Influence of some external factors on the rooting of GF677, peach and nectarine shoot hardwood cuttings

CSIRO PUBLISHING www.publish.csiro.au/journals/ajea Australian Journal of Experimental Agriculture, 2005, 45, 107 113 Influence of some external factors on the rooting of GF677, peach and nectarine shoot hardwood cuttings C. Tsipouridis A, T. Thomidis A,C and Z. Michailides B A Pomology Institute, P.C. 59200, Naoussa, Greece. B Technological Education Institute of Thessaloniki, P.C. 54101, Thessaloniki, Greece. C Corresponding author. Email: thomi-1@otenet.gr Abstract. The influence of some external factors [cultivar, indole-butyric acid (IBA) concentration, IBA dipping of shoot tip and base, preheating of cuttings, collecting date, time of cutting collection, mother tree age, cultivar, length of and diameter of cutting] on rooting of peach nectarine hardwood shoots in the field were examined. It was found that the best IBA concentration for rooting differed among peach cultivars. Rooting of cuttings whose bases only were immersed in IBA solution was higher than those that had both base and tip immersed. In addition, a higher percentage of rooting shoots was achieved with preheating of cuttings before planting. The best length for cuttings varied between cultivars and the best diameter was 10 13 mm. Cuttings collected between 25 October and 13 November (1997 and 1998) showed the highest percentage of rooting shoots. There was also a higher percentage of rooting GF677 hardwood shoot cuttings collected from 7-year-old mother trees compared with those collected from 1-year-old mother trees. Additional keywords: collection date, cutting length, indole-butyric acid, preheating. Introduction In spite of being the Queen of Fruits (Childers and Sherman 1988), the peach (Prunus persica L. Batch) has not been subjected to intense scientific study until the last 2 decades. As the economic life of peach orchards becomes shorter due to innovations in planting and the use of new varieties with better fruit quality and greater productivity, larger quantities of propagation material are required for replanting (Stylianides et al. 1988). Vegetative propagation of peach can be achieved by hardwood (Reighard et al. 1990; Toit et al. 1995; Bartolini et al. 2000), semi-hardwood (Avery and Beyl 1991; Biasi et al. 2000), and green wood cuttings (Liu et al. 1989) as well as by suckers, root cuttings and tissue culture (micrografting, microcuttings, somatic embryogenesis) (Hammerschlag and Scorza 1991). In Greece, conventional peach propagation is undertaken by tissue culture, but this method of propagation is very expensive and requires specialised laboratories and apparatus, and experienced scientists. Therefore, propagation of peach by hardwood cuttings could potentially reduce establishment costs. In addition, this method is easily applied by nurserymen. Erez and Yablowitz (1981) proposed the propagation of peach trees by hardwood cuttings in order to reduce the establishment cost and increase the feasibility of peach meadow orchard systems. Propagation of peach trees by semi-hardwood cuttings is also cheap, but the use of hardwood cuttings is a much easier method. The rooting of shoot cuttings is affected by external factors such as cultivar, indole-butyric acid (IBA) concentration, collecting date, time of cutting collection, mother tree age, cultivar, and length of and diameter of cutting. In addition, hardwood cuttings from peach rootstocks originating from the same parents can also show different proportions of rooting shoots (Cambra 1990). Edriss and Burger (1993) found that treating cuttings of Nemaguard peach rootstock with 2000 mg/l IBA was sufficient to produce adventitious roots, however, 4000 mg/l IBA did not significantly affect initiation of rooting and inhibited root growth. Bartolini et al. (2000) found that peach cuttings with 6 10 mm diameter had a higher proportion of rooting shoots in comparison with cuttings of smaller diameters. They also found that cold and basal heating treatments may enhance the rate and amount