Viticultural Information

Return to Main Viticultural Information

Subject

Chimeras

Description

Fasciated shoot chimera shows wide, flattened growth and appearance of multiple fused growth points

More commonly referred to as bud mutations or "sports," chimeras rarely affect an entire vine, unless it is propagated from the affected material. Originating from mutated single buds and involving a single shoot, chimeras can increase in proportion on the vine, if they are not pruned. The most commonly expressed chimera is variegation, sometimes described as "spilled milk." With this chimera, a mosaic pattern spreads into the new tissue of the shoot with white areas in the leaf blade. Occasionally, an entire shoot, including the cluster, will lack chlorophyll. These affected shoots generally do not inhibit the vine's performance and are commonly pruned because of poor growth.

"Bull vine" or "witches' broom," another form of chimera, can affect individual vines, especially in older vineyards. It also starts from single, mutated buds, but abnormal, vigorous, and unfruitful growth can eventually crowd out normal shoots. Shoot nodes are closely spaced with numerous buds, lateral shoots, and small leaves. Crowded, numerous shoots will eventually dominate the affected portion of the vine. All abnormal growth, once detected, must be removed with a pruning saw. Otherwise, within a few years of unproductive growth the vine may have to be removed. Never take propagation wood from affected vines.

The chimera, shoot fascination, also results in a malformation of shoots: The affected individual shoots are enlarged and flattened in shape as if several shoots are fused. The mutation occurs more frequently in certain cultivars and is especially common in Petite Sirah (Durif). Such shoots are usually pruned in winter and thus do not affect production.

People

Peter Christensen
William Peacock

Publications

Flaherty, D., Christensen, L.P., Lanini, W., Marois, J., Phillips, P., and Wilson, L.T. 1992. Grape Pest Management, 2nd edition. University of California Division of Agriculture and Natural Resources Publication 3343, Oakland, CA.

This website is a work in progress of the University of California (UC) Division of Agricultural and Natural Resources (ANR) Integrated Grape Production Workgroup. It is designed to increase accessability to the work of UC researchers, including faculty, Cooperative Extension (CE) specialists, CE advisors, and staff. UC Researchers interested in contributing content are invited to contact Deborah Golino dagolino@ucdavis.edu to discuss possible contributions.