The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
James W. Buck - One of the best experts on this subject based on the ideXlab platform.
-
Detection of Puccinia pelargonii-zonalis-infected Geranium Tissues and Urediniospores
Journal of Phytopathology, 2013Co-Authors: Erika A. Scocco, Steven N Jeffers, Ronald R. Walcott, James W. BuckAbstract:The occurrence of geranium rust (caused by Puccinia pelargonii-zonalis) in commercial greenhouses can result in unmarketable plants and significant economic losses. Currently, detection of geranium rust relies solely on scouting for symptoms and signs of the disease. The purpose of this research was to develop a rapid detection assay for P. pelargonii-zonalis-infected tissues or Urediniospores on greenhouse-grown geraniums. Two oligonucleotide primers were designed based on internal transcribed spacer sequence data from three isolates of P. pelargonii-zonalis. The primers amplified a 131-bp product from genomic DNA from each isolate of P. pelargonii-zonalis but did not amplify a product from genomic DNA from twelve other rust fungi or four other plant pathogenic fungi. A PCR product was amplified consistently from solutions that contained 1 ng or 100 pg/ml of purified P. pelargonii-zonalis DNA in conventional PCR and at 1 pg/ml using real-time PCR. The detection threshold was 102 Urediniospores/ml for real-time PCR and 104 Urediniospores/ml for conventional PCR using Urediniospores collected by vacuum from sporulating lesions. Puccinia pelargonii-zonalis DNA was amplified by real-time PCR from Urediniospores washed from a single inoculated leaf, but recovered Urediniospores were below detection threshold from one inoculated leaf with 5, 10, 25 and 50 non-inoculated leaves. Conventional and real-time PCR did not detect P. pelargonii-zonalis in infected leaf tissues, presumably due to PCR inhibitors in the geranium leaf tissue. The inhibition of both conventional and real-time PCR by geranium tissues suggests that a detection assay focusing on Urediniospore recovery and microscopic examination with subsequent species verification by PCR may be the most efficient method for assessing the presence of geranium rust in greenhouses.
-
effect of light on in vivo Urediniospore germination lesion development and sporulation of puccinia hemerocallidis on daylily and puccinia pelargoniizonalis on geranium
Mycologia, 2011Co-Authors: Weibo Dong, James W. BuckAbstract:The presence of rusts of daylily and geranium caused respectively by Puccinia hemerocalli- dis and P. pelargonii-zonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on Urediniospore germination, germ tube elongation, lesion development and sporulation of the two fungal pathogens on detached leaves and whole plants. Exposure of dry or hydrated Urediniospores of P. hemerocallidis to cool white fluorescent light (600 mmol s 21 m 22 ) or to sunlight (950-1910 mmol s 21 m 22 ) for 2 h or 4 h significantly reduced germination and germ tube elongation on detached daylily leaves. Germination but not germ tube elongation of hydrated Urediniospores of P. pelargonii-zonalis on detached geranium leaves was significantly reduced when exposed to fluorescent light for 2 h or 4 h. A 4 h exposure to either light source significantly reduced lesion development of P. hemerocallidis on detached daylily leaves with fewer lesions developing from hydrated compared to dry Urediniospores. Sunlight exposures of 1 h and 2 h of hydrated and dry Urediniospores respectively signifi- cantly reduced lesion development by either fungus on whole plants. Increasing exposure to fluorescent light negatively affected sporulation of P. hemerocalli- dis and P. pelargonii-zonalis. Complete suppression of sporulation was not observed for either fungus with up to a 24 h exposure to fluorescent light. Light exposure negatively affected disease development by P. hemerocallidis and P. pelargonii-zonalis. Exposure to high light intensities may affect spread of rust diseases on ornamental plants.
