), and GS 75 (late milk) and expressed in terms of mean rust severity and area under the disease progress curve (AUDPC). In general, fungicide treatment significantly (P ≤ 0.05) reduced rust severity, AUDPC, and losses in grain yield and 1,000-kernel weight for cv. Duma compared with the untreated control. Stem rust was severe in both years across all sites, resulting in significantly less grain yield in the control treatment. T...

Journal ArticleDOI
TL;DR: Genetic analysis determined that Zak has a single dominant gene, designated as YrZak, conferring race-specific all-stage resistance to stripe rust, which should be useful in monitoring virulence changes in the pathogen population and in studying host-pathogen interactions.
Abstract: Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici, is one of the most devastating foliar diseases of wheat (Triticum aestivum) worldwide. Growing resistant cultivars is the best approach for control of the disease. Although the stripe rust resistance in spring wheat cv. Zak has been circumvented by a group of races of the pathogen predominant in the United States since 2000, the resistance genes in Zak were unknown. To identify and map the genes for resistance to stripe rust, Zak was crossed with susceptible wheat genotype ‘Avocet Susceptible’. Seedlings of the parents and F1, F2, and F3 progeny were tested with P. striiformis f. sp. tritici races PST-43 and PST-45 under controlled greenhouse conditions. Genetic analysis determined that Zak has a single dominant gene, designated as YrZak, conferring race-specific all-stage resistance. Resistance gene analog polymorphism (RGAP), simple sequence repeat (SSR), and sequence-tagged site (STS) techniques were used to identify mol...

Journal ArticleDOI
Z.F. Wang, Penghui Li, Y. Guan, Q.F. Chen, S.K. Pu 
TL;DR: In this paper, the corrosion resistance of ultra-low carbon bainitic (ULCB) steel was compared with a weathering steel 09CuPCrNi through accelerated corrosion tests.

Journal Article
TL;DR: Considerable diversity was observed for level of partial resistance of these introduced winter wheat breeding lines, which may be advanced further for manipulation in breeding or inheritance studies.
Abstract: Thirty-seven winter wheat lines introduced from Oklahoma State University, along with local check were studied to assess their partial resistance level, at Hazara Agricultural Research Station (HARS), Abbottabad. Pathotypes of Puccinia striiformis West. tritici (Pst) prevalent at the site were found virulent on all of the introduced winter wheat lines. Partial resistance level was assessed through final rust severity (FRS), area under rust progress curve (AURPC) and coefficient of infection (CI). A considerably high disease pressure was observed with a maximum FRS up to 95% recorded for line F5-34. Six lines were having FRS value more than 70%, while remaining 24 lines along with local check were having FRS value less than 70%. Seventeen lines were having higher AURPC values while remaining 21 lines were having AURPC values ranging from 300 to 1100, marked to be partially resistant. Based on CI value, four lines (F5-64, F5-71, F5-15 and OK00611W) were marked as highly partially resistant, having CI value up to 20; F5-4, F5-21, F5-69, F5-78, F5-103, F5-122, F5-141, OK99212, OK00608W, Intrada and Ghaznavi, with CI value 21-40, were marked as moderately resistant; and F5-5, F5-9, F55-38, F5-70, F5-83, F5-99, F5-110, F5139, OK95616-56, OK98G508W, OK00421, OK00514 and OK00618W, with CI value 41-60, were designated to have low level of partial resistance. Line OK00611W performed better, producing maximum grain yield with an increase of 2736 kg ha -1 over the local check as well as having better level of partial resistance. Cluster analysis of the OSU introduced winter wheat lines revealed four major groups/cluster, based on partial resistance parameters and grain yield. Considerable diversity was observed for level of partial resistance of these introduced winter wheat breeding lines, which may be advanced further for manipulation in breeding or inheritance studies.

Journal ArticleDOI
TL;DR: Ochre and Rust: Artefacts and Encounters on Australian Frontiers by Philip Jones as mentioned in this paper is a collection of artefacts and encounters on Australian frontiers. Pp. 448.
Abstract: Ochre and Rust : Artefacts and Encounters on Australian Frontiers. By Philip Jones. Adelaide: Wakefield Press, 2007. Pp. 448. A$49.95 cloth. On the first page of Graham Connah's ‘Of the Hut I Build...

