定向筛选提高棉花抗枯萎病的病理学机制

以病圃定向筛选抗枯萎病大幅度提高的棉花材料和原感病品种为对象,研究接种枯萎病菌Fusarium oxysporum f.sp.vasinfectum后抗、感材料的病理学变化。结果表明,二者在宏观病理学方面存在差异,感病品种接种7天开始显症,25天严重发病,整株维管束变色;抗病材料生长健康或只有轻微症状,维管束变色部位仅局限在子叶节以下。在细胞和组织病理学方面二者也存在差异,侵入前期,抗病材料被侵入细胞中有细胞壁加厚现象;侵入中期,病菌可通过表皮层侵入感病品种的薄壁组织,但只能到达抗病材料的皮层组织中;侵入后期,抗病材料中出现大量寄主细胞的降解物质或分泌物将菌丝包围,阻止病菌进一步扩展。抗病材料的抗侵入和抗扩展能力均较感病品种大幅度增强。

Pathologic changes of Fusarium wilt resistant descendants obtained from susceptible cotton variety by directional selection in disease plot

The pathologic changes between susceptible cotton variety and its resistant descendants obtained by directional selection in disease plot were studied. The results showed that the differences in macroscopical symptoms is the susceptible cotton varieties showed symptom after inoculated for 7 days, and became severe after 25 days. However, there had only slight symptom or no symptom in the resistant descendants at the meantime. Furthermore, all the vascular tissues turned brown in the susceptible cotton varieties, but in the resistant descendants, the brown regions were only restricted below the hypocotyls. As to the cytology and cell ultrastructure of host, in the invading prophase, the cell wall of the invaded part of resistant descendants was congregated with wall apposition. In the invading metaphase, the hyphae of the pathogen can invade the cortical area of cells of susceptible varieties, but only can invade the outer cortex cells of resistant descendants. In the invading anaphase, more abundant aggregated deposits and secretion were emerged to surround the fungal cells in resistant descendants so as to prevent the hyphae to spread. In general, resistant descendants have more ability in resistant pathogen infection and spread than the susceptible variety.