1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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1997 - 199912000 - 20011

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Author: search.filters.author.Susha S TharaSubject: search.filters.subject.Plant Pathology

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    Biocontrol of water hyacinth using fungal pathogens
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Susha S Thara; Naseema, A
    Detailed study was conducted on the host range of the already identified fungal pathogens of water hyacinth viz. Colletotrichum gloeosporioides, Fusarium eguiseti and F.pallidoroseum on thirty cultivated plants including vegetables, pulses and oil seeds, field crops, fruits and forest crops and ornamental plants and forty one common weed plants which are seen in and around water ways infested with water hyacinth. It was observed that C. gloeosporioides could infect amaranthus, bhindi, chilli, Euphorbia hirta, Hydrocotyl asiatica and Phyllanthus niruri. Of the thirty cultivated plants and forty one weed plants tested F. eguiseti was seen to be pathogenic to amaranthus, Amaranthus viridis, Commelina . bengalensis, C. jacobi and Monochoria vaginalis. F. pallidoroseum could produce symptoms on napier grass, Axonopus sp., boerhaavia diffusa, C.benghalensis, C.jacobi, Echinochloa colonum, Euphorbia hirta, Justicia diffusa, J.prostrata, M.vaginalis and Oldenlandia umbrellata and Scorpia dulcis. For the effective destruction of the weed, lxl011 spores per ml concentration of Q. gloeosporioides, E. eguiseti and F. pallidoroseum were found to be more effective than lxl09 and lxl010 spores per ml concentration. Cell free metabolites of the pathogenic fungi were found to produce symptoms on water hyacinth plant. Metabolite produced by E. pallidoroseum caused considerable damage than by E.equiseti and C. gloeosporioides. When pathogens were applied singly and in combination on water hyacinth it was observed that the combined application of F. pallidoroseum and F. equiseti followed by F. pallidoroseum alone gave maximum intensity of infection. Eventhough C. gloeospoirioides gave least intensity of infection it can be used as a co-pathogen with E. eguiseti. Metabolite of the pathogens individually and in combination when applied on healthy water hyacinth plants, maximum damage was caused by F.pallidoroseum alone and the combination of metabolite of three fungi viz. C. gloeosporioides,F equiseti and F. pallidoroseum. Least damage was caused by metabolite of C. gloeosporioides. An experiment was conducted to find out suitable carrier materials for the mass multiplication and storage of pathogen. It was observed that for C. gloeosporioides maximum sporulation was in water hyacinth leaf followed by guinea grass straw and rice bran. But the spore viability was maximum for rice straw, and on coir pith. Maximum infection was caused by fungus grown on guinea grass straw and rice straw. In the case of E. equiseti spore counts was higher in guinea grass straw followed by coir pith. The spore germination was maximum in rice bran and coir pith. Maximum infection was produced by the fungi on guinea grass straw, coir pith and waterhyacinth leaf. E. pallidoroseum produce maximum number of spores on rice bran followed by guinea grass straw. It was observed that the germination percentage of spores were maximum on coir pith. Out of the six carrier materials used the fungus produced maximum infection when grown on rice bran and guinea grass straw. In the study for testing the storage life of metabolities, it was observed that the efficiency to produce symptom was reduced on storage in the case of C. gloeosporioides and E. pallidoroseum whereas for E. eguiseti on storage the effeciency of the metabolite to cause damage increased. Metabolite stored on refrigerated condition performed poorly for all the three fungi. Different methods of application of the three fungi were tried. Of the five treatments, placement of bits and dusting the inoculum along with the carrier materials produced maximum infection. In the experiment conducted to characterize the toxin presented in the cell free metabolite of pathogenic fungi, observed the presence of Fusaric acid in the metabolite of Fusarium spp.
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    Monographic studies on agaricus species of Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2001) Susha S Thara; Bhavani Devi, S
    The warm humid climatic conditions and wide diversity in soil types and pattern favoured a luxuriant growth of a wide variety of fungal flora in Kerala. In the present study collections were made during south-west and north-east monsoon periods of 1998-2000 in twenty agro climatic zones of Kerala and forty two species of Agaricus were collected. Among the 42 species collected A. abruptibulbus, A. actinorachis, A. altipes, A. annae, A. arenicolus, A. benesi, A. bernardii, A. bulbosus, A. caroli, A. chloroconius, A. ingrata, A. lividonitidus, A. mediojuscus, A. microflavus, A. micromegethus, A. microrubescens, A. moelleri, A. nivescens, A. ochraceous, A. ochroflavus, A. phaeolepidotus, A. pseudopratensis, A. purpurellus, A. rubicolus, A. rusiophyllus, A. semotus, A. silvicola, A. simulans, A. spissarujosa, A. squamuliferus, A. stadii, A. subperonatus, A. trisulphuratus and A. xantholepis are new reports from Kerala. Among these A. abruptibulbus, A. annae, A. arenicolus, A. benesi, A. bernardii, A. bulbosus, A. caroli, A. chloroconius, A. ingrata, A. lividonitidus, A. mediojuscus, A. microflavus, A. microrubescens, A. moelleri, A. nivescens, A. ochraceous, A. ochroflavus, A. phaeolepidotus, A. purpurel!us, A. rubicolus, A. rusiophyllus, A. simulans, A. spissarujosa, A. stadii and A. subperonatus are first reports from India. A. bulbosus, A. ochraceous, A. ochroflavus, A. microflavus, A. microrubescens, A. rubicolus and A. spissarujosa are the new reports during the study. 'f. Most of the collections were obtained during May-June and September- October months coinciding with the early south-west and north-east monsoon periods. The species of the Genus Agaricus preferred laterite soils. Growth of Agaricus species was maximum on complete medium and they preferred a temperature range between 25 and 30DC and pH 6. The results of the studies revealed that light did not play any significant role on growth of the fungi. Among the different carbon sources tried Agaricus spp. preferred glucose, sucrose and fructose. Agaricus spp. exhibited best growth in organic nitrogen compared to inorganic sources of nitrogen. From the study it was observed that wheat gram IS best for the production of spawn of A. bitorquis and maximum growth was obtained when incubated at 25 and 30DC. Spawn run of A. bitorquis was observed in traditional compost and pinheads started appearing within 30-35 days after spawning. The buttons can be harvested on fourth or fifth day after pinhead emergence. 400 g of buttons were obtained from 10 kg compost and this preliminary study showed the possibilities of commercial cultivation of this excellent mushroom species under Kerala condition.