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Titre : Survey of bacterial diseases on stone fruits in Lebanon and investigation of phenotypic and genetic diversity of the isolated Pseudomonas syringae pathovars

Auteur : Moubarak, Peter

Université de soutenance : Università degli Studi della Tuscia – Viterbo

Grade : Dottorato di ricerca in Protezione delle piante 2016

Résumé partiel
Upon evaluating the state of the art of bacterial diseases affecting stone fruits in Lebanon, we conducted an extended survey to tackle the critical and most important occurring pathogenic bacteria unveiling their biochemical, biological and molecular identity. Our survey demonstrated that bacterial canker is the main and widely spread bacterial disease of stone fruits in Lebanon. The highest disease incidence was observed on cherry and apricot followed by plum, almond, peach and nectarine, respectively. As causal agents of this disease we identified two pathovars of Pseudomonas syringae, pathovar syringae and pathovar morsprunorum race 1. The pathovar syringae was isolated from all the commercial stone fruit species (peach, almond, nectarine, plum, cherry and apricot) and all Lebanese sampled regions, while the pathovar morsprunorum race 1 was present on nectarine, plum, cherry and apricot only in mountainous areas (Mount Lebanon, North Lebanon and the mountainous part of Bekaa). None of the other bacterial species pathogenic to stone fruits were isolated in this study unless gall symptoms suspected to be induced by Agrobacterium tumefaciens that were observed twice. Molecular characterization using both MLST and BOX-PCR showed that isolates of the pathovar morsprunorum race 1 were genetically homogenous belonging all to the same phylogroup 03 (PG03) while high genetic diversity was observed among isolates of the pathovar syringae which were divided into two genetic groups (PG02b and PG02d). The phylogroups 02b (PG02b) and 02d (PG02d), that are standard phylogroups named following an international code for Pseudomonas syringae classification using MLST. It is important to note that isolates of the PG02b were never isolated from apricot trees in the conducted survey whereas those of the PG02d were detected from all stone fruit species.

Mots Clés  : Survey ;Stone fruits ;Lebanon;Pseudomonas syringae ;Characterization;AGR/12

Présentation

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