Key message

In a grafted citrus tree, the leaf and root metabolic composition and the response to the phloem-limited pathogenic bacterium Candidatus Liberibacter asiaticus are influenced by the rootstock.

Abstract

Eleven different citrus rootstock varieties were investigated for their influence on the grafted tree response to Candidatus Liberibacter asiaticus (CLas), the pathogen associated with Huanglongbing (HLB). Rootstocks included mandarin and sweet orange cultivars, sour orange, and hybrids of citrus and trifoliate orange. Leaves and roots of healthy and CLas-infected greenhouse-grown plants were collected 6 months after graft inoculation and metabolite profiles were assessed by untargeted gas chromatography–time-of-flight-mass spectrometry (GC–TOF-MS). The genetic origin of the rootstock determined their metabolic profiles in the healthy state and influenced the root metabolic response to CLas. In the leaves, metabolic differences were determined by the tree response to CLas and to a lesser extent by the rootstock cultivar on which the plants were grafted. Among the leaf metabolites that responded most consistently to infection were citrulline, ornithine, and quinic acid, which were upregulated in infected plants. The reverse was found for cerotinic acid, cyanoalanine, hexadecane, and raffinose. In both leaves and roots, several metabolites associated with plant stress and disease tolerance such as benzoic acid and proline responded differently in plants on the mandarin × trifoliate hybrid rootstocks compared with the other rootstocks. This corresponds with the different HLB field tolerance of grafted trees on different rootstocks, which is generally higher in combination with some mandarin × trifoliate hybrids. Our results demonstrate the influence of rootstock on the grafted tree response to CLas and underscore the importance of rootstocks for disease management in an HLB-endemic environment.

中文翻译：

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砧木影响甜橙嫁接对亚洲假丝酵母的代谢反应

关键信息

在嫁接的柑橘树中，根茎会影响叶和根的代谢成分以及对韧皮部有限的致病菌假丝酵母念珠菌的反应。

抽象

研究了11种不同的柑橘砧木品种对嫁接树对亚洲假丝酵母的反应的影响（CLas），与黄龙病（HLB）相关的病原体。砧木包括柑桔和甜橙品种，酸橙以及柑桔和三叶橙的杂种。移植后6个月，收集健康的和经CLas感染的温室植物的叶子和根部，并通过无目标气相色谱-飞行时间质谱（GC-TOF-MS）评估代谢产物的分布。砧木的遗传起源决定了它们在健康状态下的代谢谱，并影响了根对CLas的代谢反应。在叶片中，代谢差异取决于树木对CLas的反应，在较小程度上取决于嫁接植物的砧木品种。对感染反应最持久的叶片代谢产物是瓜氨酸，鸟氨酸和奎尼酸，在被感染的植物中被上调。发现了相反的元素，其中涉及的是脂肪酸，氰丙氨酸，十六烷和棉子糖。在叶片和根中，与普通植物×三叶杂种砧木相比，与植物胁迫和抗病性相关的几种代谢产物，例如苯甲酸和脯氨酸，对植物的反应不同。这与不同砧木上嫁接树对HLB的不同耐受性相对应，与一些普通话×三叶杂种结合使用时通常更高。我们的结果证明了砧木对嫁接树对CLas反应的影响，并强调了砧木对于HLB流行环境中疾病管理的重要性。在叶片和根中，与普通植物×三叶杂种砧木相比，与植物胁迫和抗病性相关的几种代谢产物，例如苯甲酸和脯氨酸，对植物的反应不同。这与不同砧木上嫁接树对HLB的不同耐受性相对应，与一些普通话×三叶杂种结合使用时通常更高。我们的结果证明了砧木对嫁接树对CLas反应的影响，并强调了砧木对于HLB流行环境中疾病管理的重要性。在叶片和根中，与普通植物×三叶杂种砧木相比，与植物胁迫和抗病性相关的几种代谢产物，例如苯甲酸和脯氨酸，对植物的反应不同。这与不同砧木上嫁接树对HLB的不同耐受性相对应，与一些普通话×三叶杂种结合使用时通常更高。我们的结果证明了砧木对嫁接树对CLas反应的影响，并强调了砧木对于HLB流行环境中疾病管理的重要性。这与不同砧木上嫁接树对HLB的不同耐受性相对应，与一些普通话×三叶杂种结合使用时通常更高。我们的结果证明了砧木对嫁接树对CLas反应的影响，并强调了砧木对于HLB流行环境中疾病管理的重要性。这与不同砧木上嫁接树对HLB的不同耐受性相对应，与一些普通话×三叶杂种结合使用时通常更高。我们的结果证明了砧木对嫁接树对CLas反应的影响，并强调了砧木对于HLB流行环境中疾病管理的重要性。