International Journal of Horticultural Science and Technology (2021) Vol. 8, No. 2, pp. 133-147 International Journal of Horticultural Science and Technology Journal homepage: http://ijhst.ut.ac.ir Effect of Grafting Methods and Dates on the Graft Take Rate of Persian Walnut in Open Field Condition Rabin Thapa1, Praseed Thapa2, Kafil Ahamad3 and Kourosh Vahdati4* 1. Agriculture and Forestry University, Chitwan, Nepal 2. Department of Agricultural Economics and Agribusiness Management, Faculty of Agriculture, Agriculture and Forestry University, Chitwan, Nepal 3. Senior Agriculture Officer, Ministry of Agriculture and Livestock Development, Nepal 4. Department of Horticulture, College of Aburaihan, University of Tehran, Tehran, Iran ARTICLE INFO ABSTRACT A field-based experiment was carried out in Rukum (East), Nepal, from Article history: February to June 2020, to assess the effect of different methods and dates of grafting on the graft take rate of Persian walnut (Juglans regia Received: 5 September 2020 L.) in field condition. The experiment comprised ten treatments with Received in revised form: 20 November 2020 combination of two factors. The two factors included the grafting dates Accepted: 5 December 2020 including: 13th, 19th, and 26th of February, 4th and 11th of March and grafting methods including: outdoor grafting and bench grafting (tongue grafting in both). The experiment was laid out in a Randomized Article type: Complete Block Design with three replications. The findings revealed that bench grafting resulted in significantly better outputs than outdoor Research paper method for length of scion (at 30 and 60 days after grafting) and graft take rates. Bench grafting showed 44% graft take followed by outdoor grafting (38% graft take). Plants grafted on 13th and 19th of February Keywords: showed statistically better results for growth performance over the other dates. Plants grafted on 19th of February showed 67% graft take Bench grafting, with 53% saleable plants, but statistically similar to the plants grafted Bud burst, on 13th and 26th of February. The earliest bud burst was observed in Hartley variety, plants grafted on 13th and 19th of February in 31 and 33 days, Outdoor grafting, respectively. Bench grafting on 19th February showed significantly Persian Walnut, higher length of scion (16.4 cm) at 60 days after grafting. However, Rootstocks, non-significant results were seen for other parameters due to the Scions. interaction. Therefore, bench grafting on 13th,19th and 26th of February led to the best graft take in Persian Walnut. Abbreviations: CV: Coefficient of Variation, LSD: Least Significant Difference, ha: hectare, mt: Metric tons, PMAMP: Prime Minister Agriculture Modernization Project, RCBD: Randomized Complete Block Design, SEm: Standard Error of Mean. Introduction the family Juglandaceae. It has wide Persian walnut (Juglans regia L.) is an adaptability to grow in the temperate regions important nut tree of the world and belongs to of the world (Mir & Kumar, 2011). The walnut species growing in Nepal is Juglans regia L. * Corresponding Author, Email: [email protected] (FAO, 2004), which is locally called ‘Okhar’ DOI: 10.22059/ijhst.2020.311553.401 133 Rabin Thapa et al. Int. J. Hort. Sci. Technol. 2021 8(2): 133-147 (Acharya, 2006). It is grown in the mountain (PMAMP, 2019). However, the production of regions of the country having an elevation of grafted walnut plants in Nepal is still 1000- 4000 m (Devkota, 1999) and across the insufficient to meet the demands within the temperate regions as well (Dhakal et al., country (Giri et al., 2019). 2003). Walnut is an important fruit of Hindu Around the globe, along with the work on rituals, holy festivals and weddings, thus new methods for the production of inoculating carrying an immense cultural value (Vahdati, planting material, old and reliable propagation 2014). The area under walnut cultivation in technologies are being improved (Gandev, Nepal is 2167 ha while the national average 2007). Various methods of vegetative production and yield of walnut are 8934 mt propagation in walnut have been reported to and 4.12 mt/ha respectively (MoALD, 2019). give a varying degree of success under different Rukum district, on the other hand, has a climatic conditions (Ibrahim et al., 1978; production of 742 mt (MoALD, 2019). Awasthi et al., 1982; Qureshi & Dalal, 1985; The propagation methods of walnut trees are Ozkan & Gumus, 2001; Wani et al., 2017). The divided into vegetative and sexual propagation. lower and unstable graft take rate hinders the In the sexual method of propagation, the progression of good varieties, regional seedlings have a long juvenile period and often consignment and marketability of walnut the varieties are outcrossed, due