Interactions between the mycoparasite Pythium oligandrum and two types of sclerotia of plant-pathogenic fungi (original) (raw)
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Journal of Plant Diseases and Protection
Mycoparasitism is an important process in microcosm of microorganisms. Understanding the mechanisms taking place may allow to effectively improved biocontrol of phytopathogens. A sequence of events during mycoparasitism process by three mycoparasites of different origin and aggressiveness was studied through an optical microscope. Additionally, both germination and entry procedure of mycoparasites on host's surface were observed through an electron scanning microscope. The development of sclerotia parasitism shows many common features in all three mycoparasites indicating very likely both common course and mechanisms. G21-3 (Gliocladium spp.) is the faster and more destructive mycoparasite followed by T12-9 (Trichoderma spp.) and FD6-15 (Fusarium spp.). In the present study, it was presented in a novel way both the appearance of hyphae of D6-15 isolation (Fusarium spp.) intra-cellularly and also the formation of chlamydospores (intracellularly) from G21-3 isolation (Gliocladium spp.). G21-3 germination on the sclerotial surface was completed within 15 h of incubation, and germ tubes will be strayed enough before entering into sclerotium. Appressoria and germ tube branches formation were not observed.
Physiological and Molecular Plant Pathology, 1998
Two aspects of the interaction between tomato roots and the mycoparasite Pythium oligandrum were investigated, the host's response to fungal invasion and the development of fungal hyphae within the tissues. After root inoculation, hyphae developed over the root surface and penetrated the epidermis, cortex and vascular stele. Oogonia developed in great abundance over the root surface. However, the root tissue remained free from necrotic reacting cells. Pythium oligandrum infections appeared relatively non-destructive since little damage occurred to host walls even at sites of fungal penetration. Host reactions were rapid within cells but these were confined to colonized host cells or to non-infected cells adjacent to invaded ones. Host reactions took the form of a range of types of cytoplasmic networks composed of amorphous material or fibrils which surrounded the invading hyphae. Wall appositions and papillae frequently formed at sites of attempted fungal entry. Chemical compounds, possibly phenols, coated host walls and accumulated inside invaded cells. It is likely that these substances, appearing osmiophilic or electron dense, mechanically reinforce the host's walls and create a fungitoxic environment for P. oligandrum. A typical feature of this interaction was the loss of internal cytoplasmic structures by the invading hyphae which frequently were reduced to empty shells. The relationships between the host reactions and the biocontrol capabilities of P. oligandrum are discussed.
the mycoheterotroph Arachnitis uniflora has a unique association with arbuscular mycorrhizal fungi
Achlorophyllous plants that are dependent on an association with fungi linked to photosynthetic plants for their carbon source are known as mycoheterotrophs. Arachnitis uniflora Phil., a monotypic member of the monocotyledonous family Corsiaceae, fits this category, as it relies on a glomalean fungus belonging to Glomus Group A for carbon acquisition. Although basic structural features of root colonization have been reported for A. uniflora, the nutrient exchange interface has not been studied. This is the first study to use confocal microscopy, transmission electron microscopy, and cytochemical procedures to study the interface between a glomalean fungus and the roots of a mycoheterotrophic species. Results showed that arbuscules are never formed, and that the ''vesicles in bundles'' reported earlier are unlike typical glomalean vesicles, in that they form in clusters by the enlargement of hyphal branches and have a complex multilayered wall. The thick inner wall layer consists primarily of b-1,3-glucans (callose) and is surrounded by a thin outer layer of chitin. Each structure is surrounded by host cell wall material and a perifungal membrane, suggesting an involvement in nutrient exchange. The cytoplasm contains a complex of small b-1,3-glucan-containing vacuoles, lipid bodies, endobacteria, and many nuclei. These structures enlarge to occupy most of the cortical cell volume and then degrade, releasing lipids and other materials into the host cell. We suggest that these structures should not be equated with typical glomalean vesicles but are unique structures that may be involved, along with the hyphal coils, in nutrient acquisition by the host.
Mycoparasitism within the Zygomycetes
Botanical Journal of the Linnean Society, 1985
Mycopamsitism within the Zygomycctes. The Zygomycetes includes a number of mycoparasitic genera, which differ in their strategies of parasitism. Piptocephalis, Dispira, Dimorgaris and Tieghemiomyces are typical biotrophs, and display many features associated with this niodr of infection, such as the formation of haustoria. Dirranophora, Spinellus and SyCygites, on the other hand, apparently form necrotrophic associations with moribund toadstools, although it is difficult to define the boundary between mycoparasitism and competitive saprophytism. There are also zygomycetes, such as Chaetocladium and Syncephalis, which have modes of infection which do not fit neatly into either category above, but apparently share necrotrophic and biotrophic characteristics. Initially the infection process of Syncephalis resembles that of Piptocephalis, but i t is followed by a rapid internal growth of parasitic hyphae and concomitant destruction of host cytoplasm. Chaetuclodium forms gall-like structures on suitable host fungi and its growth is enhanced by this association. Circumstantial evidence suggests that these galls are functionally different from those formed by Porasitplla during a pseudo-sexual response to the presence of another fungus. Zygomycrtes also act as hosts for several other mycoparasitic fungi.
