立枯丝核菌毒素的产生及与致病力的关系

Toxin Produced by Rhizoctonia solani and Its Relationship with Pathogenicity of the Fungus

立枯丝核菌(Rhizoctonia solani)培养滤液经活性炭吸附、甲醇洗脱、旋转蒸发浓缩获得粗毒素。生物活性测定表明:该粗毒素能诱发水稻叶片产生似纹枯病的典型症状,明显抑制水稻胚根生长,致使水稻幼苗萎蔫;粗毒素浓度越高,作用越强,当稀释至200倍时仍具有一定生物活性;不同菌株产毒能力差异明显,且与致病力呈显著正相关。这些结果显示毒素在病菌致病过程中起重要作用。病菌最佳产毒条件为:菌丝在改良Richard培养液(pH 7)中,25～30℃下黑暗培养15～20 d,每隔6或12 h人工振荡1次。水稻不同抗(特青和J-85)、感(LMNT)品种的胚根和幼苗对粗毒素的敏感性有较大差异,预示毒素可用于水稻品种抗纹枯病的初步鉴定。

The crude toxin of Rhizoctonia solani was extracted from the culture filtrate by the absorption of active carbon with methanol as eluent, and concentrated by the evaporation using rotavapor. The bioassay results showed that the crude toxin could induce the characteristic symptom of sheath blight on rice leaves, and inhibit the growth of rice radicle significantly and make rice seedling wilting. The higher the concentration of the crude toxin was, the more virulent it was. When the crude toxin was diluted by 200 times, it still had some biological activity. It was found that there was a significant difference in the ability of toxin production among the isolates of this fungus, with a positive correlation between toxin production ability and pathogenicity of the fungus, which indicated the toxin played an important role in the pathogenesis. The optimum conditions for the toxin production were studied. The mycelia should be cultured in modified Richard's medium (pH 7) for 15 - 20 days at 25 - 30 ℃ . in darkness and shaking in hand one time every 6 or 12 hours. Furthermore, it was found that the radicles and seedlings of resistant rice cultivars (TEQIN and J-85) were more tolerant to the crude toxin than those of the susceptible one (LMNT), which showed that the resistance of rice varieties could be primarily identified by the toxin treatment of rice radicles and seedlings.