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Enhancement of IBA stimulatory effect on rooting of olive cultivar stem cuttings
SCIENTIR HORTICULTUM ELSEVIER
Scientia Horticulturae62 (1995) 189-198
Enhancement of IBA stimulator-y effect on rooting of olive cultivar stem cuttings* Zeev Wiesman”, Shimon Lavee Institute of Horticulture, Agricultural
Research Organization,
The Volcani Center, Bet Dagan 50250, Israel
Accepted27 December1994
Abstract Three groups of olive cultivars were characterized as showing low, moderate or high rooting percentage after application of indole3-butyric acid (IBA) treatment. To improve the rooting of olive cuttings, urea-phosphate (UP) and paclobutrazol (PB) were tested in combination with IBA. UP alone did not stimulate rooting of olive cuttings; however, when applied together with IBA it significantly enhanced the rooting of cultivar ‘Manzanillo’ cuttings. PB alone had a weak effect on rooting of cuttings but in combination with IBA it improved the rooting of cultivars ‘Manzanillo’ and ‘Souri’ cuttings. A triple combination of IBA, UP and PB provided the most effective treatment for the improvement of rooting percentage. IBA treatments increased the number of roots per cutting in comparison with the control, but decreased the length of the roots of cultivar ‘Bamea’. IBA plus UP or PB further increased the number of newly formed roots. However, IBA plus UP markedly increased root length. The three compound treatment did not differ from IBA plus PB regarding root number per cutting, but the roots were longer than in IBA treated and control cuttings. The survival of rooted cuttings treated with IBA was relatively low, for all cultivars tested. IBA plus UP plus PB improved the survival of the rooted olive plants compared with IBA alone. Thus UP and PB were shown to enhance the effect of IBA in stimulation of rooting and survival of olive cuttings.
Kevwords:Cultivars; Cuttings; IBA; Olive; Rooting
1. Introduction During the last 40 years, olive groves have been established mainly by the use of selfrooted cultivnrs (Avidnn and Lavee, 1978; Hartmann et al., 1990). Cuttings for mist Abbreviations: IBA = indole-3-butyric acid; PB = paclobutrazol; UP= urea-phosphate * Contribution No. 1380-E. 1994 series, from the Agricultural Research Organization, Dagan, Israel. * Corresponding author. 03044238/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SsO10304-4238(95)00772-5
The Volcani Center, Bet
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propagation are usually taken during spring and summer. In spite of the high morphogenetic potential of the trees, the low rooting ability of difficult-to-root cultivars and the often unsatisfactory viability of cuttings of some easy-to-root cultivars are limiting factors (Wiesman and Epstein, 1987; Wiesman and Lavee, 1994). Adventitious root initiation in olive cuttings can be stimulated by auxins, particularly indole-3-butyric acid (IBA), but in difficult-to-root cultivars, the auxin either fails to promote rooting or promotes it only slightly. In addition, a significant number of IBA-treated, rooted olive plants do not survive in the greenhouse during the process of hardening, or even in the nursery or during the first year in the orchard. Hartmann et al. ( 1990) reported that in IBA-treated cuttings the number of roots was high but their growth was reduced in comparison with untreated cuttings. Root system development is one of the major limiting factors in the general development of rooted plants (Davis et al., 1988). Plant growth retardants have been reported as important tools in physiological research (Grossmann, 1990) and application of growth retardants together with IBA has been reported to improve rooting ability and survival in several plant species (Davis et al., 1985; Wiesman et al., 1989a; Pan and Zhao, 1994; Wiesman and Lavee, 1994). Triazole compounds have been reported to affect some major physiological processes during the rooting of cuttings (Navarro et al., 1989: Davis and Haissig, 1990; Pan and Zhao, 1994; Wiesman and Lavee, 1994). Paclobutrazol (PB), a well-studied chemical that is a member of the triazole family, has been reported as an antigibberellin agent (Rademacher et al., 1984). It has been hypothesized that PB is involved in maintaining low levels of the rooting inhibitor, gibberellin, in the cuttings (Davis et al., 1985, 1988) and in increasing the sink capacity of the base of the cuttings for carbohydrate and/or hormones (Davis et al., 1985; Wiesman and Lavee, 1994). It has also been suggested that PB reduces water loss ( Asare-Boamah et al., 1986; Wang et al., 1987) and interacts with auxin (Pan and Zhao, 1994; Wiesman and Riov, 1994). Urea-phosphate (UP) is a common fertilizer that can supply nitrogen and phosphate to plants. However, in addition, UP has also been shown to increase the uptake and activity of plant hormones such as gibberellin (Shulman and Bazak, 1986) and auxin (Wiesman et al., 1989a). Recently, UP has been found to increase the effect of PB in reducing fruit abscission (unpublished data) and has been reported to improve the effect of IBA on rooting of softwood peach cuttings (Wiesman et al., 1989a). The mechanism by which UP works is not yet known, but its effect of reducing cell pH also seems to increase the uptake of growth regulators and/or enhance their activity. In the present study, we tried to increase the rooting ability and quality of olive cuttings by using PB and UP as cofactors to IBA. Both the rooting ability of the cuttings and the survival of the rooted plants in the nursery were tested.
