This pathogen produces several types of spores, each with a slightly different function. Several are often responsible for serious diseases in plants, such as dampingoff and rot. Pythium blight is often caused by various pythium species such as pythium aphanidermaturm, pythium graminicola, pythium ultimum and pythium vanterpoolii. It presents a white, fluffy appearance and consists of long rather slender. Nov 20, 2010 pythium insidiosum is an oomycete pathogenic in mammals. It has been shown, however, that the homothallic oomycetes phytophthora sojae forster et al. After 8 clay loam in a lysimeter were collected, filtered 0. In 1971, samples of rain waters that percolated through by an unidentified substance with mw about 150.
When commercial growers switched to soilless mixes, this species became less important than when growers used field soil in the potting mix. Toward the goal of developing improved treatment options, we want to. The purpose is to contribute to an overall reduction in pesticide residues in the fruit and the environment and to a decrease. Oomycetes are of particular concern in closed hydroponic cultivation systems. The infection occurs mainly in tropical and subtropical areas, particularly in horses, dogs and humans. The pythium ultimum est sequencing was supported by the usda national research initiative cooperative state research extension education service grant 20065560516645 and 20065560504558. Five strains of trichoderma with known biocontrol activities were assessed for their effect upon pea growth and their antagonistic activity against large pythium ultimum inocula. At least 27 species of pythium were found in soybean roots, but seven species were predominant.
Root rot and dampingoff of aleppo pine seedlings caused by. Plant emergence was followed, together with bacterial rhizosphere colonization, antibiotic production and effects on. Biological control of dampingoff caused by pythium ultimum and. The most common seedling diseases that have been identified in samples submitted to the unl plant and pest diagnostic clinic are those caused by pythium and less frequently, fusarium species. This life cycle is characterized by thickwalled oospores. In a close examination of pythiuminfected plants submitted to plant disease clinics during recent years, we have found that of the over 120 known species of pythium, three are consistently causing crop losses. This present study evaluates three isolates of trichoderma as plant growth promoting or biological control agents. The specificity of these forward primers paired with its2 or its4 and reverse universal primers was tested. The tuber and seed rot phase of leak is caused by a soil borne fungus, pythium ultimum. Analysis of the pythium ultimum genome sequence suggests that not all oomycete plant pathogens contain a similar toolkit for survival and pathogenesis. Using 29 isolates of pythium ultimum twelve isolates of var.
Biological control of pythium ultimum by stenotrophomonas maltophilia w81 is mediated by. These lesions usually develop around wounds, cuts or bruises. Twenty pcr primers were designed from the sequences of the rdna internal transcribed spacer 1 its1 region from 34 pythium species. However, the pyrosequencingderived read lengths on the gs20 and flx platform are substantially shorter than. Effect of biocontrol strains of trichoderma on plant growth. Pythium pringsheim species on aleppo pine seedlings. Find, read and cite all the research you need on researchgate. Suppression of disease in tomato infected by pythium. Genome sequence of the necrotrophic plant pathogen pythium. The most common seedling diseases that have been identified in samples submitted to the unl plant and pest diagnostic clinic are those caused by. Infection is acquired through small wounds via contact with water that contains motile zoospores or other propagules zoospores or hyphae.
Responses of pythium ultimum and other fungi to a soil. A, h, c, syiiiptoius produced on the roots of young persian buttercup plants by pythium deharyanum 12 days after inoculation in the greenhou. Pythium in hydroponic systems is definitely a threat to the crops. Introduction pythium ultimum is a ubiquitous soilborne pathogen which causes dampingoff and root rot on plants. The pythium species used in this study are listed in table 1. Genetic variation among populations of pythium irregulare in. The rdna internal transcribed spacer sequences of the svalbard isolate were identical to those of canadian. Suppression of disease in tomato infected by pythium ultimum. Pythium ultimum is primarily associated with soil and sand. The effect of trichoderma inocula upon the indigenous soil microflora and soil enzyme activities in the presence and absence of pythium is assessed. Pythium oligandrum is the most common ribeiro and butler 1992. Association of resistance to preemergence dampingoff caused by pythium ultimum and gene p for flower and seed coat color was studied in two crosses of chickpeas cicer arietinum, kabuli line c 104, and desi lines t3gw and p 4362 made at icrisat, patancheru, india. Pythium and phytophthora, also known as water molds, are funguslike organisms that cause dampingoff of pre or postemerged seedlings, as well as root and crown rot diseases on mature plants. The fungus caused severe damping off of carrot, cucumber and tomato seedlings after artificial inoculation.
Diseases of agronomic and vegetable crops caused by pythium. Jul 11, 2003 in the present study, the its1 regions of 34 plant pathogenic pythium species were amplified and sequenced. It is a serious disease of coolseason turfgrasses during hot humid weather. Pythium species have filamentous sporangia, smoothwalled spherical oogonia, and stalked antheridia. Plant growth promotion and biocontrol of pythium ultimum.
Like most members of the pythium species, it causes damping off i. Various species have been associated with diseased potato tubers, including pythium splendens hans braun warm areas and pythium ultimum trow temperate areas, but given the complex taxonomy and problems associated with the identification of pythium spp. Pythium wilt is caused by zoospore infection of older plants, leading to biotrophic infections that become. Pdf stenotrophomonas maltophilia strain w81, isolated from the rhizosphere of. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses. Identification initial tuber symptoms are grey to brownish lesions with a watersoaked appearance. Differential suppression of dampingoff caused by pythium. The present study investigated the efficacy of a biosurfactant produced by pseudomonas koreensis and added as a crude extract against. Characteristics of the representative isolate opu774 included hyphae ca. Originally, the genus pythium was placed in the family saprolegniaceae by pringsheim in 1858 hendrix and campbell, 1973. Responses of pythium ultimum and other fungi to a soil extract containing an inhibitor with low molecular weight. On roots, brown discoloration and thinning of roots. Pythium are, in reality, a group of root fungi, and pertain to a group called mastigomycotina oomycetes, and their scientific name is peronosporales pythiaceae pythium.
