In Vitro Own-Root Production of Pyrus communis L. cv. Natanz

Introduction Pyrus communis L. cv. Natanz is a popular pear cultivar in Iran because of its customer-friendly attribute due to its excellent characteristics. Pear own-rooted plants has better traits such as high vigorous in growth, low levels on tree losses and damaging by insects (Spornberger et al., 2008; Stanica et al., 2000) rather than cut-rooted and grafted plants. Meristem culture widely used for micropropagation (Erij and Fortes, 2002; Postman and Sugar, 2002), in vitro germplasm preservation (Reed, 1990; Niino and Sakai, 1992; Scottez et al., 1992; Bell and Reed, 2002; Sedlak el al., 2004) and virus eradication purposes in pear (Postman, 1994; Zilka et al., 2002; Dong et al. 2002; Hong et al., 2004; Wang et al., 2006; Postman and Hadidi, 1995; Tan et al. 2010). As pear is belonged to difficult-to-root fruit tree cultivars perhaps the rooting stage is the most important, yet most difficult phase during the in vitro propagation procedure. In vitro rooting of microcuts was varied by genotypes (cultivars) (Sedlak and Paprstein, 2015), type and concentration of used auxin (A1-Maarri el al., 1994; Sedlak and Paprstein, 2015), the method of root induction and formation (Bhojwani et al., 1984; Saadat et al., 2012; Erturk, 2013; Aygun and Dumanglu, 2015), different additional materials such as PVP, polyamines, PP333 (Marino, 1988; Rugini et al., 1992; Erturk, 2013) and so on. Materials and Methods Vegetative buds were taken from current growth shoots of Pyrus communis cv. Natanz from Pear collection orchard (25.36 E, 58.54 N and altitude 1380 meter) of Agricultural and Natural Resources Research and Education Centre of Semnan Province (Shahrood city). New shoots of active buds after 4 weeks transfer to PMI media (Reed et al., 2013) containing BA (0.5, 1, 1.5 mg l-1) and Fe-EDDHA (0, 100, 150 and 200 mg l-1). Meristems (containing 2 newest leaf primordia) was excited from in vitro shoots and incubation on MS media containing BA (0.5, 1, and 1.5 mg l-1) and GA3 (0.1 and 0.5 mg l-1) plus 0.1 mg l-1 IBA for all treatments. Mersitems were kept in dark for 4 days then were transferred to growth chamber. Different concentrations and combinations of two auxins were used. 1000, 2000, 3000 and 4000 mg l-1 of IBA or NAA and two combination solutions of them (1000 IBA+1000 NAA and 2000 IBA+2000 NAA, mg l-1). Shoots were immersing quick dip in solutions for 5 seconds then transfer to PGRs-free PMI medium and kept them to growth chamber. Data of all experiments were analyzed according by completely randomized design (CRD) with 5 replications. BA (3 levels) and Fe-EDDHA (4 levels) for experiment 1; BA (3 levels) and GA3 (2 levels) for experiment 2 were considered as factorial. SAS (v. 9.1) was used for analysis and means were compared with LSD test at 5% probably level. Results and Discussion Proliferated shoot number was affected by BA (p≤0.01) and Fe-EDDHA (p≤0.05) concentrations and also interaction of them (p≤0.05) while BA (p≤0.01) was caused elongation of proliferated shoots and Fe-EDDHA had no effect. BA (p≤0.05), Fe-EDDHA (p≤0.01) concentrations and BA×Fe-EDDHA (p≤0.01) interaction had significant effect on leaf production. Shoot tip necrosis was shown in shoots grown in all media based on BA concentration with different intensities (p≤0.05). Vegetative growth was counted as a power index of medium that in our experiment was under influence of BA concentrations (p≤0.01), Fe-EDDHA (p≤0.05) and BA×Fe-EDDHA interaction (p≤0.05). Shoots were proliferated (5.50 shoot/explant) and elongated in PMI media (MS ×1.5 CaCl2. 2H2O, KH2PO4 and MgSO4. 7H2O) containing 1.5 mg l-1 BA with no Fe-NaEDDHA while the lower concentrations of both BA and Fe-NaEDDHA caused the higher mature leaf production. PMI media containing 1 mg l-1 BA plus 150 mg l-1 Fe-NaEDDHA is recommended for Natanz shoot proliferation because of the highest vegetative growth and highest quality in proliferated shoots. MS media with 0.5 mg l-1 BA+ 0.5 mg l-1 GA3 (81%) and 1 BA mg l-1 + 0.1 mg l-1 GA3 (63%) had the highest meristem establishment, respectively. The established meristems in media supplement of 0.5 mg l-1 BA + 0.5 mg l-1 GA3+0.1 mg l-1 IBA naturally grown. Different types of auxin and their concentrations had significantly effect on Natanz pear cultivar microshoots rooting (p≤0.05). NAA induced rooting in lower concentrations while IBA had positive effect on rooting with concentration increasing. Microcuts were rooted via quick dip in 1000+1000 mg l-1 (IBA+NAA) solution followed by incubation in PMI medium. The rooted shoots well adapted to environmental condition.