EFFECT OF CECROPIN-LIKE TRANSGENES ON FIRE BLIGHT RESISTANCE OF APPLE

Two synthetic analogs of native cecropin B, SB-37 and Shiva-1, had in vitro activity against Erwinia amylovora. To evaluate the ability of cecropins to enhance fire blight resistance, Royal Gala apple was transformed with 5 different plasmid binary vectors containing cecropin-like genes.
These included pWIC38 containing the gene encoding SB-37 under the control of the wound inducible pinII promoter, pCa2C38 with the SB-37 gene under the control of the constitutive CaMV 35S promoter; and pBPRB37 with the SB-37 gene fused to a signal peptide under the control of the 35S promoter. 2- and 3-yr-old field grown transgenic plants were artificially inoculated with E. amylovora and the percent of the current season’s shoot length blighted was determined.
Among 2 yr-old plants of 33 cecropin-transgenic lines, 7 pWIC38-trangenic lines, 2 pBPRB37-transgenic lines, and 1 vector-control pBI121-transgenic line, were significantly more resistant than Royal Gala parent.
The resistance of these 10 transgenic lines was statistically indistinguishable from that of resistant-control cultivar Liberty.
The range of resistance within lines derived from a single plasmid and the mean % shoot length blighted of the plasmid-group were very similar for cecropin transgenics transformed with pBPRB37, pCa2C38, pWIC38, or vector-control pBI121. With 3-yr-old plants of 17 cecropin-transgenic lines, 3 pWIC38-transgenic lines and 2 vector-control pBI121-transgenic lines were significantly more resistant than Royal Gala parent.
The similar level of resistance found in cecropin- and vector-transgenic lines suggests that biological variation, either random or somaclonal, may be a major contributor to the observed resistance.

VIII International Workshop on Fire Blight

Jay L. Norelli, JoAnn Z. Mills, M. Timur Momol, H. Aldwinckle

https://doi.org/10.17660/ActaHortic.1999.489.47