Effects of fosetyl-Al and phosphorous acid on scoparone, a phytoalexin associated with resistance of citrus to Phytophthora citrophthora

• Published in: Phytopathology Vol. 79; no. 7; pp. 736 - 739
• Main Authors: Afek, U. (The Hebrew University of Jerusalem, Rehovot, Israel), Sztejnberg, A
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 01.07.1989
• Subjects: ACIDE MINERAL; ACIDOS INORGANICOS; Agronomy. Soil science and plant productions; AGRUME HYBRIDE; Biological and medical sciences; CITRUS; CITRUS AURANTIUM; CITRUS RETICULATA; CITRUS SINENSIS; CONTROL QUIMICO; FITOALEXINA; FONGICIDE; Fundamental and applied biological sciences. Psychology; FUNGICIDAS; Generalities; Genetics and breeding of economic plants; HIBRIDO DE FRUTAS CITRICAS; ISRAEL; LUTTE CHIMIQUE; Pest resistance; PHYTOALEXINE; PHYTOPHTHORA; RESISTANCE AUX MALADIES; RESISTENCIA A LA ENFERMEDAD; Varietal selection. Specialized plant breeding, plant breeding aims; Mycosis; Citrus fruit; Coumarine derivatives; Phycomycetes; Rutaceae; Phytopathogen; Fungi; Phytophthora citrophthora; Dicotyledones; Angiospermae; Fruit tree; Thallophyta; Induction; Fungistasis; Organic phosphonate; Defense; Fungicide; Fungus resistance; Infection; Citrus; Biological compound; Phytoalexin; Fruit crop; Defense mechanism; Spermatophyta; Citrus aurantium; Phosphorous acid
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/Phyto-79-736

Two Phytophthora-resistant citrus species (macrophylla and sour orange) and two Phytophthora-susceptible citrus species (rough lemon and niva) were treated with fosetyl-Al or phosphorus acid and compared for production of scoparone and symptoms of infection of Phytophthora citrophthora. In macrophylla, sour orange, and rough lemon, concentrations of scoparone were two- to fourfold greater in inoculated branches treated with 300 micrograms of fosetyl-Al or 125 micrograms of phosphorous acid (H3PO3) per milliliter than in inoculated, untreated branches. Lesion length in these three species decreased more rapidly than in niva after treatments with 0-300 micrograms of fosetyl-Al or 0-125 micrograms of H3PO3 per milliliter, whereas lesion length in niva decreased sharply only with treatments of more than 500 micrograms of fosetyl-Al or 200 micrograms of H3PO3 per milliliter. Treatment with fosetyl-Al and H3PO3 did not influence scoparone concentrations in niva bark. ED50 values of fosetyl-Al and H3PO3 for mycelial growth of P. citrophthora were 55 and 7 micrograms/ml, respectively