Uredial Stage Research Articles

Morphology of teliospores of ravenelia sp. On forest trees

The study was conducted to show the morphology of teliospores of Ravenelia sp. This rust infects three different forest trees. These all three trees, Albizia procera, Albizia lebbeck , and Pongamia pinnata belong to family Fabaceae . Rust fungus , Ravenelia clemensae Syd. infects the leaves of Albizia procera and Albizia lebbeck , and the host tree Pongamia pinnata was infected by another species of Ravenelia , which was Ravenelia hobsoni . The rust infection starts in the month of September under favorable environmental conditions, when the new foliage is produced on the host plants. The present study showed that telial stage of Ravenelia sp . was found on all three host trees while pycnial, aecial and uredial stages were not found in these trees. The morphology of these spores, is described below. The morphological characters of these teliospores were found to be nearly similar to each other.

Puccinia subnitens: An Obscure Rust Pathogen Little-Known for More than a Century

Sugar beet seedling rust, caused by Puccinia subnitens, is a rarely occurring but essentially harmless disease in sugar beet production. However, it has caused substantial but sporadic losses to commercial spinach growers. It has the typically complex life cycle of a macrocyclic rust pathogen, but is also unusual because it is one of the few documented heteroecious rust diseases where the early spore stages (pycnial and aecial) occur on the economic host while the normally damaging, repeating, uredial stage is found on the feral, noneconomic host. Most significantly, it was one of the first heteroecious rust diseases recognized to have the ability to infect numerous, distinct host species with the aecial stage while maintaining a relatively narrow host range for its uredial and telial stages. Accepted 6 June 2014. Published 25 July 2014.

Occurrence of Telia of Phakopsora pachyrhizi on Kudzu in Texas.

The first discovery of Asian soybean rust (ASR) caused by Phakopsora pachyrhizi H. Sydow & Sydow in the continental United States was in Louisiana in 2004 (3). In Texas, the uredial stage of this fungus was first found on kudzu (Pueraria lobata) in November 2005 and 3 months later on soybean (Glycine max) (2). The telial stage of P. pachyrhizi was first reported in the continental United States on kudzu in central Florida (1). On January 5, 2008, telia of P. pachyrhizi along with uredia were found on living kudzu leaves at two locations in Polk and Liberty counties of East Texas, where only the uredial stage had been found in September of 2007. The kudzu in both locations had died back more than 99% in January. A single telium or a cluster of telia were found along with uredinia on the abaxial leaf surface. Telia and uredinia (n = 20) were similar in size, 136.3 ± 26.3 and 133.1 ± 16.4 μm in diameter, respectively. Telia were dark brown to black compared with tan colored uredinia. Elongated, oval-shaped teliospores (n = 15) were 18.1 ± 1.7 μm long and 10.6 ± 1.0 μm wide. A reexamination of herbarium specimens from previous ASR collections indicated that telia had been present on kudzu leaves from Liberty County collected in December of 2005 and 2006. In contrast, telia were not found on soybean leaves collected in February of 2006 and 2007 and January of 2008 from Hidalgo County in the Lower Rio Grande Valley (LRGV), an area with a subtropical climate where ASR hosts could survive year round. Kudzu does not occur in the LRGV. Infected kudzu in East Texas can support production of telia over the winter months. However, the hosts that can be infected by basidiospores have not been identified, and so the significance of telia as a source of genetic variation is not known. To our knowledge, this is the first report of the telial stage of P. pachyrhizi in Texas.

First report of Uredo crepidis-japonicae and Septoria crepidis on Crepis japonica in Brazil

