Abstract:

Two strawberry（Fragaria × ananassa Duch.）cultivars Toyonoka and Tutela as material，we studied the histological structure of strawberry roots，which infected by F. oxysporum f. sp. fragariae under the autotoxin 4-hydroxybenzoic acid stress by using paraffin slice. The results showed that the infection rate of hyphae of F. oxysporum f. sp. fragariae in root tissues of Toyonoka and Tutela under 4-hydroxybenzoic acid stress was faster than the treatment of only fungi-inoculated. The damages to the epidermis cells，cortex cells，stele cells and duct walls of Toyonoka and Tutela roots were more serious than the treatment of only fungi-inoculated，respectively. Moreover，the damage to the above-mentionedroot cells of Toyonoka was more serious than that of Tutela under 4-hydroxybenzoic acid stress. The proportions of vessel infected by hyphae both in the roots of Toyonoka and Tutela were increased significantly under 4-hydroxybenzoic acid stress，with 22.5% and 15.8%，respectively. The proportions of catheter with jelly was 26.3% in Tutela roots，which was higher than in Toyonoka roots with 16.3%. Under 4-hydroxybenzoic acid stress，the tylosis produced in root vessels of Tutela earlier than in root vessels of Toyonoka. The proportions of vessel with tylosis in roots of Tutela was 1.6%，higher significantly than in Toyonoka with 1.0% at both of them treated only by inoculating F. oxysporum，and higher significantly than in Tutela with 1.2% treated by inoculating F. oxysporum under 4-hydroxybenzoic acid stress. The damage to the strawberry root tissue significantly increased after inoculating F. oxysporum under 4-hydroxybenzoic acid stress，and Toyonoka roots wilt disease was more serious.

Key words: strawberry, roots, autotoxin, 4-hydroxybenzoic acid, histological structure, Fusarium oxysporum f. sp. fragariae