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Abstract
Withholding irrigation of walnut trees (Juglans regia L. cv. Ashley) for one growing season significantly reduced trunk growth and kernel weight. Tree survival and return cropping were unaffected. When irrigation was resumed kernel weight was significantly heavier than that from trees irrigated the previous year.
Walnut rootstock ‘RX1’ U.S. Plant Patent No. US PP20,649 P3 19 Jan. 2010 McGranahan, G.H. Tulecke, W. Arulsekar, S. Hansen, J.J. 1986 Intergeneric hybridization in the Juglandaceae : Pterocarya sp. × Juglans regia J. Amer. Soc. Hort. Sci. 111 627 630
Abstract
Potted vines of ‘Cabernet Sauvignon’ and ‘White Riesling’ grapes (Vitis vinifera L.) and potted ‘Bartlett’ pear (Pyrus communis L.) and ‘Hartley’ English walnut trees (Juglans regia L.) were grown in greenhouses for 2 seasons and fumigated with ambient levels of H2S, treble ambient H2S, and amounts of SO2 equivalent to the treble levels of H2S. No foliar symptoms or deleterious effects on growth or fruiting were observed which could be ascribed to the treatments.
English walnuts ( Juglans regia ) are valued for their taste and nutritional quality. English walnuts contain a higher amount of α-linolenic acid, an essential omega-3 fatty acid, than other tree nuts and also have a 4:1 ratio of linoleic acid to
Abstract
Walnut trees planted at 50’ × 30’ grew more slowly than xtrees at 50’ × 40’ or 50’ × 50’. Yields per tree were similar at all spacings early in the orchard’s life, but unit area yields later increased proportionately to the number of trees per acre. Long-term monetary returns above fixed costs were far greater as the number of trees per acre increased.
Abstract
In vitro propagation of mature cultivars of Juglans regia L. (Persian or English walnut) could have several major advantages over propagation by grafting on seedling black walnut [J. hindsii (Jeps.) Jeps.] rootstock. If commercial cultivars perform satisfactorily on their own roots, the expensive and time-consuming process of grafting could be avoided, genetic uniformity could be assured, and trees would not be subject to the lethal girdling of blackline disease (5). In addition, mature clones on their own roots might be more precocious than grafted seedlings. These factors are becoming increasingly important as walnut growers change to high-density or hedgerow orchards (D.E. Ramos, personal communication).
Abstract
A system was developed to transform walnut cultivars using the natural gene transfer system of Agrobacterium tumefaciens. We report the infection of English walnut (Juglans regia L.), northern California black walnut (Juglans hindsii), and their F1 hybrid ‘Paradox’ with A. tumefaciens carrying various recombinant derivatives of the tumor-inducing (Ti) plasmids, pTiA6 and pTiB6S3. The three walnut species, each represented by a single micropropagated clone, were found to be equally susceptible to Agrobacterium-induced tumor formation in vitro. Stable lines were established from tumors induced on each clone, and, unlike normal stem callus, these tumor cells grew rapidly in culture media without exogenous plant hormones. High-voltage paper electrophoretic analysis revealed the presence of opines in the walnut tumor tissue. The presence of a foreign gene was demonstrated by expression of a chimeric bacterial gene that encodes resistance to the antibiotic kanamycin, and also by the presence of foreign DNA sequences in genomic DNA isolated from tumors.