Effect of Grafting Dates on Graft-take Success and Sapling Growth of Persian Walnut (Juglans regia L.) Under Open Field Condition of Jumla, Nepal

A field experiment was carried out at Horticultural Research Station, Rajikot, Jumla to determine the best grafting date of walnut for the highest graft-take success and sapling growth. The experiment was conducted during the two consecutive years 2017, and 2018. Two varieties namely ‘Hartley’ and ‘Payne’ and four different dates of grafting viz. 15th March, 22nd March, 29th March, and 5th April were used as the treatment and the experiment was laid out in split-plot design. Each treatment was assigned with ten grafts with five replications per treatment. The measured parameters for the experiments included graft-take success (%), final scion diameter (cm), growth on scion diameter (%), number of primary branches per plant, plant spread (cm), and number of leaf per plant. The pooled value of observation for two years showed highly significant effect of variety and grafting date on grafting-take. ‘Hartley’ variety showed maximum graft-take success (73.2%) and ‘Payne’ with the least success (54.0%). The pooled value of two successive years showed the highest graft-take success (70.0%) on 15th of March, significantly at par with 22nd March (64.5%) and 29th March (67.0 %) grafting. Grafting on 15th March was also superior in terms of number of leaves (31.7), and least was observed for grafting on 29th March (20.5). In essence, variety ‘Hartley’ was found to record higher graft-take success with 15th March as the optimum grafting date under Jumla condition.

Unraveling Factors Affecting Micropropagation of Four Persian Walnut Varieties

Walnuts are considered recalcitrant to tissue culture, with a great genetic determinism on all stages of micropropagation; while other factors, also with great impact, become more complicated with the reproduction of newly realized varieties. In this research, a holistic approach aimed to determine the influence of genotype and the nutritive formulation throughout the whole cycle of micropropagation of four Persian walnut varieties (Juglans regia L.) was presented. During the in vitro establishment it was determined that besides genotype and culture medium, the effect of collection season and the likely interaction amongst factors had a great influence on the successful introduction of all four genotypes. However, all cultures were affected by a deep decay, being necessary the introduction of ethylenediamine di-2-hydroxyphenyl acetate ferric, as iron source, and Phloroglucinol in both Murashige and Skoog (1962) and the corrected Driver and Kuniyuki (1987) formulations. These modifications allowed the stabilization of cultures, maintaining thereafter a steady quality. Either proliferation, rooting and ex vitro survival of four clones were affected by the culture medium, obtaining the best results with the corrected Driver and Kuniyuki (1987) formulation. Finally, in vitro plants produced from all clones were acclimated with high survival rates (75.9–91.1% for the best culture medium), depending of clone and the culture medium used. Microsatellite analysis showed that micropropagated plants maintained the same genetic profiles of their corresponding donor trees. These results might contribute to deepening of the understanding of factors that determine the success of micropropagation of walnuts, and the extents of its influence; whereas, it sets the basis for the commercial micropropagation of all four clones.

Effect of Different Pre-Sowing Treatments on Germination of Persian Walnut (Juglans Regia L.) in Rukum (East) District, Nepal

A field-based experiment was carried out in Rukum (East), Nepal, from February to June 2020, to assess the effect of different pre-sowing treatments on germination of Persian walnut. The experiment was carried out in a randomized complete block design with six treatments and four replications. The treatments included hot water treatment, chilling stratification only, cracking + Gibberellic acid (500ppm) followed by chilling stratification, cracking + Gibberellic acid (750ppm) followed by chilling stratification, Gibberellic acid (500ppm) + chilling stratification and Gibberellic acid (750ppm) + chilling stratification. The minimum days for germination (15.75 days) and highest germination (53.25%) were obtained when the combination of cracking with GA3 @ 750 ppm along with chilling stratification was done. The maximum shoot length (34.83 cm) was observed in the combination of cracking with GA3 @ 500 ppm followed by stratification but statistically similar shoot length (34.63 cm) was observed when cracking, application of GA3 @ 750 ppm followed by stratification was done. Cracking, treatment with GA3 @ 500 ppm followed by chilling stratification resulted in the highest shoot fresh weight (11.93 gm) and root fresh weight (10.77 gm) compared to the other treatments used. Thus, cracking along with treatment by GA3 @ 750 ppm followed by chilling stratification could be suggested to the walnut growers for better germination and a better morphological and physiological status of the rootstocks/seedlings.