Crepis japonica Benth is a herbaceous plant native from China and Japan which was recently introduced into Brazil, where it is disseminating rapidly and already has become an important weed in nurseries (Plantas Daninhas do Brasil, 3 ed., pg.146, 2000). In July 2000 a leaf rust was observed on C. japonica growing in a citrus (Citrus sp.) nursery situated in Vicosa, Minas Gerais State, Brazil. The fungus was identified as Uredo crepidis-japonicae Lindroth which has been reported only from Australia, Continental China, Formosa (Taiwan) and Japan (Rept. Tottori Mycol. Inst., n.08, pg.1, 1980). Irregularly oval shaped leaf lesions were dark-brown due to the presence of a powdery mass of uredospores (Figure 1A). Severely infected leaves were clorotic. Morphological features for this fungus were: uredia, 0.3 to 0.5 mm diam; uredospores spherical, 14 to 20 μm diam, pale brown, with 3 to 4 germ pores, and walls 1μm thick. U. crepidis-japonicae is the uredial stage of Puccinia crepidisjaponicae Dietel, but no teliospores were found in the material examined (VIC 22136). However, size and shape of uredospore alone suffices for distinguishing this species from other rust fungi on Crepis spp. (Table 1). In January 2001 another foliar disease on young and old leaves was also observed on C. japonica, at a different site in Vicosa. The inciting agent was identified as Septoria crepidis Vestrerg. (Syll. Fung., XIV, pg. 974, 1899) known from USA, Europe and Asia. Lesions were necrotic, irregular, pale-brown, 1 to 8mm diam. The fungus had immersed, globose pycnidial conidiomata (Figure 1B), 60 to 70 μm diam, pale-brown, ostiolate, conidiophores were absent; conidia were hyaline, filiform, multiseptate, 25 to 35 μm x 1.0 to 1.5 μm (VIC 22137). These are the first reports of occurrence of these fungi in Brazil. Both fungi were probably introduced into Brazil TABLE 1 Morphological characteristics of uredospores of rust fungi (Puccinia spp.) with uredial stage on Crepis spp.

Ultrastructural Studies of the Intercellular Hypha aud Haustorium of Puccinia recondita f.sp. tritici

AbstractThe ultrastructure of intercellular hyphae and D‐hati‐storia of P. recondita f.sp. tritici, and the host response to haustorial invasion, was investigated. The intercellular hyphae share common characteristics with those of other uredial stage rust fungi. Anastomosis was observed between intercellular hyphae. Two nucleoli were frequently observed in a single nucleus in the haustorium, indicating possible nuclear fusion between the two nuclei in D‐haustoria of this fungus. The close association of host organelles, such as the nucleus, Golgi bodies, endo‐plasmic reticulum, vesicles and mitochondria, with the developing haustorium, is described.

The Dynamics of the Plant Lactuca sibirica and the Frequency of Its Rust Puccinia minussensis in River Valleys in Northern Sweden

The population dynamics of the rust Puccinia minussensis and its host plant Lactuca sibirica were studied in four localities. Three of the localities were subjected to different degrees of erosion and/or deposition (Kukkola, Aspliden and Hummelholm) during flooding, while one locality (La˙nged) was situated above the flood level. At Kukkola and Hummelholm both the densities of the host plant L. sibirica and the frequency of the rust P. minussensis varied markedly within transects. At the other two localities, La˙nged which is not disturbed and Aspliden which is dry and subjected to erosion, densities and disease frequencies remained constantly low between the years. There was a positive correlation between host densities and frequency of aecia-producing shoots at Hummelholm. However, it is suggested that this correlation is caused by similar responses to variation in environmental conditions and not by a response of the pathogen to host plant densities. Furthermore we found that systemically diseased shoots (aecia) at all localities died before August, while uredial and telial stages did not cause death of shoots. It is suggested that (1) the host densities are primarily regulated by stochastic disturbances and (2) the direct and close fit in the response of the fungus is due to resource limitation

Variation in virulence among single-aeciospore isolates from single-gall isolates of Cronartiumquercuum f.sp. fusiforme

Single aeciospores from single-gall isolates of Cronartiumquercuum (Berk.) Miyabe ex Shirai f.sp. fusiforme previously shown to have virulence toward resistant half-sib loblolly pine (Pinustaeda L.) families 10-5, 11-20, or 29R were propagated in the asexual uredial stage on leaves of oak seedlings. Only 80 of 1086 single aeciospores from a single-gall isolate with virulence towards family 10-5 produced symptoms of infection on the oaks, and 17 infections produced telia directly. Thirty-two single-aeciospore isolates were propagated from the 63 uredinia. Half-sib progeny of 10-5 were inoculated with each of the 32 isolates, and after 9 months incidence of seedlings with galls varied from 46 to 93%. Six isolates produced galls on more than 90% of the seedlings. Average gall length ranged from 30 to 56 mm among the 32 isolate treatments. Similarly, 20 single-aeciospore isolates propagated from two single-gall isolates with virulence towards family 11-20 caused galls on 19–59% of 11-20 progeny. Finally, 12 single-aeciospore isolates propagated from a single-gall isolate with virulence towards family 29R produced galls on 38–91% of the half-sib progeny of 29R. Thus, in three separate experiments virulence among single-aeciospore isolates toward a resistant source ranged from normal to very high.