of rooting. Combining favourable levels of these external factors could improve the rooting of peach hardwood cuttings. This study invesigated possible increases in the percentage of rooting peach nectarine cultivars and GF677 (almond peach hybrid used as peach rootstock) shoot cuttings using various combinations of the external factors listed above. Material and methods All experiments described in this study were performed in 2 consecutive years (1997, 1998) and all the vegetative material (shoot cuttings) was taken from the experimental orchards of the Pomology Institute, Naoussa, Greece. The cuttings were collected from the base of annual shoots and used the same day. CSIRO 2005 10.1071/EA03120 0816-1089/05/010107

108 Australian Journal of Experimental Agriculture C. Tsipouridis et al. In all experiments non-rooted cuttings were checked for infections by pathogens (pieces from the bases of cuttings were transferred onto cornmeal agar, hemp seed agar, potato dextrose agar and Lutz medium) immediately after recording the results. No pathogen was isolated from the non-rooted cuttings. Preparation of chemical solutions Solutions of auxin were prepared by dissolving accurately weighted amounts of auxin (IBA) in 3 ml absolute ethanol and making each solution up to 500 ml (adding absolute ethanol), with continuous stirring. Another 500 ml of distilled water was then added. Control solutions contained similar amounts of ethanol (50%) and distilled water without IBA. All solutions were stored in the dark in a refrigerator (1 3 C) for no longer than 2 months. Effect of cultivar and indole-butyric acid concentration on rooting and survival of peach nectarine cultivars and GF677 hardwood shoot cuttings On 25 October 1997, 20-cm long cuttings were taken from 3-yearold peach nectarine cultivars (Early Crest, May Crest, Spring Crest, Flavour Crest, Red Heaven, Sun Crest, Early Gem, Arm King, May Grand, Red Gold), and from the peach rootstock GF677 (7-years-old). Immediately after collection, the cuttings were treated for 15 s with 10 different IBA concentrations (0, 500, 1000, 1500, 2000, 2500, 3000, 4000, 5000 and 6000 mg/l). After surface drying, their bases were treated with Captan 75% (1:9 in talcum powder). Cuttings were then planted in specially prepared raised nursery beds (20 cm height from soil surface) to avoid waterlogging. Soil characteristics are presented in Table 1. During dry weather in the spring, the cuttings were irrigated by sprinklers (120 mm/h) every 15 days and sprayed (1.5 Captan 83VP and 0.4 pyrethroid) to prevent fungal, bacterial and insect attacks. The experimental design used was completely randomised with a factorial arrangement (10 cultivars 10 IBA concentrations 2 replications of 10 cuttings). The final record was taken on 25 May 1998. Cuttings that were growing were recorded as successful. Effect of indole-butyric acid dipping of shoot tip and base on rooting of GF677 hardwood shoot cuttings Twenty-centimetre long cuttings of GF677 were taken from 7-year-old mother trees on 21 November 1997. Two IBA concentrations (500 and 1000 mg/l) and 2 types of immersion (base only immersion, and both base and tip immersion) were applied in a factorial combination with 5 replications of 100 cuttings each. The experimental design used was completely randomised. The preparation, planting and recording of rooting and survival were similar to those described in the previous experiments. Effect of preheating and sampling date on rooting of peach cultivars and GF677 shoot hardwood shoot cuttings The experiments were started on 20 October 1997. Cuttings of 3 cultivars, GF677 (7 years old), Early Crest and Arm King (both 3years old), were taken from experimental orchards of the Pomology Institute at 5-day intervals until 4 December 1997. The bases of the cuttings (1 cm) were treated as described previously with IBA as a quick dip at 2000 mg/l and Captan 75% (9:1 in talcum powder). Half of the cuttings were planted immediately in the nursery. The other half were placed in polyethylene bags containing peat and perlite (3:1) substrate and kept preheating in a growth cabinet at 26 C for 10 days. After this preheating, the callused cuttings remained at room temperature for a further 3 days (for acclimation) and were then planted close to unheated ones in the nursery. Records of rooting (survival) data were taken on 25 May 1998 (cuttings which started growing were recorded as successful ones). The experimental design was completely randomised with a factorial arrangement of treatments (3 cultivars 2 heatings 10 collecting dates 3 replications of 10 cuttings). Effect of time of cutting collection, stock tree age and cultivar on rooting of peach cultivar rootstock cuttings The experiments were conducted on 23 and 29 of October 1997 and continued to the 4, 8, 13, 18, 22, 27 November, and 2 and 6 December. Cuttings of peach cultivars Early Crest, May Crest, Arm King, Red Haven (3 years old) and GF677 from 7-year-old and 1-year-old (from nursery) trees, were taken at each date and treated with 2000 mg/l IBA and Captan 75% (1:9 in talcum powder). The experimental design was completely randomised with a factorial arrangement of treatments (10 collecting dates 6 cultivars 2 replicates of 10 cuttings each). The preparation, planting and recording rooting percentages were similar to those described in previous experiments. Cultivar and length of cutting effects on rooting of peach nectarine hardwood shoot cuttings This experiment was designed to find out optimum cutting length for rooting. Five lengths (20, 25, 30, 35 and 40 cm) were tested on 7November with four, 3-year-old cultivars (Early Crest, May Crest, Arm King Red Haven) and 1 peach rootstock (7-year-old GF677). The experimental design was completely randomised with a factorial arrangement of treatments (5 cultivars 5 cutting lengths 2 replications of 20 cuttings each). The cuttings were treated with 1000 mg/l IBA and were prepared, planted and measured as in previous experiments. The only difference wasinthe way soil was accumulated around the longer cuttings, so that in all treatments only 2 cm of the cuttings was exposed above the soil after planting. Great attention was given to ensure that the base of the cuttings wasatleast 2 cm above the lower part of the furrow between the rows. The effect of cutting stem diameter on rooting of different peach nectarine cultivars and GF677 hardwood shoot cuttings Eleven diameter sizes (5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15 mm) were tested in 4 cultivars: Early Crest, May Crest, Arm King and Red Haven (3 years old) and the peach rootstock GF677 (cuttings from 7-year-old and cuttings from 1-year-old trees) in a completely randomised design with a factorial arrangement of treatments (11 levels of diameters 6 cultivars 2 replicates of 10 cuttings). The cutting diameter was measured at the base of each (20-cm long) cutting. After dipping the cuttings for 15 s (1 cm deep) in a 1000 mg/l solution of IBA, they were allowed to dry for several minutes and treated with Captan 75% (as in previous experiments). They were planted on 25 November in nursery rows (1 m wide, 10 cm apart and 18 cm deep). Rooting and survival measurements were taken on 9 May of the following year. Table 1. Soil characteristics of the experimental nursery Depth (cm) Mechanical analysis Soil Electrical Organic ph in CaCO 3 Water-holding Clay Loam Sand texture conductivity matter pulp (%) capacity (%) (%) (%) (%) (ms/cm) (%) 0 30 34.2 29.8 36 Clay loam <3 1.7 7.2 4.7 51 30 60 44.4 25.2 30.4 Clay <3 7.5 7.8 65 60 90 39.6 30 30.4 Clay loam <3 7.8 59

