Induction of Systemic Resistance to Anthracnose in Cucumber by Phosphates

Solutions of K 3 PO 4 , K 2 HPO 4 , NA 3 PO 4 , and NA 2 HPO 4 sprayed on the undersides of the first and second true leaves of cucumber induced systemic resistance in leaves 3 and 4 to anthracnose caused by Colletotrichum lagenarium. Solutions of KH 2 PO 4 , NAH 2 PO 4 , CaHPO 4 , (NH 4 ) 2 HPO 4 and NH 4 H 2 PO 4 were less active, and a suspension of Ca 3 PO 4 was inactive. Induced resistance in leaves 3 and 4 depended on the concentration of K 3 PO 4 applied to leaves 1 and 2. Spraying leaves 1 and 2 each with 1-2ml of a solution of K 3 PO 4 at concentration of 100, 50, 10, 5, and 1 mM protected leaves 3 and 4 99, 96, 78, 54, and 15% respectively. (...)