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Detrimental and Protective Effects of Rust in Flax Plants of Varying Age. J. A. Hoes, Research scientist, Plant Pathology, Agriculture Canada, Research Station, Morden, Manitoba, R0G 1J0; D. G. Dorrell, head, Crop Science Section, Agriculture Canada, Research Station, Morden, Manitoba, R0G 1J0. Phytopathology 69:695-698. Accepted for publication 13 December 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-695.

Flax (Linum usitatissimum) plants in growth chambers showed differential effects on disease development, agronomic characteristics, and quality of the seed following inoculation one to three times, at different stages of development, with the virulent rust fungus, Melampsora lini race 371. Vulnerability increased with age of the plant and reached a maximum at the prebloom stage. Light to moderate infections reduced yield 3455% and severe infections reduced it 6479%. Oil and protein contents were reduced when plants were inoculated at prebloom and again at the flowering stage. Iodine number was not affected. Flax inoculated 3548 days after planting during the vegetative stage, and re-inoculated 1130 days later at the prebloom stage, showed an induced resistance to rust. Pre-inoculated plants were less severely rusted, and produced more seed capsules and seeds than those inoculated only at the prebloom stage. The induced resistance appeared to be systemic; the effect was apparent in foliage that developed after pre-inoculation. The protective effect lasted at least 30 days in flax cultivar Redwood 65. The significance of the protection phenomenon is discussed.

Additional keywords: linoleic acid, linolenic acid, oleic acid, systemic protection.