壳聚糖对烟草黑胫病菌抑制作用

以烟草黑胫病菌（Phytophthora parasitica var nicotianae,Ppn）为材料，探讨了4种不同分子量的壳聚糖、壳聚糖的浓度和pH对烟草黑胫病菌的影响。结果表明，壳聚糖处理后烟草黑胫病菌菌丝出现畸变，正常的新陈代谢和细胞壁结构受到明显影响和破坏。在低浓度下（0．625mg·L^-1），壳聚糖抑菌效果随分子量增大而增强；分子量越小受浓度影响越大，浓度≥5mg·L^-1时，分子量为4．7×10^4的壳聚糖抑菌效果最强。除分子量5．0×10^3的壳聚糖外，其它分子量较大的壳聚糖受pH影响明显。壳聚糖分子量不同，其抑菌主要机理可能也不同，浓度、pH和分子量对其抑菌活性具有较强的影响。

Antifungal Activity of Chitosan against Phytophthora parasitica var nicotianae

The antifungal activity of chitosans with different molecule weights（MWs）, concentrations and pH against Phytophthora parasitica var nicotianae （Ppn）were investigated in the study, and the antifungal mechanisms were analyzed at the same time. As a result, the aberrance of mycelium was found, and the metabolism and cell wall were destroyed too. At the lowest concentration （0.625 mg· L^-1）, the antifungal effect increased with MWs increasing; and chitosans with lower MW would be more easily affected by its concentrations. At≥5 mg·L^-1 , the chitosan sample with the MW of 4.7 ×10^4 had the strongest antifungal activity. Chitosans were affected greatly by pH except for the one of 5.0×10^3. Chitosans had different antifungal mechanism with various MWs. The chitosan of 5.0×10^3 basically penetrated the fungi to kill or inhibit their growth, on the other hand, chitosans of 2.01×10^5 and 9.0×10^5 would be on the surface of fungi to form a membrane which could interfere the metabolism of Ppn, and the 4.7×10^4 one probably had the two mecha- nisms.