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Occurrence and Distribution of Indigenous Isolates of Pythium Species in Northern India

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Occurrence and Distribution of Indigenous Isolates of Pythium Species in Northern India Advances in Plants & Agriculture Research Research Article Open Access Occurrence and distribution of indigenous isolates of Pythium species in northern India Abstract Volume 4 Issue 4 - 2016 Twelve different species of Pythium were isolated from different soil types, water types, vegetables and ornamentals of Delhi. Pythiumultimum and P. vexans were common in Muthu Kumar A soil than in water. P. middletonii was more common in water than soil followed by P. Division of Forest & Wood Protection, Institute of Wood deliense. The rhizosphere samples collected from the nursery bed of chilli showed the Science & Technology, India maximum diversity of Pythium species, out of the 12 species studied. The ornamentals like marigold, canna and chrysanthemum were more proned to Pythium. The occurrence Correspondence: Muthu Kumar A, Forest & Wood Protection of Pythium species in soil, water, vegetable and ornamentals fluctuated with seasonal Division, Institute of Wood Science & Technology, Bangalore, variations. Results obtained from the taxonomic investigations showed that out of 12 India species of Pythium studied except in P. afertile, P. catenulatum and P. graminicola June 06, 2016 | September 06, 2016 where the characters of sporangia were tallied with the original description and while Received: Published: rest of the species did not tallied. Description of the other species of Pythium were amended accordingly. In the case of P. aphanidermatum, P. aquatile, P. debaryanum, P. dissotocum, P. diclinus mostly occurred in several localities of Delhi. The size of the oogonia found to be larger than reported in literature. The filamentous sporangia of P. afertile which was similar to vegetative hyphae differed from the original description by its increase in length. Intercalary catenulate oogonia with papilla of P. dissotocum was recorded for the first time. P. graminicola was very well predominent in the samples from irrigation channels mostly near by the paddy fields, conforming the previous reports. The isolates of P. middletonii obtained during summer season produced bigger sporangia than those of winter and rainy season isolates. P. ultimum and P. vexans was mostly similar in their globose nature of sporangia, which was recorded for the first time from the area of Delhi, but they differed in their nature of oogonia and antheridial attachment. Keywords: pythium, oomycetes, fungal characterization, pythium morphology Introduction necrosis of higher plants. Middleton JT8 reported that about 60 species of this organism have the potential to initiate infection in higher plants The genus Pythium was erected by Pringsheim in 1858 and placed both in cultivated and forest soils. However, they are most commonly in the family Saprolegniaceae. By the end of 19th century taxonomic encountered in cultivated soils where they pose serious problems details of the genus had been clarified and many new species for various agronomically important crops, causing pre9 and post had been described. The relationship with other Oomycetes was emergence damping-off and other root rot diseases. The species of established and the genus was included in a new family, Pythiaceae, Pythium are potent producers of pectic and cellolytic enzymes which by Schroter in 1897. The fungus Pythium belongs to the subdivision was proved effective for its pathogenesis.10 Mastigomycotina, class Oomycetes, order Peronosporales and family Pythiaceae. The genus, its taxonomical position, and relationship Pythium affects most of the economically important crops which to other fungi have remained unchanged since that time. There are ranges from wheat, mustard, forest pine trees to grasses.11,12 It causes almost 307 described Pythium species (www.mycobank.org) which notable economic losses to tomato, chilli, cotton, leguminaceous crops are classified in the Kingdom Straminopila.1 The genus perception and trees like citrus, peach, pear and apple. Soft fleshy plants and plant of Pythium is still a continuing debate and there is no harmony on parts such as squash, cabbage, beans and potatoes also may be rotted the alternative genera.2–4 Several other researchers made an attempt by certain species of Pythium. They often cause great havoc in green to work on Pythium spp. into other genera based on the sporangial houses, seed beds and nurseries. Another interesting feature of genus shapes.5 Pythium is apart from its nature of pathogenicity,13 a certain species of Pythium have an ability to grow as a mycoparasite,14,15 which may Pythium are soil inhabiting organisms that are cosmopolitan in probably