LABORATORY PROCEDURES FOR PLANT CELL VIRUSES
PVC/1998/2.02 Appendix 3
GRAFTING OF VIRUS INFECTED PLANT MATERIAL TO HEALTHY HOST PLANTS
Graft transmission of viruses to susceptible host plants is indicated when the virus strain is not readily or not at all mechanically transmissible. It is used for initial establishment of infection and, for maintenance and in situ preservation of non mechanically transmissible viruses. Graft inoculation is not selective and all pathogens invading the vascular system are transmitted provided a susceptible host is used. Therefore, within the virus control check, graft transmission is a means for establishment of the original sample. Symptoms induced in a graft inoculated recipient rootstock also must not indicate for a respective virus since disease phenotype can be different from that of natural infections.
Graft transmission of virus infected plants to susceptible rootstocks and to establish infection in the recipient plant is already realised when the graft partners have reached a vascular connection for only a short period. Hence, for virus transmission, only a short vascular contact is sufficient and organic union with survival of the scion is no precondition for successful graft transmission and therefore, grafting experiments for virus transmission can also be performed with incompatible graft partners. However, for effective virus transfer, compatible partners – same species – and the establishment of the scion on the rootstock is aimed at.
For graft transmission, scions are excised from symptomatic parts of the virus infected plant. Depending on the virus to be transmitted and the recipient plant, meristematic tissues, older stem parts, or distal vines are used for grafting. Inoculation is done by cleft grafting.
The material to be used for grafting should not be to far apical tissue and rather woody than too soft, to guarantee virus presence and to support growing on of scion to the rootstock. One to two nodes are taken and leaves or part thereof and the apical tip are removed to reduce evaporation and early abort of the scion. The vascular system of the scion is exposed by a long cut on two sides to create a wedge. In the recipient plant, depending on the virus/host combination, leaves around the scion insertion side are removed or, the plant is topped, or only the apical tip is removed to prepare for the graft transmission. A longitudinal cut of is made into the stem in which the wedge cut scion is inserted so that both vascular systems join. The graft insertion side is taped tightly with parafilm to prevent desiccation and the grafted plant is protected from excessive evaporation by a plastic bag cover. This cover is removed after 2-3 days.
Guidelines prepared for CABRI by DSMZ, 3 Feb. 1998
© The CABRI Consortium 1999-2013.