performance ( Bonhomme et al., 2005 , 2010 ; Lacointe et al., 2004 ). As persian walnut orchards are long-term investments, mediating the effects of winter temperature changes may become a major task for orchard management in the near future ( Melke, 2015
Aude Tixier, Adele Amico Roxas, Jessie Godfrey, Sebastian Saa, Dani Lightle, Pauline Maillard, Bruce Lampinen and Maciej A. Zwieniecki
Mohammad Sadat Hosseini Grouh, Kourosh Vahdati, Mahmoud Lotfi, Darab Hassani and Nejat Pirvali Biranvand
purpose of this research was to evaluate the use of gamma-irradiated pollen for production of parthenogenetic haploid plants in persian walnut. Viability of irradiated pollen, percent fruit set, parthenogenetic embryos formation, and the first production
Asadolah Aslani Aslamarz, Kourosh Vahdati, Majid Rahemi and Darab Hassani
the chilling requirement of walnut cultivars between 400 and 1500 h below 7 °C. Table 1. Chilling requirement of Persian walnut cultivars and genotypes (hours below 7 °C) to reach 50% of lateral and terminal buds and catkins to the balloon or green tip
Greg T. Browne, Joseph A. Grant, Leigh S. Schmidt, Charles A. Leslie and Gale H. McGranahan
Phytophthora crown and root rot (PCRR) is among the most serious diseases of Persian walnut worldwide. In California, more than 10 species of Phytophthora have been implicated in the disease, but Phytophthora cinnamomi and P. citricola are
William H. Olson and David Ramos
The Persian or English walnut (Juglans regia) is widely cultivated, with commercial production in France, Italy, Turkey, China, and the United States. Practically all of the U.S. production of Persian walnuts is in the central valley of California, which now has about 169,000 bearing acres with an average yield of around one and one-third short tons per acre. Many orchards produce over two tons, and three tons per acre are common in many modern plantings. Walnuts have two major outlets: the exported in-shell market (about 35% of production) and the domestic shelled market (about 68% of production). A cooperative handles about half the crop, while several independent handlers sell the remainder. Walnuts are sensitive to both low and high temperatures. Temperatures in excess of 90 °F will begin to sunburn nuts. Freezing temperatures will damage tender growth in the spring and fall. Dormant trees can tolerate 15 °F without injury if soils are moist. Dry winter soils and cold temperatures cause winter kill. A minimum of 800 hours of winter chilling are required to avoid delayed bud break and poor crops. Walnuts do best on deep, medium textured, well drained soil. Under these conditions, both rootstocks, the Northern California Black Walnut (J. hindsii) and Paradox (J. regia x J. hindsii), do well. Under less favorable soil conditions, Paradox is the preferred rootstock. A mature walnut orchard requires 4 to 4.5 acre-feet of water per acre per year if the trees are to produce the maximum number of high quality nuts possible. Hartley, preferred for its in-shell quality, is the leading cultivar, with about 30% of the acreage. In recent years, the Chandler variety has accounted for most new plantings. It is known for high kernel quality and yields. Yield factors include: bearing habit, bearing area, flower differentiation, fruit set, nut size, kernel percentage, and kernel quality. Major insect pests of walnut include codling moth, navel orangeworm, and walnut husk fly. The major diseases are walnut blight, deep bark canker, Phytophthora, and blackline. Major research efforts include the walnut breeding program, which includes blackline and Phytophthora susceptibility of new cultivars and root-stocks, codling moth and walnut husk fly control, epidemiology and control of walnut blight, pruning and planting strategies, and clonal propagation.
Asadolah Aslani Aslamarz, Kourosh Vahdati, Majid Rahemi, Darab Hassani and Charles Leslie
. 2009 Estimation of chilling and heat requirement of some Persian walnut cultivars HortScience 44 697 701 Bartolozzi, F. Fontanazza, G. 1999 Assessment of frost tolerance in olive Sci. Hort. 81 309 319 Bierman, J. Stushnoff, C. Burk, M.J. 1979
Zhan Shu, Xue Zhang, Dianqiong Yu, Sijia Xue and Hua Wang
Hybridization between species of the genus Juglans is common because of weak reproductive isolation mechanisms between closely related species with sympatric distributions. In this research, we investigated the possibility of naturally occurring interspecific hybrids between two species in the genus Juglans: persian walnut (Juglans regia) and chinese walnut (Juglans cathayensis). We used 12 pairs of microsatellite markers to analyze introgression between the two species. All amplified microsatellites were polymorphic in the two species. The result of Bayesian admixture analyses showed that introgression between the two species is rare; only three of nine individuals tentatively identified as hybrids, based on intermediate morphological characteristics, were defined as mixed genotypes. The other six putative hybrids and 156 morphologically pure individuals showed no sign of introgression.
Kourosh Vahdati, Charles Leslie, Zabihollah Zamani and Gale McGranahan
In vitro rooting of three commercial cultivars of Persian walnut (Juglans regia L.), `Sunland', `Chandler', and `Vina', was examined using a two-phase rooting procedure: root induction in the dark on Murashige and Skoog (MS) medium with 15 μm IBA followed by root development in the light on a mixture of one-quarter strength Driver Kuniyuki Walnut (DKW) basal medium and vermiculite (1:1.25, v/v). Rooting percentages were: `Sunland' (94%), `Chandler (55%), and `Vina' (27%). A positive relationship was observed between the vigor of cultivars and rooting ability, but shoot length did not affect rooting success. Rooting was optimum when shoots were cultured on root induction media for 6 to 8 days. Increasing the sucrose level in the root induction medium to 40 g·L-1 improved rooting, and shoots induced to root at 22 °C rooted more readily than those induced at 30 °C. Either increasing or decreasing the nitrogen level in the multiplication medium had a negative effect on rooting. Rooted walnut shoots often cease growth during acclimatization, resulting in shoot rosetting. Spray application of Promalin® (25 mL·L-1) caused buds to break and induced elongation of shoots. Chemical name used: indole-3-butyric acid (IBA).
Rohollah Karimi, Ahmad Ershadi, Kourosh Vahdati and Keith Woeste
The family Juglandaceae consists of seven genera, comprising ≈60 monoecious tree species. The genus Juglans contains 20 species, all producing edible nuts. Among these, the English or Persian walnut ( Juglans regia ) is the most widely cultivated
Kourosh Vahdati, Naser Lotfi, Bahman Kholdebarin, Darab Hassani, Reza Amiri, Mohammad Reza Mozaffari and Charles Leslie
seed or by grafting on rootstocks ( Vahdati, 2003 ). Hence, there is huge genetic diversity among rootstock traits. For example, there are many old Persian walnut ( Juglans regia L.) trees in Iran that have been planted on the banks of rivers. The long