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University of Saskatchewan (2012)

Fungal endophytes that confer heat and drought tolerance to wheat

Hubbard, Michelle

Titre : Fungal endophytes that confer heat and drought tolerance to wheat

Auteur : Hubbard, Michelle

Université de soutenance : University of Saskatchewan

Grade : Doctor of Philosophy (PhD) 2012

Résumé
Fungal endophytes can improve plant tolerance to abiotic stresses such as heat and drought. I hypothesized that the six endophytic fungi SMCD 2204, 2206, 2208, 2210, 2214 and 2215 would promote heat and drought tolerance in wheat during both seed germination and at later developmental stages. The Vujanovic and Germida laboratories originally discovered these fungi from the roots of Saskatchewan grown wheat (Triticum turgidum L.). I assessed mycomediated enhancement of seed germination (mycovitality) including seedling performance, in vitro in terms of percent germination, seedling fresh weight, energy of germination (EG) and hydrothermal time (HTT) of germination. Endophytes SMCD 2206, 2210 and 2215 improved seedling heat or drought resistance, while SMCD 2204, 2208 and 2214 did not. In the greenhouse and phytotron, I evaluated the ability of the same six endophytes to enhance wheat tolerance for heat or drought stress by measuring photosynthetic stress (PS), carbon isotopic discrimination (∆), average seed weight (ASW), total seed weight (TSW) and the EG and percent germination of the F1 seeds produced. SMCD 2206, 2201 and 2215 increased performance of pot-grown wheat under heat and drought. Epigenetic modifications frequently involve changes in DNA methylation. Methyl-sensitive amplified polymorphism (MSAP) revealed that drought stressed wheat seedlings colonized with SMCD 2206 had DNA methylation patterns more similar to those of unstressed plants (with or without the endophyte) than to uncolonized drought stressed plants. Plant DNA sequences – similar to a cytochrome p450 EST and three transposable elements (TEs) – were differentially methylated between endophyte-free and endophyte colonized drought stressed plants. I tested the hypothesis that the endophyte-free progeny of SMCD 2206 colonized wheat grown in the phytotron or greenhouse under heat or drought stress would have heightened resistance for the same abiotic stressors to which their parents were exposed, compared to uninoculated first generation plants. Data on PS, ASW, TSW and ∆ showed that F2 plants incompletely inherited stress tolerance. This research demonstrated that fungal endophytes SMCD 2206, 2210 and 2215 improve wheat tolerance for heat and drought both in vitro and in pot studies. If field trials produce similar results, these isolates could be agriculturally important.

Mots clés : Fungal endophytes, wheat, heat, drought, agriculture

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Page publiée le 22 novembre 2015, mise à jour le 31 août 2019