-
effect of postsymptom application of fungicides on Urediniospore production by puccinia triticina on wheat and p hemerocallidis on daylily
Plant Disease, 2011Co-Authors: James W. Buck, K Wise, Weibo DongAbstract:Abstract Greenhouse experiments were conducted to evaluate the effect of post-symptomatic fungicide applications on Urediniospore production of leaf rust of wheat, Puccinia triticina, and daylily rust, P. hemerocallidis. Fungicides from five chemical classes were evaluated for their effect on Urediniospore production at 24-h intervals post application for 96 h. The quinone outside inhibitor (QoI) fungicide (azoxystrobin) significantly reduced cumulative Urediniospore production by P. triticina (40.1 and 11.3% of control) and P. hemerocallidis (37.9 and 35.6% of control) in both trials. The demethylation inhibitor, myclobutanil, significantly reduced Urediniospore production by P. hemerocallidis 24 h post treatment in both trials and cumulative production in one trial. Myclobutanil did not affect Urediniospore production by P. triticina. Four QoI fungicides significantly reduced Urediniospore production by P. triticina at all collection times (24, 48, and 72 h) and cumulative production in both trials. No ...
-
toxicity of fungicides to Urediniospores of six rust fungi that occur on ornamental crops
Plant Disease, 2005Co-Authors: Daren S Mueller, Steven N Jeffers, James W. BuckAbstract:ABSTRACT The recent introduction and rapid spread of rust on daylilies, caused by Puccinia hemerocallidis, suggested a need for fungicide treatments that reduce Urediniospore viability on plant surfaces. Twelve fungicides in seven chemical classes were evaluated in vitro for toxicity to Urediniospores of rust fungi that occur on daylily (P. hemerocallidis), geranium P. pelargonii-zonalis), iris (P. iridis), oxalis (P. oxalis), mint (P. menthae), and Florida azalea (Pucciniastrum vaccinii). Germination of Urediniospores of all six rust fungi on potato dextrose agar in the absence of fungicides ranged from 54 to 88%. Germination of Urediniospores of all rust species during and after exposure to azoxystrobin, chlorothalonil, copper sulfate pentahydrate, mancozeb, and trifloxystrobin was less than or near 1%. Germination during exposure to fenhexamid, iprodione, myclobutanil, propiconazole, thiophanate-methyl, triadimefon, and triflumizole ranged from 0 to 60% and usually was greater (0 to 75%) after fungicid...
-
effects of light temperature and leaf wetness duration on daylily rust
Plant Disease, 2003Co-Authors: Daren S Mueller, James W. BuckAbstract:ABSTRACT Experiments in controlled environments were completed to determine the influence of light intensity, temperature, and leaf wetness duration on daylily rust caused by Puccinia hemerocallidis. As light intensity increased, there was a significant decrease in Urediniospore germination (R2 = 0.88 and Y = 96 - 0.6x). Urediniospores germinated in vitro between 7 and 34°C with an optimal temperature of 22 to 24°C. To test the effect of temperature on infection efficiency, plants were inoculated with Urediniospores, incubated under high relative humidity at 4, 10, 22, 30, or 36°C, and then transferred to a greenhouse at 23°C for 15 days. Plants incubated at 22°C had an average of 13 lesions cm leaf-1. Incubation temperatures of 4, 10, 30, or 36°C resulted in less than 1.5 lesions cm leaf-1. Plants were inoculated, incubated at 22°C for 24 h, and then incubated at different temperatures for 15 days to test the effect of temperature on disease development. There were no significant differences in disease d...
Glen L. Hartman - One of the best experts on this subject based on the ideXlab platform.
-
Prediction of Short-Distance Aerial Movement of Phakopsora pachyrhizi Urediniospores Using Machine Learning.
Phytopathology, 2017Co-Authors: Liwei Wen, C. R. Bowen, Glen L. HartmanAbstract:Dispersal of Urediniospores by wind is the primary means of spread for Phakopsora pachyrhizi, the cause of soybean rust. Our research focused on the short-distance movement of Urediniospores from within the soybean canopy and up to 61 m from field-grown rust-infected soybean plants. Environmental variables were used to develop and compare models including the least absolute shrinkage and selection operator regression, zero-inflated Poisson/regular Poisson regression, random forest, and neural network to describe deposition of Urediniospores collected in passive and active traps. All four models identified distance of trap from source, humidity, temperature, wind direction, and wind speed as the five most important variables influencing short-distance movement of Urediniospores. The random forest model provided the best predictions, explaining 76.1 and 86.8% of the total variation in the passive- and active-trap datasets, respectively. The prediction accuracy based on the correlation coefficient (r) betwee...