Influence of external factors on shoot hardwood cuttings Australian Journal of Experimental Agriculture 109 Table 2. Percentage of peach cultivar hardwood cuttings rooting in response to different levels of indole-butyric acid (IBA) Cultivar Regression equation d.f. r P-value IBA level Max. response (mg/l) (%) Early Crest y = 1.8807 + 0.1150x (0.02 10 5 )x 2 6 0.7962 0.049 2700 15 May Crest y = 2.4342 + 0.0222x (0.08 10 5 )x 2 + (0.07 10 9 )x 3 7 0.8167 0.064* 1700 21 Spring Crest y = 7.8430 + 0.0711x 0.03 10 4 )x 2 + (0.03 10 8 )x 3 7 0.8319 0.056* 1400 57 Flavour Crest No significant curvilinear response A 1500 40 Red Haven y = 21.6949 + 0.0128x (0.03 10 5 )x 2 7 0.7701 0.043 1800 35 Sun Crest y = 9.5307 + 0.0929x (0.04 10 4 )x 2 + (0.043 10 8 )x 3 7 0.8056 0.081* 1500 73 Early Gem No significant curvilinear response A 500 70 Arm King No significant curvilinear response A 3000 5 May Grand y = 7.9815 + 0.0247x (0.07 10 5 )x 2 5 0.8911 0.019 1800 30 Red Golden No significant curvilinear response A 500 55 A No significant curvilinear response was detected. To compare responses to indole-butyric acid (IBA) levels and to determine the level of maximum response for these cultivars, the was used [comparisons with = 16.32 after ANOVA]. *P = 0.05. Results Effect of cultivar and indole-butyric acid concentration on rooting and survival of peach nectarine cultivars and GF677 hardwood shoot cuttings The different cultivars studied did not show the same pattern of response to changes in the application level of IBA. Early Crest, May Crest, Spring Crest, Red Haven, Sun Crest and May Grand followed multinomial curvilinear regression, while Flavour Crest, Early Gem, Arm King and Red Golden did not show any steady pattern of curvilinear response. The results show differences among cultivars in the concentration of IBA that gave the highest percentage of rooting shoots (Table 2). Each cultivar also had different maxima. Effect of indole-butyric acid dipping of shoot tip and base, on rooting of GF677 hardwood shoot cuttings The analysis of variance showed significant differences between base only and base plus tip immersions (Table 3). When bases only were immersed in IBA solution, the Table 3. Effect of indole-butyric acid (IBA) concentration and base or base and tip immersion on percentage of rooting GF677 hardwood cuttings Values are the means of 2 experiments; results were similar according to the Bartlett s test of homogeneity of variance, therefore data were combined IBA (mg/l) Immersion in IBA Base only Base + tip Mean 500 31.8 17.2 24.5 1000 36.2 23.4 29.8 Mean 34 20.3 Immersion = 7.48 IBA = 7.48 Immersion IBA = 10.58 proportion of shoots rooting was higher compared with shoots that had both bases and tips immersed. No significant difference in this pattern was observed at different IBA concentrations (Table 3). The rooting of cuttings when bases only were immersed in 500 mg/l IBA solution was significantly higher than those where both base and tip immersion were applied in 500 mg/l IBA solution. However, no significant difference was observed in rooting percentage between cuttings of which bases were immersed in 500 mg/l IBA solution and cuttings of which both base and tip were immersed in 1000 mg/l IBA solution. The rooting of cuttings when bases only were immersed in 1000 mg/l IBA solution was significantly higher than those of which both base and tip were immersed in 500 or 1000 mg/l IBA solution. Effect of preheating and collecting date on rooting of peach nectarine cultivars and GF677 hardwood shoot cuttings Two-way analysis of variance showed an influence of preheating and collecting date on the rooting of cuttings (Table 4). For GF677 cuttings, preheating significantly increased the rooting of shoots collected on 9 November. A positive influence of preheating on the rooting of Early Crest cuttings was observed when cuttings were collected on 30 October, and 4 and 9 November. In contrast, preheating negatively affected the rooting of Early Crest cuttings collected on 25 October. Preheating of Arm King cuttings before planting increased the rooting percentage when they were collected on 4 and 9 November. For GF677, the best time of cutting collection was generally from 20 October to 9 November, while for Early Crest and Arm King the best time was from 30 October to 9 November. Preheating was of greater benefit to the difficult to root cultivars Arm King and Early Crest than GF677. GF677 cuttings were rooted easier than cuttings from Arm King and Early Crest. Preheating improved rooting of Arm King and Early Crest more than GF677 (Table 4).

