Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, 79409, USA.
Cropping Systems Research Laboratory, USDA-ARS, Lubbock, TX, 79415, USA.
Planta. 2023 Jul 20;258(2):46. doi: 10.1007/s00425-023-04194-0.
We found four indicative traits of innate immunity. Sorghum-resistant varieties had a greater trichome, stomatal and chloroplast density, and smaller mesophyll intercellular width than susceptible varieties. The sorghum aphid (SA), Melanaphis sorghi (Theobald), can severely reduce sorghum yield. The contribution of structural traits to SA resistance has not been extensively studied. Moreover, the current screening method for resistance is inherently subjective for resistance and requires infestation in plants. Quantifying the microanatomical basis of innate SA resistance is crucial for developing reliable screening tools requiring no infestation. The goal of this study was to identify structural traits linked to physical innate SA resistance in sorghum. We conducted controlled environment and field experiments under no SA infestation conditions, with two resistant (R. LBK1 and R. Tx2783) and two susceptible (R. Tx7000 and R. Tx430) varieties. Leaf tissues collected at the fifth leaf stage in the controlled environment experiment were analyzed for the epidermal and mesophyll traits using light and transmission electron microscopy. Leaf tissues collected at physiological maturity in the field experiment were analyzed for surface traits using scanning electron microscopy. Our results showed that stomatal density, trichome density, trichome length, and chloroplast density are key leaf structural traits indicative of physical innate SA resistance. We found that resistant varieties had a greater density of trichomes (39%), stomata (31%), and chloroplast (42%), and smaller mesophyll intercellular width (- 52%) than susceptible varieties. However, the chloroplast, mitochondria, and epidermal cell ultrastructural traits were ineffective indicators of SA resistance. Our findings provide the foundation for developing an objective high-throughput method for SA resistance screening. We suggest a follow-up validation experiment to confirm our outcomes under SA infestation conditions.
我们发现了先天免疫的四个指示特征。与感病品种相比，高粱抗性品种的表皮毛、气孔和叶绿体密度更大，叶肉细胞间隙更小。高粱蚜虫（SA），麦二叉蚜（Melanaphis sorghi），可以严重降低高粱产量。结构特征对 SA 抗性的贡献尚未得到广泛研究。此外，目前的抗性筛选方法对于抗性来说具有内在的主观性，并且需要在植物上进行侵染。量化先天 SA 抗性的微观解剖基础对于开发不需要侵染的可靠筛选工具至关重要。本研究的目的是确定与高粱物理先天 SA 抗性相关的结构特征。我们在没有 SA 侵染的条件下进行了受控环境和田间实验，使用了两个抗性（R. LBK1 和 R. Tx2783）和两个感病（R. Tx7000 和 R. Tx430）品种。在受控环境实验中，从第五叶期采集叶片组织，使用光镜和透射电子显微镜分析表皮和叶肉特征。在田间实验中，从生理成熟时采集叶片组织，使用扫描电子显微镜分析表面特征。我们的结果表明，气孔密度、表皮毛密度、表皮毛长度和叶绿体密度是指示物理先天 SA 抗性的关键叶片结构特征。我们发现，抗性品种的表皮毛（39%）、气孔（31%）和叶绿体（42%）密度较大，叶肉细胞间隙较小（-52%），而感病品种则较小。然而，叶绿体、线粒体和表皮细胞超微结构特征不是 SA 抗性的有效指标。我们的发现为开发客观的高通量 SA 抗性筛选方法奠定了基础。我们建议进行后续验证实验，以确认我们在 SA 侵染条件下的结果。
