Winetech Technical Yearbook 2022

TABLE 1. GLRaV-3 variants and viruses detected in source plants.

Plant number

Cultivar

GLRaV-3 variant

Other viruses

26/22/18

Chardonnay

I, VI

GVA, GVE, GRSPaV

8/7/1

Cabernet Sauvignon

II, III

GVA

3/17/16

Cabernet Sauvignon

II, VI

-

14/12/4

Cabernet franc

I, III

GVE

20/7/2

Cape Riesling

I, II, VI

GVA, GVE

10/20/6

Shiraz

I, II

-

13/2/19

Cabernet Sauvignon

II, VI

GRSPaV

ants and this was resolved by undertaking a second analysis using a primer set that clearly separated these groups (figure 1B). In the study, 155 mealybug transmissions were carried out, 20 first-instar nymphs were transmitted to recipient plants after feeding on infected source plants. The suc cess rate of the transmissions was above 80% for five of the source plants as a result of using 20 first-instar nymphs to induce a higher vector pressure. The following results were obtained from plants infected with a mixture of GLRaV-3 variants and other viruses: • Plant 20/7/2: The source plant was infected with variants I, II and VI; the group II variant was transmitted at a higher frequency, as well as the combi nation of group I + II variants. GVA was

transmitted to 60% of the plants, GVE was not transmitted. • Plant 13/2/19: The source plant was infected with group II and VI variants; again the group II variant was trans mitted more efficiently. GRSPaV was transmitted to 5% of the plants. • Plant 14/12/4: The source plant was in fected with group I and III variants; the group I variant was slightly more read ily transmitted, but the combination of variants I + III was transmitted most efficiently. GVE was not transmitted. • Plant 8/7/1: The source plant was in fected with group II and III variants; the group II variant was transmitted more efficiently than the group III vari ant. GVA was transmitted to 22% of the plants. • Plant 3/17/16: The source plant was

infected with group II and VI variants; the group II variant was transmitted most efficiently. • Plant 10/20/6: The source plant was infected with group I and II variants; the combination of group I + II variants was transmitted slightly more efficiently. • Plant 26/22/18: The source plant was infected with group I and VI variants; the group I variant was transmitted most efficiently. GVE was transmitted to 18% of the plants. The transmission results indicated that variants I and II were transmitted more frequently to recipient plants either as a single transmission or in combination with each other. The group VI variant was not transmitted as effectively as the group I and II variants in this study. In a similar

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WINETECH TECHNICAL YEARBOOK 2022