Effect of Cultivar, Grafting Method and Epibrassinolide on Grafting Success Rate in Persian Walnut (Juglan regia L.)

Document Type : Research Paper

Authors

1 Assistant professor, Kerman Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Kerman, Iran.

2 Researcher, Kerman Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Kerman, Iran.

3 Expert, Kerman Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Kerman, Iran.

10.22092/spj.2026.371269.1454

Abstract

This study was conducted to investigate the effects of cultivar, grafting method and epibrassinolide (EBr) and their interaction effects on grafting success rate and walnut scion growth. The experiment was carried out as factorial arrangements in randomized complete block design with five replications in agricultural and natural resources research and education center of Kerman province in 2023 and 2024. Experimental factors included: walnut cultivar at two levels, EBr at four levels and grafting method at two levels. The results showed that Cultivar × EBr interaction significantly affected graft success in 2023, and scion bud breaking time (SBBT), and shoot diameter in 2024. Cv. Fernor + 0.05 mM EBr or without EBr had highest grafting success rate (80-100%) in 2023. Cv. Fernor + whip budding + 0.05 mM EBr had the latest SBBT (July 7-11) in 2024. Cv. Fernor + whip budding had the greatest shoot length (35.53 cm) in 2023, and 85 cm in cv. Fernor + 0.15 mM EBr in 2024. Maximum shoot diameters (1.73 cm) were recorded in cv. Fernor + 0.05 mM EBr in 2023, and in cv. Fernor + patch budding + 0.05 mM EBr (2.5 cm) in 2024. Cv. Fernor + whip budding + 0.25 mM EBr had the highest leaf number (39 leaves) in 2024. Walnut cultivar had more pronounced effect on grafting success rate and was identified as the most important factor in walnut seedling growth compared to high concentration levels of EBr and grafting methods.
 
Keywords: Walnut, scion, cv. Chandler, cv. Fernor, chip budding, patch budding, hormone.
 
Introduction
Commercial walnut production using seedlings is inefficient due to genetic variability and poor nut quality (Hartman et al., 2011). Despite the ease and tradition of seedling propagation in Iran, it fails to meet growers’ economic expectations. Grafting is a practical and low-cost method for propagating late-blooming, high-yield walnut varieties. However, its success rate is limited. Studies have identified patch budding as the most practical and efficient grafting method with success rates up to 93.3% (Khajeali and Mohammadkhani, 2015).
Factors such as grafting time, method, genotype, temperature, and humidity influence grafting success rate (Vahdati, 2003). Research has also highlighted the role of plant hormones especially brassinosteroids (BRs) in vascular tissue formation and graft union success (Engine and Gökbayrak, 2022). Although BRs have improved flower development in cv. Chandler (Engine and Gökbayrak, 2022), their effect on walnut grafting success rate remains unexplored. Therefore, development of commercial vegetative propagation protocols for producing superior walnut cultivars adapted to Kerman’s climatic and resources limited conditions is essential.
This study aimed to identify the most effective combination of EBr concentration and grafting method to improve grafting success arte and scion growth of cv. Chandler and cv. Fernor walnut.
 
Materials and Methods
The experiment was conducted at the Rabor walnut research station (RWRS) situated at 2290 meter above the sea level, 57˚02′45″–57˚02′48″ E and 29˚16′31″–29˚16′44″ N. The annual rainfall and temperature of the experimental site were 210 mm, and 23 °C, respectively. Two walnut cultivars, Chandler and Fernor were selected due to their late leafing, high lateral bearing, and high‑quality of nuts which are popular among local walnut growers in Kerman province.
The experiment was carried out as factorial arrangements in randomized complete block design with five replications in agricultural and natural resources research and education center in 2023 and 2024 Experimental factors included: grafting method (patch budding and whip grafting), cultivar (Chandler and Fernor), and EBr concentration (0, 0.05, 0.15, 0.25 mM), comprised in 16 treatments. In October 2021, 100 walnut fruits were sown in pots (35 × 10 cm), and after 21 months 80 seedlings were chosen. Scions of cv. Chandler and cv. Fernor were grafted on seedling rootstocks during June 15–17.
Seedling growth traits were evaluated at the end of the growing season. Traits included graft success (qualitative evaluation in 2023), SBBT, shoot length, shoot diameter, and leaf number (measured in both 2023 and 2024). Data were analyzed based on factorial experiment in randomized complete block design using SAS 9.1. LSD test was used for mean comparisons, and graphs were depicted using Excel 2013 software.
 
Results and Discussion
Grafting success rate in walnuts were significantly influenced by the cultivar × EBr concentration interaction. EBRs are plant hormones, but their specific role in graft success needs further investigation alongside other crucial factors like phenolic compounds, vigorous rootstocks, and optimal environmental conditions. In 2023, cv. Fernor + 0.05 mM EBr showed the highest grafting success rate, but as the EBr concentrations inceased the grafting success rate decreased.
In 2023 and 2024, cultivar × EBr × grafting method interactions significantly affected SBBT. Cv. Fernor + low concentration or without EBr had the latest SBBT, but cv. Chandler + 0.25 mM EBr had the earliest. Chip budding advanced SBBT by 7–9 days compared to patch budding likely due to better tissue contact. Cv. Fernor + chip budding + 0.15 or 0.05 mM EBr had the longest shoots, whereas cv. Chandler + low EBr produced shorter shoots. Leaf number was consistent in 2023, but varied significantly in 2024 in cv. Fernor + chip budding + 0.05 mM EBr producing the highest leaf number (39 leaves). Cv. Chandler + chip budding + 0.25 mM EBr had lowest leaf number the fewest (9 leaves). Shoot diameter also varied in different treatments, and the thickest shoots was produced in cv. Fernor + patch budding + 0.05 mM EBr.
In conclusion, walnut cultivar had more pronounced effect on grafting success rate, and was identified as the most important factor in walnut seedling growth compared to high concentration levels of EBr and grafting methods.
 
References 
Engine, H. and Gökbayrak, Z. 2022. Effect of brassinosteroid applications on flower sex distribution of 'Chandler' walnut cultivar. Journal of Agricultural Sciences, 32(3), pp.548-554. DOI: 10.29133/yyutbd.1053275
Hartmann, H.T., Kester, D.E., Davies, F.T. and Geneve, R.L. 2011. Plant propagation: principles and practices. Pearson Education publication.USA. 425 pp.
Khajeali, M. and Mohammadkhani, A. 2015.  The Effects of timing and grafting methods on graft success and scion growth in walnut (Juglans regia L.). Journal of crop production and processing, 5(15), pp.47-55 (in Persian). DOI: 20.1001.1. 22518517. 13
Vahdati, K. 2003. Nursery management and grafting of walnut. Khaniran Publications. Tehran, Iran. 128 pp. (in Persian).

Keywords

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Seed and Plant Journal
Volume 40, Issue 4
August 2025
Pages 654-625

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