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Sultan Qaboos University (2019)

The role of endophytic fungi in suppressing damping-off diseases and promoting drought tolerance in selected vegetable crops

Halo, Boshra Ahmed Abdulmunem

Titre : The role of endophytic fungi in suppressing damping-off diseases and promoting drought tolerance in selected vegetable crops

Auteur : .Halo, Boshra Ahmed Abdulmunem

Université de soutenance : Sultan Qaboos University

Grade : Doctor of Philosophy in Crop Sciences 2019

Résumé partiel
Pythium-induced diseases and drought are two challenges limiting vegetable production in Oman. In this thesis entitled : “The role of endophytic fungi in suppressing damping-off diseases and promoting drought tolerance in selected vegetable crops” endophytic fungi were isolated from native desert plants, which naturally live under extreme stressful conditions such as drought and heat, and were used to mitigate the biotic and abiotic factors in crop plants, particularly tomatoes. The three main objectives of this study were to investigate : (1) fungal diversity in desert plants in Oman ; (2) the ability of the isolated fungi in suppressing Pythium- induced damping-off of vegetable crops ; and (3) the ability of fungal isolates in improving drought tolerance. The first part of this study focused on isolation and identification of endophytic fungi from native desert plants. The identified endophytes were Aspergillus terreus from Rhazya stricta and Tephrosia apollinea desert plants and Talaromyces variabilis from R. stricta and Zygophyllum coccineum desert plants. In addition, the study identified two novel fungal species in Oman, Cladosporium omanense sp. nov. and Talaromyces omanensis. C. omanense was obtained from Z. coccineum, and its identity was confirmed based on morphological characteristics as well as phylogenetic analysis based on the combined internal transcribed spacer (ITS), partial translation elongation factor 1-alpha (TEF) and partial actin (ACT) sequence data. C. omanense differed from its phylogenetically related species C. endophyticum by its fast growing colonies and in having longer macronematous and micronematous conidiophores, thick-walled conidia with conspicuously protuberant shrivelling surface ornamentation. The second new species, T. omanensis was isolated from the desert plant R. stricta. The new species forms a distinct sister clade to the section Subinflati in the phylogeny of internal transcribed spacer (ITS), β-tubulin (benA) and Calmodulin (CaM). This fungus remains distinct and unique from the other species in the section Subinflati in having monoverticillate conidiophore.

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