Fruit Disease
Phytoplasmen
One focus of the fruit diseases working group is the study of fruit tree phytoplasma diseases: apple proliferation (AP), European stone fruit yellows (ESFY) and pear decline (PD). In addition, work is being carried out to identify Flavescence dorée-like phytoplasmas in the vicinity of vineyards.
Phytoplasmas are cell wall-less bacteria that only occur in the phloem of infected plants. They are transmitted by phloem-sucking insects (psyllids, cicadas). We are developing environmentally friendly control strategies against the further spread of these diseases. This starts with a good pathogen diagnosis and a molecular characterization of the phytoplasmas. Furthermore, we identify the transmitting insects and elucidate the exact transmission parameters. On the plant side, we try to minimize the damage caused by the phytoplasmas with the help of genetic and induced resistance.
Typical symptoms of apple proliferation are witches' brooms (Fig. 1) and enlarged stipules. The economic damage of the disease is caused by the small fruit size, which makes it impossible to market the fruit. The phytoplasma (Candidatus Phytoplasma mali) is transmitted very efficiently by the psyllid Cacopsylla picta (Fig. 2).
Fig. 1: Witches' broom
Fig. 2: Cacopsylla picta
Stone fruit yellows (ESFY) is a quarantine disease that causes major economic damage to apricot and peach in particular due to the death of the trees. Typical symptoms are chlorotic, conical leaf rolling in summer (Fig. 3) and premature bud break in late winter. The phytoplasma (Candidatus Phytoplasma prunorum) is transmitted very efficiently by the psyllid Cacopsylla pruni (Fig. 4).
Fig. 3: ESFY-induced leaf roll
Fig. 4: Cacopsylla pruni
A closely related disease is pear decline (PD). It can lead to a more or less rapid death of the pears. However, the symptoms such as leaf reddening (Fig. 5) are non-specific and reliable detection requires a molecular test. The phytoplasma (Candidatus Phytoplasma pyri) is transmitted by various pear psyllids: Cacopsylla pyri (Fig. 6), Cacopsylla pyricola and Cacopsylla pyrisuga.
Fig. 5: Leaf reddening
Fig. 6: Cacopsylla pyri
Phytoplasmas in vitro
As phytoplasmas cannot be cultivated, research must always be carried out with the whole infected plant or insect. For this purpose, plant tissue culture has been established as a platform technology in the fruit diseases working group. In this in vitro system, we test both the genetic resistance of apple rootstock genotypes and the effect of bacterial and fungal endophytes (Fig. 7).
Fig. 7: In vitro grafting of phytoplasma-infected plant onto test plant
for screening of genetic and induced resistance in the laboratory
for screening of genetic and induced resistance in the laboratory
PhenoTruckAI: Mobile laboratory for the rapid and reliable identification of quarantine pests in agriculture (BLE project)
Development of a biological repellent against psyllids based on mineral raw materials (Psyllid-Repell) (DBU project); project completed
Digital fruit growing: Early detection of apple proliferation and pear decline through remote sensing and analysis using machine learning methods (BLE Rentenbank); project completed
Development of monitoring methods (air, soil) for the identification of phytoplasmoses in vineyards with a view to the quarantine pathogen Flavescence dorée Phytoplasma - PhytoMo (BLE project)
Control of fruit phytoplasmoses using endophytes (funded by the Rhineland-Palatinate Foundation for Innovation and the Fund for the Development of Rural Areas in Rhineland-Palatinate FELR); project completed
Einsatz von pflanzenbürtigen Infochemikalien zur Bekämpfung von Obstphytoplasmosen mittels Repellenzstrategien (Förderung ZIM Kooperationsprojekt sowie Fonds für die Entwicklung ländlicher Räume in Rheinland-Pfalz FELR; Projekte abgeschlossen)
Use of plant-borne infochemicals to control fruit phytoplasmoses by means of repellency strategies (funded by the ZIM cooperation project and the Rhineland-Palatinate Rural Development Fund FELR; projects completed)
INTERREG V project InvaProtect: Sustainable plant protection against invasive pests in fruit growing and viticulture; project completed.
PhenoTruck (Projektseite)
phenotruck.de
InvaProtect
dbu.de
innovationstage-digital.de
www.apfeltriebsucht.de
www.psyllidkey.info