ユウガオつる割病の種子伝染に関する研究 : III. 保菌種子の発芽から発病に至る過程

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Seed coat of bottle gourd, Lagenaria siceraria STANDL, remained, in most cases, attached to the pegs of seedlings after germination and serves as primary inoculum for the increment of inoculum potential of Fusarium oxysporum f. sp. lagenariae. Infection rate of seedlings with pegs accompanied by seed coat was 14-18%, while that of seedlings having their seed coats attached to cotyledons was 2-3%. Among various parts of seedlings, the density of Fusarium propagules was highest in pegs followed by roots, When roots or pegs were inoculated, the rate of disease outbreak was as high as 90-100% irrespective of inoculation methods. When hypocotyls or cotyledons were wound-inoculated, seedlings were infected, but practically no disease occurred when these parts were inoculated without wounding, Thus the pegs and roots were the major sites for the penetration by the fungus. Histological observation indicated that the fungus penetrates lower side epidermis of the pegs and extends its hyphae throughout the tissues of the pegs. The results suggest that in the process of germination of seeds the fungus latent in the infected seed coat multiplies in the tissues to build up the inoculum potential to a level that is sufficient for establishing infection and that the penetration of the fungus to seedling takes place mostly from the lower side epidermis of pegs.
1977-07-25