271 The Influence of Ecological Conditions and Genotype on Walnut Yield North of Oltenia – Romania M. Botu 1 , G. Achim 1 , S. Cosmulescu 1 , T. Tsampas 1 and I. Botu 2 1 University of Craiova, Faculty of Agriculture and Horticulture, Department of Horticulture and Food Science, Str. Al. I. Cuza nr. 13, Craiova 200585, Romania 2 University of Craiova, Fruit Growing Research and Extension Station (SCDP) Vâlcea, Str. Calea lui Traian nr. 464, Rm. Vâlcea 240273, Romania Keywords: Juglans regia, walnut, cultivars Abstract Walnut culture in Romania and particularly in Oltenia has historical, traditional and economic importance. Since most walnut trees grown in this area are natural hybrids (ungrafted) their yield and quality are variable and not desirable for commercial production. Successful walnut production will require cultivars suitable for this area. More than 26 walnut cultivars are native to Romania and several others have been introduced from foreign countries. This study investigates the horticultural performance of 10 native and eight introduced walnut cultivars planted in the North of Oltenia region of Romania. Data were collected from 2006 to 2012. During the 7-year study, the minimum temperature varied from -7.6 to -22.7°C and the annual rainfall varied from 493 to 808 mm. Walnut yield varied from 1.85 to 2.56 t/ha for terminal bearing cultivars and 2.15 to 3.15 t/ha for lateral bearing cultivars with no supplemental water from irrigation. The influence of genotype (G), environment (E) and their interaction (G×E) on walnut yield using estimated and expected variances is presented. The influence of the genotype on walnut yield varied from 43.9% for terminal bearing cultivars and 42.2% for lateral bearing cultivars. The environment contributed with 24.44 and 29.1% respectively and the G×E interaction with 12.22 and 14.6%. INTRODUCTION Walnut (Juglans regia L.) growth and production has traditional, economical and social importance for Romania. Walnut trees can be found growing in semi-cultivated and cultivated status from a variety of ecological conditions from the Danube Delta, the plains, hill area up to 800 m elevation and even higher (Botu and Achim, 2014). Romania currently produces about 32 to 34 thousand tons of walnuts, placing Romania amongst the top seven walnut producing countries in the world (Botu et al., 2010). The average production from 1961-2011 is 32,952 t of in shell walnuts (FAO Stat Database, 2013). There are less than 2,000 ha of walnut orchards and over 5 million walnut which are ungrafted natural hybrids. This genetic diversity needs investigation to identify valuable genetic resources currently in Romania (Cociu et al., 2003; Botu et al., 2010; Cosmulescu and Botu, 2012; Botu and Achim, 2014). In the last 40 years 32 walnut cultivars and 3 rootstocks were identified, most are selections from local Juglans regia populations. All of these cultivars have the terminal bearing characteristic. Unfortunately, most of these cultivars have not been propagated on large scale. The cultivars that have been used for establishing walnut orchards in the last decade are: ‘Jupâneşti’, ‘Mihaela’, ‘Roxana’, ‘Valcor’, ‘Valrex’, ‘Valmit’, ‘Germisara’, ‘Geoagiu 65’ and ‘Velniţa’. Foreign walnut cultivars have also been introduced into Romania. Terminal bearing ‘Franquette’ and lateral bearing cultivars ‘Fernor’, ‘Lara’ and ‘Fernette’ have been planted in different locations throughout Romania. In the last years cultivars from the Republic of Moldova (‘Cazacu’, ‘Chişinău’, ‘Corjeuţi’, ‘Costiujeni’ and ‘Schinoasa’) and Hungary (‘Milotai 10’) have been also planted (Botu and Achim, 2014). The favorable ecological conditions for walnut cultivation, especially in the Proc. VII th International Walnut Symposium Ed.: Jianbao Tian Acta Hort. 1050, ISHS 2014