110 Australian Journal of Experimental Agriculture C. Tsipouridis et al. Table 4. Effect of date of cutting collection and preheating of cuttings on rooting of peach nectarine cultivar and rootstock shoots [data were angular-transformed before analysis, then retransformed to original (percentage) values after analysis] Values are the means of 2 experiments; results were similar according to the Bartlett s test of homogeneity of variance, therefore data were combined Date Non-treated Preheating Mean GF677 E. Crest A. King GF677 E. Crest A. King 20.x.97 53.33 3.53 0.25 50 3.33 0.25 18.45 25.x.97 26.67 40 3.33 36.67 10 6.67 20.56 30.x.97 43.33 6.67 13.33 43.33 23.33 13.33 23.89 04.xi.97 50 3.33 13.33 56.67 60 53.33 39.44 09xi.97 40 3.33 3.33 60 26.67 23.33 26.11 14.xi.97 6.67 3.33 3.33 10 3.33 6.67 5.53 19.xi.97 3.33 10 0.25 6.67 10 6.67 6.13 23.xi.97 6.67 3.33 0.25 6.67 3.33 3.33 3.93 29.xi.97 6.67 3.33 3.33 3.33 0.25 0.25 2.86 04.xii.97 3.33 0.25 0.25 0.25 0.25 0.25 0.76 Mean 24 7.71 4.1 27.36 14.05 13.41 Heating = 3.57 Cultivar = 3.57 Date = 4.61 Heating cultivar date = 11.30 Effect of cutting collection date, mother tree age and cultivar on rooting of peach nectarine cultivar rootstock hardwood shoot cuttings Overall rooting of GF677 cuttings from 7-year-old trees (40% of shoots) was not significantly different to cuttings from 1-year-old trees (35.7% of shoots), although there were significant differences at specific dates (23 and 29 October; 4, 8 and 13 November; 2 December). Cuttings from older trees seem to do better when taken earlier in the season than those from 1-year-old trees. The cultivar Arm King again had the lowest percentage of rooting shoots, while GF677 had the highest (Table 5). The highest percentage of rooting for 7-year-old GF677 cuttings was between 29 October and 8 November, for seven, 1-year-old GF677 cuttings between 29 October and 13 November and for Arm King cuttings between 8 and 13 November. No significant difference was found in percentage of shoots rooting between Early Crest, May Crest and Red Haven. However, significant differences were found at specific dates (Table 5). The highest percentage of rooting shoots for both Early Crest and May Crest was on 13 November, and for Red Haven between 4 and 8 November. Rooting percentage of Early Crest, May Crest Table 5. Effect of time of cutting collection, mother tree age and cultivar on rooting percentage of peach cultivar and GF677 cuttings [data were angular-transformed before analysis, then retransformed to original (percentage) values after analysis] Values are the means of 2 experiments; results were similar according to the Bartlett s test of homogeneity of variance, therefore data were combined Date GF677 (7 years) GF677 (1 year) E. Crest M. Crest Arm King R. Haven Mean 23.x.97 53.33 16.67 0.25 13.42 0.25 0.25 14.03 29.x.97 70.00 60.00 3.50 6.75 6.75 23.33 28.39 04.xi.97 70.00 50.00 10.08 20.00 3.50 40.00 32.26 08.xi.97 80.00 53.33 46.67 16.67 26.67 33.33 42.79 13.xi.97 43.33 63.33 50.00 50.00 13.33 13.42 38.90 18.xi.97 23.33 26.67 16.75 13.33 6.75 10.08 16.15 22.xi.97 16.67 16.67 10.08 6.75 10.00 20.00 13.36 2.xi.97 16.67 13.42 6.83 10.00 0.25 3.50 8.45 02.xii.97 13.33 40.00 10.08 16.67 0.25 6.75 14.51 06.xii.97 13.33 16.67 0.25 16.67 3.50 6.75 9.53 Mean 40.00 35.70 15.50 17.30 7.10 15.70 Cultivar = 4.83 Date = 6.24 Cultivar date = 15.27

Influence of external factors on shoot hardwood cuttings Australian Journal of Experimental Agriculture 111 Table 6. Effect of cultivar and cutting length on percentage of rooting shoots for peach cultivars and GF677 hardwood cuttings planted in the nursery Values are the means of 2 experiments; results were similar according to the Bartlett s test of homogeneity of variance, therefore data were combined Cutting length (cm) GF677 E. Crest M. Crest Arm King R. Haven Mean 20 50.00 7.50 70.00 17.50 7.50 30.50 25 80.00 20.00 75.00 10.00 12.50 39.50 30 32.50 20.00 32.50 7.50 20.00 22.50 35 12.50 17.50 10.00 5.00 15.00 12.50 40 5.00 7.50 7.50 5.00 15.00 8.00 Mean 35.90 14.50 38.90 9.00 14.00 Cultivar = 6.67 Cutting length = 6.67 Cultivar cutting length = 14.91 and Red Haven was significantly lower than GF677 (for both 1- and 7-year-old mother trees). Cultivar and length of cutting effects on rooting of peach