氟乐灵处理后棉苗对枯萎病菌的抗侵入及抗扩展特性

 以1μg/g土的氟乐灵播前土壤处理,棉花出苗后移栽到无氟乐灵的土壤中并接种棉花枯萎病菌(Fusarium axysporum f.sp.vasinfectum)。结果表明氟乐灵处理明显降低了棉苗枯萎病的株发病率和病情指数,提高了棉苗对枯萎病的抗病性。氟乐灵处理组棉苗根部和茎部枯萎病菌侵染率均低于对照组,特别是上部茎片段中处理组侵染率降低更为明显。氟乐灵处理组棉苗根部和茎部的菌量明显降低,而且处理组茎部菌量的增长明显滞后于对照。以上结果表明,病菌对氟乐灵处理棉苗根部的侵入和病菌在棉苗体内的纵向扩展及增殖受到了阻抑,因而氟乐灵处理后棉苗对枯萎病菌的抗性表现了抗侵入和抗扩展的特性。试验还证明,氟乐灵处理并接种病菌的棉苗茎部组织中类萜烯醛的含量明显提高;并产生一种能抑制病菌大型分生孢子萌发的真菌毒性物质。这些抑菌物质的产生和积累可能与抗扩展特性有关。

TRIFLURALIN INDUCED RESISTANCE OF COTTON SEEDLINGS AGAINST INVASION AND DEVELOPMENT OF FUSARIUM OXYSPORIJM F. SP. VASINFECTUM

Cotton (Gossypium hirsutum) seedlings grown in the soil incorporated with trifluralin at 1@g a. i/g soil were transplanted into trifluralin-free soil inoculated with Fusarium oxysporum f. sp. vasinfectum. It was found that the disease incidence and severity of trifluralin-treated seedlings were significantly reduced in comparison with those of untreated ones. The infection rates of the fungus in the treated root samples were lower than those in the untreated plants. The reduction of the fungal infection rates was also demonstrated in the stem samples of treated seedlings, especially in the upper sections of the stem. Moreover, the inoculum densities recovered from both roots and stems of the treated seedlings were much lower than those from corresponding segments of the untreated ones. In comparison with the control, the treated seedlings showed delayed increase of the inoculum density in their stem samples after the inoculation. It was suggested that trifluralin treatment suppress the fungal invasion in the roots and its upward development in cotton seedlings. Accumulation of terpenoid aldehyde was detected in the stem tissues of trifluralin-treated seedlings. The extracts from the treated and inoculated stem tissues shown inhibition effect on germination of the fungal macroconidia. Therefore, the production and accumulation of terpenoid aldehyde and unidentified substances with inhibition effect on the fungus may be involved in the induced-resistance to the fungal development in cotton tissues.