-
First Report of Orange Rust Caused by Puccinia kuehnii in Sugarcane in Louisiana
Plant disease, 2013Co-Authors: M. P. Grisham, J W Hoy, J. S. Haudenshield, Glen L. HartmanAbstract:In June 2012, lesions typical of rust were observed on sugarcane cultivar Ho 05-961 (a complex hybrid of Saccharum L. spp.) on a farm near Schriever, Louisiana. Incidence and severity of disease symptoms were low. Two types of pustules were observed on leaves of the infected plants. One pustule type was reddish-brown in color turning brown with age, characteristic of brown rust which has been observed in Louisiana since 1979 (2). The other pustule type was orange and did not turn brown with age. Urediniospore samples from the two pustule types were collected. The morphology of the Urediniospores from the reddish-brown pustules was consistent with that described for Puccinia melanocephala Syd. & Syd., the fungus that causes brown rust of sugarcane, while the morphology of the Urediniospores from the orange pustules was consistent with those described for P. kuehnii E.J. Butler, the causal organism of orange rust of sugarcane (3). Telia and teliospores were not observed. The identity of the two species of P...
-
First Report of Orange Rust Caused by in Sugarcane in Louisiana
Plant Disease, 2013Co-Authors: M. P. Grisham, J W Hoy, J. S. Haudenshield, Glen L. HartmanAbstract:In June 2012, lesions typical of rust were observed on sugarcane cultivar Ho 05-961 (a complex hybrid of Saccharum L. spp.) on a farm near Schriever, Louisiana. Incidence and severity of disease symptoms were low. Two types of pustules were observed on leaves of the infected plants. One pustule type was reddish-brown in color turning brown with age, characteristic of brown rust which has been observed in Louisiana since 1979 (2). The other pustule type was orange and did not turn brown with age. Urediniospore samples from the two pustule types were collected. The morphology of the Urediniospores from the reddish-brown pustules was consistent with that described for Puccinia melanocephala Syd. & Syd., the fungus that causes brown rust of sugarcane, while the morphology of the Urediniospores from the orange pustules was consistent with those described for P. kuehnii E.J. Butler, the causal organism of orange rust of sugarcane (3). Telia and teliospores were not observed. The identity of the two species of Puccinia causing the brown and orange rust lesions was verified using the species-specific quantitative PCR assays (1). Two DNA samples extracted from the pustules identified as P. kuehnii were independently subjected to PCR amplification using primers Pk1F and Pk1R (1) to yield a product from the rDNA that was then bidirectionally sequenced using the same primers. The resulting 480-nt sequences were identical to each other, and a BLAST search of GenBank revealed 100% identity to 19 previously reported isolates of P. kuehnii but not more than 89% similarity to any isolate of P. melanocephala (4). To our knowledge, this is the first report of orange rust in Louisiana. In the 4 months following the detection of orange rust, observations of the disease have been limited to Ho 05-961. Seed cane increase plots of this newly released cultivar were surveyed, and orange rust symptoms and Urediniospores were detected in 17 of 38 (45%) fields. The incidence and severity of the disease remained low, and the distribution appeared to be limited to the southern portion of the Louisiana sugarcane production area. References: (1) N. C. Glynn et al. Plant Pathol. 59:703, 2010. (2) H. Koike. Plant Dis. 64:226, 1980. (3) C. C. Ryan et al. Page 189 in: Diseases of Sugarcane: Major Diseases. C. Ricaud et al., eds. Elsevier, Amsterdam, 1989. (4) E. V. Virtudazo et al. Mycoscience 42:447, 2001.
-
Culturing Phakopsora pachyrhizi on Detached Leaves and Urediniospore Survival at Different Temperatures and Relative Humidities.
