坪草腐霉病菌毒素产生除草活性物质的条件优化

从多年生黑麦草上分离得到了5株腐霉菌(编号依次为PA1、PA2、PA3、PA4、PA5),通过鉴定,PA1和PA5菌株为瓜果腐霉菌(Pythiumaphanidermatum)。将所得5株菌株分别在PD培养基、PS培养基、玉米粉培养基、改良Fries培养基、Czapek-Dox培养基和Richard培养基中进行培养,所得培养滤液、粗毒素对马唐和反枝苋的除草生物活性进行了测定。结果表明,在PD培养基中所产生的毒素除草生物活性最强,在供试的5株菌株中以PA1菌株所产生的毒素除草活性最强。PA1菌株在PD培养基中培养所得粗毒素对马唐、反枝苋、虎尾草、金色狗尾草、野燕麦、稗草、藜7种杂草的生长有明显的抑制作用;对玉米、小麦有轻微药害,而对大豆安全。试验发现,PA1菌株产毒的适宜pH值为7.0,以培养5d的毒素除草活性最强;在100~150r/min条件下,振荡培养所得粗毒素的除草活性要明显高于静止培养。

The optimum production condition of the herbicidal substance from Pythium aphanidermatum

Five isolates (PA1, PA2, PA3, PA4, PA5) were isolated from Perennial ryegrass, of which PA1 and PA5 were identified to be Pythium aphanidermatum. All these 5 isolates were cultured in PD, PS, corn powders, modified Fries, Czapek-Dox and Rrichard media respectively then the bioactivity of the culture filtrate, crude toxin to Digitaria sanguinalis L.and Amaranthus retroflexus L. was tested. The results showed that the toxin from PD medium had the strongest herbicidal bioactivity, especially the toxin from isolate PA1. The crude toxin from PA1 in PD medium could significantly inhibit the growth of Digitaria sanguinalis L., Chloris virgata swartz, Setaria glauca L., Echinochloa crus-galli L., Avena fatua L.,Amaranthus retroflexus L.,Chenopodium album L. and had venial lesion to corn and wheat, but was safe to soybean. The results also showed that the toxin amount from PA1 was the highest 5th days' culturing, 100150 r/min vibration, and pH 7.0. PA1 could assimilate much more glucose than sucrose from the media.