Ultrastructural Observations on the Dikaryotic Haustorium ofCronartium Flaccidum(Alb. & Schw.) Wint. inVincetoxicum HirundinariaMedicus

SUMMARYThe haustorium of the uredial stage of Cronartium flaccidum in Vincetoxicum hirundinaria was studied with TEM. The observations concern the haustorial mother cell and its relation to the host cell wall, the penetration peg, the shape and the cytoplasm of the haustorium and some host cell organelles in relation to the haustorium. The presence of collars was noted. These features are similar to those described for host-dikaryotic haustorium relationship in other rusts. The extrahaustorial matrix however shows a unusual development. In fact, it wraps the whole length of haustorial neck although it is separated from the haustorial neck wall by the extrahaustorial membrane doubled in this region. The probable significance of this host-parasite interface, perhaps limited to the genus Cronartium, is discussed.

Scanning electron microscopy of early infection in the uredial stage of Puccinia sorghi in Zea mays

An SEM study was made of the infection process of Puccinia sorghi in Zea mays. A uredospore germ tube grows across epidermal cells and along their anticlinal walls, often branching and altering direction of growth. The fungus, on attaining a stoma, delimits an appressorium over it. Infection peg initials enlarge linearly and centripetally along the appressorium base, forcing open the stomatal slit. Having penetrated the stomatal aperture, the infection peg develops a substomatal vesicle. From the vesicle, two short primary infection hyphae develop synchronously, a septum later forming between the vesicle body and each hyphal base. A further septum divides the primary hypha into two cells. Secondary infection hyphae emerge later from the fully expanded vesicle on the proximal side of each vesicle/primary hypha septum. Secondary hyphae are narrower than primary hyphae, form their proximal septum some distance along the hypha, develop asynchronously, and proliferate to form the intercellular mycelium. Infection processes and epidermal stripping are discussed.

Ultrastructural Aspects of the Aecial, Uredial and Telial Stages of Puccinia Asparagi DC

Puccinia asparagi DC is a macrocyclic, autoecious rust occurring on Asparagus officinalis. The most apparent manifestations of the disease are the aecial pustules on the stalks in the spring and the uredial and telial pustules on the fern stems during the summer. Pycnia are inconspicuous and were not observed in the first year of this studyAecidioid aecia occur in groups on stems (Fig. 1). Hyphae is both inter- and intra-cellular. Aecia have a well-defined peridium, 1 cell layer thick. Aeciospores are binucleate (Fig. 2) and finely verrucose. Verrucae are electron transparent in ultrathin sections. Wedge-shaped disjunctor cells separate the aeciospores.Uredia occur on the stems of the fern growth during the summer. The pustules are subepidermal and erumpent. Urediospores are pedicillate early during development and at maturity are echinulate (Fig. 3) with 4 equatorial pores. Echinulations are electron transparent in ultrathin sections.

Epidemiology of Melampsoramedusae leaf rust of poplars in the north central United States

Development of the aecial and uredial stages of Melampsoramedusae leaf rust of poplar in relation to the phenology of its hosts (Populus spp. and Larix spp.) was monitored from March until October during two consecutive growing seasons in central Iowa, east central Minnesota, and north central Wisconsin. Both years, in Wisconsin, larch needles flushed in early May and poplar leaves flushed in mid-May to late May. Aeciospores of M. medusae were found on spore traps only at the Wisconsin site (within the natural range of larch) from May 19 until the end of June in 1975 and 1976. Uredospores were present in the north central United States from mid-June through late September during both years. Temperatures between 15° and 20 °C and periods of precipitation favored uredospore production. Poplar leaf rust was found successively later at more southerly locations.

Cytological studies on rust fungi. (vi) fine structures of infection process of Kuehneola japonica (diet.) dietel

The behavior of rust fungi in their host plants has been elucidated by electron microscopy. However, most of the ultrastructural studies on rust fungi have focused on the uredial stage. In order to elucidate the features of the sporidial stage, we studied the fine structure of Kuehneola japonica, a short-cycle rust, in rose leaves. Infection pegs arising from appressoria penetrated the host walls. Papillae formed at the time of penetration against the outer epidermal cell walls. The papillae which had formed at the penetration sites grew extensively and partially surrounded the intracellular hyphae which were connected with the infection pegs. The intracellular hyphae in the epidermal cells developed further and entered adjacent parenchyma cells. Walls of parenchyma cells either invaginated or thin papillae formed at penetration sites and the invaginated walls or papillae surrounded the necks of the intracellular hyphae. Intracellular hyphae in both epidermal and parenchyma cells were not enveloped by the sheath before 20 days after inoculation. In specimens prepared 20 days after inoculation, some of the intracellular hyphae were enveloped by a sheath in both palisade and spongy parenchyma cells. The sheathed hyphae resembled haustoria of other rust fungi which had been described previously. Teliospore initials were formed in mycelial masses in intercellular spaces between the epidermal cells and palisade parenchyma cells 20 days after inoculation. Uninucleate teliospores developed from teliospore initials 30 days after inoculation.

