SPOTS on stems and leaves, ovate to prolate, at first yellow greenish, later yellow greyish, finally grey, depressed, with a purple to black border. With time, pycnidia appear within the spots.

PYCNIDIA (p) globose to subglobose, yellow brown to brownish black, immersed or slightly erumpent, subepidermal, separate, unilocular, 130-600 µm diam, with a subcircular to elliptical ostiolum, 8-35 µm diam.

Wall (w) 6-16 µm thick, composed of 3-5 layers of cells; cells of the outer layer thick-walled, yellow brown to dark brown, more or less flattened, merging with inner layers of smaller, relatively thin-walled, angular, nearly isodiametric, subhyaline to pale yellow cells.

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CONIDIA (c) hyaline, cylindrical to ellipsoidal, sometimes slightly curved, with rounded ends, aseptate, 0.8-2 x 1.5-6 µm.

PLANT HOST AND DISTRIBUTION. The hosts of P. lingam are different plant species of the family Brassicaceae (Arx 1987; Brandenburger 1985; Brooks 1953).

Phoma lingam is widespread in the world.

NOTES. The teleomorph of P. lingam is Leptosphaeria maculans (Desm.) Ces. & De N.

Phoma lingam is a serious pathogen causing black leg, canker, and dry rot of brassicas and other crucifers (Agrios 1988; Brooks 1953; Madej 1993). Sometimes, the fungus also produces a "damping-off" effect (Brooks 1953).

Initial infections are mainly caused by ascospores dispersed from pseudothecia on infected debris (Smith et al. 1988). Once established in a crop, the pathogen spreads by rain-splashed conidia. Epidemic development is favoured by mild wet conditions.

Phoma lingam overwinters in infected plant debris and seeds (Agrios 1987; Brooks 1953; Madej 1993). The fungus is able to survive for at least three years on crop debris in the soil (Smith et al. 1988).

REFERENCES

Arx J. A. 1987. Plant pathogenic fungi. Beih. Nova Hedwigia 87, 1-288.

Agrios G. N. 1988. Plant pathology, 3rd edition. Academic Press, INC. San Diego, New York, Berkeley, Boston, London, Sydney, Tokyo, Toronto.

Brandenburger W. 1985. Parasitische Pilze an Gefässpflanzen in Europa. G. Fischer Verl. Stuttgart. New York.

Brooks F. T. 1953. Plant diseases. Geoffrey Cumberlege. Oxford University Press. London, New York, Toronto.

Madej T. 1993. Badania do patologii roslin krzyzowych. In: Materialy do patologii i ochrony roslin oraz srodowiska, 39-71.

Smith I. M., Dunez J., Lelliott R. A., Phillips D. H., Archer S. A. 1988. European handbook of plant diseases. Blackwell Scientific Publications.