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Ethylene Production by Bipolaris sorokiniana and Curvularia geniculata on Methionine and Inorganic Salts. Mei-Yu Su, Junior Specialist of Technique Division, Department of Agriculture and Forestry, Taiwan Provincial Government, Chung-Hsing Village, Taiwan 54054, Republic of China. Clinton F. Hodges, Professor of Horticulture and of Plant Pathology, Department of Horticulture, Iowa State University, Ames 50011. Plant Dis. 73:398-401. Accepted for publication 21 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0398.

Chlorosis of Poa pratensis leaves infected by Bipolaris sorokiniana is due in part to elevated levels of endogenous ethylene in response to infection. The severity of the disease also is often enhanced by fertilization. Chlorosis does not occur in response to leaf infection by Curvularia geniculata, and the lesions produced are not affected by fertilization. B. sorokiniana requires methionine (MET) for the production of ethylene, but the effect of fertilizer salts on ethylene production by the pathogen is unknown. The ability of C. geniculata to produce ethylene on MET or fertilizer salts is unknown. Research was initiated to evaluate the ability of B. sorokiniana and C. geniculata to produce ethylene on a complex medium (leaf blade infusion of P. pratensis) and on a synthetic medium amended with 1 and 10 mM MET, (NH4)2 SO4, NH4NO3, or K2SO4. The two organisms produced ethylene in similar quantities on the unamended complex medium; no detectable level of ethylene was produced by either organism on the unamended synthetic medium. The addition of 1 or 10 mM MET to both media resulted in increased ethylene production by both organisms. Production was greatest (2,6003,000 pmol) on the complex medium, with the two organisms producing similar amounts, except that production by C. geniculata declined after 5 days of growth on the complex medium amended with 10 mM MET. The two organisms produced similar amounts of ethylene on the MET-amended synthetic medium, but not as much as on the complex medium. The inorganic salts at 1 or 10 mM had no effect on ethylene production by either organism when added to the complex medium, and at 1 mM they had no effect in the synthetic medium. The addition of 10 mM (NH4)2SO4 or NH4NO3 to the synthetic medium stimulated low-level ethylene production by B. sorokiniana but had little effect on C. geniculata.