Production of volatiles from decomposing plant tissues and effect of these volatiles on Rhizoctonia solani in culture

Abstract

Volatiles, of which NH₃ is a major component, were evolved from decomposing immature corn tissue (C:N 9) and affected R. solani in culture two ways: they supplied additional nitrogen to the growth medium so that fungal mycelial growth increased; and they raised substrate pH from 5.5 to 8.2 which induced melanization of mycelium. Volatiles increased fungus growth and pigmentation within 2 weeks of amendment addition to soil. Increases were concomitant with NH₃ production from corn tissue. More NH₃ evolved from decomposing corn tissues of C: N 9 and 17 than from those of C:N 33 and 81. More growth and pigmentation occurred in flasks through which volatiles from decomposing corn (C: N 9) were passed than in flasks through which volatiles from nonamended soil or decomposing com (C: N 81) were passed. Carbon dioxide from decomposing tissues did not affect growth or pigmentation. Twice as much NH₃ evolved from corn tissue (C: N 9) which decomposed in saturated soil than from tissue which decomposed in soil at 50% of its water-holding capacity. Pigment production doubled under saturated conditions.