act as natural regulators of the populations of other fungi. nature. Pythium is generally considered a primitive parasite because The ability of the Pythium to grow as a mycoparasite was tested on it attacks juvenile or succulent tissues of young seedlings. The fungus 0.1% CMA against a range of filamentous fungi selected to represent quickly attacks seeds and emerging radicles causing seed decay most of the major taxa.16 Some species of Pythium are even found to and pre-emergence damping-off respectively. It also attacks young cause disease in mammals. Pythiuminsidiosum causes a disease called seedlings above the soil level causing post-emergence damping-off. Pythiosis, a cosmopolitan granulomatous disease common in horses, Such symptoms can be prominently seen in nursery beds, greenhouse cattle and dogs and are even occasionally reported in humans.17 and row crops because the mortality is sudden and fast.6,7 Pythium spp. are generally considered to be root pathogens, but occasionally, Pythium also produces sexual spores in the roots or in the soil some species of this fungus also causes severe foliage bight, root that are resistant to adverse environmental conditions such as Submit Manuscript | http://medcraveonline.com Adv Plants Agric Res. 2016;4(4):319‒327. 319 ©2016 Muthu. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Copyright: Occurrence and distribution of indigenous isolates of Pythium species in northern India ©2016 Muthu. 320 drying or cold temperatures and can survive in a dormant state was treated as baits and observation of different stages required for for months or years. These spores germinate in the presence of identification are made by making micro slide preparation. a susceptible host when environmental conditions are favorable. The hyphae then penetrate the host root, to continue the disease Preparation of slides cycle. The fungus Pythium is successful in its infectivity even in Whole mount preparation: Slides were prepared by scrapping the coexistence with other microorganisms. Interaction between Pythium diseased material with the help of a blade on to the slide in a drop aphanidermatum and Meloidogyne incognita indicated severe pre and of lactophenol-cotton blue solution. The slides were slightly heated 18 post emergence damping off in chilli and brinjal. The coexistence of over a bunsen flame and covered by slip. Excess mounting fluid was P. aphanidermatum with Pratylenchuscoffae showed a significantly drained off with clean blotting stripes. In case of the baited samples 19 high inoculum level. the fresh hyphal tips was used for slide preparation. Pythium are true fungi having coenocytic branched mycelium, Hand sections: Free hand thin sections of the infected materials were and phylogenetic comparisons place them close to algae and higher cut with the help of blade for getting the sporangia stages, which are 20 plants. Unlike most of the eumycetes, the members of this genus the most important features for identification of the fungusPythium . remain diploid throughout their life cycles with meiosis occurring in the gametangia before fertilization.21 Both asexual and sexual Petri-dish culture: The soil and water samples, also the diseased reproductive phases are very distinct in this genus. specimen were placed in a petridish with 75ml of sterile distilled water. After 5-7days incubation following baiting at room temperature, Species separation in the genus Pythium has been mainly the bait is observed microscopically for hyphal and zoo sporangial dependent upon morphological structures, since they are relatively growth. easy to observe. The morphological criteria most often used are the mature structure and size of the oogonia, oospores, sporangia Stains and mounting media: Temporary slides were prepared and hyphal swellings. The female gametangia (oogonia) is usually by using following stains and mounting media for microscopic smooth walled, but species having ornamental oogonia are not rare examinations in order to observe the sporangial and reproductive for the genus, the most commonly occurring species with such structures. oogonia is P. echinulatum. The wall ornamentations are usually Lacto phenol-cotton blue preparation: For identifying the hyaline 22 spines and are merely extensions of the oogonial wall. The spines nature of sporangia 0.05-0.1% cotton blue solution was added.12,35 may be short or long, conical or curved with sharp or blunt apices or may be digitate, mammiform or papillate.8 However, the emphasis D.P.X. mountant: For preparing permanent slides, D.P.X. mountant placed on these different structures as valid taxonomical criteria has was used. It has the advantage of rapid setting quality and does not varied considerably. In recent days, the morphological descriptions require sealing with the wax or nail
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