Comparison of Some Local and Foreign Walnut Cultivars

The performance of 12 walnut cultivars (‘Şebin’, ‘Şen1’, ‘Kaman1’, ‘Maraş18’, ‘Maraş12’, ‘Şen 2’, ‘Fernette’, ‘Chandler’, ‘Howard’, ‘Midland’, ‘Fernor’, ve ‘Pedro’) were evaluated under the ecological conditions at Niksar. The research orchard was established planted in 2008 with 7×7 m spacing. Phenological, pomological attributes and yield of cultivars were determined, between 2012 to 2015 years. Leafing of all of Turkish walnut cultivars in this research were found earlier than foreign cultivars. The leafing time of ‘Fernor’, ‘Fernette’, and ‘Chandler’ cv. were the latest among all cultivars. The cultivars with the earliest leaf fall dates were observed as ‘Maraş12’, ‘Maraş18’ and Şen2, the latest leaf fall dates were observed as ‘Chandler’, ‘Midland’ and ‘Pedro’. Nut weight was found between 10.32 g (‘Maraş12’) 20.15 g (‘Şen 1’), kernel weight 6.17 g (‘Maraş12’) 10.69 g (‘Şen1’), kernel percentage between 44.92% (‘Pedro’) 65.54 (‘Şebin’). Shell thickness was noted between 0.85 mm (‘Şebin’) – 1.97 mm (‘Fernor’). The total yield (kg/tree) of cultivars was determined between 2.29 (‘Maraş12’) and 23.56 (‘Pedro’). Later leafing cultivars seem to be more suitable for Niksar ecological region.


Introduction
Walnut (Juglans regia L.), a member of the family Juglandaceae, is the most important species among other 18 species. Natural walnut populations grown from seed are usually located within the borders of the rivers or agricultural areas as scattered trees in Turkey. In the past years, the walnut orchards in Turkey were from seedling trees and therefore the nut production was various and nut quality were differed (Şimsek2010; Gülsoy et al. 2016).
But, the new commercial plantings have been established with standard domestic and foreign walnut varieties on Juglans regia L. seedling rootstocks in the major fruit areas.
According to the agricultural statistics, Turkey has derived 210 000 tons of walnut from the total number of 16 661 339 trees in 92 013 ha. production area, and the average yield is about 24 kg/tree (TSI 2017). Domestic walnut cultivars such as 'Yalova1', 'Şebin', 'Yalova2', 'Bilecik', 'Yalova3' have long been the important choice of Turkish growers (Şimşek 2015;Akça 2016). These cultivars have not been planted in recent years due to their early leafing habit and these local cultivars are susceptible to pests and diseases especially bacterial blight, and spring frost. The yields of these cultivars are very low when compared to Californian and French cv. (Akça 2016). 'Chandler' and 'Fernor' cultivars have been used in the establishing of new walnut orchards in Turkey.
The aim of this research is to compare the main agronomic characteristics of Turkish and foreign walnut varieties in Niksar ecological conditions.

Material and Method
The research orchard was established in 2008. The trees were planted in 7 x 7 m spacing. In this study, the walnut cultivars 'Şebin ','Şen1','Kaman1','Maraş18','Maraş12','Şen2','Fernette','Chandler','Howard','Midland','Fernor',and 'Pedro' were evaluated. Juglans regia L. seedlings were used as rootstocks in this orchard. The experiment was designed according to completely randomized design (CRD). The observations were made on 12 walnut trees for each cultivar (4 repetitions and 3 plants for each cultivar). The chemical and organic fertilization has been applied annually. 30 kg/ha pure nitrogen, 40 kg/ha net phosphorus and 50 kg/ha potassium fertilization were made in the research orchard in 2013. Also, 10 tons / ha of manure was used annually. The standard pest and diseases management has been applied. The drip irrigation system was used in the orchard.
The research orchard area is characterized by minimum temperature -15.16 °C, maximum temperature of 38.17 °C and average annual rainfall is 405.5 mm. The most important climate restriction for walnut production is early spring frosts in Niksar region. The soil characteristics of orchard soil are given Table 1. The phenological, pomological and yield traits that are listed below were investigated according to UPOV between 2012 and 2015 years. The symptoms of walnut blight were also evaluated. Based on the number, size and distribution of lesions on leaves, 0 to 4 severity scale was used according to Özaktan et al (2011).
Phenological characteristics: Leafing date, male and female blooming date, harvest date, date of leaf fall.

Morphological characteristics:
Trunk diameter, growth habit, vigor and density of branches. Tree of trunk diameter was measured at 10 cm above grafting point.
Yield: Average and total yield was determined as kg/tree.

Results and Discussion
This study was made to compare main Turkish cultivars with foreign commercial varieties from France and California between 2012 and 2015 years. Leafing dates of cultivars are given in Table  2.
'Serr' walnut variety leaves 15 days earlier than 'Pedro' cv. in Italy's Piemonte region. The late leafing cultivars; 'Pedro', 'Hartley, 'Corne', 'Parisienne', 'Marbot', 'Mayette', 'Grandjean' and 'Franquette' were found to be high enough to adapt to ecological conditions than other varieties in Piemonte region of Italy (Radicati et al. 1990). David (1998) reported that the bud break time of 'Pedro', 'Chandler' and 'Howard' cultivars were 15 to 17 days later than 'Serr' cv. in California ecological conditions. The earliest leafing cultivar was 'Payne' (Hendricks, 1998). The leafing dates of 'Hartley, 'Chandler', 'Howard' and 'Hartley, are later than 'Payne' as 17, 17, 16 and 14 days, respectively. The leafing date of 'Chandler' is 7 days before 'Fernor' in Patagonia region of Argentina (Iannamico et al. 2006). In our study, leafing time of 'Chandler' was observed earlier than 'Fernor' as 9 days. The data obtained in from our study are consistent with the information obtained from the above mentioned sources. The earliest catkin pollen shed was observed in 'Serr' cultivar as the earliest, and the latest in Franquette cv. (Botu et al. 2007). The cultivars 'Fernor' and 'Fernette' have the advantage of late female flowering which is similar to our results.
Fruits were harvested from early September to the beginning of October. The earliest harvested varieties were 'Maraş12' and 'Maraş18', the latest harvest varieties were 'Chandler' and 'Pedro' (Table 2). Early harvest time and early defoliation time are important for the ecological region with short vegetation period. Also, 'Kaman1' walnut cultivars have late leafing and early harvest time and early defoliation according to 'Şebin', 'Şen1' and 'Şen2'.