Bacterial Leaf Spot of Araliaceous Plants Caused by Xanthomonas campestris pv. Hederae in Egypt

Abstract

A leaf spot symptoms consentient with bacterial leaf spot disease of araliaceous plants were observed on plants of Schefflera actinophylla grown in different plots located in Cairo and Giza governorates during 2014. Eight bacterial isolates resemble Xanthomonas campestris pv. hederae obtained from symptomatic plants were characterized based on physiological and biochemical tests, pathogenicity test and Biolog microbial ID system. Furthermore, the isolates were characterized by comparing them by ERIC PCR which showed highly similar DNA fragment banding patterns between all isolates. Some variance in the isolates virulence were detected when differences in virulence between the isolates were evaluated on the leaves of Schefflera actinophylla and Schefflera elegantissima. Host range of the isolates within Araliaceae family was determined on 7 araliaceous plants where, all isolates were pathogenic on Schefflera arboricola, Schefflera elegantissima and Hedera helix in addition to Schefflera actinophylla and conversely, none of the isolates were pathogenic on Aralia nudicaulis, Dendropanax trifidus and Fatsia japonica. Incidence and severity of the disease were evaluated on araliaceous plants grown in 10 plots located in Cairo and Giza governorates. The disease incidence values significantly differed within surveyed plots whereas these values ranged from 0 to 56.5 % by overall mean equal to 22.9%. The mean of the disease severity ratings ranged from 38.0 to 77.5 % by overall mean equal to 43.5%.

Antagonistic potential of some bacterial strains against Xanthomonas campestris, the cause of bacterial blight in Hordeum vulgare

“…Moreover, there was a remarkable elevation of flavonoids due to the antagonistic strains in barley plants in infested and non-infested soils, and these results agree with the results of Salaheddin (2002), Salaheddin et al (2005), and Zhang et al (2001). The effectiveness of biological control achieved by the biocontrol agents of the present study showed distinctive control mechanisms that may be due to additional or synergistic effects (Zohurul et al 2003;Robe`ne-Soustrade et al 2006;Salaheddin et al 2010;Tolba 2017). The capability to produce bioactive molecules by this species of antagonistic microorganisms can trigger systemic resistance in the infected Hordeum vulgare seedlings and may be applicable than using the whole organism in future.…”