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Rooting of jojoba cuttings: the effect of clone, substrate composition and temperature
Industrial Crops and Products 9 (1998) 47 – 52
Rooting of jojoba cuttings: the effect of clone, substrate composition and temperature Loreto Prat a, Claudia Botti a,*, David Palzkill b a
Facultad de Ciencias Agrarias y Forestales, Uni6ersidad de Chile, Santa Rosa 11315, P.O. Box 1004, Santiago, Chile b Drylands Institute, 2509 N. Campbell c 405, Tucson, AZ 85719, USA Received 10 December 1997; accepted 14 May 1998
Abstract Propagation of jojoba (Simmondsia chinensis (Link) Schneider) clones for commercial use is expensive. An investigation was conducted to improve the efficiency of this process. Rooting of semi-hardwood stem cuttings of jojoba was studied beginning on 14 April 1994 (mid-autumn). A factorial study using five clones and five substrates showed significant differences in rooting among clones, but no effect of substrate. When substrate temperature was varied, 20–25 and 27–30°C, an interaction was observed between clone and temperature. Only one of the five clones, the one with the lowest rooting percentage, rooted significantly better than the others at the higher temperature range. In another study using the two clones with the highest and lowest percent rooting in the first study, six substrates (the same five as in the first study plus a 100% sand substrate), and two substrate temperature ranges (10 – 12 and 20–25°C), significant differences in rooting between these two clones were again observed. Substrates had no significant effects on rooting. In this study, only the rooting of the lowest-rooting clone was increased by heating the substrate. In both studies with temperature differences, rooting of this clone was increased at the higher temperature. Rooting of the other clones, in both studies, was about the same at both substrate temperatures. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Vegetative propagation; Asexual propagation; Substrate Temperature
1. Introduction Jojoba (Simmondsia chinensis (Link) Schneider) is very heterogeneous and, due to its long life* Corresponding author. Tel.: + 56 2 6785768; fax: + 56 2 6785700; e-mail: [email protected]
cycle, development of true-breeding seed-propagated cultivars is unlikely in the foreseeable future. Because relatively large numbers of jojoba plants are planted per hectare, and nursery-produced plants are expensive, plant material costs are a significant part of the overall expense of establishing a commercial planting with high-
0926-6690/98/$ - see front matter © 1998 Elsevier Science B.V. All rights reserved. PII S0926-6690(98)00013-2
48
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
yielding clones. For profitable commercial production, an efficient vegetative propagation procedure is necessary. Several superior clones of jojoba that perform well in northern Chile have been identified; however, information on their rooting response is not available. For these, as well as for introduced clones, the need to optimize rooting of jojoba cuttings under Chilean conditions was recognized. Factors affecting the propagation of jojoba by stem cuttings have been reviewed (Palzkill, 1989). However, information is not available on the rooting response of the new Chilean clones, nor on responses to different propagation temperatures and to substrate materials commonly available. Several studies have found large differences in rooting between clones (Cardran, 1980; Low and Hackett, 1981; Lee and Palzkill, 1984) with some clones rooting so poorly as to be non-economical. In one study (Cardran, 1980), rooting response was observed to range from 0 to 96%. Substrates used successfully for jojoba propagation include: sand, vermiculite, perlite, sand and vermiculite (1:1), peat and polystyrene (1:1), perlite and vermiculite (1:1) and half-strength Hoagland’s solution (Maisari, 1966; Abramovich et al., 1978; Feldman et al., 1989; Low and Hackett, 1981; Lee and Palzkill, 1984; Palzkill and Feldman, 1993). Although various substrates have been used, comparative studies of the commonly used substrates have not been conducted, even though substrate cost can significantly affect production cost. For the commonly used substrate of perlite:vermiculite (1:1), the cost in Chile was estimated to be 15% of the total production cost. Peat, the other most commonly used ingredient in rooting substrates for jojoba, is equally, if not more, expensive on a volume basis. Currently, the costs ($US) of substrates in Chile per m3 are: peat= 107, perlite= 125, vermiculite = 108, sand = 17. In neighboring Argentina, where jojoba is also of interest, costs are even higher. In addition to being expensive, these materials can be difficult to obtain. Thus, identifying alternatives are desirable. Even though sand was reported to be satisfactory for jojoba propagation (Maisari, 1966), its use has been limited. Because sand is readily available and inexpensive (cost in
Chile $US 17/m3), it was included in the comparison of the other more expensive materials. Specific studies on effect of substrate temperature have not been reported for jojoba propagation, although experience has suggested that best results are obtained with temperatures of 25– 30°C. Also, commonly used substrate temperatures for temperate and tropical species are 18–25 and 25–32°C, respectively (Hartmann et al., 1990). Because jojoba is considered to be more tropical than temperate, it is expected to root better at high temperatures. Also, recent studies on other Sonoran and Chihuahuan Desert species indicate that high temperatures can be beneficial for rooting stem cuttings of plants from hot deserts (Hagen, 1990; Kelly, 1997). Because energy for providing substrate heat is a major cost of the entire process (an estimated 17% in Chile), there is a need to quantify such a response. The objective of this investigation was to optimize a propagation system for the commercial production of five jojoba clones, which have gone through two cycles of selection in northern Chile. Studies of rooting of these clones in six different media, with or without substrate heating, were conducted.
2. Materials and methods Three studies were conducted, the first two from 14 April to 23 June 1994 and the third from 4 April to 28 June 1995. In the first study, the rooting of cuttings of five clones in five substrates was evaluated (Table 1). Substrates were comTable 1 Substrates and clones used in rooting study of jojoba, 14 April to 2 June 1994 Substratea
Cost ($US/m3)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1)
113 125 117 89 119
Clones studied: 3.57.43, 3.10.10, 4.15.63, 4.19.1, 4.16.29. a Ratios given are on a volume basis.
