Efficiency of Application of Salcylic Acid on Induction of Systemic Acquired Resistance in Host Plant Against Fire Blight in Apple and Pear

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Abstract

 Fire blight causal agent (Erwinia amylovora) naturally induces systemic acquired resistance (SAR) in host plants. This study was carried out to evaluate the induction of SAR by salicylic acid (SA) on fire blight infections in two host plant species, apple (Malus domestica Borkh.) and pear ( Pyrus communis L.). Apple rootstocks, MM-111 (tolerant) and MM-106 (moderately-susceptible) and pear cultivars, Harrow Sweet (tolerant) and Spadona (moderately-susceptible) were micropropagated and inoculated from basal parts with strain Ea273 of E. amylovora. The pathogen activity was traced by adding Green Bromo Cresol, and evaluating the pH variation in media. SA treatments were applied by concentration (0.05, 0.1, 0.5, 1, 2, 5, 10 and 0 mgl-1 as control) and days before co-culture (1, 3, 5, 7 days and 0 as control). Effects of SA on the disease development were evaluated by necrosis progress rate, as well as number of necrosed internodes in a 240 h period from inoculation. Results showed that SA did not cause similar effects on disease development in two tested host plant species, apple and pear. SAR induction by salicylic acid application, could not reduce the disease progress in tested apple rootstocks, but also increased development of bacteria on this host plant. In pear, presence of SA successfully decreased disease development rate in shoots. Results confirm that E. amylovora uses induced SAR to become more virulent in interaction with host apple tissues. It is conduded that, the interaction mechanisms of pathogen with SAR in pear and apple are different, and only in pear the SAR induction could be an efficient strategy for management and control of the disease development.

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Seed and Plant Production Journal
Volume 25, Issue 2
June 2009
Pages 153-168

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