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Potassium Influence on Susceptibility of Bermudagrass to Helminthosporium cynodontis Toxin
Author(s) -
Richardson M. D.,
Croughan S. S.
Publication year - 1989
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1989.0011183x002900050038x
Subject(s) - cynodon dactylon , biology , tifton , human fertilization , cynodon , agronomy , horticulture , botany , hay
Inadequate K fertilization of bermudagrass, Cynodon dactylon (L.) Pers., can lead to stand loss and increased disease symptoms. This study was conducted to determine the relationship between fungal leaf spot ( Helminthosporium cynodontis Marig.) susceptibility and K status of hybrid bermudagrass ‘Grazer’ and ‘Tifton 78’ bermudagrass were grown in washed sand under six K fertilization rates (10, 30, 70, 100, 200, and 400 mg kg −1 ) in a greenhouse. Plants were clipped three times at 28‐d intervals and the K concentration in the tissue was determined. Prior to the final clipping, 4 mL of culture filtrate containing toxin (CFT) produced by H. cynodontis was sprayed in a fine mist on each plant. Plants were rated for disease severity according to leaf spot coverage after approximately 36 h. A curvilinear relationship was observed between disease severity and tissue K concentration. Leaf spotting increased when tissue K levels decreased below about 25 g/kg. Tifton 78 was more resistant than Grazer to CFT. Tifton 78 maintained higher tissue K levels at all fertilization rates due to lower biomass production and comparable amounts of K removed. Varietal differences should be considered when determining proper K fertilization rates from tissue analysis.