Transgenic Disease Resistance in Vitis vinifera: Potential Use and Screening of Antimicrobial Peptides

To increase resistance to important grapevine pathogens, Chardonnay was transformed with a construct containing two antimicrobial peptides (AMPs), Magainin-2 and PGL. Five lines expressing Magainin-2 transcripts showed increased resistance to two strains of Agrobacterium vitis, TM4 and CG450. These results led to a comprehensive study of the effects of nine AMPs on in vitro growth of four pathogens: two bacterial (A. tumefaciens and A. vitis strains CG450 and TM4) and two fungal (Botrytis cinerea and Erysiphe necator). Cecropin B, MSI-99, and Shiva I were most effective against the two A. vitis strains, but ESF-12 had no effect. The growth of TM4 was always more sensitive to AMPs than was CG450, a pattern commensurate with the observations of crown gall resistance among transformed vines expressing Magainin-2. Botrytis cinerea required more than 10 mu M alpha-Purothionin, PGL, or ESF39 for effective growth inhibition. None of the AMPs studied could reproducibly control E. necator spore germination or lesion formation. MSI-99 and Cecropin B were most promising for future increased resistance to crown gall disease in transgenic grapevines.