2. Materials and methods 2.1. Plant material Eleven-year-old olive trees of 34 cultivars of various origin (Italian, Spanish, Greek, North African, Turkish, South American and east Mediterranean), growing at the experi-
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mental farm of The Volcani Center at Bet Dagan, Israel, were used to test the stimulating effects of IBA on rooting and survival and the influence of UP and PB on this stimulation. Subterminal cuttings, 15 cm in length, were taken between May and August and all but the four distal leaves removed. 2.2. Rooting experiments The cuttings were treated routinely with 0.8% IBA talc powder (Asia-Riezel Inc., Natanya, Israel) and placed on a rooting table on a mixture of peat and crushed plastic foam ( 1: 1, v:v) maintained at 25°C. The cuttings were misted for 6 s every 5 min during the first week. The intervals between mistings were increased by 1 min every week. Rooting percentage was recorded after about 10 weeks. For the UP experiment cuttings of the cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ (respectively easy, moderate and difficult to root) were dipped in water for 30 min and thereafter dipped in increasing concentrations of UP (NH,CONH, .2H,PO,), i.e. 0, 1, 2 and 5 g l- ‘. UP powder was applied alone or mixed with 0.8% IBA in talc powder (w/w). For the PB experiment, cuttings of the same three cultivars were dipped for 30 min in aqueous solutions containing 0, 0.1, 1 and 5 g l- ’ PB (b- [ (4-chlorophenyl)methyl] -a( l,l-dimethyl) - 1H- 1,2,4-triazol- l-ethanol). PB was applied alone or followed by dipping the cuttings in 0.8% IBA in talc powder. The effect of the triple treatment with IBA+UP+PB was examined for the cultivars ‘Manzanillo’, ‘Uovo de Piccione’ and ‘Souri’. The first two are moderate-rooting cultivars and the third is difficult to root. The cuttings were treated with IBA, UP, PB, IBA + UP or IBA + PB as described above and untreated cuttings served as control. For the triple treatment, cuttings were first dipped for 30 min in 5 g 1-l aqueous solution of PB and then in a mixture of 0.8% IBA talc powder plus 5 g 1-l UP powder (w/w). Sixty cuttings arranged in three blocks (20 cuttings per block) were used for each of the experiments. Statistical analysis was performed using Student’s t-test or Duncan’s multiple range test (P = 5%) to compare treatment effects and ANOVA to test the interaction between cultivars and treatments. 2.3. Root system development
and survival experiment
Cuttings of the cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ were treated with IBA, IBA + UP, IBA + PB or IBA + UP + PB as described above. Untreated cuttings served as controls. The number of roots per cutting and root lengths were determined for cuttings of the cultivars ‘Barnea’ and ‘Manzanillo’. Ten weeks after the initiation of rooting, all rooted cuttings were planted in 2 1 containers and placed in an environmentally controlled greenhouse. The percentage of surviving plants was determined after 10 weeks for all three cultivars. 3. Results 3. I. IBA effect on rooting of olive cuttings The promotive effect of IBA on the rooting of cuttings of 34 olive cultivars from different origins was determined as part of a study of olive propagation lasting many years. IBA
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Table 1 Effect of 0.8% IBA talc powder on rooting of olive cultivars from various origins. Cuttings were rooted under mist in the summer (June-August). Rooting percentage was recorded 10 weeks tier planting. Results are expressed as rooting percentage of 60 cuttings except for six cultivars, marked by an asterisk where only 35 cuttings were rooted with or without IBA Cultivar
IBA
Cultivar
-
+
41
71 37 15 4 11 6 19 11 23 33
-
+
47 32 42 6
79 50 69 17
24 26 17
46 35 33
41 52
63 83
0 11 49 27 3 5 11 0
8 25 88 52 14 16 39 6
North African origin
Italian origin
‘Leccino’ ‘Santa Caterina’ ‘Leucco carpa’ ‘Giarraffa’ ‘Ascolana’* ‘San Francisco’* ‘Coratina’ ‘Grosso de Sardenia’ ‘San Agestino’* ‘Uovo de Piccione’
IBA
20 57 0 5 0 10 0 14 0
‘Telmcen’* ‘Picholine’ ‘Doche de Marocco’ ‘Shimlal’ Turkish origin
‘Gemelek’* ‘Ayvalic’ ‘Memeki’ South American origin
Spanish origin
‘Sevillano’ ‘Carasquena’ ‘Corenzuello’ ‘Manzanillo’
21 56 25 34
33 96 31 56
29 0 19
63 4 46
Greek origin
‘Koronaiki’ ‘Kalamata’ ‘ Amigdalolea’
‘Azapa’* ‘Arauka’ East Mediterranean
‘Shami’ ‘Sde Elijahu’ ‘Barnea’ ‘Kadesh’ ‘Souri’ ‘Merhavia’ ‘Muhasan’ ‘Nabali’
origin
markedly stimulated the rooting of cuttings of almost all tested cultivars (Table 1). However, we were able to characterize a group of 11 well known difficult-to-root cultivars (about 32%), that even after application of the widely used IBA treatment, rooted very poorly and non-economically. Less than 20% of cuttings of this group rooted (Table 2). The majority of the cultivars (16, i.e. 47%), were included in the group that showed a moderate rooting percentage, between 20 and 65%, after IBA application. The easy-to-root group, in which more than 65% of the cuttings rooted was the smallest and included only seven cultivars (about 20%). Among the easiest-to-root cultivars, that are also generally recognized as commercially easy to root, were ‘Carasquena’, ‘Bamea’, ‘Telmcen’ and ‘Leuco carpa’. 3.2. Interaction of UP and PB with IBA In order to improve the rooting ability of olive cultivars of difficult-to-root, moderaterooting and easy-to-root groups we examined the interaction of IBA with two compounds,
2. Wiesman, S. Lavee/Scientia Horticulturae 62 (1995) 18%198 Table 2 Grouping of olive cultivars based on their rooting percentage based on data from Table 1
No. of cultivars %
after application
193
of IBA treatment. The grouping is
Low (<20%)
Moderate (2065%)
High (>65%)
‘Giaraffa’ ‘San Francisco’ ‘Coratina’ ‘Ascolana’ ‘Gross0 de Sardenia’ ’Kalamata’ ‘Shimlal’ ‘Shami’ ‘Nabali’ ‘souri’ ‘Merhavia’
‘Santa Caterina’ ‘San Agestino’ ‘Uovo de Pi&one’ ‘Sevillano’ ‘Corenzuello’ ‘Manzanillo’ ‘Koronaiki’ ‘Picholine’ ‘Gemelek’ ‘Ayvalic’ ‘Memeki’ ‘Azapa’ ‘Sde Elijahu’ ‘Kadesh’ ‘Muhasan’ ‘Amigdalolea’