Comparison of Uredo Eichhorniae, the Waterhyacinth Rust, and Uromyces Pontederiae

The waterhyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae), is a troublesome aquatic weed in the tropics and subtropics. In Florida, several control methods have been tried against it including control with plant pathogens (3, 8). Among potentially useful pathogens is Uredo eichhorniae Fragoso & Ciferri (4) which may be specific to waterhyacinth. This rust has not been recorded since its original description in 1927, but as a result of surveys in the past 4 yr it (4) was found in the Entre Rios province of Argentina (FIGS. 1, 4, 5, 7). There have been doubts concerning the propriety of the generic name of this rust (4). The similarity of Uredo eichhorniae to Uromyces pontederiae Gerard on the related genus Pontederia (pickerelweed) has been suggested (4, 5). Uromyces pontederiae has been reported from Uruguay in its uredial stage on Eichhornia azurea (Swartz) pre s a preciation to Drs. M E. Barr-Bigelow, Department of , University of Massachusetts, Amherst, and E. S. Luttrell, t ent of Plant Path logy and Plant Genetics, University of ia, Athens, for exam ing cultures and providing he pful advice. . . P. Rogers, Department of Botany, University of Illinois, Urbana, l prepared the Latin diagnosis.

Ultrastructure of tissue cultures of Pinus monticola infected by Cronartium ribicola. II. Penetration and post-penetration

The pycnial-aecial (mononucleate) thallus of Cronartium ribicola was grown in vitro on a tissue culture of Pinus monticola. Tissues from the host-parasite interface were prepared for electron microscopy 12 days after inoculation. Ultrastructural observations of haustoria show distinct collars and neckband rings and indicate that in most respects these haustoria are similar to those previously described for uredial (binucleate) stages of other rust fungi. During host penetration intense vacuolar activity occurs in both the host and the parasite. The possible significance of the vacuoles and their contents to the development of the disease phenomenon are discussed. In many respects the susceptible response of White pine tissue cultures to blister rust infection resembles certain resistance responses described for other pathogenic fungi.

The fine structure of two rust fungi, Puccinia helianthi and Melampsora lini

The parasitic phase of the uredial stage of rust fungus infection is characterized by the formation of a specialized structure—the haustorium. The haustorial neck contains a band of darkly staining wall material, the length of which is dependent on the fungal species. In older infected tissues a collar sometimes develops at the site of penetration. In such cells, the host plasmalemma appears to double back on itself between the collar and the haustorial neck. The mitochondria of the haustorium contain many plate-like cristae and, less frequently, concentric whorls of membranes. Cytoplasmic microtubules are also observed in both the neck and body of the haustorium. Centriolar plaques are found appressed to the nuclear envelopes in both the hyphae and haustoria. They frequently consist of two amorphous regions which are connected by a rod-shaped, layered structure. The septal pore of the intercellular hyphae contains a plug of electron-transparent material. Surrounding it is a matrix of dense amorphous cytoplasm devoid of organelles which is bordered by a hemispherical array of microbodies containing crystals. Axenic cultures of Melampsora lini mycelium were examined and found to contain similar septal pore regions. These cultures also show some differences from the parasitic hyphae. The septa-associated microbodies in these cells appear to derive from an aggregate of tubular endoplasmic reticulum cisternae. Their mitochondria differ from those of the intercellular hyphae in having more and longer, plate-like cristae and a denser staining matrix. They therefore represent a type intermediate between those of the intercellular hyphae and the haustoria. The pseudoparenchymatous stroma of the axenic cultures contains cells of widely divergent ages. Some are young as determined by their dense cytoplasmic contents and large lobed nuclei. However, others are older, with large vacuoles and many lipid bodies. In some cases they have thick cell walls consisting of many layers.

