Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2003
Publication Date: 8/4/2004
Citation: Hammerschlag, F.A. 2004. In vitro inhibitory activity of antimicrobial peptides cecropin, alpha-thionin db4 and gamma-thionin rsafp1 against several pathogens of strawberry and highbush blueberry. Hortscience. 39:1053-1055 Interpretive Summary: Cultivated strawberry and highbush blueberry are host to a large and diverse number of fungal and bacterial pathogens that are considered major obstacles to maintaining or increasing production. Although genetic sources of resistance to disease exist for blueberry and strawberry, a severe impediment to crop improvement is that many generations of hybridization and selection are required to produce commercial quality fruit with disease resistance. Increased disease resistance to both fungal and bacterial pathogens has been achieved in a range of plants following the introduction of genes encoding one of a number of small antimicrobial peptides. In the present study, we investigated the effect of several antimicrobial peptides on the growth of a range of pathogens of strawberry and blueberry as a prerequisite to utilizing a gene transfer approach to generate increased levels of disease resistance. The peptides cecropin, DB4 and RsAFP1 were highly inhibitory to the emerging strawberry pathogen Xanthomonas fragariae and thus these results suggest that introducing these peptides into strawberry may be useful for controlling bacterial angular leaf spot disease (BALD)caused by X. fragariae. The present study should be of value to scientists interested in using alternative breeding strategies for obtaining BALD resistance in strawberry.
Technical Abstract: As part of a program to develop transgenic highbush blueberry (Vaccinium corymbosum L.) and strawberry (Fragaria x ananassa Duchesne) cultivars with increased levels of disease resistance, we have investigated the feasibility of introducing genes for the antimicrobial peptides cecropin B and MB39, and thionins DB4 and RsAFP1 by testing the effects of these peptides on several important pathogens of these two crop species. A thin-layer plate bioassay was conducted with these peptides and the pathogens Botrytis cinerea (Pers.ex. Fr.), Botryosphaeria dothidea (Mouq.ex. Fr.) Ces & de Not., Colletotrichum acutatum Simmonds, C. gloeosporioides (Penz.) Penz.et Sacc., C. fragariae Brooks, Monilinia vaccinii-corymbosi Reade (Honey), Phytophthora fragariae Hickman and Xanthomonas fragariae Kennedy and King. The minimum inhibitory concentration (micromole) for cecropin ranged from 0.02 for X. fragariae strains 10 and 128 to 72.8 for C. gloeosporioides isolate Akp1. For DB4, the minimum inhibitory concentration (micromole) ranged from 0.03 for X. fragariae strain 6 to 87.2 for B. cinerea isolate-ATCC. For RsAFP1, the minimum inhibitory concentration (micromole) ranged from 0.13 for X. fragariae strain 6 to 61.4 for M. vaccinii-corymbosi isolate 9423-x-45. These results indicate that introducing genes for either cecropin, DB4 or RsAFP1 into strawberry may be useful for controlling bacterial angular leaf spot disease caused by X. fragariae.