Apple proliferation disease is caused by the phloem-dwelling bacterium ‘Candidatus Phytoplasma mali’, inducing morphological changes in its host plant apple, such as witches’ broom formation. Furthermore, it triggers physiological alterations like emission of volatile organic compounds or phytohormone levels in the plant. In our study, we assessed phytoplasma-induced changes in the phloem by sampling phloem sap from infected and non-infected apple plants. In infected plants, the soluble sugar content increased and the composition of phloem metabolites differed significantly between non-infected and infected plants. Sugar and sugar alcohol levels increased in diseased plants, while organic and amino acid content remained constant. As ‘Ca. P. mali’ is vectored by the phloem-feeding insect Cacopsylla picta (Foerster, 1848), we assessed whether the insect–plant interaction was affected by ‘Ca. P. mali’ infection of the common host plant Malus domestica Borkh. Binary-choice oviposition bioassays between infected and non-infected apple leaves revealed C. picta’s preference for non-infected leaves. It is assumed and discussed that the changes in vector behavior are attributable to plant-mediated effects of the phytoplasma infection.

苹果增殖病是由韧皮部栖菌“引起暂定植原体马里”，诱导在其宿主植物苹果形态变化，例如丛枝形成。此外，它还会触发生理变化，例如植物中挥发性有机化合物的排放或植物激素水平。在我们的研究中，我们通过从感染和未感染的苹果植物中提取韧皮部液汁来评估韧皮部的植物质诱导变化。在被感染植物中，未感染植物和被感染植物之间的可溶性糖含量增加，韧皮部代谢产物的组成明显不同。患病植物中糖和糖醇含量增加，而有机和氨基酸含量保持恒定。作为“钙。P. mali'是由韧皮部食虫Cacopsylla picta（Foerster，1848）引诱的，我们评估了昆虫与植物之间的相互作用是否受Ca的影响。P. mali'感染了常见寄主植物Malus domestica Borkh。受感染和未感染的苹果叶片之间的二元选择产卵生物测定法揭示了C. picta偏爱未感染的叶片。假定并讨论了载体行为的变化可归因于植物介导的质体感染的影响。