The etiology of head rot disease of broccoli [Pseudomonas marginalis]

Wimalajeewa, D.L.S. . Plant Research Inst.; Hallam, N.D. . Dept. of Botany; Hayward, A.C. . Dept. of Microbiology; Price, T.V. . School of Agriculture

The etiology of head rot disease of broccoli [Pseudomonas marginalis]

1987

Wimalajeewa, D.L.S. (Victorian Dept. of Agriculture and Rural Affairs, Burnely (Australia). Plant Research Inst.) | Hallam, N.D. (Monash Univ., Clayton (Australia). Dept. of Botany) | Hayward, A.C. (Queensland Univ., St Lucia (Australia). Dept. of Microbiology) | Price, T.V. (La Trobe Univ., Bundoora (Australia). School of Agriculture)

Transmission and scanning electron microscope studies of broccoli florets affected by head rot, at various stages of disease development, strongly indicated a bacterial etiology for the disease. Bacteria isolated from diseased heads using standard techniques failed to reproduce symptoms in pathogenicity tests. However, a modified isolation technique, using broccoli heads showing incipient watersoaking symptoms, yielded a fluorescent pseudomonad which reproduced disease symptoms readily in glasshouse and field tests. The pathogenic bacterium was identified as a highly pectolytic pathovar of Pseudomonas marginalis. The bacterium also caused the rotting of potato, tomato and swede turnip slices, and also of intact and detached tomato fruit. However, it was not pathogenic on lettuce, parsnip or lucerne, and also failed to rot carrot slices.

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