Journal ArticleDOI
TL;DR: This study is the first attempt to develop PCR-based sequence specific markers linked to partial rust resistance in Coffee leaf rust, Hemileia vastarix, exhibiting significant association with partial resistance.
Abstract: The objective of this study was to identify polymorphic molecular markers associated with partial resistance to coffee leaf rust, Hemileia vastarix. A segregating F2 population derived from a cross between the susceptible Coffea arabica cv. Caturra and a C. canephora-introgressed Arabica line exhibiting high partial resistance was analyzed. Rust resistance measured as rust incidence (RI) and defoliation (DEF) was evaluated in field conditions in three consecutive years (2003–2005). During the 2003 season, which was characterized by favorable conditions for a rust epidemic, the F2 plants exhibited different levels of resistance ranging from very susceptible (50.1% for DEF and 49.5% for RI) to highly partial resistance (9.1% for DEF and 3.7% for RI). Molecular analysis enabled identification of seven polymorphic markers (5 AFLP and 2 SSR) exhibiting significant association with partial resistance. Coexistence of resistance homozygous alleles (RR) at codominant SSR loci was correlated with high resistance. This study is the first attempt to develop PCR-based sequence specific markers linked to partial rust resistance in coffee.

Journal ArticleDOI
TL;DR: Genomic in situ hybridization showed that the lines with LM phenotype had a significantly higher rust resistance than the non-LM lines, and lm from Ning7840 may have pleiotropic effects on APR to leaf rust.
Abstract: Lesion mimics (LM) that resemble plant disease symptoms in the absence of plant pathogens may confer enhanced plant disease resistance to a wide range of pathogens. Wheat line Ning7840 has adult plant resistance (APR) to leaf rust (Puccinia triticina) and shows LM symptoms at heading. A recessive gene (lm) was found to be responsible for LM in Ning7840 and located near the proximal region of chromosome 1BL using a population of 179 recombinant inbred lines (RIL) derived from the cross Ning7840/Chokwang. Genomic in situ hybridization showed that Ning7840 carries the short arm of 1R chromosome from rye (Secale cereale L.), on which the race-specific gene Lr26 resides. The RILs were infected with the isolate PRTUS 55, an isolate virulent to Lr26, at anthesis in two greenhouse experiments. The result showed that the lines with LM phenotype had a significantly higher rust resistance than the non-LM lines. Composite interval mapping consistently detected a QTL, Qlr.pser.1BL, for APR on chromosome 1BL. Qlr.pser.1BL peaked at lm and explained up to 60.8% of phenotypic variation for leaf rust resistance in two greenhouse experiments, therefore, lm from Ning7840 may have pleiotropic effects on APR to leaf rust.

Journal ArticleDOI
TL;DR: A fast response sensor was developed based on surface plasmon resonance to detect Asian rust in soybean leaf extract at early stages of the disease, providing new perspectives on using SPR technology for the development of a highly sensitive sensor for agricultural applications.

Journal ArticleDOI
TL;DR: Results indicated that all concentrations and treatments reduced the severity of rust disease caused by P. recondita f.
Abstract: Leaf rust of wheat (Triticum aestivum L.), incited by Puccinia recondita ex Desm. f. sp. tritici Eriks, is one of the most important wheat diseases in Egypt. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defense reactions in conifers and might be used to increase systemic resistance against biotic damage. In the greenhouse, different concentrations of MJ (10, 20 and 30 mM) were applied as seed soaking plus foliar spray or only as foliar spray to control leaf rust and induction of secondary compound production in leaves of wheat plants. Foliar spray was applied after 30 and 50 days of sowing. Results indicated that all concentrations and treatments reduced the severity of rust disease caused by P. recondita f. sp. tritici in wheat leaves during 45 days of inoculations. Disease incidence was decreased significantly in MJ-treated plants as seed soaking plus foliar spray with 20 and 30 mM when compared to 10 mM MJ or control plants. The stud...

01 Jan 2009
TL;DR: Emphasis will be given to wheat stripe/ yellow rust and the development and application of a near-isogenic set of materials based on the spring wheat cultivar Avocet, selected because of its high degree of susceptibility to the disease, agronomic adaptability, and resistance to stem rust.
Abstract: The purpose of monitoring cereal rust pathogens is to provide a basis for disease control strategies that include breeding for resistance, predicting disease response in commercial cultivars and responding to the dynamics of pathogen change. The means of achieving this vary from regular collection surveys based on assessments of sample collections in greenhouse tests, to monitoring and recording static trap plots. Factors governing the method of approach include the size of the target region, the available research resources and the experience of staff involved. This paper is a brief review of the development of near-isogenic lines as a means of monitoring cereal rust pathogens. Emphasis will be given to wheat stripe/ yellow rust and the development and application of a near-isogenic set of materials based on the spring wheat cultivar Avocet. This parent was selected because of its high degree of susceptibility to the disease, agronomic adaptability (semidwarf, spring habit, moderate vernalisation and day-length requirements), and resistance to stem rust. The relative benefits of using these materials will be discussed in the context of available data.

