Antagonistic effect of Leuconostoc mesenteroides on grapevine crown gall and fire blight

ABSTRACT Grapevine crown gall, caused by Allorhizobium vitis (A. vitis) and fire blight, caused by Erwinia amylovora (E. amylovora) of rosaceous plants, have been recognized as serious bacterial diseases and responsible for major crop losses in grapevine (Vitis vinifera L.), pear (Pyrus communis L.) and apple (Malus domestica Borkh.) worldwide. To develop an effective biocontrol method against the two bacterial pathogens, lactic acid bacteria (LAB) isolated from agricultural irrigation canals were tested as biocontrol agents. Thirty-two bacterial isolates were screened for their in vitro antagonistic activity. Four isolates (MS-1, MS-2, MS-3, and MS-4), identified by partial sequencing of 16S rRNA as Leuconostoc mesenteroides subsp. Jonggajibkimchii, were found to significantly inhibit the growth of A. vitis and E. amylovora in vitro. The biocontrol efficiency of these strains was tested against E. amylovora on immature pear fruits under laboratory conditions, and against A. vitis in tomato (Solanum lycopersicum L.) and kalanchoe (Kalanchoe daigremontiana) plants, under greenhouse conditions. Results showed that all selected antagonists were able to suppress fire blight disease on immature pear fruits. On tomato plants, the MS-1 and MS-2 strains were able to reduce the A. vitis infection by 82% and 99%, respectively. Similarly, the MS-2 strain reduced gall formation on kalanchoe plants by 99%. We concluded that Leuconostoc mesenteroides subsp. Jonggajibkimchii strains could serve as a potential biocontrol agent against fire blight and grapevine crown gall diseases.