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Showing 2 results for Fire Blight

A. Davoodee, E. Majidi, H. Rahimian, M. Valizadeh,
Volume 9, Issue 2 (7-2005)
Abstract

The fire blight with the bacterial causal agent, Erwinia amylovora (Burrill) winslow etal. is one of the most important diseases of the pome fruits that causes the economical losses to quince, pear and apple productions, respectively, in some parts of country. To determine the infection severity of the 43 raturally infected pear cultivars in collection of karaj horticulture research division and also for studing the reaction of these cultivars against disease, the evaluation was performed by the USDA standard system for these cultivars in collection. In this study, although the most of cultivars had been infected on the natural conditions, but disease severity was significantly different between them. By the USDA system, pear cultivars were divided in the 2 classes. Percentage of pear cultivars in very susceptible and moderately susceptible classes were 81.4 and 18.6 respectively. Also for dividing the pear cultivars, beside of USDA method, SPSS software and the cluster analysis were also by the UPGMA method and cultivars were divided into 3 clusters, but it seems that the classification of cluster analysis did not conform with USDA system. Correlation of I.V.S in the artificial tests and the disease severity by natural infection was very significant (r= -0.83).
M. Niknejad Kazempour, E. Kamran, B. Ali,
Volume 11, Issue 40 (7-2007)
Abstract

Fire blight caused by Erwinia amylovora, is a serious disease of pome fruits in many areas in the world which causes evaluative necrosis. Indeed, E. amylovora can invade the whole tree solely by internal progression through the host tissues. In this research, symptoms of necrotic shoots and exudates production on infected pear trees in different areas of Guilan province (Astaneh Ashrafieh, Lahijan and Kiashahr) were surveyed. Samples were taken from infected tissues of diseased trees. For isolation of bacterial causal agent, the infected tissues were crushed in pepton water, then 100µl of the extracts were cultured on Sucrose Nutrient Agar (SNA) and Luria Berthani (LB) containing Cyclohexamid antibiotic (50 µg / ml). The isolated bacteria were rod-shaped , gram negative and facultatively an-aerobic. The bacteria produced Levan on media including sucrose , but could not produce fluorescent pigments on King’s B medium. All strains made hypersensitive reaction on tobacco leaves. All isolates were oxidase , nitrate, urease and indole negative and were not able to rot potato tuber slices, produce H2S and grow in 36 °C. The isolates could use citrate, acetoin, sorbitol and trehalose and their gelatin test was positive. Based on morphological, biochemical, physiological characteristics and production of a 937 bp with specific primer Ea1 and Ea2 in PCR method, the strains were identified as E. amylovora. This is the first report of the existence of this bacterium on pear fruit trees in Guilan province.

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