Articles
PERFORMANCE OF ‘NAPOLEON’ TREES TOPWORKED ON SELECTED GIESSEN, M X M, GM, COLT, AND MAZZARD ROOTSTOCKS
Five replicate trees of Mazzard seedling, F12/1, M x M 2, M x M 39, M x M 46, M x M 60, Colt, Gisela 6 (Gi 14-1), Gisela 12 (Gi 195-2), Gi 154-4, Gi 196-4, and GM 61/1 rootstocks were planted.
During the subsequent three growing seasons, ‘Napoleon’ was topworked at 1-1.5 m in height onto 3-5 scaffold limbs.
Beginning in 1994 and until the present, we have recorded yields, trunk cross-sectional area, fruit size, and soluble solids concentration.
Yield efficiencies have been calculated and other observations such as overgrowth of the graft union have been recorded.
Mazzard seedling, F12/1, and GM61/1 are the lowest yielding rootstocks in this trial.
In 1997, trees grafted onto M x M 2, M x M 46, Gi 196-4, and Gi 154-4 were the highest yielding trees, with ranges from 16.0 to 26.1 kg/tree.
The M x M 39, Gisela 12, Colt, and Gisela 6 topworked trees had intermediate yields and yielded from 11.2 to 15.5 kg/tree, while F12/1, GM61/1, and Mazzard trees yielded only 4.2 to 5.4 kg/tree.
Tree size also varies considerably in this trial.
The trees with the largest trunk cross-sectional area (TCSA) are those on Mazzard seedling, F12/1, M x M 60, and M x M 46 rootstocks.
GM61/1, GI154-4, Gisela 12, and Gisela 6 rootstocks produce trees with the smallest TCSA. The Giessen rootstocks have the highest yield efficiencies, followed by Colt and the M x M series.
The least efficient rootstocks are F12/1, Mazzard seedling, and GM61/1. Overgrowth of the graft unions is of concern for all of the Giessen selections with the exception of Gi 196-4 and may preclude their use in mechanically-harvested orchard systems.
Gi 196-4 may have a use for both mechanically-harvested and handpicked orchards.
The M x M series continues to be a promising set of rootstocks for the Willamette Valley of Oregon.
Trees are easy to topwork, have a high tolerance to Pseudomonas syringae, and have better production and yield efficiencies than Mazzard seedling and F12/1.