The effect of reduced phytoalexin production on the resistance of upland cotton (Gossypium hirsutum) to Verticillium and Fusarium wilts

摘要

The effect on disease development of inhibiting the production of the sesquiterpenoid phytoalexin hemigossypol in cotton resistant to Verticillium and Fusarium wilts, was investigated. Inhibition was achieved by treating the plants with the sodium salt of compactin, a competitive inhibitor of hydroxy-methylglutaryl (HMG) CoA reductase. Compactin treatment (150 mug/litre) reduced hemigossypol production by a mean of 48%. The enzyme inhibitor did not mimic symptoms in uninfected plants or significantly reduce conidial germination of Fusarium oxysporum f.sp. vasinfectum or V. dahliae. Treatment of infected plants with compactin resulted in a breakdown of resistance to Verticillium wilt but not to Fusarium wilt. It is suggested that hemigossypol production is the primary mechanism of resistance to Verticillium wilt, but not to Fusarium wilt.