Plant disease, 2010Co-Authors: M. Twizeyimana, Glen L. HartmanAbstract:Soybean rust, caused by Phakopsora pachyrhizi, is one of the most important foliar diseases of soybean worldwide. In a series of experiments, multiple objectives were addressed to determine the (i) longevity of detached soybean leaves, (ii) reproductive capacity of uredinia on leaves inoculated and/or incubated on the abaxial versus adaxial side of the leaf, (iii) reproductive capacity of uredinia and Urediniospore germination when spores were harvested at regular intervals or all at once, and (iv) effect of temperature and relative humidity (RH) on Urediniospore germination. A detached-leaf assay using agar medium amended with 6-benzylaminopurine performed better in retarding leaf chlorosis than filter paper alone among five soybean genotypes. Among the three susceptible genotypes tested, detached leaves of cv. Williams 82 had the lowest level of leaf chlorosis and often allowed for the greatest Urediniospore production and germination rate. Temperature and RH played significant roles in survival of Urediniospore as measured by germination rates. Viable Urediniospores were harvested from infected soybean leaves maintained at room temperature (23 to 24°C at 55 to 60% RH) for up to 18 days, whereas freshly harvested Urediniospores that were desiccated for 12 h before being placed in vials and maintained at room temperature remained viable for up to 30 days. Urediniospore hydration was the major factor for the dormancy reversion; thermal shock with hydration and no thermal shock with hydration treatments had consistently similar Urediniospore germination rates. In the RH experiment, Urediniospores harvested from inoculated leaf pieces maintained at 85% RH had the highest germination rates compared with higher and lower RH. Improvement in P. pachyrhizi cultural techniques and understanding of Urediniospore survival will enhance our knowledge of the pathogen biology, host-plant relationship, and conditions that favor the infection, reproduction, and survival of the pathogen.
-
The effect of solar irradiance on the mortality of Phakopsora pachyrhizi Urediniospores
Plant disease, 2006Co-Authors: Scott A. Isard, Nicholas S. Dufault, M. R. Miles, Glen L. Hartman, J. M. Russo, E. D. De Wolf, W. MorelAbstract:Isard, S. A., Dufault, N. S., Miles, M. R., Hartman, G. L., Russo, J. M., De Wolf, E. D., and Morel, W. 2006. The effect of solar irradiance on the mortality of Phakopsora pachyrhizi Urediniospores. Plant Dis. 90:941-945. Soybean rust, caused by Phakopsora pachyrhizi, may be the most important foliar disease of soybean. Within the last 10 years, the fungus has moved to many new geographical locations via spread of airborne Urediniospores. The objective of this study was to determine the relationship between Urediniospore viability and exposure to solar radiation. Urediniospores of P. pachyrhizi were exposed in Capitan Miranda, Paraguay, to determine the deleterious effects of sunlight. Concomitant total solar (0.285 to 2.8 µm) and ultraviolet (0.295 to 0.385 µm) irradiance measurements were used to predict Urediniospore germination. Urediniospores exposed to doses of solar and ultraviolet (UV) radiation ≥27.3 MJ/m 2 and ≥1.2 MJ/m 2 , respectively, did not germinate. The proportions of Urediniospores that germinated, normalized with respect to the germination proportion for unexposed Urediniospores from the same collections, were a linear function of solar irradiance (R2 = 0.83). UV measurements predicted normalized germination proportions equally well. Results of inoculation experiments with exposed P. pachyrhizi Urediniospores supported the results of the germination trials, although the effects of moderate levels of irradiance varied. The relationship between Urediniospore viability and exposure to solar radiation has been incorporated into the U.S. Department of Agriculture’s soybean rust aerobiological model that provides North American soybean growers with decision support for managing soybean rust.
Weibo Dong - One of the best experts on this subject based on the ideXlab platform.
-
effect of light on in vivo Urediniospore germination lesion development and sporulation of puccinia hemerocallidis on daylily and puccinia pelargoniizonalis on geranium
Mycologia, 2011Co-Authors: Weibo Dong, James W. BuckAbstract:The presence of rusts of daylily and geranium caused respectively by Puccinia hemerocalli- dis and P. pelargonii-zonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on Urediniospore germination, germ tube elongation, lesion development and sporulation of the two fungal pathogens on detached leaves and whole plants. Exposure of dry or hydrated Urediniospores of P. hemerocallidis to cool white fluorescent light (600 mmol s 21 m 22 ) or to sunlight (950-1910 mmol s 21 m 22 ) for 2 h or 4 h significantly reduced germination and germ tube elongation on detached daylily leaves. Germination but not germ tube elongation of hydrated Urediniospores of P. pelargonii-zonalis on detached geranium leaves was significantly reduced when exposed to fluorescent light for 2 h or 4 h. A 4 h exposure to either light source significantly reduced lesion development of P. hemerocallidis on detached daylily leaves with fewer lesions developing from hydrated compared to dry Urediniospores. Sunlight exposures of 1 h and 2 h of hydrated and dry Urediniospores respectively signifi- cantly reduced lesion development by either fungus on whole plants. Increasing exposure to fluorescent light negatively affected sporulation of P. hemerocalli- dis and P. pelargonii-zonalis. Complete suppression of sporulation was not observed for either fungus with up to a 24 h exposure to fluorescent light. Light exposure negatively affected disease development by P. hemerocallidis and P. pelargonii-zonalis. Exposure to high light intensities may affect spread of rust diseases on ornamental plants.
