Studies on the Fusarium Disease of Crops

1. The relation between rhizosphere fungi and the occurrence of damping-off of cucumber seedlings

Abstract

The present paper deals with the result of experiments on the rhizosphere microflora of cucumber seedlings and the effect of rhizosphere fungi on the damping-off of cucumber seedlings inoculated with Fusarium oxysporum f. cucumerinum.
Fusarium sp., Botrytis sp., Trichoderma sp., Penicillium sp., Aspergillus sp. and unidentified Basidiomycetes etc. were isolated from rhizosphere of cucumber seedlings. Fusarium spp. were most frequently isolated from the rhizosphere of cucumber seedlings.
^{Fusarium oxysporum} f. cucumerinum (F 22), when inoculated in sterilized soil, attacked cucumber seedlings and caused typical damping-off. Occurrences of pre-emergence and post-emergence damping-off of seedlings, however, were somewhat influenced by the presence of rhizosphere fungi in soil, and the occurrence of the both type damping-off was extensively delayed by the concomitant inoculation of F 22 with rhizosphere fungi. The extent of delay was remarkable when several fungi were inoculated concomitantly with F22. The retarded growth of seedlings due to the infection of F22 was also negated by additional presence of rhizosphere fungi.
These results suggested that occurrence pattern of pre-emergence and post-emergence damping-off in the field might be extensively influenced by the rhizosphere fungi.