to which, the production in a straight way (Dehghan et al., seedlings fail to be true to type in nature 2010). Therefore, it is very urgent to discover the (Hartman et al., 2001; Ahmed et al., 2012; main factors affecting the survival of walnut Wani et al., 2017). Thus, due to heterozygosity, grafting, to standardize the grafting procedure seed propagation does not lead to the and to resolve the problem of poor survival inheritance of characters of a definite variety percentage of grafted seedlings. In fact, it is a (Gandev, 2018). Therefore, at present, walnut work of immense importance to study the cultivars are preferably propagated by grafting uniting process of grafting and the factors methods (Gandev, 2007). Although true to type affecting graft take rates in walnut (Gandev, seedlings can be produced via grafting, most of 2014). This would assist to meet the the grafting methods are confronted with international standards for the quality characters encounters such as long time for bearing and of nut and kernel. Hence, the knowledge of an poor graft take rates (Gandev, 2009). It is due appropriate method and appropriate time of to increased water loss and tissue mortality in grafting is important to enhance the production, the graft union of walnut, which is higher productivity, and area under walnut cultivation compared to other easily grafted trees (Vahdati, (Barut, 2001; Raufi et al., 2017). 2003). The low graft take rates of walnut The commercial cultivation of deciduous grafting has been of major interest in different fruits in Nepal is not a traditional practice and countries (Ozkan & Gumus, 2001; Vahdati, the propagation methods haven’t evolved 2003; Rezaee and Vahdati, 2008) like Turkey, throughout the decades (Schnelle, 2012). The Iran etc. In Nepal, the area under walnut classical method of propagation in walnut is plantation has extended and the demands for tongue grafting (Devkota, 1999). Although grafted walnut plants have been increasing tongue grafting is being practiced since decades, (FAOSTAT, 2018; MoALD, 2019). Rukum (East) the walnut growers are often disappointed with district of Nepal was declared as the ‘zone’ for the low graft take rate. So far, there have been walnut production in 2015/16, owing the agro- limited studies regarding the graft take rate of climatic suitability of the district for walnut walnut in Nepal. Ahamad (2020) claim that the plants production and the potential of walnut poor knowledge regarding the appropriate time commercialization as a high value commodity and appropriate method of grafting have 134 Rabin Thapa et al. Int. J. Hort. Sci. Technol. 2021 8(2): 133-147 constrained the higher graft take rate in walnut. nursery, located in Syalapakha, Sisne Rural Thus, there is a need to determine the suitable Municipality-08 under the command area of methods and appropriate grafting time of walnut PM-AMP (Walnut-zone), Rukum (East) district, in Nepal. Besides, the high-yielding varieties need Nepal (Fig. 2). The research site is located at a to be propagated with a higher graft take rates to latitude of 28.66o North and a longitude of make Nepal’s walnut industry competitive in the 82.49o East. The altitude of the place is 1200 global market (Ahmed et al., 2012). meters above the mean sea level. The climate This implies that a significant improvement of Syalapakha is characterized by three in the production of walnut could be achieved distinct seasons; rainy monsoon (June- via increase in graft take rate of high yielding October), cool winter (November-February), grafted seedlings. In this limelight, the current and mild spring (March-May) (Ahamad, 2020). study was aimed to determine the appropriate The temperature of the site over the methods and date of grafting in walnut to experimental period (February-June) is shown increase graft take rate in open field conditions. in Figure 1. The average precipitation was 1.042 mm per day, the total incident solar Materials and Methods radiation during the study period was 640.93 Experimental site kW-hr/ m2/ day and the average relative The experiment was carried out in a private humidity was 40.27% (NASA-Power, 2020). Fig. 1. Temperature of the nursery during research period in Rukum (East) district, Nepal. Source: (NASA-Power, 2020) Fig. 2. Research site of walnut grafting study located at Syalapakha (Sisne Rural Municipality-08), Rukum (East), Nepal. Source: (Authors archive, 2020) 135 Rabin Thapa et al. Int. J. Hort. Sci. Technol. 2021 8(2): 133-147 Experiment details grafting and outdoor grafting method (tongue The experiment comprised of five different grafting incorporated in both methods) as the dates of grafting; 13th February, 19th February, second factor. Thus, the experiment comprised 26th February, 4th March and