-
effect of postsymptom application of fungicides on Urediniospore production by puccinia triticina on wheat and p hemerocallidis on daylily
Plant Disease, 2011Co-Authors: James W. Buck, K Wise, Weibo DongAbstract:Abstract Greenhouse experiments were conducted to evaluate the effect of post-symptomatic fungicide applications on Urediniospore production of leaf rust of wheat, Puccinia triticina, and daylily rust, P. hemerocallidis. Fungicides from five chemical classes were evaluated for their effect on Urediniospore production at 24-h intervals post application for 96 h. The quinone outside inhibitor (QoI) fungicide (azoxystrobin) significantly reduced cumulative Urediniospore production by P. triticina (40.1 and 11.3% of control) and P. hemerocallidis (37.9 and 35.6% of control) in both trials. The demethylation inhibitor, myclobutanil, significantly reduced Urediniospore production by P. hemerocallidis 24 h post treatment in both trials and cumulative production in one trial. Myclobutanil did not affect Urediniospore production by P. triticina. Four QoI fungicides significantly reduced Urediniospore production by P. triticina at all collection times (24, 48, and 72 h) and cumulative production in both trials. No ...
Makoto Kakishima - One of the best experts on this subject based on the ideXlab platform.
-
Qualitative morphological characteristics recognized in this study.
2015Co-Authors: Peng Zhao, Qing-hong Wang, Cheng-ming Tian, Makoto KakishimaAbstract:(A) Urediniospores with a smooth apex. (B) Urediniospores without a smooth apex. (C) Uredinia with intermixed paraphyses. (D) Uredinia without intermixed paraphyses. (E) Urediniospores with echinulate type 1 spines. (F) Urediniospores with echinulate type 2 spines. (G) Urediniospores with echinulate type 3 spines. (H) Urediniospores with biozonate germ pores. (I) Urediniospores with scattered germ pores. (J) Paraphyses with evenly thickened membranes. (K) Paraphyses with an apparently thickened apex. (L) Subepidermal teliospores. (M) Subepidermal or subcuticular teliospores. (N) Subcuticular teliospores. Bars: A, H, J, K, M, N = 20 mm; B, F, G, I = 10 mm; C = 50 μm; D = 60 μm; E = 5 μm; L = 30 μm.
-
A new species of Melampsora on Populus yunnanensis from China
Mycoscience, 2006Co-Authors: Ying-mei Liang, Makoto Kakishima, Cheng-ming TianAbstract:Melampsora nujiangensis, a rust fungus found on Populus yunnanensis in China, is described as a new species. Light and scanning electron microscopy with herbarium specimens of the rust fungus show that the shape of its Urediniospores differs from that of other known species of Melampsora, and its Urediniospore walls are thinner than the other species. Furthermore, in phylogenetic trees based on the DNA sequences (28S and ITS) the rust fungus is phylogenetically separated by high bootstrap values. These results indicate that the fungus is an isolated species among the genus Melampsora.
-
Morphological and phylogenetic analyses of Uromyces appendiculatus and U. vignae on legumes in Japan
Mycoscience, 2004Co-Authors: Wen H. Chung, Takao Tsukiboshi, Makoto KakishimaAbstract:Uromyces appendiculatus , inclusive of three varieties, is distinguished from U. vignae primarily by the position of Urediniospore germ pores and putative host specificity. However, opinions concerning these morphological and physiological features as taxonomic characters have varied greatly, and distinction of these species has often been confused. To clarify the taxonomy of these two species, morphological features of Urediniospores and teliospores of 225 rust fungus specimens on species of Phaseolus , Vigna , Apios , Lablab , and Dunbaria were examined by light microscopy and scanning electron microscopy. Forty-five specimens were subjected to molecular phylogenetic analyses. As a result, the position of germ pores in Urediniospores and the teliospore-wall thickness were considered as good characters to separate three morphological groups. In molecular analyses, the specimens fell into two and three clades based on the nucleotide sequence at D1/D2 domain of LSU rDNA and ITS regions, respectively. One of the D1/D2 clades corresponded to one morphological group whereas another D1/D2 clade included two other morphological groups. In contrast, each of the three ITS clades corresponded to a separate morphological group. Neither morphological groups nor molecular clades were host limited. It is suggested that the three morphological groups that corresponded to three distinct ITS clades constitute distinct species.
