WINETECH Technical Yearbook 2020

PHOTO 2. Obvious symptoms of leafroll disease in a number of red cultivars of Vitis vinifera (Merlot, Cabernet Sauvignon, Shiraz and Pinotage), in this case autumn 2017, on Vergelegen in a vineyard where infected vines are rogued annually.

PHOTO 1. Prevalence of grapevine leafroll disease in many vineyards in South Africa and inter- nationally.

Samples were processed by removing the outer bark and preparing phloem shavings separately of the scion and rootstock mate- rial of each vine and then extracting RNA from these. RT-PCR was then performed separately on the scion and rootstock. Clear

usually pruned in practice, such plants were relatively rare, but 69 such vines with Richter 99 rootstocks were collected over three seasons. In this regard, we were fortunate to have had access to an abandoned vineyard (photo 8).

and Stellenbosch during 2014, 2015 and 2016. Specimens were selected based on the occurrence of clear GLD symptoms on the scions. Only vines with sizeable lignified Richter 99 canes were selected for sampling. As rootstock suckers are

Cane material was collected separately (photo 7) from both the scion and rootstock individual vines grafted on Richter 99 ( Vitis berlandieri X Vitis rupestris). These were from two commercial wine estates and two trial sites in Wellington

WINETECH TECHNICAL YEARBOOK 2020 13