Suwandi Suwandi, Akino Seishi, Kondo Norio
Laboratory of Plant Pathology, Faculty of Agriculture, Sriwijaya University, Palembang, Indonesia.
Laboratory of Plant Pathology, Division of Bioresources and Product Science, Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Mycology. 2017 Jun 9;9(1):20-28. doi: 10.1080/21501203.2017.1336497. eCollection 2018.
spp., which are common inhabitants of oil palm leaves, are weak pathogens of common spear rot (CSR). We investigated the influence of osmotic stress on the growth, virulence, and activity of cell wall-degrading enzymes of CSR fungi, using potato dextrose agar (PDA) supplemented with KCl or sucrose (hyperosmotic medium). Hyperosmotic stress significantly inhibited mycelial growth, but growth rapidly recovered when mycelia were transferred to control medium. When inoculated into oil palm spear leaflets, sp., and precultured on 1.0 and 1.5 M KCl-hyperosmotic medium induced lesions that were two to four times larger than those in non-stressed cultures, suggesting enhanced virulence of the weak pathogens. Lesion size was not greatly affected in hyperosmotic cultures of moderately virulent . No activity of pectin lyase was detected in liquid cultures of the isolates. All isolates except BT48 secreted polygalacturonase (PG), which was active in both liquid cultures and inoculated leaves. Significantly increased PG activity (5-32-fold) was observed on leaves inoculated with hyperosmotic cultures of sp. and . These findings suggest that sp., and exhibit an adaptive physiological plasticity to hyperosmotic stress that results in enhanced virulence.
某些物种是油棕叶的常见栖息者，是常见叶斑病（CSR）的弱病原菌。我们使用添加了氯化钾或蔗糖的马铃薯葡萄糖琼脂（PDA）（高渗培养基），研究了渗透胁迫对CSR真菌生长、毒力及细胞壁降解酶活性的影响。高渗胁迫显著抑制菌丝生长，但当菌丝转移至对照培养基时，生长迅速恢复。当接种到油棕嫩叶片中时，某些物种在1.0和1.5M氯化钾高渗培养基上预培养后诱导产生的病斑比未受胁迫培养物中的病斑大两到四倍，这表明弱病原菌的毒力增强。在中等毒力的某些物种的高渗培养物中，病斑大小受影响不大。在所研究的某些物种的液体培养物中未检测到果胶裂解酶活性。除BT48外的所有分离株均分泌多聚半乳糖醛酸酶（PG），该酶在液体培养物和接种叶片中均有活性。在用某些物种和其他物种的高渗培养物接种的叶片上观察到PG活性显著增加（5至32倍）。这些发现表明，某些物种以及其他物种对高渗胁迫表现出适应性生理可塑性，从而导致毒力增强。