-
Phylogenetic analyses of Uromyces viciae-fabae and its varieties on Vicia, Lathyrus, and Pisum in Japan
Mycoscience, 2004Co-Authors: Wen H. Chung, Yoshitaka Ono, Takao Tsukiboshi, Makoto KakishimaAbstract:A pea rust fungus, Uromyces viciae - fabae , has been classified into two varieties, var. viciae - fabae and var. orobi , based on differences in Urediniospore wall thickness and putative host specificity in Japan. In principal component analyses, morphological features of Urediniospores and teliospores of 94 rust specimens from Vicia , Lathyrus , and Pisum did not show definite host-specific morphological groups. In molecular analyses, 23 Uromyces specimens from Vicia , Lathyrus , and Pisum formed a single genetic clade based on D1/D2 and ITS regions. Four isolates of U. viciae - fabae from V. cracca and V. unijuga could infect and sporulate on P. sativum . These results suggest that U. viciae - fabae populations on different host plants are not biologically differentiated into groups that can be recognized as varieties.
Xianming Chen - One of the best experts on this subject based on the ideXlab platform.
-
Estimated Puccinia striiformis f. sp. tritici of 5 mg Urediniospores at three storage conditions using the qPCR of DNA (dashed lines) and RNA (solid lines).
2015Co-Authors: Jiaxing Qiao, Xinyu Kong, Yiping Zou, Xianming ChenAbstract:Dashed lines with triangles, squares and circles represent DNA from dead Urediniospores at ambient temperature, fresh Urediniospores at ambient temperature and at -20°C, respectively. Solid lines with triangles, squares and circles represent RNA from dead Urediniospores at ambient temperature, and fresh Urediniospores at ambient temperature and at -20°C, respectively. The experiment was done three times. The vertical bar of each treatment at each time point represents the standard deviation of the three mean values from three experiments; significant treatment differences were based on the pooled residual error in the repeated measurement ANOVA. Treatments with different letters for the 12-days means were significantly different at P = 0.05. There were no significant differences among the treatments on 0, 4 and 8 days at P = 0.05.
-
Example standard curves of real-time quantitative PCR of RNA (A) and DNA (B).
2015Co-Authors: Jiaxing Qiao, Xinyu Kong, Yiping Zou, Xianming ChenAbstract:The quantifications were expressed in terms of Urediniospore weight. There were three replicates in each experiment.
-
wheat stripe yellow rust caused by puccinia striiformis f sp tritici
Molecular Plant Pathology, 2014Co-Authors: Wanquan Chen, Xianming Chen, C R Wellings, Zhengsheng KangAbstract:SUMMARY Stripe (yellow) rust,caused by Puccinia striiformis f.sp.tritici (Pst), is a serious disease of wheat occurring in most wheat areas with cool and moist weather conditions during the growing season.The basidiomycete fungus is an obligate biotrophic parasite that is difficult to culture on artificial media. Pst is a macrocyclic, heteroecious fungus that requires both primary (wheat or grasses) and alternate (Berberis or Mahonia spp.) host plants to complete its life cycle. Urediniospores have the capacity for wind dispersal over long distances, which may, under high inoculum pressure, extend to thousands of kilometres from the initial infection sites. Stripe rust, which is considered to be the current major rust disease affecting winter cereal production across the world, has been studied intensively for over a century. This review summarizes the current knowledge of the Pst‐wheat pathosystem, with emphasis on the life cycle, uredinial infection process, population biology of the pathogen, genes for stripe rust resistance in wheat and molecular perspectives of wheat‐Pst interactions. Taxonomy: The stripe rust pathogen, Puccinia striiformis Westend. (Ps), is classified in kingdom Fungi, phylum Basidiomycota, class Urediniomycetes, order Uredinales, family Pucciniaceae, genus Puccinia. Ps is separated below the species level by host