‘Leccino’ ‘Leuco carpa’ ‘Carasquena’ ‘Temcen’ ‘Dolche de Marocco’ ‘Arauka’ ‘Barnes’
11 32.3
16 47.0
7 20.6
UP and PB, using three representative cultivars: ‘Barnea’, ‘Manzanillo’ and ‘Souri’. UP applied alone did not increase the rooting ability of any of the three cultivars. However, a combined treatment of IBA plus UP increased the rooting of ‘Manzanillo’ cuttings more than IBA applied alone (Table 3). The data show that elevating the concentration of UP from 1 to 5 g l- ’ had no negative effect on rooting, and suggest that UP had no toxic effect. PB applied alone had no effect on rooting of cuttings from the three cultivars, but the treatment of IBA + PB markedly increased the rooting ability of ‘Manzanillo’ and ‘Souri’. A positive concentration effect was obtained (Table 4). This treatment increased the rooting of the difficult-to-root cultivar ‘Souri’ from 11% with IBA alone to 22% with IBA plus the highest concentration of PB. In practical terms, the improvement of the moderate-rooting ‘Manzanillo’, from 51 to 74% is economically most important. To test if there was any additive effect of the combination of IBA with both UP and PB we examined the rooting ability of two moderate-rooting olive cultivars, ‘Manzanillo’ and ‘Uovo de Piccione’ and the difficult-to-root cultivar ‘Souri’ (Table 5). The effects of IBA with UP and IBA with PB were similar to those described above. The triple treatment of IBA, UP and PB was most effective in promoting rooting in all three cultivars. It should be noted that the triple treatment increased rooting of ‘Souri’ to an economic level. 3.3. Effect on root system and survival
of rooted olive plants
IBA increased the average number of adventitious roots per cutting in ‘Manzanillo’ and ‘Barnea’ but the average length of the roots decreased (Table 6). Treatment with IBA plus
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Table 3 Effect of UP on the rooting percentage of olive cuttings treated with or without IBA. Three representative cultivars were used. ‘Bamea’ (easy to root), ‘Manzanillo’ (moderate to root) and ‘Souri’ (hard to root). Cuttings were rooted under mist in July. Rooting was recorded 10 weeks after planting. Values are means of 60 cuttings (arranged in three blocks) UP (g 1-1) 0
1
2
5
‘Bamea’ Control IBA
44a 85 a
46a 92a
41 a 90a
43 a 93 a
‘Manzanillo Control IBA
36a 51b
35 a 51 ab
31 a 59ab
31 a 63 a
‘Souri’ Control IBA
2a lla
4a 14a
2a 16a
4a 17 a
Mean separation in rows by Duncan’s multiple range test at P = 5%.
further increased the average root number per cutting in the case of ‘Manzanillo’, but less than the IBA+ PB treatment in ‘Barnea’. However, IBA+PB significantly reduced root length in ‘Barnea’, while IBA + UP increased it in both cultivars, compared with the untreated control. In cuttings treated with IBA + UP + PB, the number of roots was high, being similar to that of cuttings treated with IBA + PB, but root elongation was also induced and the roots reached a length significantly higher than those of the untreated control in ‘Barnea’ and lower than those receiving the IBA + UP treatment. ANOVA test showed that no significant interaction between treatments and cultivars existed. The survival rate of rooted plants treated with IBA, after 10 weeks in a greenhouse was not significantly lower than that of untreated control cuttings in all three cultivars (Table UP
Table 4 The effect of PB on rooting percentage 3
of olive cuttings with or without IBA. Experimental
details are as in Table
PB (g 1-l) 0
0.1
1
5
‘Bamea’ Control IBA
44a 85 a
48 a 89 a
53 a 94 a
56a 95 a
‘Manzanillo Control IBA
36a 51 c
33 a 5oc
39 a 64b
37 a 14a
‘souri’ Control IBA
2a llb
4a 14 ab
7a 18ab
7a 22 a
Mean separation in rows by Duncan’s multiple range test at P = 5%.
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Table 5 The effect of PB and UP on enhancement of IBA stimulated rooting of cvs. ‘Manzauillo’, ‘Uovo de Pi&one’ and ‘Sour-i’.The concentrations of the compounds were: IBA 0.8%, UP 5 g I-’ and PB 5 g I-‘. All the other experimental conditions were as in Table 3 Treatment
Rooting percentage
Control IBA UP PB IBA + UP IBA+PB IBA+UP+PB
‘Manzanillo’
‘Uovo de Piccione’
‘Souri
33 d 53 c 36 d 40d 59 c 71 b 81 a
lld 3oc 14 d 17 d 36 bc 42b 51 a
4e 12 d 2e 7 de 18c 26b 37 a
Mean separation in columns by Duncan’s multiple range test at P= 5%. Table 6 Effect of combined treatment of IBA, UP and PB on the root number and root length of rooted cuttings of cvs. ‘Barnea’ and ‘Manzanillo’. Experimental details are as in Table 3 Treatment
Control IBA IBA + UP IBA + PB IBA+UP+BP
No. of roots per cutting
Length of roots (mm)
‘Bamea’
‘Manzanillo’
‘Bamea’
‘Manzanillo’
4.3 c 7.6 b 9.8 b 14.0 a 14.7 a
2.5 c 5.0b 8.6 a 9.9 a 10.3 a
6.5 c 5.1 d 11.3 a 3.9 d 8.1 b
4.3 bc 3.7 c 8.4 a 3.2 c 5.1 b
Mean separation in columns by Duncan’s multiple range test at P= 5%. Table 7 Effect of combined treatment of IBA, UP and PB on survival of rooted cuttings of cvs. ‘Ban-tea’, ‘Manzanillo’ and ‘Souri’. Sixty rooted cuttings of each treatment (arranged in three blocks) were used in September to determine survival rate 10 weeks after transfering from rooting bench to the greenhouse Treatment
Survival percentage ‘Barnea’
‘Manzanillo’
‘souri’
Control
85 ab
81 ab
72bc
IBA IBA + UP IBA + PB IBA+UP+PB
78 b 87 a 84 ab 89 a
74b 79 ab 77 ab 84a
67 c 79 ab 71 bc 83 a
Mean separation in columns by Duncan’s multiple range test at P= 5%.
7). However, the combined treatment with IBA plus UP significantly increased the survival of rooted plants of ‘Barnea’ and ‘Souri’ in comparison with IBA treatment. The combined treatment with all three regulators increased the survival of all cultivars compared with IBA
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alone. Only for ‘Souri’ did the combined treatment give a higher survival rate than the control. No significant interaction between the treatments and cultivars was obtained in relation to their survival.
