桉树叶片的解剖结构与其对焦枯病抗性的关系

Relationship between the leaf anatomical characteristics of Eucalyptus and its resistance to dieback

选取福建省11个桉树(Eucalyptus spp)主栽种系中对焦枯病(Clindrocladium quinqueseptatum)的高抗种系巨赤桉9224和高感种系巨桉5号进行叶片解剖结构特征研究,结果表明:(1)巨赤桉9224的叶片蜡质含量明显高于巨桉5号,桉树叶片的蜡质层是抵抗和延迟病原菌侵入的最外层防线;(2)2种桉树下表皮气孔密度与其抗病性相关性小,而巨赤桉9224的气孔小,气孔下陷更深,不利于病原侵入,表现出抗性高;(3)巨赤桉9224的叶片比巨桉5号厚,表现为上下表皮角质层厚,栅栏组织细胞层数更多,栅栏组织/海绵组织比大,叶肉细胞排列更紧密,可以抵抗病菌的侵入和扩展,成为抗病的又一个结构屏障;(4)巨赤桉9224的叶绿体数量多,累积淀粉多,抗性也随之增强。据此可以把桉树叶片蜡质含量作为鉴定桉树种系抗性的一种快速手段,桉树叶片厚度、栅栏组织厚度及其细胞排列紧密度作为桉树抗焦枯病的辅助指标。

Eucalyptus grandis × urophylla No. 9224 with highly resistant to Clindrocladium quinqueseptatum and E. grandis No. 5 with low resistance to Clindrocladium quinqueseptatum were selected from 11 cultivars in Fujian Province to reveal their leaf anatomical structure characteristics. The results showed： 1 ） Since the wax layer is the outermost resistant layer to resist and delay the infection of pathogens, the wax content of E. grandis × urophylla No.9224 was significantly higher than that of E. grandis No.5;2） The stomatal density of the abaxial epidermis of the 2 cultivars had little relationship with its resistance to C. quinqueseptatum. The leaf structure characteristics of smaller stomatal size and deeper depression stomata of E. grand/s × urophylla No. 9224 could resist to the invasion of pathogens and showed higher resistance to Eucalyptus dieback;3） Compared with E. grand/s No.5, E. grand/s × urophylla No.9224 had thicker leaf, thicker cuticular, more cell layers of palisade tissue, higher ratio of palisade tissue/sponge tissue, compacter misophyll tissue, which becomes another structural barrier for resisting the invasion and extension of pathogens;4） E. grand/s × urophylla No. 9224 had more chloroplast, more starch and other organic matter which makeits resistance stronger. Therefore, the content of leaf wax layer could be used as a key measure to identify the resistance of the different cultivars. The thickness of leaf, palisade tissue and palisade tissue density also could be used as assistant indexes for detecting the resistance to Eucalyptus dieback.