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Title: Transgenic expression of a plant defensin in alfalfa (Medicago sativa) leads to increased resistance to crown rot pathogens

item SATHOFF, ANDREW - University Of Minnesota
item VELIVELLI, SIVA - Danforth Plant Science Center
item SHAH, DILIP - Danforth Plant Science Center
item Samac, Deborah - Debby

Submitted to: International Congress of Plant Pathologists
Publication Type: Abstract Only
Publication Acceptance Date: 3/28/2018
Publication Date: 7/29/2018
Citation: Sathoff, A., Velivelli, S., Shah, D., Samac, D.A. 2018. Transgenic expression of a plant defensin in alfalfa (Medicago sativa) leads to increased resistance to crown rot pathogens. International Congress of Plant Pathologists. July 29-August 3, 2018, Boston, Massachusetts.

Interpretive Summary:

Technical Abstract: Plant defensins are small cationic peptides with a conserved signature of cysteines. These peptides inhibit the growth of a broad range of fungi and bacteria. Alfalfa crown rot is a disease complex that reduces alfalfa stand density and causes substantial losses in productivity in all alfalfa-growing areas. Currently, there are no effective methods of disease control. To evaluate plant defensins as a potential control for alfalfa crown rot, the amount of defensin needed to inhibit growth of pathogen strains by 50% (IC50) was calculated. MtDef5, a bi-domain defensin from Medicago truncatula, displayed high activity against both bacterial and fungal crown rot pathogens in vitro. MtDef5 had IC50 values against Pseudomonas syringae pv. syringae and Phoma medicaginis of 0.198 microM and 1.50 microM, respectively. Agrobacterium-mediated transformation was used to create transgenic lines of alfalfa (cultivar Regen SY27x) constitutively expressing MtDef5. Expression of the transgene was confirmed by qRT-PCR and by Western blots using the polyclonal anti-MtDef5 antibody. Disease bioassays demonstrated increased resistance against fungal crown rot pathogens, especially against P. medicaginis in transgenic lines expressing MtDef5. These experiments show promise for not only controlling crown rot pathogens, but potentially a wide array of economically important fungal and bacterial pathogens through the transgenic expression of a plant defensin.