4. Discussion Auxin is well known to stimulate the rooting of cuttings (Davis et al., 1988; Hartmann et al., 1990). The most widely used auxin for commercial rooting is IBA (Nickel& 1982). Olive propagation by cuttings was established 40 years ago. However, it has been found in various studies (Avidan and Lavee, 1978; Wiesman and Epstein, 1987; Hartmann et al., 1990; Wiesman and Lavee, 1994) that the rooting of many cultivars is very poor. Most olive growers know that a rooting percentage lower than 20% in most cases means that vegetative propagation is not economically viable (Wiesman and Lavee, unpublished data, 1994). From a list of 34 olive cultivars of diverse worldwide origin, we found only seven cultivars with satisfactory rooting ability after application of IBA. The majority of the cultivars showed a moderate or low rooting ability even in response to IBA treatment. Successful rooting of cuttings is determined both by the number of roots formed and by root elongation and growth (Hartmann et al., 1990). In olive cuttings treated with IBA, there is an enhancement of root number and reduction of root length in comparison with untreated cuttings (Table 6). As a result, the survival of cuttings treated with IBA is much often lower than that of untreated cuttings (Wiesman and Lavee, 1994). Based on these observations, we aimed in the present study to look for ways to increase the rooting of cultivars that respond weakly or moderately to IBA and to try to improve the root system development and survival of rooted cuttings of the various cultivars. It is well documented that a delicate balance between endogenous stimulatory and inhibitory factors controls the rooting of cuttings (Eliasson, 1981). It is generally accepted that while auxin stimulates rooting, cytokinins and gibberellin inhibit it (Davis and Haissig, 1990; Hartmann et al., 1990). Nutritional factors have also been reported to promote the rooting of cuttings (Johnson and Hamilton, 1977). In the present study, we tested two such chemicals: PB, that has been reported to inhibit gibberellin biosynthesis (Rademacher et al., 1984), and UP, a common fertilizer that has been reported to enhance hormone uptake and activity (Shulman and Bazak, 1986). These two compounds have recently been shown to interact with IBA and improve rooting and survival of mung bean and peach cuttings (Wiesman et al., 1989a; Pan and Zhao, 1994; Wiesman and Riov, 1994). Both UP and PB showed a very weak or no stimulatory effect on rooting of the olive cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ used to represent the groups of easy-to-root, moderate-rooting and difficult-to-root cultivars (Tables 3 and 4). These findings are in agreement with previous reports on these two compounds (Davis et al., 1985, 1988; Wiesman et al., 1989a; Davis and Haissig, 1990). However, when they were applied together with IBA, rooting ability was increased, with PB appearing to be more effective than UP for enhancement of IBA induction of root formation (in the case of ‘Bamea’, Table 6). The strong effect of PB applied together with IBA on root formation was studied systematically in a model plant system using mung bean cuttings. It was suggested that PB may counter the inhibitory effect of gibberellin on root primordia formation (Davis et al., 1985; Pan and
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Zhao, 1994). PB was found to affect the metabolism of IBA (Wiesman and Riov, 1994) and to increase the sink capacity of the base of the cuttings (Davis et al., 1988). Free auxin, provided by conjugates of auxin, is required during all the stages of the rooting process (Wiesman et al., 1989b) and since it takes about 2 months for olive cuttings to root, we suggest that both the direct effect of PB on IBA metabolism and indirect effects on the partitioning of assimilates and water status (Wang et al., 1987) may enhance the stimulatory effect of IBA on the rooting of olive cuttings. In agreement with various reports on the promotive effect of fertilizers on rooting of cuttings (Johnson and Hamilton, 1977; Hartmann et al., 1990) we demonstrated that the combined application of UP plus IBA promoted root elongation and thus overcame the inhibitory effect of IBA alone, at least with cv. ‘Barnea’ (Table 6). The triple treatment of IBA + UP + PB showed additive effects leading to a significantly improved rooting of all cultivars (Table 5) and better root growth at least of cv. ‘Barnea’ (Table 6). These additive effects were also expressed by a better survival rate of the rooted olive plants of all cultivars after planting compared with IBA treatment (Table 7). The results of the present study clearly demonstrated the effect of a combined treatment of IBA + UP + PB on stimulation of rooting and survival of rooted cuttings compared with a treatment of IBA alone. This treatment is of particular importance for rooting of difficultto-root and moderate-rooting cuttings, but is also beneficial for easy-to-root cuttings, in increasing the survival rate of rooted plants compared with the common treatment of IBA alone.
Acknowledgements We would like to thank R. Durel and Y. Many for their technical assistance in taking care of the cuttings and plants that were used in our study.
References Asare-Boamah, N.K., Fletcher, R.A. and Dumbroff, E.B., 1986. Triamefon protects bean plants from water stress through its effects on abscisic acid. Plant Cell Physiol., 27: 383-390. Avidan, B. and Lavee, S., 1978. Physiological aspects of the rooting ability of olive cultivars. Acta Hortic., 79: 93-101. Davis, T.D. and Haissig, B.E., 1990. Chemical control of adventitious root formation in cuttings. Bull. Plant Growth Regul. Sot. Am., 18: 1-17. Davis, T.D., Sankhla, N., Waker, R.H. and Upadhyaya, A., 1985. Promotion of adventitious root formation on cuttings by paclobutrazol. HortScience, 20: 883-884. Davis, T.D., Haissig, N. and Sankhla, N., 1988. Adventitious Root Formation in Cuttings. Advances in Plant Sciences Series Vol. 2. Dioscorides Press, Portland, OR. Eliasson, L., 1981. Factors affecting the inhibitory effect of indolylacetic acid on root formation in pea cuttings. Physiol. Plant., 51: 23-26. Grossmann, K., 1990. Plant growth retardants as tools in physiological research. Physiol. Plant., 78: 640-648. Hartmann, H.T., Kester, D.E. and Davies, J.T., Jr., 1990. Plant Propagation. Principles and Practices. 5th edn. Prentice-Hall, Englewood Cliffs, NJ.