Journal ArticleDOI
TL;DR: Data suggest that multilines may select for complex virulence or "super races" and any resistance effect may not be durable when used in oat cultivars.
Abstract: Crown rust, caused by Puccinia coronata f. sp. avenae is the most important disease of cultivated oat in North America. Numerous race-specific (Pc) genes for crown rust have been found in Avena spp. but this type of resistance has not been durable when used in oat cultivars. Increasing diversity for resistance within a crop by the use of multiline cultivars or varietal mixtures has been proposed as a means of achieving durable resistance to highly variable pathogens such as P. coronata f. sp. avenae. Multiline cv. E77 was evaluated over multiple seasons in the University of Minnesota buckthorn nursery in St. Paul. Buckthorn (Rhamnus cathartica, the alternate host of P. coronata) supports a sexually recombining, highly diverse crown rust population in the St. Paul nursery. Crown rust severity on flag leaves was measured multiple times on E77 and its 10 component lines during grain filling. Single-urediniospore isolates taken from crown rust samples during early stages of the epidemic and at the end of the epidemic were tested for virulence on the 10 component lines of E77 in greenhouse seedling tests. Crown rust development was reduced in E77 compared with the weighted mean of the component lines at all stages of the crown rust epidemics. The mean virulence of single-urediniospore isolates tended to increase late in the epidemic on E77. These data suggest that multilines may select for complex virulence or "super races" and any resistance effect may not be durable.

Journal ArticleDOI
TL;DR: Este estudo proporcionou uma nova perspectiva da utilizacao do metodo para o diagnostico precoce da doenca na plantacao previne varias perdas para o agricultor bem como para as culturas vizinhas.
Abstract: Soybean rust is a disease that occurs on soybean leaves and is considered very aggressive, reducing product quality. Early identification of fungus in the plants prevents severe farming losses as well as spreading to neighboring cultures. In this paper, a label-free immunosensor was developed based on impedance measurements to detect Asian rust on soybean leaf extract at the early stages of the disease. The antibody anti-mycelium of Phakopsora pachyrhizi fungus (disease agent) was immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols using covalent cysteamine coupling. This immunosensor presents a limit of detection of 385 ng mL-1. The optimization of experimental conditions and surface blocking to minimize non-specific adsorption on the immunosensor response were evaluated. These studies, based on electrochemical impedance spectroscopy (EIS), provide new perspectives on using this method for early diagnosis of soybean rust.

Journal ArticleDOI
26 Nov 2009-Genome
TL;DR: The small size of the terminal wheat-alien translocation, as established precisely with respect to Chinese Spring deletion bins and the syntenic rice genomic sequence, further confirmed the escaping nature of cryptic wheat-Alien translocations in introgressive breeding.
Abstract: The cryptic wheat–alien translocation T5DL·5DS-5MgS(0.95), with leaf rust and stripe rust resistance genes Lr57 and Yr40 transferred from Aegilops geniculata (UgMg) into common wheat, was further a...

Journal ArticleDOI
T. Terefe, I. Paul, J. Mebalo, K. Naicker, L. Meyer 
TL;DR: The virulence patterns of pathotypes detected in 2007 was similar to those observed in previous seasons and new pathotypes were not observed, meaning a significant change in the response of current commercial cultivars is not expected considering the results.
Abstract: A survey was conducted during 2007 to determine the occurrence and pathogenicity of Puccinia triticina Eriks., the cause of wheat leaf rust, in South Africa. Leaf rust was widely observed in the wheat growing areas of the Western Cape but only at a few localities in the Free State. A low incidence of leaf rust was detected at Cedara (KwaZulu-Natal). Leaf rust widely occurred within trap nurseries but it was observed only occasionally in farmers’ fields. Five pathotypes were identified from the total of 80 leaf rust samples collected. The most frequently detected pathotype was 3SA133 (76.8%) which was found in samples from all the localities followed by pathotype 3SA126 (11.0%). Other pathotypes detected were 3SA140 (7.3%), 3SA132 (3.7%) and 3SA137 (1.2%). None of the isolates tested was virulent on the resistance genes Lr3bg and Lr16 with the majority of the isolates (>73%) found virulent on the resistance genes Lr3a, 3ka, 11, 20, 24 and 30. No isolates avirulent on Lr1, 2c, 10 and 14a were found. The vir...

