Abstract
This paper reports the results of experiments on the influence of Forsyth's fractions A, B, C, and D of Tiurin's fulvic acid on the growth of Helicobasidium mompa Tanaka and Rosellinia necatrix (Hartig) Berlese, the causal agent of violet root rot and white root rot, respectively.
The results obtained are summarized as follows:
1. The Forsyth's fractions A and B showed marked growth-promoting effects on H. mompa and R. necatrix. The same effects were not evident in the case of the fractions C and D.
2. The fraction A was well utilized by both H. mompa and R. necatrix as a carbon source, and the latter also slightly utilized the fraction as a nitrogen source.
3. The fraction B had no nutritive effect on the growth of H. mompa and R. necatrix.
4. The fraction C was utilized by both H. mompa and R. necatrix as carbon and nitrogen sources.
5. The fraction D had no nutritive effect on the growth of H. mompa, but exhibited a marked growth-inhibiting effect on it. The fraction, however, was slightly utilized by R. necatrix as a carbon source, showing no evident inhibiting effect on the growth of the fungus.
6. It seems that the predominance of H. mompa in uncultivated soil and its extinction in old cultivated one are connected with the variation of the organic constituents of fulvic acid in soil, i.e., the increasing fraction D of fulvic acid in cultivated soil retards the growth of H. mompa, and therefore accelerates the decrease of the fungus.