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Johnson, C.R. and Hamilton, D.F., 1977. Effect of media and controlled-release fertilizer on rooting and leaf nutrient composition of Juniperus conferta and Ligustrumjaponicum cuttings. J. Am. Sot. Hortic. Sci., 102: 320-322. Navarro, C., Benlloch, M. and Femandez-Escobar, R., 1989. Effect of paclobutrazol on growth of rooted olive cuttings. Acta Hortic., 239: 265-268. Nickell, L.G., 1982. Plant Growth Regulators. Agricultural Uses. Springer, New York, pp. 4-5. Pan, R. and Zhao, Z., 1994. Synergistic effects of plant growth retardants and IBA on the formation of adventitious roots in hypocotyl cuttings of mungbean. Plant Growth Regul., 14: 15-19. Rademacher, W., Jung, J., Graebe, J.E. and Schwenen, L., 1984. On the mode of action of tetcyclasis and triazole growth retardants. Br. Plant Growth Regul. Group Monogr., 11: l-1 1. Shulman, Y. and Bazak, H., 1986. Enhanced effect of gibberellin on grape size by addition of urea-phosphate. Alon Hanotea, 40: 761-765. (In Hebrew.) Wang, S.Y., Ji, T.S.Z.L. and Faust, M., 1987. Effect of paclobutrazol on water stress-induced abscisic acid in apple seedling leaves. Plant Physiol., 84: 1051-1054. Wiesman, Z. and Epstein, E., 1987. Metabolism and transport of 5-3H-indole-butyric acid in cuttings of olive. Olea, 18: 29-33. Wiesman, Z. and Lavee, S., 1994. Vegetative growth retardation, improved rooting and viability of olive cuttings in response to application of growth retardants. Plant Growth Regul., 14: 83-90. Wiesman, Z. and Riov, J., 1994. Interaction of paclobutrazol and indole-3-hutyric acid in relation to rooting of mung bean (Vigna radiata) cuttings. Physiol. Plant., 92: 608-612. Wiesman, Z., Riov, J. and Epstein, E., 1989a. Paclobutrazol and urea-phosphate increase rooting and survival of peach ‘Maravilha’ softwood cuttings. HortScience, 24: 908-909. Wiesman, Z., Riov, J. and Epstein, E., 1989b. Characterization and rooting ability of indole-3-butyric acid conjugates formed during rooting of mung bean cuttings. Plant Physiol., 91: 1080-1084.
Scientia Horticulturae62 (1995) 189-198
Enhancement of IBA stimulator-y effect on rooting of olive cultivar stem cuttings* Zeev Wiesman”, Shimon Lavee Institute of Horticulture, Agricultural
Research Organization,
The Volcani Center, Bet Dagan 50250, Israel
Accepted27 December1994
Abstract Three groups of olive cultivars were characterized as showing low, moderate or high rooting percentage after application of indole3-butyric acid (IBA) treatment. To improve the rooting of olive cuttings, urea-phosphate (UP) and paclobutrazol (PB) were tested in combination with IBA. UP alone did not stimulate rooting of olive cuttings; however, when applied together with IBA it significantly enhanced the rooting of cultivar ‘Manzanillo’ cuttings. PB alone had a weak effect on rooting of cuttings but in combination with IBA it improved the rooting of cultivars ‘Manzanillo’ and ‘Souri’ cuttings. A triple combination of IBA, UP and PB provided the most effective treatment for the improvement of rooting percentage. IBA treatments increased the number of roots per cutting in comparison with the control, but decreased the length of the roots of cultivar ‘Bamea’. IBA plus UP or PB further increased the number of newly formed roots. However, IBA plus UP markedly increased root length. The three compound treatment did not differ from IBA plus PB regarding root number per cutting, but the roots were longer than in IBA treated and control cuttings. The survival of rooted cuttings treated with IBA was relatively low, for all cultivars tested. IBA plus UP plus PB improved the survival of the rooted olive plants compared with IBA alone. Thus UP and PB were shown to enhance the effect of IBA in stimulation of rooting and survival of olive cuttings.
Kevwords:Cultivars; Cuttings; IBA; Olive; Rooting
1. Introduction During the last 40 years, olive groves have been established mainly by the use of selfrooted cultivnrs (Avidnn and Lavee, 1978; Hartmann et al., 1990). Cuttings for mist Abbreviations: IBA = indole-3-butyric acid; PB = paclobutrazol; UP= urea-phosphate * Contribution No. 1380-E. 1994 series, from the Agricultural Research Organization, Dagan, Israel. * Corresponding author. 03044238/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SsO10304-4238(95)00772-5
The Volcani Center, Bet
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propagation are usually taken during spring and summer. In spite of the high morphogenetic potential of the trees, the low rooting ability of difficult-to-root cultivars and the often unsatisfactory viability of cuttings of some easy-to-root cultivars are limiting factors (Wiesman and Epstein, 1987; Wiesman and Lavee, 1994). Adventitious root initiation in olive cuttings can be stimulated by auxins, particularly indole-3-butyric acid (IBA), but in difficult-to-root cultivars, the auxin either fails to promote rooting or promotes it only slightly. In addition, a significant number of IBA-treated, rooted olive plants do not survive in the greenhouse during the process of hardening, or even in the nursery or during the first year in the orchard. Hartmann et al. ( 1990) reported that in IBA-treated cuttings the number of roots was high but their growth was reduced in comparison with untreated cuttings. Root system development is one of the major limiting factors in the general development of rooted plants (Davis et al., 1988). Plant growth retardants have been reported as important tools in physiological research (Grossmann, 1990) and application of growth retardants together with IBA has been reported to improve rooting ability and survival in several plant species (Davis et al., 1985; Wiesman et al., 1989a; Pan and Zhao, 1994; Wiesman and Lavee, 1994). Triazole compounds have been reported to affect some major physiological processes during the rooting of cuttings (Navarro et al., 1989: Davis and Haissig, 1990; Pan and Zhao, 1994; Wiesman and Lavee, 1994). Paclobutrazol (PB), a well-studied chemical that is a member of the triazole family, has been reported as an antigibberellin agent (Rademacher et al., 1984). It has been hypothesized that PB is involved in maintaining low levels of the rooting inhibitor, gibberellin, in the cuttings (Davis et al., 1985, 1988) and in increasing the sink capacity of the base of the cuttings for carbohydrate and/or hormones (Davis et al., 1985; Wiesman and Lavee, 1994). It has also been suggested that PB reduces water loss ( Asare-Boamah et al., 1986; Wang et al., 1987) and interacts with auxin (Pan and Zhao, 1994; Wiesman and Riov, 1994). Urea-phosphate (UP) is a common fertilizer that can supply nitrogen and phosphate to plants. However, in addition, UP has also been shown to increase the uptake and activity of plant hormones such as gibberellin (Shulman and Bazak, 1986) and auxin (Wiesman et al., 1989a). Recently, UP has been found to increase the effect of PB in reducing fruit abscission (unpublished data) and has been reported to improve the effect of IBA on rooting of softwood peach cuttings (Wiesman et al., 1989a). The mechanism by which UP works is not yet known, but its effect of reducing cell pH also seems to increase the uptake of growth regulators and/or enhance their activity. In the present study, we tried to increase the rooting ability and quality of olive cuttings by using PB and UP as cofactors to IBA. Both the rooting ability of the cuttings and the survival of the rooted plants in the nursery were tested.
