Project title
Factors involved in abnormal graft union development

Project leader
Steenkamp, J

Institution
ARC Infruitec-Nietvoorbij

Team members
Hunter, J J
Volschenk, C G
Le Grange, E
Fouche, G W
Adams, L F
Marais, E

Project description
The South African Wine Industry is experiencing problems in the vineyards with abnormal enlargement of graft unions. This phenomenon increased during the past season, but apparently already started some 8 years ago. It varied between 0.2% and 30% in the 2006/2007 season for three locations. It often leads to premature death of young vines (1st and 2nd leaf). Cultivars and rootstocks are differentially affected and more symptoms seem to occur on heavier (and wetter) soils. The reason for the abnormal development of the graft union is not clear.

Information is required regarding the origin, cure and prevention of this phenomenon. The potential impact on economic viability of plantings and sustainability of production and grape quality is enormous.

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