Dec 25, 2001 pythium ultimum had a significant effect on all the plant measurements, which is in accordance with the fact that it is a major pathogen of pea and is most destructive at the seedling stage kommedahl et al. If pythium infests a cutting bed, large losses occur. Pythium potato rot disease is prevalent in seed raising beds. Oospores are a result of the fertilization of oogonium by antheridium, which is the male sex organ of the organism.
Pythium ultimum was chosen as the seedling pathogen since pythium spp. Materials and methods fungal cultures and dna extraction. Jul, 2010 pythium ultimum is a ubiquitous oomycete plant pathogen responsible for a variety of diseases on a broad range of crop and ornamental species. It causes the damping off and root rot diseases of hundreds of diverse plant hosts including corn, soybean, potato, wheat, fir, and many ornamental species. Effect of biocontrol strains of trichoderma on plant.
The most common species are pythium aphanidermatum. Pdf biological control of pythium ultimum by stenotrophomonas. Pythium aphanidermatum, the most aggressive of the three, is the one. The present study investigated the efficacy of a biosurfactant produced by pseudomonas koreensis and added as a crude extract against the. To develop a specific method for distinguishing and detecting pythium species. The objective was to select specific primers to distinguish pythium species by pcr. It causes the damping off and root rot diseases of.
Plant emergence was followed, together with bacterial rhizosphere colonization, antibiotic production and effects on fungal growth. Advances in enzyme stabilization and immobilization make the use of enzymes for industrial applications increasingly feasible. On seeds, infected seeds may not germinate and seeds may turn brown and decompose. Such antifungal activity may be due partially to production of gliotoxin, a relatively nonselective. The feet of the fungus gnat are frequently a vector for their transmission. In a close examination of pythium infected plants submitted to plant disease clinics during recent years, we have found that of the over 120 known species of pythium, three are consistently causing crop losses. Pythium insidiosum is an oomycete pathogenic in mammals. Plant growth promotion and biocontrol of pythium ultimum by. Seedling diseases appearing in corn cropwatch university. Pythium ultimum is a ubiquitous soilborne pathogen which causes dampingoff and root rot on plants. Previous efforts to resolve whether the two varieties are genetically distinct have produced conflicting results.
The stems of young seedlings are constricted near the soil line, develop a soft, dark lesion, and frequently topple over. Most species are plant parasites, but pythium insidiosum is an important pathogen of animals, causing pythiosis. The use of biosurfactants is a promising alternative in biological control of zoosporeproducing oomycetes, which are a major plant pathogen worldwide in a wide variety of crops. Agriculture, college station, tx, for providing certain isolates of gliocladium virens and pythium ultimum. Termorshuizen, in potato biology and biotechnology, 2007. The optimum growth temperature range for phythophthora cryptogea is 7177f. Resistance to phytophthora erythrosepticaand pythium. Pythium ultimum is a ubiquitous oomycete plant pathogen responsible for a variety of diseases on a broad range of crop and ornamental species. This disease complex usually involves other pathogens such as phytophthora and rhizoctonia. Gliocladium virens is a common, soildwelling saprophyte that is useful in controlling pythium ultimum and rhizoctonia solani, organisms that cause dampingoff disease in greenhouses.
The pythium ultimum species complex is comprised of two morphological varieties. Rubin, in handbook of pesticide toxicology second edition, 2001. Due to this, the pythium genome database was taken offline on february 8, 2017. Resistance to phytophthora erythrosepticaand pythium ultimum in a potato clone derived from s. Diseases can be expressed as seed decay, pre or postemergence damping off and infection of the roots or stems of young plants. Pythium irregulare is a soilborne pathogen found world wide on hundreds of different plant hosts. Pythium ultimum is a cosmopolitan plant pathogen with a broad host range. There are many pythium species with varying degrees of host specificity and pathogenicity. Genetic variation among populations of pythium irregulare. Common names associated with pythium blight include cottony blight and grease spot. Pythium irregulare is homothallic and it is assumed that sexual reproduction occurs solely by self. Pythium dampingoff, root rot and stem rot pythium spp. Analysis of the pythium ultimum transcriptome using sanger and.
Growth inhibition of the root pathogen pythium ultimum by the biocontrol agent pseudomonas fluorescens dr54 inoculated on sugar beet seeds was studied in a soil microcosm. Stabilized lpo and glucose oxidase gox enzymes were combined with glucose, potassium iodide, and ammonium thiocyanate to create an antifungal formulation. Gudmestad2 1department of plant sciences, north dakota state university, fargo, nd. Pdf a pythium species without sporangia and zoospores, having terminal as. Pythium oligandrum exists in its sexual life stage about 20% of the time1. The tuber and seed rot phase of leak is caused by a soil borne fungus, pythium ultimum pythium seed rot symptoms. Pythium ultimum and pythium aphanidermatum, the most commonly encountered pythium species in the greenhouse, have an optimal growth temperature range of 6368f and 8093f, respectively.
26 219 1429 1510 1619 530 804 245 1520 108 937 1418 691 1509 1529 272 634 66 480 1441 1234 1138 1210 348 941 400 98 1600 1349 1230 663 1493 938 489 890 976 397 653 210 390 1095 213 627 813 1069 539 986 117 1351