2. Materials and methods 2.1. Plant material Eleven-year-old olive trees of 34 cultivars of various origin (Italian, Spanish, Greek, North African, Turkish, South American and east Mediterranean), growing at the experi-
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mental farm of The Volcani Center at Bet Dagan, Israel, were used to test the stimulating effects of IBA on rooting and survival and the influence of UP and PB on this stimulation. Subterminal cuttings, 15 cm in length, were taken between May and August and all but the four distal leaves removed. 2.2. Rooting experiments The cuttings were treated routinely with 0.8% IBA talc powder (Asia-Riezel Inc., Natanya, Israel) and placed on a rooting table on a mixture of peat and crushed plastic foam ( 1: 1, v:v) maintained at 25°C. The cuttings were misted for 6 s every 5 min during the first week. The intervals between mistings were increased by 1 min every week. Rooting percentage was recorded after about 10 weeks. For the UP experiment cuttings of the cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ (respectively easy, moderate and difficult to root) were dipped in water for 30 min and thereafter dipped in increasing concentrations of UP (NH,CONH, .2H,PO,), i.e. 0, 1, 2 and 5 g l- ‘. UP powder was applied alone or mixed with 0.8% IBA in talc powder (w/w). For the PB experiment, cuttings of the same three cultivars were dipped for 30 min in aqueous solutions containing 0, 0.1, 1 and 5 g l- ’ PB (b- [ (4-chlorophenyl)methyl] -a( l,l-dimethyl) - 1H- 1,2,4-triazol- l-ethanol). PB was applied alone or followed by dipping the cuttings in 0.8% IBA in talc powder. The effect of the triple treatment with IBA+UP+PB was examined for the cultivars ‘Manzanillo’, ‘Uovo de Piccione’ and ‘Souri’. The first two are moderate-rooting cultivars and the third is difficult to root. The cuttings were treated with IBA, UP, PB, IBA + UP or IBA + PB as described above and untreated cuttings served as control. For the triple treatment, cuttings were first dipped for 30 min in 5 g 1-l aqueous solution of PB and then in a mixture of 0.8% IBA talc powder plus 5 g 1-l UP powder (w/w). Sixty cuttings arranged in three blocks (20 cuttings per block) were used for each of the experiments. Statistical analysis was performed using Student’s t-test or Duncan’s multiple range test (P = 5%) to compare treatment effects and ANOVA to test the interaction between cultivars and treatments. 2.3. Root system development
and survival experiment
Cuttings of the cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ were treated with IBA, IBA + UP, IBA + PB or IBA + UP + PB as described above. Untreated cuttings served as controls. The number of roots per cutting and root lengths were determined for cuttings of the cultivars ‘Barnea’ and ‘Manzanillo’. Ten weeks after the initiation of rooting, all rooted cuttings were planted in 2 1 containers and placed in an environmentally controlled greenhouse. The percentage of surviving plants was determined after 10 weeks for all three cultivars. 3. Results 3. I. IBA effect on rooting of olive cuttings The promotive effect of IBA on the rooting of cuttings of 34 olive cultivars from different origins was determined as part of a study of olive propagation lasting many years. IBA
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Table 1 Effect of 0.8% IBA talc powder on rooting of olive cultivars from various origins. Cuttings were rooted under mist in the summer (June-August). Rooting percentage was recorded 10 weeks tier planting. Results are expressed as rooting percentage of 60 cuttings except for six cultivars, marked by an asterisk where only 35 cuttings were rooted with or without IBA Cultivar
IBA
Cultivar
-
+
41
71 37 15 4 11 6 19 11 23 33
-
+
47 32 42 6
79 50 69 17
24 26 17
46 35 33
41 52
63 83
0 11 49 27 3 5 11 0
8 25 88 52 14 16 39 6
North African origin
Italian origin
‘Leccino’ ‘Santa Caterina’ ‘Leucco carpa’ ‘Giarraffa’ ‘Ascolana’* ‘San Francisco’* ‘Coratina’ ‘Grosso de Sardenia’ ‘San Agestino’* ‘Uovo de Piccione’
IBA
20 57 0 5 0 10 0 14 0
‘Telmcen’* ‘Picholine’ ‘Doche de Marocco’ ‘Shimlal’ Turkish origin
‘Gemelek’* ‘Ayvalic’ ‘Memeki’ South American origin
Spanish origin
‘Sevillano’ ‘Carasquena’ ‘Corenzuello’ ‘Manzanillo’
21 56 25 34
33 96 31 56
29 0 19
63 4 46
Greek origin
‘Koronaiki’ ‘Kalamata’ ‘ Amigdalolea’
‘Azapa’* ‘Arauka’ East Mediterranean
‘Shami’ ‘Sde Elijahu’ ‘Barnea’ ‘Kadesh’ ‘Souri’ ‘Merhavia’ ‘Muhasan’ ‘Nabali’
origin
