Phytoplasma transmission by in vitro graft inoculation as a basis for a preliminary screening method for resistance in fruit trees

Abstract

In vitro grafting was tested as a technique for inoculating Prunus rootstock Prunus marianna GF 8-1 with European stone fruit yellows (ESFY) phytoplasmas and apple rootstock Malus pumila MM106 with apple proliferation (AP) phytoplasmas. In vitro shoot cultures of ESFY-infected Prunus marianna GF 8-1 and AP-infected Malus pumila MM106 were used as graft inoculum to transmit the phytoplasmas to the respective healthy rootstock. Phytoplasma transmission was assessed after a graft contact of 1, 2 or 3 months. Healthy autografts were used as controls to monitor parameters of in vitro grafting. Successful graft union formation ranged from 58 to 79% irrespective of the plant species and the sanitary state of the graft. Pathogen-specific polymerase chain reaction (PCR) was used to test the inoculated rootstocks for the presence of ESFY and AP phytoplasmas, respectively. The rate of ESFY phytoplasma transmission in successful Prunus-grafts increased from 69 to 94% with the time of contact. AP phytoplasma transmission to Malus occurred in 80 to 97% of successful grafts. To our knowledge this is the first report of phytoplasma transmission by grafting in vitro. The results provide a good basis for the establishment of a preliminary in vitro screening method for phytoplasma resistance in Prunus and Malus.

Resistance Inducers and Plant Growth Regulators Show Only Limited and Transient Effects on Infection Rates, Growth Rates and Symptom Expression of Apple Trees Infected With ‘candidatus Phytoplasma mali’

“…P. mali' do not always develop symptoms (Baric et al 2011), the roots of asymptomatic trees were tested using qualitative PCR and trees tested positive were included in the calculation of infection (or transmission) rates. The transmission rates from 75 to 87% are in a similar range as those reported by Jarausch et al (1999) for in vivo inoculation, whereas the same authors found higher transmission success for 'Ca. P. mali' inoculation in vitro (80 -97%), using cultured infected tissue for grafting.…”

Contrasting Susceptibilities to Flavescence Dorée in Vitis vinifera, Rootstocks and Wild Vitis Species

“…and Malus sp. rootstocks by in vitro grafting (Jarausch et al, 1999; Seemüller et al, 2007). In the case of phytoplasma, mechanical inoculation of plants never succeeded, and grafting of FDp-infected grapevines led to low transmission efficiency.…”

Biological Characterization of Sesamum Phyllody Disease in Assam, India

“…Due to this nature probably they are transmitted in the process of grafting. Jarausch et al, (1999) observed successful transmission of European stone fruit yellows (ESFY) phytoplasma by graft transmission. Kamińska and Korbin (1999) reported graft transmission of phytoplasma affecting Lily plant.…”