01 Jan 2009
TL;DR: The QTLs and their closely linked molecular markers identified in this study will benefit to marker-assisted selections and wheat germplasm enhancement in breeding wheat cultivars for leaf rust resistance.
Abstract: 【Objective】 The CIMMYT wheat cultivar Saar has exhibited a high level of adult-plant resistance to leaf rust, stripe rust and powdery mildew in Europe, Asia, and South America, and identification of its QTL for leaf rust resistance will play an important role in breeding wheat cultivars for durable resistance. 【Method】 A total of 142 SSR and 209 DArT markers were used to map QTL for resistance to leaf rust in a recombinant inbred line (RIL) population with 109 F6 families derived from the cross Avocet/Saar. The field trials were conducted in Baoding, Hebei province and Xinxiang, Henan province in 2006-2007 cropping season. 【Result】 Linkage analysis indicated that the genetic map consisting of 142 SSR markers and 209 DArT markers covered 21 wheat linkage group with a total genetic distance of 3083 cM. Using composite interval mapping (CIM), five QTLs for resistance to leaf rust were detected on chromosomes 1BL, 2DS, 5BL, 6AL and 7DS, explaining 4.5%-6.4%, 12.2%-12.5%, 4.9%-11.2%,4.9%-7.8%, and 14.0%-67.6% of phenotypic variance, respectively. 【Conclusion】 The QTLs and their closely linked molecular markers identified in this study will benefit to marker-assisted selections and wheat germplasm enhancement in breeding wheat cultivars for leaf rust resistance.

Journal ArticleDOI
TL;DR: Results from this study indicated that coffee plants were inefficient in uptaking Si from the nutrient solution and translocating it to the shoot, which did not guarantee an increase in coffee resistance to rust.
Abstract: Coffee leaf rust, caused by Hemileia vastatrix, is the most important disease on coffee. This study aimed to evaluate the effect of silicon (Si) on some components of coffee resistance to rust and to determine if it could increase the activity of chitinases (CHI), β-1,3-glucanases (GLU), and peroxidases (POX). Coffee plants (cultivar "Catuai vermelho 44") were grown on aerated Clarck’s nutrient solution containing 0 (-Si) or 2 mmol L-1 Si (+Si) for 45 days and inoculated with H. vastatrix. There was no significant difference between the -Si and +Si treatments for Si content in leaf tissue, but Si content in root tissue was significantly higher for the +Si treatment. The -Si and +Si treatments were not significantly different for incubation period, latent period, number of pustules per leaf, pustule size, pustule expansion, and area under rust progress curve. The activity of CHI, GLU, and POX increased after inoculation with H. vastatrix, even with increase or decrease in activities during the sampling times. There was not a pronounced effect of Si in increasing the activity of these enzymes, except for rare increases in specific sampling times. Results from this study indicated that coffee plants were inefficient in uptaking Si from the nutrient solution and translocating it to the shoot. Silicon was exclusively restricted to the root system, which did not guarantee an increase in coffee resistance to rust.


Journal ArticleDOI
TL;DR: Foliar application of KSi, regardless of the pH, was efficient in decreasing rust severity and the application of ASM was inefficient to potentiate the activity of these six enzymes studied, even though it had a great impact on reducing rust severity.
Abstract: The major method for control of coffee leaf rust, caused by Hemileia vastatrix, is the use of fungicides. The supply of silicon (Si) to plants is an interesting control strategy because this element can increase the resistance of many plant species to pathogens. This study aimed to evaluate the effect of foliar application of Si on reducing rust severity as well as to determine if it can potentiate the activity of enzymes related to host resistance to pathogens. Coffee plants (cultivar Catuai Vermelho 44) were sprayed with distilled water, potassium silicate (KSi) solution (35 g/L, pH 10.5), KSi (35 g/L, pH 5.5), and acibenzolar-S-methyl (ASM) solution (200 µg/L) 24 hours before inoculation. There was no significant difference among the treatments regarding the content of Si and potassium in the leaf tissue. Rust severity was significantly higher on plants sprayed with water as compared to the other treatments. The ASM significantly decreased rust severity by 70% in comparison to the water spray treatment. Foliar application of KSi, regardless of the pH, was efficient in decreasing rust severity. The ASM was efficient in increasing the activity of chitinases and β-1,3-glucanases. On the other hand, the application of KSi, regardless of the pH, was inefficient to potentiate the activity of these six enzymes studied, even though it had a great impact on reducing rust severity.

Journal ArticleDOI
TL;DR: In this paper, a pilot twin roll strip caster was used to construct low carbon steels with different P contents (0.08, 0.15, and 0.26%).

Book
24 Jul 2009
TL;DR: Clowes as discussed by the authors stated that pure lead will dissolve to a slight extent in perfectly pure water, as iron did in the experiments made by Whitney and repeated by the American investigators, when they brought iron into contact with water under conditions similar to those which I had secured.
Abstract: IN a letter to NATURE of April 16, Dr. Frank Clowes states his belief that pure lead will dissolve to a slight extent in perfectly pure water “as iron did in the experiments made by Whitney and repeated by the American investigators, when they brought iron into contact with water under conditions similar to those which I had secured”.