Resistance to Sphaerotheca pannosa in roses induced by 2,6-dichloroisonicotinic acid |
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| Authors: | T HIJWEGEN M A VERHAAR & J C ZADOKS |
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| Institution: | Department of Phytopathology, Wageningen Agricultural University, PO Box 8025, 6700 EE, Wageningen, The Netherlands |
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| Abstract: | The susceptible rose cv. Madelon and the partially resistant cv. Sonia both responded with reduced development of rose powdery mildew when they were treated with the synthetic inducer 2,6-dichloroisonicotinic acid (INA). The EC50 for number of colonies cm−2 was approximately 0.4 mg L−1 in both cultivars when treated 4 days prior to inoculation. However, conspicuous differences were observed with respect to number of spores per cm2. For sporulation, the EC50 was 0.37 mg L−1 in cv. Madelon and only 0.08 mg L−1 in cv. Sonia. A comparison with the pathosystems cucumber/ Sphaerotheca fuliginea and red cabbage/ Peronospora parasitica is made and the importance of the observed phenomenon for the selection of parents in a breeding programme for (partial) resistance is discussed. |
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