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Ecology and Epidemiology

Competition Between Ergots of Claviceps purpurea and Rye Seed for Photosynthates. C. W. Bacon, Toxicology and Biological Constituent Research Unit, USDA-ARS, Richard Russell Agricultural Research Center, Athens, GA 30613; E. S. Luttrell, Department of Plant Pathology, University of Georgia, Athens 30602. Phytopathology 72:1332-1336. Accepted for publication 17 March 1982. 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, 1982.. DOI: 10.1094/Phyto-72-1332.

Competition between developing ergots (sclerotia) of Claviceps purpurea and developing seed for 14C-labeled photosynthates translocated from leaves of intact infected rye plants was compared with translocation of 14C-labeled photosynthates into seeds of healthy plants. The study included the 6-wk period between anthesis and maturation of the rye seed on plants grown under field conditions. The assimilation of the 14C-labeled photosynthates by seeds and ergots during this period was determined by measuring total sugars, sugar alcohols, amino acids, organic acids, lipids, proteins, RNA, and DNA. Competition for photosynthates followed the early establishment of the stromatic foot, the absorbing organ of the parasite, which remained active during the entire 6 wk even though the sclerotial tissue located above had matured in 34 wk and no longer incorporated photosynthates. The flow of nutrients into the sclerotium decreased as it developed acropetally. Seeds and sclerotia of diseased rye plants incorporated more 14CO2 than did seed of healthy plants, which reflected a larger and more efficient energy sink. Seeds from healthy plants completed development at the end of the 6-wk period as indicated by dry weights and decline in the uptake of photosynthates. However, development of competing seeds on infected plants was retarded until the fourth week when high levels of translocation and increases in dry weight resumed after a concurrent decline in photosynthate translocated to competing ergots.

Additional keywords: Secale cereale, infection, parasitic development, host-parasite relationships, 14CO2 assimilation.