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Effect of Cluster Tightness on Botrytis Bunch Rot in Six Chardonnay Clones

January 1998 , Volume 82 , Number  1
Pages  107 - 109

M. E. Vail , Vino Farms, Inc., Healdsburg, CA 95448 ; J. A. Wolpert , Department of Viticulture and Enology ; and W. D. Gubler and M. R. Rademacher , Department of Plant Pathology, University of California, Davis, 95616

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Accepted for publication 25 September 1997.

Cluster tightness was measured and Botrytis bunch rot was evaluated for six Chardonnay clones in each of two trials, one cane-pruned and the other spur-pruned. In both locations, University of California (UC) Foundation Plant Materials Service (FPMS) clone 4 was most compact and FPMS 15 was the least compact (P < 0.01). Cluster tightness among the six clones, measured by the UC Firmness Tester Method, ranged from 0.0028 newtons (N) for clone 15 to 0.0112 N for clone 4. Cluster tightness was positively correlated with cluster weight. Botrytis bunch rot development was greater in the cane-pruned trial than in the spur-pruned trial. In the cane-pruned trial, disease incidence was greatest in FPMS 16 (81.5%) and least in clone 15 (44.5%; P< 0.025), while disease severity did not differ significantly. Neither incidence nor severity were significant in the spur-pruned trial. Clone 15, the clone with the least compact clusters, had the lowest disease severity levels.

© 1998 The American Phytopathological Society