Protoplasma, 1988
Major sclerotial polypeptides from the psychrophiles, Myriosclerotinia borealis (W 51), Coprinus psychromorbidus (LRS 13 I), Typhula idahoensis (W21), and Typhula incarnata (W21) were purified by using polyacrylamide gel electrophoresis and electroelution. Polyclonal antibodies were raised against these major sclerotial polypeptides. Immunofluorescence microscopy showed that the major sclerotial polypeptides from all four psychrophilic species were sequestered in discrete protein bodies of cultured and field-grown sclerofla. Western blot analysis indicated that all antisera reacted positively with their respective antigens, the major sclerotial polypeptides. Reciprocal immunological cross-reactions were observed between the major sclerotial polypeptides ofM. borealis (W 51) and T. idahoensis (W21). Antiserum to the major sclerotial polypeptides of both M. borealis and T. idahoensis also recognized the major sclerotial polypeptides of C. psychromorbidus (LRS 131). It is suggested that the major sclerotial polypeptides of these psychrophilic plant pathogens may act as storage proteins.
Anatomy and histochemistry of resting and germinating sclerotia of Sclerotium cepivorum
Transactions of the British Mycological Society, 1987
Sclerotia of Sclerotium cepivorum had a rind one or two cells thick, no cortex, and a medulla in which all interhyphal spaces were filled with a polysaccharide gel. The main reserve materials were protein bodies in medullary hyphae. Sclerotia recovered from soil after several years burial showed extensive loss of hyphal contents although their rinds remained intact and many hyphae appeared healthy. During germination renewed hyphal growth in the outermost parts of the medulla led to bulging and rupture of the rind followed by radiation of hyphae from a germinative plug.
Mycological Research, 2006
Mycoparasites Sclerotinia Sclerotium a b s t r a c t The gfp gene from the jellyfish Aequorea victoria, coding for the Green Fluorescent Protein (GFP), was used as a reporter gene to transform a Trichoderma virens strain I10, characterized as having a promising biocontrol activity against a large number of phytopathogenic fungi. On the basis of molecular and biological results, a stable GFP transformant was selected for further experiments. In order to evaluate the effects of GFP transformation on mycoparasitic ability of T. virens I10, sclerotia of Sclerotium rolfsii, Sclerotinia sclerotiorum and S. minor were inoculated with the T. virens strain I10 GFP transformant or the wild type strain. Statistical analysis of percentages of decayed sclerotia showed that the transformation of the antagonistic isolate with the GFP reporter gene did not modify mycoparasitic activity against sclerotia. Sclerotium colonization was followed by fluorescent microscopy revealing intracellular growth of the antagonist in the cortex (S. rolfsii) and inter-cellular growth in the medulla (S. rolfsii, and S. sclerotiorum). The uniformly distributed mycelium of T. virens just beneath the rind of sclerotia of both S. rolfsii and S. sclerotiorum suggests that the sclerotia became infected at numerous randomly distributed locations without any preferential point of entry. a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m y c r e s m y c o l o g i c a l r e s e a r c h 1 1 0 ( 2 0 0 6 ) 179 -187
Canadian Journal of Botany, 1989
SHISHKOFF, N. 1989. Zoospore encystment pattern and germination on onion roots, and the colonization of hypodermal cells by Pythium coloraturn. Can. J . Bot. 6 7 258 -262. The behavior of the fungus Pythium coloratum Vaartaja on onion (Allium cepa L.) roots with a hypodermis of long and short cells was studied. Frequency of encystment adjacent to long versus short cells was compared in live and heat-killed roots. To determine whether the state of suberization of hypodermal cells was correlated with the number of zoospores encysting next to the cell, roots on which zoospores had encysted were stained with toluidine blue to quench most autofluorescence except that caused by lamellar suberin. Penetration of fluorescent long cells, nonfluorescent long cells, and nonfluorescent short cells was compared. Encystment of zoospores on the onion epidermis was more frequent adjacent to short cells of the hypodermis than could be expected for random encystment. More zoospores encysted next to short cells on heat-killed roots than on live roots. Encystment was more frequent over nonfluorescent long cells than over fluorescent long cells. Penetration by the fungus was more frequent into short cells and nonfluorescent long cells than into fluorescent long cells. SHISHKOFF, N. 1989. Zoospore encystment pattern and germination on onion roots, and the colonization of hypodermal cells by Pythiurn coloratum. Can. J . Bot. 67 : 258-262. L'auteur a Ctudik le comportement du champignon Pythium coloratum Vaartaja sur racines d'oignon (Allium cepa L.), lesquelles comportent une structure ii hypoderme avec cellules longues et cellules courtes. I1 a cornpark la frequence de l'enkystement dans les cellules adjacentes aux cellules longues et aux cellules courtes dans des racines vivantes et dans des cellules tuCes par la chaleur. Afin de vkrifier s'il existe une corrklation entre l'ktat de subtrisation des cellules hypodermiques et les nombres de zoospores qui s'enkystent au voisinage de ces cellules, les racines portant des kystes ii zoospores ont etC colorkes par le bleu de tolui'dine pour masquer la majeure partie de l'autofluorescence causee par la subkrine lamellaire. I1 a ainsi pu comparer les pknetrations dans des cellules longues fluorescentes, dans des cellules longues non fluorescentes et dans des cellules courtes non fluorescentes. L'enkystement des zoospores sur l'tpiderme d'oignon s'est avtrk plus fkquent au voisinage des cellules courtes de l'hypoderme qu'une distribution au hasard l'aurait fait. Un plus grand nombre de zoospores s'enkystent au voisinage des cellules courtes sur les racines tuCes par la chaleur que sur les racines vivantes. L'enkystement est plus frequent au-dessus de cellules longues non fluorescentes que de cellules longues fluorescentes. Le champignon pinktre plus frkquemment par les cellules courtes et les cellules longues non fluorescentes que par les cellules longues fluorescentes.