Population genomic analysis of factors influencing Phytoplasma transmission
Abstract
Phytoplasmas are obligatory endosymbiontic bacteria that colonize the phloem of many plant species and cause hundreds of plant diseases worldwide. In nature, phytoplasmas are primarily transmitted by hemipteran vectors of the families Cicadellidae, Cixiidae, and Psyllidae. While, in principle, all phloem sucking insects could transmit phytoplasmas, only a limited number of species have been confirmed as vectors. This is because the transmission efficiency of phytoplasmas is a function of the complex tripartite association between the insect vector, the host plant, and the phytoplasma itself. Recent findings revealed that the microbial communities of both the insect vector and the host plant may interfere with phytoplasma transmission, making this system an even more complex multipartite one. Apple proliferation (AP) is a disease caused by the phytoplasma ‘Candidatus Phytoplasma mali’, causing proliferation of auxiliary shoots and a decrease in fruit size and quality. It is not possible to cure infected apple trees, and the only way to limit the spread of the disease is to completely remove infected trees from the orchards. ‘Candidatus P. mali’ is mainly vectored between apple trees by two psyllids, Cacopsylla picta and Cacopsylla melanoneura. The genus Cacopsylla contains both transmitters and non-transmitters of phytoplasma, and transmission efficiency is not necessarily species-specific, that is, within a species, some geographic variants can transmit phytoplasmas, while others cannot. In detail, C. melanoneura, assumed to be the main vector of AP phytoplasma in Northwestern Italy, but is a poor transmitter in Northern Italy and other parts of Europe. In contrast, C. picta is the primary vector in most European populations with variable transmission rates among populations. Other occurring Cacopsylla species do not transmit phytoplasmas. Knowledge about factors influencing the transmission efficiency of ‘Ca. P. mali’ is currently scarce. We aim to address the question of what causes different phytoplasma transmission efficiencies. We propose to use, for the first time, population genomic tools to study the tripartite interaction between the phytoplasma, the vector, and its microbiome. Specifically, we will perform: 1) genome sequencing and characterization of various vector populations; 2) genome characterization of the ‘Ca. P. mali’ strains carried by these populations, and 3) comparative genome sequencing of various endosymbionts present in the vector populations. Our goal is to determine key factors affecting transmission and test transmission efficiency directly via in vivo acquisition trials. We shall determine if AP acquisition and transmission depends on the genotype of the insect vector, on the vector's microbial community, and/or on the phytoplasma strain. Our results will provide novel insights into the complex biology of ‘Ca. P. mali’ transmission and will be therefore an important milestone in combatting this disease.
Phytoplasma Psyllidae Microbiome Endosymbionts Genome
Publikationen
Project staff
Christian Stauffer
Ao.Univ.Prof. Dipl.-Ing. Dr.nat.techn. Christian Stauffer
christian.stauffer@boku.ac.at
Tel: +43 1 47654-91631
BOKU Project Leader
01.02.2020 - 31.10.2024
BOKU partners
External partners
University of Turin
Dr. Rosemarie Tedeschi
partner
Free University of Bozen-Bolzano
Dr. Hannes Schuler
partner
Fondazione Edmund Mach
Dr. Omar Rota-Stabelli
partner
Research Centre Laimburg
Dr. Katrin Janik
partner