Effect of Grafting Time and Method on Grafting Success Rate of Two Commercial Walnut Cultivars on Seedling Rootstock under Greenhouse Conditions

 The aim of this research was to investigate the effect of different grafting methods and grafting times on the grafting success rate of and two commercial walnut cultivars (scion) under greenhouse conditions. The experiment was carried out as factorial arrangements in completely randomized design with three replications under greenhouse conditions of West Azarbaijan agricultural and natural resouces research and eduction cenetre, Urmia, Iran, in 2015-2016. The experimental treatments included three levels of grafting methods; whip grafting, chip budding, and T-budding, two times of grafting; early spring and late spring, and two commercial walnut cultivars; Chandler and Franquette. The highest final grafting success rate (58.33%) was related to whip grafting followed by T-budding (38.33%) and chip budding (31.66 %), resspectively. The highest grafting success rate was obtained with whip grafting (64.45%) in early spring. Also, interaction effect of grafting method × grafting time × cultivar was significant on the final grafting success rate. The highest final grafting success rate (83.33%) related to T-budding of cv. Chandler in late spring.
 
Keywords: Walnut, Chandler cultivar, Final grafting success rate, Whip grafting,
T-budding.
 
Introduction
An important step for development of walnut cultivars with high-yielding and desirable quality is propagation using grafting methods (Soleimani et al., 2009). Many researches in different walnut growing countries have studied the effect of different grafting methods and grafing time on the success and productivity of grafted walnut cultivars and orchards. The degree of grafting success rates in these studies is very variable and depends on various internal and external factors (Vahadati et al, 2009). In addition to low graft coverage, frost damage to walnut grafted seedlings is considered as the second problem for production of outdoor grafted seedling nurseries (Ebrahimi et al., 2007).
Rezaee and Naghilou (2016) studied the effect of grafting method and grafting time of seedlings in the open-air environment with application of micronutrient elements on grafting success rate, and concluded that the lowest frost damage of the top branches was related to saddle and chisel grafting methods. Ebrahimi et al. )2007) evaluated three methods of grafting in walnut; patch grafting, chip budding and T-budding, under greenhouse conditions in Niriz, Fars province in Iran, and reported that all three grafting methods were more successful as compared with open air conditions. The purpose of present research was to investigate the effect of different grafting methods and grafting times on the grafting success rate of two commercial walnut cultivars (scion) on seedlings rootstock under greenhouse conditions.
 
Material and Methods
This research was conducted using completely randomized design with three replications in a plastic greenhouse in agricultural and natural resources research center of West Azarbaijan province, Urmia, Iran, in 2015-2016. In this research, three grafting methods; whip grafting, chip budding and T-budding, two commercial walnut cultivars (scion); Chandler and Franquette were used in the early spring (first half of April) and late spring (second half of June). Necessary husbundary practices for the nursery including; weeding, irrigation, and fertilizers application was accomplished until the end of the growing season. Since there were zero values in data, the data was subjected to square root transformation, and then analysis of variance was performed using SPSS software. Duncan's Multiple Range Test, at the 5% probability level, was employed for mean comparsion. Graphs were drawn using SPSS and Excel softwares.
 
Results and Discussion
The analysis of variance showed that the grafting method, grafting time and cultivar had significant (p ≤ 0.01) effect on the early and final grafting success rate, and scion length and diameter growth. The highest final grafting success rate (58.33%) was related to whip grafting followed by the T-budding (38.33%) and chip budding (31.66 %). The highest grafting success rate was obtained by using whip grafting (64.45%) in early spring (first half of April). Interaction effect of grafting method × grafting time × cultivar (scion) on final grafting success rate was also significant (p ≤ 0.01). The highest final grafting success rate (83.33%) and growth vigor obtained by using T-budding of cv. Chandler in the late spring (second half of June). Also, the least final grafting success rate (0%) was related to the chip budding of both cultivar and whip grafting of cv. Franquete in late spring.
The results obtained from this research are consistent with the results of Ebrahimi et al. (2007). Thes researchers experimented three grafting methods, whip grafting, chip budding, and T-budding under greenhouse conditions, and reported that the highest grafting success arte was related to patch grafting (91%), followed by T-budding (31%) and the lowest grafting success rate associated with chip budding (19%). Also, the findings of the present resreach are consistent with the results of Ozkan and Gumus (Ozkan and Gumus, 2001) in Turkey.
 
References
Ebrahimi, A., Vahdati, K. and Fallahi, E., 2007. Improved success of Persian Walnut grafting under controlled environmental conditions. International Journal of Fruit Science, 6(4), pp.3-12.
Kuden, A. and Kaska, N., 1997. Studies on the patch budding of walnuts in different budding periods under subtropical conditions. Acta Horticuturae, 422, pp.299- 301. DOI: 10.17660/ActaHortic.1997.442.46
Ozkan, Y. and Gumus, A., 2001. Effects of different applications on grafting under controlled conditions of walnut. Acta Horticuturae, 544, pp.515- 519. DOI: 10.17660/ActaHortic.2001.544.71
Soleimani, A., Rabiei, V., Hassani, D. and Amiri, M.E., 2009. Effects of rootstock and cultivar on propagation of walnut (Juglans regia L.) using hypocotyl grafting. Seed and Plant Production, 25(2), pp.93-101. (In Persian).