Cucurbit Genetics Cooperative Report 4:32-33 (article 16) 1981

Hypersensitivity to Anthracnose Infection in Citrullus lanatus

B. B. Rhodes

Edisto Experiment Station, P. O. Box 247, Blackville, SC 29817

Van der Plank (3) discussed the hypersensitivity reaction in plants as first defined by Muller. It includes the morphological and histological change that when produced by an infectious agent, elicit the premature dying of the infected tissue as well as the inactivation and localization of the infectious agent.

Two very different types of hypersensitive reactions to Colletotrichum lagenarium, isolate CIBR (2), have been noted in Citrullus lanatus. The most common type is rapid wilting and death of the infected leaf. The other type is not as common and does not elicit rapid wilting and death of the leaf. Instead, yellowing occurs around the lesion and may extend over the entire leaf. In some plants the pale area of the leaf is well defined; in others, the entire plant may be notably paler than normal.

In a line derived from PI 189225, initial lesions on plants showing leaf yellowing were smaller than lesions on plants hypersensitive to the pathogen. Plants in this line segregated into 38 non-hypersensitive, 16 hypersensitive. Another line derived from a single plant of PI 299778, which did not demonstrate the yellowing response to inoculation, did not exhibit the traits among eight progeny. F₂ progeny from a cross of 'Dixielee' with a plant of PI 299778, which did exhibit the trait, segregated 31: 5 for non-hypersensitivity: hypersensitivity.

Extracts from four young lesion-free leaves were taken from a single hypersensitive plant and a single non-hypersensitive plant of the PI 189225 progeny. Slab gel electrophoresis with SDS (1) revealed an additional protein in the extract from the hypersensitive plant.

Literature Cited

1. Conejero, V. and J. S. Semancik. 1977. Analysis of the proteins in crude plant extracts by polyacrylamide slab gel electrophoresis. Phytopathology 67: 1424-1426.
2. Sowell, Jr., G., B. B. Rhodes and J. D. Norton. 1980. New sources of resistance to watermelon anthracnose. J. Amer. Soc. Hort. Sci.105: 197-199.
3. Van der Plank, J. E. 1968. Disease Resistance in Plants. Academic Press, New York. p. 124.