nectarine hardwood shoot cuttings Two-way analysis of variance indicated significant differences between the rooting of cuttings with different cutting lengths and from different cultivars (Table 6). The cultivar Red Haven rooted better with 30-cm long cuttings (20% rooting), while the nectarine Arm King rooted best with shorter 20-cm cuttings (17.5%). Generally, the best cutting length varied from cultivar to cultivar (Table 6). The cultivar May Crest gave the highest percentage of rooted cuttings and was significantly different from the other mutants Spring Crest and Early Crest. The best cutting lengths for May Crest were 20 cm (70%) and 25 cm (75%). The best cutting length for GF677 was 20 cm (80% rooting), which was the highest percentage of rooting shoots across all cultivars, however, there was no significant difference found between this value and the percentage of rooting shoots for the 20 and 25 cm May Crest cuttings. A comparison between GF677 and other cultivars should be made with caution because of the different age of the mother trees. The effect of the stem diameter on rooting of different peach nectarine cultivars and GF677 hardwood shoot cuttings Two-way analysis of the data showed significant differences between cultivars (and age in the case of GF677) and diameters of the cuttings as well as significant interactions (Table 7). GF677 cuttings from older trees (7-year-old) had significantly higher percentages of rooting shoots, while cuttings from the nursery rooted less well. GF677 trees from the nursery dropped their leaves about 5 15 days later than the older ones (C. Tsipouridis unpublished data). Early Crest had a higher percentage of rooting shoots than May Crest, Arm King and Red Haven. No significant difference in the percentage of shoots rooting was observed between May Crest and Red Haven. Arm King showed the lowest percentage of rooting cuttings. Table 7. Effect of cutting diameter on percentage rooting of different peach cultivars or GF677 hardwood cuttings For treatments without rooting the value 0.25 was used for the statistical analysis Values are the means of 2 experiments; results were similar according to the Bartlett s test of homogeneity of variance, therefore data were combined Cultivar 5 mm 6 mm 7 mm 8 mm 9 mm 10 mm 11 mm 12 mm 13 mm 14 15 mm Mean GF677 (7 years old) 0.25 10.00 80.00 55.00 95.00 100.00 90.00 85.00 80.00 65.00 66.02 GF677 (1 year old) 10.00 5.00 35.00 35.00 45.00 15.00 50.00 65.00 60.00 50.00 37 E. Crest 0.25 10 40 15 15 60 67.5 15 50 15 28.77 M. Crest 0.25 5 15 5 15 15 50 60 15 5 18.52 Arm King 0.25 0.25 0.25 0.25 0.25 10 5 5 15 5 4.12 R. Haven 0.25 5 5 20 10 15 15 35 35 15 15.52 Mean 1.87 5.87 29.21 21.71 30.04 35.83 46.25 44.17 42.5 25.83 Cultivar = 6.45 Diameter = 8.33 Cultivar cutting diameter = 20.4

112 Australian Journal of Experimental Agriculture C. Tsipouridis et al. The results also showed that overall the best cutting diameter to promote rooting was between 10 and 13 mm. Cultivars which dropped their leaves earlier (old GF677 trees, Early Crest, C. Tsipouridis unpublished data) showed better rooting with cuttings of smaller diameter than cultivars which dropped their leaves later (e.g. GF677 from the nursery and May Crest in relation to Early Crest, Arm King, C. Tsipouridis unpublished data). Maturation of the annual shoots progresses from the base to the tip. Discussion This study provides important data for the influence of cultivar, IBA concentration, IBA dipping of shoot tip and base, preheating of cuttings, collecting date, time of cutting collection, mother tree age, cultivar, and length of and diameter of cutting on the rooting of peach nectarine hardwood shoot cuttings in the nursery. Differences were observed among cultivars in the concentration of IBA that led to the highest percentage of rooting shoots (Table 2). Each cultivar had different maximum rooting percentages. This may have been due to the different origins of each cultivar (e.g. GF677 is a almond peach hybrid) and on the different growth rate of cultivars. Erez and Yablowitz (1981) also reported variation in rooting percentage of cuttings between peach cultivars. According to Hwang (1991), easy rooting peach cultivars appeared to produce auxin-like substances more quickly than the