markedly stimulated the rooting of cuttings of almost all tested cultivars (Table 1). However, we were able to characterize a group of 11 well known difficult-to-root cultivars (about 32%), that even after application of the widely used IBA treatment, rooted very poorly and non-economically. Less than 20% of cuttings of this group rooted (Table 2). The majority of the cultivars (16, i.e. 47%), were included in the group that showed a moderate rooting percentage, between 20 and 65%, after IBA application. The easy-to-root group, in which more than 65% of the cuttings rooted was the smallest and included only seven cultivars (about 20%). Among the easiest-to-root cultivars, that are also generally recognized as commercially easy to root, were ‘Carasquena’, ‘Bamea’, ‘Telmcen’ and ‘Leuco carpa’. 3.2. Interaction of UP and PB with IBA In order to improve the rooting ability of olive cultivars of difficult-to-root, moderaterooting and easy-to-root groups we examined the interaction of IBA with two compounds,
2. Wiesman, S. Lavee/Scientia Horticulturae 62 (1995) 18%198 Table 2 Grouping of olive cultivars based on their rooting percentage based on data from Table 1
No. of cultivars %
after application
193
of IBA treatment. The grouping is
Low (<20%)
Moderate (2065%)
High (>65%)
‘Giaraffa’ ‘San Francisco’ ‘Coratina’ ‘Ascolana’ ‘Gross0 de Sardenia’ ’Kalamata’ ‘Shimlal’ ‘Shami’ ‘Nabali’ ‘souri’ ‘Merhavia’
‘Santa Caterina’ ‘San Agestino’ ‘Uovo de Pi&one’ ‘Sevillano’ ‘Corenzuello’ ‘Manzanillo’ ‘Koronaiki’ ‘Picholine’ ‘Gemelek’ ‘Ayvalic’ ‘Memeki’ ‘Azapa’ ‘Sde Elijahu’ ‘Kadesh’ ‘Muhasan’ ‘Amigdalolea’
‘Leccino’ ‘Leuco carpa’ ‘Carasquena’ ‘Temcen’ ‘Dolche de Marocco’ ‘Arauka’ ‘Barnes’
11 32.3
16 47.0
7 20.6
UP and PB, using three representative cultivars: ‘Barnea’, ‘Manzanillo’ and ‘Souri’. UP applied alone did not increase the rooting ability of any of the three cultivars. However, a combined treatment of IBA plus UP increased the rooting of ‘Manzanillo’ cuttings more than IBA applied alone (Table 3). The data show that elevating the concentration of UP from 1 to 5 g l- ’ had no negative effect on rooting, and suggest that UP had no toxic effect. PB applied alone had no effect on rooting of cuttings from the three cultivars, but the treatment of IBA + PB markedly increased the rooting ability of ‘Manzanillo’ and ‘Souri’. A positive concentration effect was obtained (Table 4). This treatment increased the rooting of the difficult-to-root cultivar ‘Souri’ from 11% with IBA alone to 22% with IBA plus the highest concentration of PB. In practical terms, the improvement of the moderate-rooting ‘Manzanillo’, from 51 to 74% is economically most important. To test if there was any additive effect of the combination of IBA with both UP and PB we examined the rooting ability of two moderate-rooting olive cultivars, ‘Manzanillo’ and ‘Uovo de Piccione’ and the difficult-to-root cultivar ‘Souri’ (Table 5). The effects of IBA with UP and IBA with PB were similar to those described above. The triple treatment of IBA, UP and PB was most effective in promoting rooting in all three cultivars. It should be noted that the triple treatment increased rooting of ‘Souri’ to an economic level. 3.3. Effect on root system and survival
of rooted olive plants
IBA increased the average number of adventitious roots per cutting in ‘Manzanillo’ and ‘Barnea’ but the average length of the roots decreased (Table 6). Treatment with IBA plus
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Table 3 Effect of UP on the rooting percentage of olive cuttings treated with or without IBA. Three representative cultivars were used. ‘Bamea’ (easy to root), ‘Manzanillo’ (moderate to root) and ‘Souri’ (hard to root). Cuttings were rooted under mist in July. Rooting was recorded 10 weeks after planting. Values are means of 60 cuttings (arranged in three blocks) UP (g 1-1) 0
1
2
5
‘Bamea’ Control IBA
44a 85 a
46a 92a
41 a 90a
43 a 93 a
‘Manzanillo Control IBA
36a 51b
35 a 51 ab
31 a 59ab
31 a 63 a
‘Souri’ Control IBA
2a lla
4a 14a
2a 16a
4a 17 a
Mean separation in rows by Duncan’s multiple range test at P = 5%.
further increased the average root number per cutting in the case of ‘Manzanillo’, but less than the IBA+ PB treatment in ‘Barnea’. However, IBA+PB significantly reduced root length in ‘Barnea’, while IBA + UP increased it in both cultivars, compared with the untreated control. In cuttings treated with IBA + UP + PB, the number of roots was high, being similar to that of cuttings treated with IBA + PB, but root elongation was also induced and the roots reached a length significantly higher than those of the untreated control in ‘Barnea’ and lower than those receiving the IBA + UP treatment. ANOVA test showed that no significant interaction between treatments and cultivars existed. The survival rate of rooted plants treated with IBA, after 10 weeks in a greenhouse was not significantly lower than that of untreated control cuttings in all three cultivars (Table UP
Table 4 The effect of PB on rooting percentage 3
of olive cuttings with or without IBA. Experimental
details are as in Table
PB (g 1-l) 0
0.1
1
5
‘Bamea’ Control IBA
44a 85 a
48 a 89 a
53 a 94 a
56a 95 a
‘Manzanillo Control IBA
36a 51 c
33 a 5oc
39 a 64b
37 a 14a
‘souri’ Control IBA
2a llb
4a 14 ab
7a 18ab
7a 22 a
Mean separation in rows by Duncan’s multiple range test at P = 5%.