Fine Structure of the Host-Parasite Interfaces in Mycoparasitism

This review is not intended as a computerized compendium of literature citations but as a personalized discussion utilizing selected references in ad­ dition to unpublished data to synthesize previous work, illustrate the present state of knowledge, and propose fruitful areas for further investigations. The emphasis throughout is on broad concepts as they relate to the host­ parasite interface in plant disease, rather than on minute details. Every host-parasite-environment combination is unique in itself, and every investi­ gator has his own technical touch. It is, therefore, not unexpected that micrographs of the same disease syndrome may differ from one another in minor (or even major) ways, but a sufficient body of data has now accumu­ lated so that common factors are emerging. It seems most fruitful to place emphasis on these common factors and selective coverage of the literature so that our allotted space may be used to convey the vital concepts that are evolving as a result of just a decade of research in this area of phytopatho­ iogical research. Particular emphasis has been placed on the literature that has appeared since the reviews of Hawker (52) and Bracker (11). A living fungal cell (or part of a living cell) may enter a living host cell and establish (at least temporarily) a functional relationship there via haustorial formation as in the rusts and mildews, or via thallus formation as in cabbage clubroot. We believe that on the basis of ultrastructural research to date, three, or possibly four, major haustorial types can be distinguished from one another. The type of morphological association between the haus­ torium and the host cell is onc of the diagnostic criteria on which the separa­ tion into types is made. For purposes of this discussion, Type I is represented by the uredial stage of Puccinia graminis tritici; Type II by the conidial stage of Erysiphe graminis,' Type III by Phytophthora infestans; and the still uncertain type IV by various Peronospora spp.

Ultrastructural Studies on the Uredial Stage of Wheat Stem Rust

Ultrastructural Studies on the Uredial Stage of Wheat Stem Rust

The Uredial Stage in Gymnosporangium

The Uredial Stage in Gymnosporangium

Puccinia chrysanthemi . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Puccinia chrysanthemi . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Chrysanthemum boreale, C. decaisneanum, C. hortum, C. indicum, C. makinoi, C. pacificum, C. shimotomaii, C. shiwagiku, C. sinense and C. zawadskii . DISEASE: Black rust of cultivated chrysanthemum. Attacks mainly leaves, killing them and causing premature defoliation. Severe foliar infection in certain varieties is accompanied by slight infection of stems and occasionally of the involucre. Affected plants often become stunted and produce few flowers. Heavy damage was caused in Germany during 1926-27 (8: 242). GEOGRAPHICAL DISTRIBUTION: Africa (Congo, Ethiopia, Kenya, Malawi, Mauritius, Morocco, Rhodesia, South Africa, Tanzania, Uganda); Asia (China, India, Israel, Japan, Korea, U.S.S.R.); Australasia and Oceania (Australia, Hawaii, New Zealand, Tasmania); Europe (Azores, Belgium, Bulgaria, Denmark, Finland, France, Germany, Great Britain, Holland, Iceland, Italy, Malta, N. Ireland, Norway, Poland, Portugal, Spain, Sweden, Switzerland, U.S.S.R., Yugoslavia); N. America (Bermuda, Canada, U.S.A.); Central America & W. Indies (Dominican Republic); S. America (Argentina, Chile, Uruguay). (CMI Map 117, Ed. 2, 1964). TRANSMISSION: Teliospores have been reported from Japan, N. America and Sweden; elsewhere the fungus is known in the uredial stage only. It has been shown that urediospores wintered in the open can germinate in the spring (Jacky, Z. Pfl.-Krankh . 10: 132, 1900; Zbl Bakt . II, 10: 369, 1903; 18: 88, 1907). It is believed that urediospores can remain viable through winter on woodwork, glass, fallen leaves or in the soil (Pape, Gartenwelt 32: 623, 1928). No perennial mycelium has been found (Gibson, New Phytol . 3: 188, 1904).

Melampsora lini . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Melampsora lini . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Linum usitatissimum, L. catharticum and other species of Linum . The American Aecidium lini Dearness & House on L. virginianum differs from M. lini in having cupulate, not caeomoid, aecia. DISEASE: Flax rust. Characterized by light-yellow to orange-yellow sori containing pycnia and aecia on leaves and stems early in the growing season, followed by reddish-yellow uredia on leaves, stems and capsules during the growing season, and later, brown to black telia covered by the epidermis, chiefly on the stems. Causes serious damage to flax by weakening and disfiguring the fibres and reduces the quality and yield of linseed. GEOGRAPHICAL DISTRIBUTION: Africa, Asia, Australasia, Europe, North and South America. (CMI Map 68, 2nd Ed.) TRANSMISSION: Sporidia produced in the spring from teliospores over-wintering on crop refuse are the most common source of primary inoculum. Teliospores may also be carried on fragments of infected host tissue with the seed. Volunteer flax plants, including some wild species, may also serve as important sources of infection (Millikan, 1951), and provide a means of over-wintering of the uredial stage in New Zeland (32: 79).