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LEWIS J. A.; PAPAVIZAS, G. C.
Soil Science: September 1974
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ABSTRACTPlant tissues of low C:N ratio decomposed in soil with the formation of volatiles which increased growth of R. solani in culture and induced pigmentation of its mycelium. The effective plant tissues included vegetable crop residues of C:N <15 and immature grain crop residues (corn, oat, rye, barley, sorghum, buckwheat). Volatiles from decomposing plant tissues of high C:N ratio did not affect the fungus mycelium in any way. The dark pigment, formed in culture, is melanin or a melaninlike pigment. An assay procedure for the pigment is described. The effective volatile is a low molecular weight alkaline fraction containing ammonia and/or an amine soluble in boric acid. Both pigmentation and fungus growth increased in response to greater amouts of effective volatiles. Five isolates of R. solani responded similarly to the volatiles. Saprophytic activity of the fungus in soil, through which effective volatiles were passed, decreased significantly. Viability of the pathogen in buckwheat-stem segments in response to decomposing cabbage tissue vapor decreased over the control by 56 percent. The same vapors reduced colonization of the substrate by R. solani from soil by 74 percent.

Plant tissues of low C:N ratio decomposed in soil with the formation of volatiles which increased growth of R. solani in culture and induced pigmentation of its mycelium. The effective plant tissues included vegetable crop residues of C:N <15 and immature grain crop residues (corn, oat, rye, barley, sorghum, buckwheat). Volatiles from decomposing plant tissues of high C:N ratio did not affect the fungus mycelium in any way. The dark pigment, formed in culture, is melanin or a melaninlike pigment. An assay procedure for the pigment is described. The effective volatile is a low molecular weight alkaline fraction containing ammonia and/or an amine soluble in boric acid. Both pigmentation and fungus growth increased in response to greater amouts of effective volatiles. Five isolates of R. solani responded similarly to the volatiles. Saprophytic activity of the fungus in soil, through which effective volatiles were passed, decreased significantly. Viability of the pathogen in buckwheat-stem segments in response to decomposing cabbage tissue vapor decreased over the control by 56 percent. The same vapors reduced colonization of the substrate by R. solani from soil by 74 percent.

© Williams & Wilkins 1974. All Rights Reserved.