477 Scion/Rootstock Influence on Grafting Success, Early Performance, Tree Survival and Efficiency of Nutrient Uptake of Some Asian Pear (Pyrus serotina Rehd.) Cultivars K. Arzani 1 , H. Khoshghalb 2 and G. Karimzadeh 3 1&2 Department of Horticulture, Faculty of Agriculture, Tarbiat Modarres University (TMU), P.O.Box 14155-4838 Tehran, Iran 3 Department of Plant Breeding, Faculty of Agriculture, Tarbiat Modarres University (TMU), P.O.Box 14155-4838 Tehran, Iran Keywords: Asian pear, European pear, rootstock, propagation, tree survival, nutrient uptake, growth, compatibility Abstract This experiment was conducted in order to evaluate performance of some Asian (Japanese) pear cultivars (Pyrus serotina Rehd.) on European pear (Pyrus communis L.) seedling rootstock under Tehran environmental conditions during 2000 and 2001 growing seasons. The experiment was started in 2000 with budding of nine Asian pear cultivars named ‘KS’ 6 , ‘KS’ 7 , ‘KS’ 8 , ‘KS’ 9 , ‘KS’ 10 , ‘KS’ 11 , ‘KS’ 12 , ‘KS’ 13 , ‘KS’ 14 and the local ‘Shahmiveh’ (‘Sh’) cultivar (European pear) on European pear seedling rootstocks. The performance of budded trees was evaluated with some growth and physiological measurements during two complete growing seasons (2000 and 2001) at the Department of Horticultural Science, Tarbiat Modarres University (TMU), Tehran, Iran. Results showed more than 80% grafting success in the first season. Microscopic examination in the grafting site of all cultivars 2 to 4 weeks after budding showed a good callus formation. In the second season after budding 10% of grafted trees failed to grow, but differences between cultivars were not statistically significant. There were significant differences between cultivars in leaf mineral concentrations such as N, P and K. The highest N, P and K were observed in ‘KS’ 9 , ‘KS’ 12 and ‘KS’ 6 respectively, and the lowest concentrations in ‘Sh’, ‘KS’ 6 and ‘Sh’ respectively. INTRODUCTION Asian pear cultivars are almost propagated through budding/grafting onto pear (P. communis and P. serotina) and quince (Cydonia oblonga L.) seedling rootstocks. The main problem with the existing quince rootstocks is their graft incompatibility. It has been reported that the average budding survival of Asian pear cultivars on quince seedling rootstocks was less than 6%, so there was an evidence of incompatibility between some Asian pear cultivars and quince seedling rootstock (Arzani 2000a and 2004). Musacchi et al. 2002 mentioned that graft-incompatibility of pear and quince is a widespread phenomenon. In addition, a wide range of incompatibility reported by Carrera, 1994 among twenty five European pear studied cultivars on quince seedling rootstock. The aim of present research was to evaluate scion/rootstock interaction on early tree performance of some Asian pear cultivars budded on pear and quince seedling rootstocks under Tehran environmental conditions. MATERIALS AND METHODS Nine Asian pear cultivars ‘KS’ 6 , ‘KS’ 7 , ‘KS’ 8 , ‘KS’ 9 , ‘KS’ 10 , ‘KS’ 11 , ‘KS’ 12 , ‘KS’ 13 , ‘KS’ 14 (Arzani, 2000b, 2002a and 2002b) and one local European pear ‘Shahmiveh’ (‘Sh’) cultivar were budded on two–years-old P. communis L. seedling rootstocks on June 2000 at the nursery of Department of Horticultural Science, Tarbiat Modarres University (TMU), Tehran, Iran. Scion buds were collected from healthy three- years-old trees located in the TMU Asian pear mother block. The randomized complete block design (RCBD) was used for 10 scion cultivars with 5 replications and 4 sub- replications (four plants per replicate). Rows were oriented north–south in the nursery with a sandy-clay-loam soil. Experimental trees were irrigated using furrow Irrigation. Proc. IX th IS on Pear Ed.: K.I. Theron Acta Hort. 671, ISHS 2005