specialization on various grass genera,comprising up to nine formae speciales, of which P. striiformis f. sp. tritici Erikss. (Pst) causes stripe (or yellow) rust on wheat. Host range: Uredinial/telial hosts: Pst mainly infects common wheat (Triticum aestivum L.), durum wheat (T. turgidum var. durum L.), cultivated emmer wheat (T. dicoccum Schrank), wild emmer wheat (T. dicoccoidesKorn) and triticale (Triticosecale).Pst can infect certain cultivated barleys (Hordeum vulgare L.) and rye (Secale cereale L.),but generally does not cause severe epidemics. In addition,Pst may infect naturalized and improved pasture grass species, such as Elymus canadensis L., Leymus secalinus Hochst, Agropyron spp. Garetn, Hordeum spp. L., Phalaris spp. L and Bromus unioloides Kunth. Pycnial/aecial (alternative) hosts: Barberry (Berberis chinensis, B. koreana, B. holstii, B. vulgaris, B. shensiana, B. potaninii, B. dolichobotrys, B. heteropoda, etc.) and Oregon grape (Mahonia aquifolium). Disease symptoms: Stripe rust appears as a mass of yellow to orange Urediniospores erupting from pustules arranged in long, narrow stripes on leaves (usually between veins), leaf sheaths, glumes and awns on susceptible plants. Resistant wheat cultivars are characterized by various infection types from no visual symptoms to small hypersensitive flecks to uredinia surrounded by chlorosis or necrosis with restricted Urediniospore production. On seedlings, uredinia produced by the infection of a single Urediniospore are not confined by leaf veins, but progressively emerge from the infection site in all directions, potentially covering the entire leaf surface. Individual uredinial pustules are oblong, 0.4‐0.7 mm in length and 0.1 mm in width. Urediniospores are broadly ellipsoidal to broadly obovoid, (16‐ )18‐30(‐32) × (15‐)17‐27(‐28) μm, with a mean of 24.5 × 21.6 μm, yellow to orange in colour, echinulate, and with 6‐18 scattered germ pores. Urediniospores can germinate rapidly when free moisture (rain or dew) occurs on leaf surfaces and when the temperatures range is between 7 and 12 °C. At higher temperatures or during the later growing stages of the host,black telia are often produced, which are pulvinate to oblong, 0.2‐0.7 mm in length and 0.1 mm in width. The teliospores are predominantly two-celled, dark brown with thick walls, mostly oblong-clavate, (24‐)31‐56(‐65) × (11‐)14‐25(‐29) μm in length and width,and rounded or flattened at the apex.
-
SEM observations of Pst inoculated with C. cladosporioides.
2014Co-Authors: Gangming Zhan, Xianming Chen, Min Jiao, Jun Guo, Yuan Tian, Fuping Wang, Lili Huang, Zhensheng KangAbstract:A: 12 h after inoculation, the spore of C. cladosporioides contacted the Urediniospore surface (×7,000), B: 24 h after inoculation, spores of C. cladosporioides germinated (×700), C: 36 h after inoculation, direct penetration by germ tube of C. cladosporioides into a Urediniospore (×10,000), D: 48 h after inoculation, amount of Urediniospores were surrounded with germinated spores of C. cladosporioides (×2,000), E: 72 h after inoculation, germ tubes of C. cladosporioides have penetrated Urediniospores (×3,000), F: 120 h after inoculation, C. cladosporioides has colonized the Urediniospores (×1,300).
-
Uredinia and Urediniospores of Pst are parasitized by Cladosporium cladosporioides.
2014Co-Authors: Gangming Zhan, Xianming Chen, Min Jiao, Jun Guo, Yuan Tian, Fuping Wang, Lili Huang, Zhensheng KangAbstract:A: A uredinium infected by C. cladosporioides (×800), B: A non-infected uredinium filled with Urediniospores (×700), C: Hyphae of C. cladosporioides growing from or between Urediniospores at an early stage of infection (×2,000), note the shriveled Urediniospores, D: Numerous hyphae of C. cladosporioides growing on a uredinium at a late stage of infection (×400), note presence of very few normal Urediniospores, E: Urediniospores invaded by C. cladosporioides hyphae (×1,800), F: High magnification of a C. cladosporioides hypha invading a Urediniospore (×11,000).
