Studies on antagonistic effect against plant pathogenic fungi from Endophytic fungi isolated from Hottuynia Cordata Thunb and screening for Siderophore and indole-3-acetic acid production

Abstract

The endophytic fungi that colonizes internal plant tissues without causing apparent harm to their host were isolated from healthy leaf, root and stem of Hottuynia cordata Thunb. Twelve fungal isolates found were identified by their morphological characteristic and using molecular technique. The result showed that ten isolates belonging to Ascomycota were presumed to be in genus Colletotrichum, Lasiodiplodia and Fusarium in eight isolates and two isolates were identified to class Dothideomycetes and Sordariomycetes. Two unidentified isolates (R14 and R15), confined only to root segments were isolated, these members may be from the group of Mycelia-Sterilia. The evaluation of antagonistic activity of twelve fungal endophytes isolated from healthy Houttuynia cordata Thumb against Trichoderma harzianum and five plant pathogenic fungi (Fusarium oxysporum, Sclerotium rolfsii, Rhizoctonia sp., Alternaria brassicicola and Phytophthora palmivora) by dual culture technique were performed. The in vitro antagonistic activities as two types of activities in this study; mycoparasitism and competition were found. Endophyte isolate B06, B12, B09 and R15 gave the highest percent inhibition of radial growth against to the plant pathogenic fungi (F. oxysporum, S. rolfsii, A. brassicicola) and T. harzianum within 24.22%, 29.07%, 13.54 and 24.15%, respectively. Endophyte isolate R14 showed the highest antagonistic activity to Rhizoctonia sp. and P. palmivora with 39.33% and 33.34% respectively. For the siderophore production, the seven active endophyte isolates showed orange halo formed around the colonies more than 30 mm on CAS agar. Three endophyte isolates efficiently produced IAA more than 24 µg/ml. The active endophyte isolates B06 identified as Lasiodiplodia pseudotheobromae showed the highest ability to produce IAA (37.034 µg/ml) and also showed the highest orange halo formed around the colonies which determined to siderophore production.