Studies on Fusarium species associated with a field planting of 'pathogen-tested' potatoes

Abstract

Bacillus subtilis (isolate 1-B80) and Streptomyces griseus (isolate 2-A24), both antagonistic to Fusarium species, were applied to 'pathogen-tested' cuttings of the potato cultivars Kennebec and Sequoia, and to their potting soil, before transplanting to the field. No data were obtained to indicate that either microorganism reduced Fusarium infection of tubers from these transplants. However, the Fusarium population was significantly less at 70 days in soil proximal to Sequoia transplants treated with either microorganism, and to Kennebec transplants treated with S. griseus. Tuber yields were significantly greater from Sequoia, but not from Kennebec when treated with either microorganism. Six Fusarium species were isolated from infected tubers, F. oxysporum being the commonest. In most instances, infection was confined to one tuber per plant. There was no correlation between tuber infection and stem injury, nor between tuber infection and soil population. In the laboratory, the addition of B. subtilis and S. griseus to soil from the experimental site significantly reduced estimates of the Fusarium population for 70 and 140 days respectively.