Effect of Transgenic Cotton Plants Transformed with Antimicrobial Synthetic Peptide D4E1 On Cotton Seedling Disease, Soil Microbial Diversity.

Cotton seedling disease (CSD) which causes the largest yield losses of any cotton disease in the U.S., is a fungal disease complex comprised of several fungal pathogens.  These fungal pathogens function either separately or in concert, from day of planting through seedling stage.  In Alabama, the pathogens primarily responsible for CSD are Rhizoctonia solani and Pythium spp. which belong to the fungal classes Basiodomycetes and Oomycetes, respectively.  In the state of Alabama alone, CSD  is responsible for an average of 10-million dollars per year in revenue. Its economic importance, coupled with the fact that cotton has no known disease resistant cultivars to CSD, make it an ideal candidate for genetic modification of disease resitance.  D4E1 is a synthetic antimicrobial peptide which, when transformed into cotton, in vitro and in planta, confers broad spectrum antimicrobial and antifungal properties against many fungal classes, including Basiodomycetes and Oomycetes.  The effectiveness of D4E1 against these pathogens is however, yet to be tested in situ.  Over two consecutive growing seasons, test plots were assigned treatemtns in a completely randomized design.  Treatments were: a control with GUS reporter gene, a non-transgenic parent variety, or one of 3 isogenic lines of cotton seed transformed with D4E1 (designated 357, 358, and 373).  Evidence of disease symptoms was evaluated and the soil was randomly sampled, composited and subjected to DNA extraction, pyrosequencing and phosphatase enzyme assays.  Overall results show that introduction of D4E1 resulted in an increase (p=   ) in seedling viability when compared to the control, but did not result in a change in the microbial diversity or the enzymatic activity.