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Subject: Plant Pathology × Author: Ajit, Kumar × Author: KAU × End date: 2019 × Start date: 2010 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Endophytic and epiphytic microbial diversity in major tree spices and their potential for biocontrol of foliar pathogens
    (College of Horticulture, Vellanikkara, 2015) Ajit, Kumar; KAU; Koshy, Abraham
    The study on “Endophytic and epiphytic microbial diversity in major tree spices and their potential for biocontrol of foliar pathogens’’ was carried out during 2013-2015. The organisms causing various foliar diseases of tree spices were isolated from infected leaves and their pathogenicity established. Based on cultural and morphological characters, pathogens were identified upto the species level. Endophytes and epiphytes were isolated from leaf samples collected from different locations of Kerala. The population of endo and epiphytic microflora varied among the samples collected from different locations. Bacteria and fluorescent Pseudomonads population were more in number than fungi. A total of 118 endophytes and epiphytes were isolated. Among these, 52 isolates, consisting of 32 epi and 20 endophytes were found to exert antagonism towards pathogens of nutmeg, clove and cinnamon. On further in vitro evaluation, eight isolates including four each belonging to fungi and bacteria of epi and endophytic origin were selected as efficient antagonists. Mutual compatibility of the selected antagonists was studied. All the bacterial antagonists were compatible with each other. Among the four fungal antagonists, all except one combination (Nt ep f 1 X Nt ed f 2) were compatible. For studying the mechanism of antagonism of the selected isolates, they were subjected to various tests like production of ammonia, HCN, IAA, volatile and non volatile metabolites. The bacterial isolates Nt ed b 6, Cl ed b 2 and Cl ep b 6 produced more ammonia. All isolates were negative to HCN while others produced varying levels of IAA. The selected fungal isolates produced non-volatile metabolites inhibitory to the pathogens tested. Further, the compatibility of selected antagonists with 10 fungicides and four insecticides were studied. In general, the fungal antagonists were incompatible with fungicides like Bordeaux mixture, copper oxy chloride (Fytolan50 WP), carbendazim (12%) + mancozeb (64%) (Saaf), hexaconazole (Contaf 5 EC), propiconazole (Tilt 25 EC) and insecticides chlorpyriphos (Dursban 20 EC) and quinalphos (Ekalux 20 EC).Others showed varying levels of inhibition. The bacterial antagonists were compatible with Saaf, Tilt, mancozeb (Indofil M-45 75WP), cyamoxanil (8%) + mancozeb (64%) (Curzate M8) while they were incompatible with BM, copper hydroxide (Kocide 77 WP), Fytolan, Carbendazim (Bavistin 50WP), difenoconazole (Score 25 EC). All concentrations of Ekalux and lower concentration of dimethoate (Rogor 30 EC) were compatible with antagonists while the reverse was with that of chlorpyriphos and flubendiamide (Fame 480 SC). An attempt has been made to identify the selected epi and endophytic antagonists. The fungal antagonists were identified as Acremonium kilense (Nt ed f 2), Phytophthora cactorum (Nt ep f 1), Trichoderma viride (Cl ed f 2) and Trichoderma harzianum (Cn ep f 5). Three of the bacterial isolates (Nt ep b 2, Nt ed b 6, Cl ed b 2) were tentatively identified as Pseudomonas spp. while the other one (Cl ep b 6) as Bacillus sp.