甾醇生物合成抑制剂粉锈宁对苹果黑星病菌发育的影响

摘要

采用电子显微镜和细胞化学技术，研究了杀菌剂粉锈宁（甾醇生物合成抑制剂）对苹果黑星病菌在苹果叶片上发育的影响。观察结果表明，接种前24h施药对病菌入侵有明显的影响。表现为分生孢子的萌发受阻，推迟萌发及萌发率降低；并引起芽管畸形，不能形成附着胞。接种后6天（显症前）施药，可引起叶片角质层下菌丝细胞和子座细胞的原生质坏死、细胞壁不规则增厚及液泡增大，从而使菌丝进一步发育受阻。接种后12天（显症后）施药，不仅导致菌丝、子座细胞发生上述变化，而且引起分生孢子和分生孢子梗塌陷、畸形，阻止了病菌的进一步产孢和扩展。细胞化学定位分析结果表明，β-1,3-葡聚糖和几丁质这两种胞壁主要成分在对照菌丝和药剂处理后的菌丝细胞壁内含量有很大差异。在药剂处理的菌丝细胞壁中，这两种成分的标记密度明显高于对照菌丝，表明杀菌剂对病菌质膜透性的不利影响使β-1,3-葡聚糖和几丁质在菌丝细胞壁中过度累积。%The effects of Triadimefon, an ergosterol biosynthesis-inhibitingfungicide, on development of apple scab pathogen, Venturia inaequalis on the leaves were examined by means of scanning and transmission electron microscopy as well as cytochemical labeling techniques. The results showed that the fungicide retarded the germination of conidia, caused deformation of germ tubes and inhibited formation of appressoria on the leaves treated with fungicide 1 day before inoculation. The application of the fungicide 6 days after inoculation (before symptom appearing) caused the pronounced ultrastructural changes in the subcuticular hyphae and the conidial stroma. These changes included protoplasm necrosis, irregularly thickenings of cell walls and enlargement of vacuoles in the hyphal cells, which disrupt the further development of the pathogen in fungicide-treated leaves. Furthermore, the collapsed or flattened conidia and conidiophore were often detected on the leaves treated with the fungicide 12 days after inoculation (after symptom appearing), and the subcuticular hyphae, conidial stroma and conidiophore also showed markedly alterations in the cytoplasm and cell walls. These results indicated that the fungicide had adverse effects on the continuing sporulation and development of the pathogen. Moreover, cytochemical labeling of β-1,3-glucan and chitin occurred in the cell walls of the hyphae from the fungicide-treated and the untreated leaves. However, the labeling densities for these two cell wall components were much greater in the cell walls of the hyphae from the fungicide-treated leaves than those from the untreated leaves, indicating the excessive accumulation of β-1,3-glucan and chitin in the cell walls after fungicide treatment due to the detrimental effects of the fungicide on the structure and functions of the hyphal membrane.