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Disease Note. Occurrence of Sunflower Stalk Rot Incited by Erwinia carotovora in South Africa. B. L. Jones, Grain Crops Research Institute, Private Bag X1251, Potchefstroom 2520, Republic of South Africa. L. van der Walt, Grain Crops Research Institute, Private Bag X1251, Potchefstroom 2520, Republic of South Africa. Plant Dis. 72:994. Accepted for publication 29 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0994B.
Bacterial stalk rot of sunflower (Helianthus annuus L.) occurred in
South Africa in 1985 and 1986 showing all the symptoms reported
earlier by Gudmestad et al (1). The bacterium isolated from diseased
tissue degraded pectate, reduced nitrate, grew at 36 C, and was rodshaped,
gram-negative, peritrichously flagellated, facultatively
anaerobic, fermentative, H,S-positive, acetoin-positive, and ureasenegative.
Koch's postulates were completed when the bacteria were
introduced into induced wounds but not when they were sprayed onto
unwounded plants. The bacterium was repeatedly isolated from lesions
caused by Alternaria helianthi (Hansf.) Tubaki & Nishihara before
bacterial stalk rot developed. Bacterial stalk rot developed in test plants
infected with A. helianthi before being sprayed with the bacterium but
not in plants uninfected with A. helianthi when sprayed. We concluded
that the bacterium was Erwinia carotovora (Jones) Bergey et al and that
it entered sunflower tissue through lesions caused by A. helianthi. |