Winetech Technical Yearbook 2022

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Impact of grapevine leafroll disease on grape and wine composition GRAPEVINE LEAFROLL DISEASE (GLD) IS THE MOST COMMON GRAPEVINE DISEASE, WHICH IS PRESENT IN GRAPE-GROWING REGIONS GLOBALLY. IT HAS BEEN PROVEN THAT GLD IMPACTS GRAPEVINE PHYSIOLOGY AND THE SUBSEQUENT BERRY COMPOSITION. VERY LITTLE INFORMATION IS AVAILABLE ON GLD IMPACT ON GRAPEVINE PHYSIOLOGY, GRAPE RIPENING AND THE WINE COMPOSITION UNDER SOUTH AFRICAN CONDITIONS.

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BY ERNA BLANCQUAERT & WESSEL DU TOIT

INTRODUCTION To date 70 viruses and five viroids have been identified to infect grapevines. 1 Vi rus and virus-like diseases are a great threat to grapevine vineyards globally. 1 Grapevine leafroll disease (GLD) has been identified as one of the most important viral diseases. 2 Within the South Afri can context, grapevine leafroll disease is widely accepted to be the most damaging grapevine virus disease, with grapevine leafroll-associated virus 3 (GLRaV-3), the most prevalent leafroll-associated virus. 3,4 This virus is transmitted by vine

mealybug Planococcus ficus which is the predominant mealybug in South African vineyards, as well as the more restricted Pseudococcus longispinus and a number of scale insect species. 5,6 The spread of a systemic virus such as GLRaV-3 is influenced by the direction of the carbohydrate movement in the phlo em. 7 The sieve elements are blocked and ruptured in the parenchyma cells in the leaves which will result in a delay of the carbohydrate translocation. 8 Subsequently, carbohydrates cannot be mobilised and transported further from the leaves to oth er grapevine organs which subsequently

HANNO VAN SCHALKWYK

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WINETECH TECHNICAL YEARBOOK 2022