Addition of 4–40 μm 2,4-dichlorophenoxyacetic acid (2,4-D) plus 2–6 μm kinetin induced callus formation in fresh cotyledons of walnut (Juglans regia L.), but the presence of phenolic compounds prevented a stable culture. Roots were obtained from callus on a half-strength K(h) medium supplemented with indolebutyric acid (IBA) or naphthaleneacetic acid (NAA) at 40 μm plus kinetin or benzylamino purine (BA) at 2 μm. The origin of roots was usually endogenous.
10.21273/JASHS03999-16 Ikhsana, A.S. Topçua, H. Sütyemezb, M. Kafkas, S. 2016 Novel 307 polymorphic SSR markers from BAC-end sequences in walnut ( Juglans regia L.): Effects of motif types and repeat lengths on polymorphism and genetic diversity Sci
Phenolic acids, syringaldehyde, and juglone in fruits of different cultivars of Juglans regia L J. Agr. Food Chem. 53 6390 6396 10.1021/jf050721n Constabel, C.P. Ryan, C.A. 1998 A survey of wound- and methyl
pollination between Juglans regia × Juglans nigra and/or × Juglans major ; Jr = J. regia; Jmi = Juglans microcarpa var. microcarpa genotypes. The difference in necrosis length displayed by inoculated Juglans genotypes during the two seasons
Walnut ( Juglans regia L.) is an important crop that is cultivated extensively worldwide for nut production. China is one of the major producers of this crop. Traditional Chinese medicine purports that the nutmeat of walnut is nutrient-dense and
Fifty trees each of 1-year-old Paradox rootstock June-budded to `Chandler' walnut and 2-year-old Paradox whipgrafted to `Chandler' were planted in a 28 × 28-ft spacing on a Hanford sandy loam soil. Ten trees of each type were selected at time of planting and the number of roots, individual root diameter, trunk diameter, root dry weight, scion dry weight, and total dry weight were compared. All parameters, with the exception of root number, were significantly greater for the grafted 2-year-old rootstocks. Growth of the trees measured as trunk circumference 20 cm above the graft union was significantly greater for the grafted 2-year-old rootstocks following the first season. There was no significant different in trunk circumference between the 1- and 2-year-old rootstocks following the second or third growing seasons.
When walnut trees were bark-grafted leaving nurse-limbs, xylem exudation was observed at a few slashes made low on the tree but not at graft junctures. Scions grew equally well on trees with slashes (74%) as those without slashes (86%). When the same treatments were made without nurse-limbs, 83% of the scions grew where exudates did not appear but only 21% grew where xylem sap exuded nearby. No dormant patch-bud placed in August-September grew the following spring if the sap flowed from any side of the patch, whereas 96% grew where no exudation occurred. Analysis of the xylem exudate revealed the presence of substances which inhibited growth of walnut calli and cucumber seedlings. A strong zone of inhibition on paper chromatograms coincided with the Rf of juglone, a powerful toxin which was identified by absorption spectrophotometry.
Heading back of 2nd flush growth to basal buds on vigorous young trees at different times of the year indicated that buds were converted from a vegetative to a reproductive state within 4 weeks after they were formed at the shoot apex. Defoliation or defoliation plus etiolation of 7 terminal nodes in July did not deter the buds at these nodes from differentiating pistillate flowers for the next season. Pruning greatly accelerated the differentiation processes.
The time of initiation of pistillate flowers was determined for each of 7 cultivars of walnut (Juglans regia L.). Flower formation (flattened apex) was evident during the first 2 weeks of June for ‘Chico’, ‘Vina’, ‘Serr’, ‘Tehama’, and ‘Pedro’ and mid-July for ‘Hartley’ and ‘Franquette’. Initiation of floral parts also occurred at different times depending on the cultivar. Pistil development began in February for ‘Chico’ and in April for ‘Franquette’. Fertilization occurred throughout April for most of the cultivars, but in the middle of May for ‘Franquette’.
Walnuts (Juglans regia L.) with and without (2-chloroethyl)phosphonic acid (ethephon) treatment were harvested at the earliest practical time and 3, 7, and 10 days later. With both treatments a delay in harvest resulted in kernels of lower quality and subsequent value. Furthermore, lower quality was found in earlier maturing than in later maturing walnuts when harvested from the same tree on the same day. In all comparisons kernels from ethephon-treated nuts were of higher value than controls. Walnuts left in the drier beyond the time necessary to remove excess moisture lost negligible quality and value.