poorrooting cultivars. Loach (1988) found that the effectiveness of auxin applications in promoting adventitious root formation in cuttings is influenced by hormone concentration. Also, cultivars differed in the optimal IBA concentration. However, for all cultivars tested, the best IBA concentration was between 500 and 2000 mg/l. Similar results were produced for the rooting of peach nectarine hardwood and semi-hardwood cuttings planted in a mist unit (Tsipouridis et al. 2003). Rana and Chadha (1989) reported that 2000 mg/l IBA was most effective to root dormant cuttings of 4 Prunus rootstocks. According to Tofanelli et al. (2001), the best rooting results were obtained using woody cuttings of the peach cultivar Diamante treated with 2000 mg/l IBA. The percentage of rooting GF677 cuttings was lowest when both shoot tip and base were dipped in IBA solution. A possible explanation for this is that tip and base immersions could disturb the natural hormone balance of cuttings and the total soluble carbohydrate (Tsipouridis 1993). The involvement of polar auxin transport in supplying the auxin for rooting was reported by Guerrero et al. (1999). Data showed that preheating of cuttings had a positive effect on rooting percentage depending on the collecting time (Table 4). According to Lila (1977), soluble carbohydrate and organic nitrogen content were more dependent on drying conditions especially after preheating. The high natural temperatures during the later part of October favoured rooting of cuttings planted early, while the lower outdoor temperatures of November, in addition to rain (which also lowered soil temperatures) were unfavourable for rooting of cuttings planted in November. It was observed that a preheating period of 10 days was optimal, while 5, 15 or 20 days were less favourable (Tsipouridis 1993). This study also showed that the best time for collecting cuttings was between 25 October and 13 November. Similarly, Gill and Chitkara (1990) found that peach cuttings taken in November rooted better than those taken in December. Moreover, Edriss and Burger (1993), reported that peach hardwood cuttings collected in October rooted more successfully than those collected in August or September. The effect of length of the cutting on rooting must be related to weather conditions. Toit et al. (1995) found that cuttings from main shoots of GF677 rootstock with a diameter of between 6 and 16 cm gave a satisfactory survival response, as long as they were at least 30 cm in length. Survival percentage decreased as cutting length decreased from 30 to 15 cm. Peach cultivars also differed significantly in the optimum diameter of stem cuttings. Fege (1983) gave evidence for the physiological basis of collecting of Populus hardwood cuttings. Bartolini et al. (2000) reported that the cuttings of peach trees (Prunus persica L. Batsch.) with a 6 10 mm diameter showed a higher percentage of rooting in comparison with those of smaller diameters. The higher rooting of Early Crest must be related to the most favourable time for cutting collection (Early Crest drops its leaves 2 10 days earlier than May Crest so early cutting collection favoured Early Crest). In conclusion, before taking hardwood cuttings, nurserymen should consider that the percentage of rooting cuttings differs from cultivar to cultivar. For any cultivar, an IBA concentration between 500 and 2000 mg/l must be used. Rooting of cuttings can be improved when their bases only are immersed in IBA solution. Since the effect of preheating of cuttings depends on the collecting date, preliminary investigations should be performed for each cultivar or rootstock before preheating is applied. This study showed that preheating of GF677 hardwood cuttings should be applied when cuttings are collected from 25 October to 9 November, while, for Early Crest and Arm King, preheating of cuttings should be applied when they are collected from 30 October to 9 November. Cuttings, 30 cm in length and 10 13 mm in diameter are preferable. The best time of cutting collection seems to be between 25 October and 13 November. This study has indicated that many external factors may play an important role in the rooting of hardwood cuttings in nurseries.

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