葱叶枯病菌在活体外可以产生致病毒素, 用改良PS 培养基培养所得滤液经TLC 分离获得Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ 5 种组分, 其Rf 值分别为0.31、0.47、0.74、0.80 和0.90, 在乙醇中最大紫外吸收峰分别为240、247、223、236 和258 nm。生物测定结果表明, 组分Ⅱ、Ⅲ、Ⅳ对马唐的生长有明显的抑制作用, 其中以组分Ⅳ 生物活性最高。粗毒素对禾本科杂草种子萌发抑制效果高于对阔叶杂草, 而对玉米、水稻、油菜等种子萌发影响很小。试验还发现, 毒素对马唐的防效最高, 与百草枯药效相当。毒素对马唐叶绿素a 的含量影响不大, 但对叶绿素b 和叶绿素总含量影响较大。
S temp hy lium botry osum could p roduce patho toxin in v itro. F ive fract ions (Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ ) had been obtained by TLC and HPLC ch romatography, their Rf-values w ere 0.31, 0.47, 0.74, 0.80 and 0.90,and their max. ult ravio let abso rp t ion w ere 240, 247, 223, 236 and 258nm , respectively. Three fractions (Ⅱ、Ⅲ、Ⅳ ) st rongly inh ibited the growth of Digitaria sanguinalis, among them the fraction Ⅳ had the highest activity. The inh ibito ry effect of crude toxin on the germination of gramineous weed seeds was much higher than that of the broad-leaf weeds. This toxin has little influence on the seeds ofmaize, rice, rape and Chinese cabbage. The results of the greenhouse potexperiment indicated that the defensive effect of the crude toxin on Digitaria sanguinalis was the highest, equal to the effect of paraguar. Mo reover the toxin could affect the content of Chlorophyll in Digitaria sanguinalis; and especially the content of Chlorophyll-b.