Detection of grapevine viruses in grapevine rootstocks
Kasdorf, G G F
ARC Plant Protection Research Institute
In 1970 Nel and Engelbrecht declared that almost 100% of South African grapevine propagation sources, which consisted of scion varieties and rootstocks were infected with a number of plant viruses (Asteroid mosaic, fleck, fanleaf group, and corky bark and leafroll-associated viruses). These results were based on conventional indexing which took up to three years before results could be obtained in some cases.
This study resulted in the establishment of a plant improvement scheme for wine and table grapes in terms of the South African Plant Improvement Act (Act No 53 of 1976). Since the implementation of the scheme more sensitive techniques for the detection of grapevine viruses were developed which include ELISA and to a certain extend PCR. These techniques made it possible to test larger numbers of scion material in a shorter period of time than the traditional indexing on rooted grapevine indicator plants in the field or under controlled glasshouse conditions.
The known virus status of rootstock is of importance to the industry especially when virus free scion material is grafted in mother blocks, nurseries and commercial fields.
In ad hoc testing, using the new techniques and ISEM, grapevine viruses in rootstock material could not readily be detected although scion material tested positive. Question regarding the sensitivity of the different detection methods currently available to the South African grapevine industry were raised.
In 2003 this project was launched to, under semi-controlled conditions, evaluate the sensitivity of the detection methods, as well as, factors that influence the sensitivity of the methods currently used in the industry. To obtain this target, known grapevine viruses had to be forced by mechanical transmission into virus-free rootstocks. Target viruses were the different grapevine leafroll-associated viruses (GLRaV types -1 , -2, -3) belonging to the Closterovirus group.
Kasdorf, G G F. 2004. Detection of viruses on rootstocks. Presentation at the 4th Grapevine Virus Workshop. 11 May, Stellenbosch.
Kasdorf, G G F and Van der Merwe, M. 2005. Detection of viruses on rootstocks. 5th Grapevine Virus Workshop. May, Stellenbosch.