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Table 5 The effect of PB and UP on enhancement of IBA stimulated rooting of cvs. ‘Manzauillo’, ‘Uovo de Pi&one’ and ‘Sour-i’.The concentrations of the compounds were: IBA 0.8%, UP 5 g I-’ and PB 5 g I-‘. All the other experimental conditions were as in Table 3 Treatment
Rooting percentage
Control IBA UP PB IBA + UP IBA+PB IBA+UP+PB
‘Manzanillo’
‘Uovo de Piccione’
‘Souri
33 d 53 c 36 d 40d 59 c 71 b 81 a
lld 3oc 14 d 17 d 36 bc 42b 51 a
4e 12 d 2e 7 de 18c 26b 37 a
Mean separation in columns by Duncan’s multiple range test at P= 5%. Table 6 Effect of combined treatment of IBA, UP and PB on the root number and root length of rooted cuttings of cvs. ‘Barnea’ and ‘Manzanillo’. Experimental details are as in Table 3 Treatment
Control IBA IBA + UP IBA + PB IBA+UP+BP
No. of roots per cutting
Length of roots (mm)
‘Bamea’
‘Manzanillo’
‘Bamea’
‘Manzanillo’
4.3 c 7.6 b 9.8 b 14.0 a 14.7 a
2.5 c 5.0b 8.6 a 9.9 a 10.3 a
6.5 c 5.1 d 11.3 a 3.9 d 8.1 b
4.3 bc 3.7 c 8.4 a 3.2 c 5.1 b
Mean separation in columns by Duncan’s multiple range test at P= 5%. Table 7 Effect of combined treatment of IBA, UP and PB on survival of rooted cuttings of cvs. ‘Ban-tea’, ‘Manzanillo’ and ‘Souri’. Sixty rooted cuttings of each treatment (arranged in three blocks) were used in September to determine survival rate 10 weeks after transfering from rooting bench to the greenhouse Treatment
Survival percentage ‘Barnea’
‘Manzanillo’
‘souri’
Control
85 ab
81 ab
72bc
IBA IBA + UP IBA + PB IBA+UP+PB
78 b 87 a 84 ab 89 a
74b 79 ab 77 ab 84a
67 c 79 ab 71 bc 83 a
Mean separation in columns by Duncan’s multiple range test at P= 5%.
7). However, the combined treatment with IBA plus UP significantly increased the survival of rooted plants of ‘Barnea’ and ‘Souri’ in comparison with IBA treatment. The combined treatment with all three regulators increased the survival of all cultivars compared with IBA
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alone. Only for ‘Souri’ did the combined treatment give a higher survival rate than the control. No significant interaction between the treatments and cultivars was obtained in relation to their survival.
4. Discussion Auxin is well known to stimulate the rooting of cuttings (Davis et al., 1988; Hartmann et al., 1990). The most widely used auxin for commercial rooting is IBA (Nickel& 1982). Olive propagation by cuttings was established 40 years ago. However, it has been found in various studies (Avidan and Lavee, 1978; Wiesman and Epstein, 1987; Hartmann et al., 1990; Wiesman and Lavee, 1994) that the rooting of many cultivars is very poor. Most olive growers know that a rooting percentage lower than 20% in most cases means that vegetative propagation is not economically viable (Wiesman and Lavee, unpublished data, 1994). From a list of 34 olive cultivars of diverse worldwide origin, we found only seven cultivars with satisfactory rooting ability after application of IBA. The majority of the cultivars showed a moderate or low rooting ability even in response to IBA treatment. Successful rooting of cuttings is determined both by the number of roots formed and by root elongation and growth (Hartmann et al., 1990). In olive cuttings treated with IBA, there is an enhancement of root number and reduction of root length in comparison with untreated cuttings (Table 6). As a result, the survival of cuttings treated with IBA is much often lower than that of untreated cuttings (Wiesman and Lavee, 1994). Based on these observations, we aimed in the present study to look for ways to increase the rooting of cultivars that respond weakly or moderately to IBA and to try to improve the root system development and survival of rooted cuttings of the various cultivars. It is well documented that a delicate balance between endogenous stimulatory and inhibitory factors controls the rooting of cuttings (Eliasson, 1981). It is generally accepted that while auxin stimulates rooting, cytokinins and gibberellin inhibit it (Davis and Haissig, 1990; Hartmann et al., 1990). Nutritional factors have also been reported to promote the rooting of cuttings (Johnson and Hamilton, 1977). In the present study, we tested two such chemicals: PB, that has been reported to inhibit gibberellin biosynthesis (Rademacher et al., 1984), and UP, a common fertilizer that has been reported to enhance hormone uptake and activity (Shulman and Bazak, 1986). These two compounds have recently been shown to interact with IBA and improve rooting and survival of mung bean and peach cuttings (Wiesman et al., 1989a; Pan and Zhao, 1994; Wiesman and Riov, 1994). Both UP and PB showed a very weak or no stimulatory effect on rooting of the olive cultivars ‘Barnea’, ‘Manzanillo’ and ‘Souri’ used to represent the groups of easy-to-root, moderate-rooting and difficult-to-root cultivars (Tables 3 and 4). These findings are in agreement with previous reports on these two compounds (Davis et al., 1985, 1988; Wiesman et al., 1989a; Davis and Haissig, 1990). However, when they were applied together with IBA, rooting ability was increased, with PB appearing to be more effective than UP for enhancement of IBA induction of root formation (in the case of ‘Bamea’, Table 6). The strong effect of PB applied together with IBA on root formation was studied systematically in a model plant system using mung bean cuttings. It was suggested that PB may counter the inhibitory effect of gibberellin on root primordia formation (Davis et al., 1985; Pan and
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Zhao, 1994). PB was found to affect the metabolism of IBA (Wiesman and Riov, 1994) and to increase the sink capacity of the base of the cuttings (Davis et al., 1988). Free auxin, provided by conjugates of auxin, is required during all the stages of the rooting process (Wiesman et al., 1989b) and since it takes about 2 months for olive cuttings to root, we suggest that both the direct effect of PB on IBA metabolism and indirect effects on the partitioning of assimilates and water status (Wang et al., 1987) may enhance the stimulatory effect of IBA on the rooting of olive cuttings. In agreement with various reports on the promotive effect of fertilizers on rooting of cuttings (Johnson and Hamilton, 1977; Hartmann et al., 1990) we demonstrated that the combined application of UP plus IBA promoted root elongation and thus overcame the inhibitory effect of IBA alone, at least with cv. ‘Barnea’ (Table 6). The triple treatment of IBA + UP + PB showed additive effects leading to a significantly improved rooting of all cultivars (Table 5) and better root growth at least of cv. ‘Barnea’ (Table 6). These additive effects were also expressed by a better survival rate of the rooted olive plants of all cultivars after planting compared with IBA treatment (Table 7). The results of the present study clearly demonstrated the effect of a combined treatment of IBA + UP + PB on stimulation of rooting and survival of rooted cuttings compared with a treatment of IBA alone. This treatment is of particular importance for rooting of difficultto-root and moderate-rooting cuttings, but is also beneficial for easy-to-root cuttings, in increasing the survival rate of rooted plants compared with the common treatment of IBA alone.
Acknowledgements We would like to thank R. Durel and Y. Many for their technical assistance in taking care of the cuttings and plants that were used in our study.
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