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Janet Caprile and Steve Grattan

In areas of California with a high incidence of walnut blackline disease, walnut orchards are increasingly being planted on English walnut (Juglans regia) rootstocks that are tolerant to the virus. There is limited documentation on the salt tolerance of this rootstock. This work was done to quantify the response of English walnut rootstocks to high boron (B), chloride (Cl), and sodium (Na) and to compare this to the more common rootstocks, Northern California Black (J.hindsii) and Paradox (J. hindsii × J. regia). The trial was configured as a randomized complete-block design with 20 plots. Plots consisted of three proximate, matched `Chandler' trees, each on a different rootstock. Leaf samples over a 2-year period showed that trees on the English rootstock had a significantly higher salt uptake than trees on Paradox, which had a significantly higher uptake than trees on Black. Bark cores showed little difference in B uptake between any of the rootstocks. Bark cores also showed that all rootstocks accumulated significantly more B than the scion portion of the tree, indicating that B transport may be limited by the graft union. Trees on English rootstock had significantly more B in the scion bark cores than trees on either Black or Paradox, indicating that rootstocks with a J. hindsii parent may be better at reducing salt transport across the graft union.

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Kendra Baumgartner, Phillip Fujiyoshi, Greg T. Browne, Chuck Leslie and Daniel A. Kluepfel

effects of isolate with P values ≥ 0.07). Discussion AX1 had the lowest percent mortality of all nine walnut rootstocks, and this finding was consistent for three isolates of A. mellea and in three replicate experiments. Our finding of significantly

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Janine K. Hasey, Dave Ramos, Warren Micke and Jim Yeager

In a comparison of six walnut rootstocks either nursery-grafted or field-grafted to `Chandler' (Juglans regia), the highest-yielding trees after 9 years are on either seedling or clonal Paradox rootstocks. Trees growing on both Paradox rootstocks had higher yield efficiency than trees on the black rootstocks in both 1995 and 1996. Since 1993, relative tree size based on trunk circumference has not changed: southern California black (J. californica), seedling Paradox and northern California black (J. Hindsii) have remained significantly larger than clonal Paradox, Texas (J. microcarpa) or Arizona (J. major) black rootstocks. The smaller size of clonal as compared with seedling Paradox trees might be explained by a delay in field grafting success. Although both northern and southern California black rootstock trees were significantly larger than clonal Paradox trees, they did not differ significantly in yield and had significantly lower yield efficiency in 1996. Clonal Paradox trees have significantly smaller nut size than northern California black rootstock trees that can be explained by its higher yield efficiency. An adjacent trial planted in 1991 compares micropropagated `Chandler' on its own root vs. `Chandler' on seedling Paradox rootstock. In 1995 and 1996, own-rooted `Chandler' had significantly greater trunk circumference, yield, and yield efficiency than did `Chandler' on Paradox rootstock. Many of the trees on Paradox rootstock are growing very poorly compared to the own rooted trees. This could be due to diversity within the Paradox seed source. If own-rooted `Chandler' trees become commercially available, they may have potential in areas where other rootstocks are undesirable because of hypersensitivity to cherry leafroll virus.

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John E. Preece and Gale McGranahan

hardwood that could be used for cabinetry ( Whitson et al., 1914, 1915 ), but this never caught on. By 1912, Smith et al. (1912) had tested seedling ‘Paradox’ as walnut rootstocks. They were disappointed with the results of grafting onto F 2 ‘Paradox

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Gregory T. Browne, Charles A. Leslie, Joseph A. Grant, Ravindra G. Bhat, Leigh S. Schmidt, Wesley P. Hackett, Daniel A. Kluepfel, Reid Robinson and Gale H. McGranahan

( Mircetich et al., 1998 ), and treatments with phosphonate (also referred to as phosphite) ( Browne et al., 2011b ), but rootstocks with improved resistance to the pathogens are needed. Compared with NCB ( J. hindsii ) and persian walnut rootstocks, Paradox

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Greg T. Browne, Joseph A. Grant, Leigh S. Schmidt, Charles A. Leslie and Gale H. McGranahan

that superior seed sources of Chinese wingnut could be identified for use in breeding or propagating walnut rootstocks. Materials and Methods Plant materials. Seven sources of WN were used for evaluation of resistance to Phytophthora and graft

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Xiaobo Song, Shengke Xi, Junpei Zhang, Qingguo Ma, Ye Zhou, Dong Pei, Huzhi Xu and Jianwu Zhang

excellent walnut rootstocks for walnut industry growing in China. Origin ‘Zhong Ning Sheng’ (ZNS) is the result of a cross between JH-8202 ( Juglans hindsii ) and LNJR-01 ( Juglans regia ) performed at a seedling field in Luoning County, Henan, China. The

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Mehmet Sütyemez, Şakir B. Bükücü and Akide Özcan

‘Chandler’, 10 replicates (i.e., scions) of both cultivars were grafted onto walnut rootstocks of the same age in 2001. The walnut breeding program was carried out at the University of Kahramanmaraş Sütçü İmam, Nut Application and Research Center (SEKAMER

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Kelly M. Oates, Thomas G. Ranney and Darren H. Touchell

Reproductive behavior of diploid and allotetraploid Rhododendron L. ‘Fragrant Affinity’ HortScience 42 31 34 Driver, J.A. Kuniyuki, A.H. 1984 In vitro propagation of paradox walnut rootstock HortScience 19 507 509 Fulcher, A. Dunwell, W.C. Wolfe, D. 2003

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Cristian Silvestri, Gianmarco Sabbatini, Federico Marangelli, Eddo Rugini and Valerio Cristofori

Driver, J.A. Kuniyuki, A.H. 1984 In vitro propagation of Paradox walnut rootstock HortScience 19 507 509 Fira, A. Joshee, N. Cristea, V. Simu, M. Harta, M. Pamfil, D. Clapa, D. 2016 Optimization of micropropagation protocol for Goji berry ( Lycium