Abstract
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.
Highlights
Most phloem-limited plant pathogens, such as viruses and bacteria
The plants infection status had a significant influence on Brix value of phloem sap samples (LM, F = 12.73, df = 1,31, p = 0.001) with increased values in ‘Ca. P. mali’ infected plants compared to non-infected apple plants (Fig. 1)
Online Resource 2), sorbitol, sucrose and quinic acid were the compounds with the greatest quantities
Summary
Most phloem-limited plant pathogens, such as viruses and bacteria The provisional genus ‘Candidatus Phytoplasma’ (Firmicutes: Mollicutes) (formerly known as mycoplasma-like organisms) combines obligate biotrophic prokaryotes characterized by the lack of a cell wall as well as a reduced genome (IRPCM Phytoplasma/Spiroplasma Working Team–Phytoplasma Taxonomy Group 2004; Oshima et al 2004) These Mollicutes can only survive endocellularly in plant phloem or different tissues of vector insects (Lee et al 2000). We assessed the impact of ‘Ca. P. mali’ infection on the phloem composition of apple plants and investigated possible effects on the host acceptance behavior of the vector insect C. picta. We investigated the host acceptance behavior of the vector C. picta in binary-choice oviposition bioassay on apple plants infected and non-infected with ‘Ca. P. mali’. The importance of this multitrophic interaction of the vectorphytoplasma–plant-system was considered with regard to the epidemiology of ‘Ca. P. mali’ and to pest control approaches of the vector C. picta
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