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
posed of ingredients that have been previously found to be satisfactory (Maisari, 1966; Abramovich et al., 1978; Feldman et al., 1989; Low and Hackett, 1981; Lee and Palzkill, 1984; Palzkill and Feldman, 1993). Cuttings were collected from plants maintained in fields in the extreme north of Chile (Region I) and were transported to Santiago in insulated boxes. Up to 5 days elapsed between the time cuttings were collected and placed on the propagation bench. Prior to planting them on the bench, they were re-cut below a node to approximately 20 cm length, and disinfected in a suspension of Captan (0.15%) and Benlate (0.04%). The basal ends of the cuttings were then submerged for 15 s in a solution of indole butyric acid (IBA, 2000 ppm) based on earlier studies (Botti et al., 1990). Cuttings were then inserted in containers (Pey-Pots, METSA Chile S.A., Santiago) with the appropriate substrate and placed on a propagation bed provided with electrical resistance heaters to control substrate temperature. During the course of the first study, the temperature of the substrate in the containers fluctuated between 27 and 30°C. Temperatures were monitored and recorded three times daily. Cuttings were misted 15 s every 30 min with a clock-controlled misting system. Relative humidity within the passively cooled, plasticcovered greenhouse fluctuated between 60 and 80%, and the ambient temperature ranged from 20 to 30°C. After 30 days on the propagation bench, fertilization was begun by drenching the rooting containers with a 100 ppm solution of nitrogen (urea) once every 15 days until the cuttings were removed from the propagation bench on day 75. A randomized complete block design was used with 25 treatments; five clones× five substrates. For each treatment, eight cuttings contained in an eight-celled Pey-Pot were used in each of five blocks positioned successively along the length of the propagation bench. For statistical analysis of data, the rooting percentage data were transformed using the Bliss method (Dickson and Massey, 1957). The second study was made to determine whether increasing basal temperature would improve rooting. This study was done in two propagation beds, the first with electrical resistance
49
cables set to maintain a substrate temperature of 27–30°C, and the second, without heating where substrate temperatures ranged from 20 to 25°C. A completely randomized design with 20 treatments was used. Treatments consisted of combinations of three factors: the two substrate temperatures, two substrates (peat:perlite:vermiculite, 1:1:1 and perlite:vermiculite, 2:1, by volume) and the same five clones used in the first study. Eight cuttings were used for each treatment in each of five blocks. Due to facility limitations, the temperature treatments in the different blocks were not randomized relative to each other, but were in adjacent benches at about the middle of the greenhouse. Ambient humidity and temperature were the same as the first study. The third study was used to corroborate the results obtained in the earlier studies, using only two clones (those of highest and lowest rooting in the first study), six substrates and two substrate temperatures (unheated (10–12°C) and heated (20–25°C)). Ambient temperature in the greenhouse in 1995 ranged from 6°C (minimum, night) to 28°C (maximum, day). A substrate consisting of 100% sand was included, along with the same five substrates used in the first study (Table 1). Clones used were 4.15.63 and 3.57.43. Cuttings were prepared using the same methods described for the first study. A completely randomized design with 24 treatments was used. For each treatment, a Pey-pot with six cuttings was used in each of three blocks.
3. Results and discussion The overall rooting of the studies conducted in 1994 was unexpectedly high under the conditions imposed on the plants, where the stock plants in the saline soils received minimal maintenance, the cuttings were transported about 2000 km, and there was a delay of 5 days between collection and beginning of propagation. Average rooting in this year was 74.3% and compares favorably with other values reported in the literature (Low and Hackett, 1981; Botti et al., 1990). In 1995, rooting was much less than the previous year, averaging only 47.4%. An obvious difference in the condi-
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
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Table 2 Rooting percentage of stem cuttings of five jojoba clones; 14 April to 2 June 1994 Clone
Rooting (%)
3.57.43 4.19.1 3.10.10 4.16.29 4.15.63
43.5a* 72.5b 80.1b 81.5c 93.5c
* Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
tions between the two years was the much lower minimum air temperatures in the greenhouse in 1995, 6 vs. 10°C in 1994, and the associated lower substrate temperatures.
3.1. Clone effects (study 1) A significant clone effect on rooting was observed with clones 4.15.63 and 4.16.29 rooting significantly better than the others (Table 2). The range between lowest and highest rooting clones, 43.5 –93.5%, is large, but similar to the large clonal differences reported by others (Cardran, 1980; Low and Hackett, 1981; Lee and Palzkill, 1984). The cuttings were collected from mother plants located at two locations that are close to each other (Lluta, source of clones 3.57.43 and 3.10.10; Chaca, source of clones 4.19.1, 4.16.29 and 4.15.63) and where light, temperature and precipitation were similar (Santiba´n˜ez et al., 1981, 1982). This suggests that the large differences between clones were not due to the location of mother plants, but rather to genetic differences. The fact that the two highest rooting clones were not from the same location also supports this.
3.2. Substrate effect (study 1) Rooting substrate had little effect on rooting success (Table 3). Highest rooting percent occurred in perlite:vermiculite (2:1), but the results were not significantly better than in perlite:sand (2:1), perlite:vermiculite (1:1), or perlite (100%). Perlite:vermiculite:peat (1:1:1) resulted in the low-
est rooting percent, and the response was significantly less than in the two best substrates. It is likely that excessive water was retained by this medium causing damage to the base of the cuttings. Possibly by simply reducing the amount of water applied, rooting could be improved in this medium. It is important to note that rooting was as good in the substrate composed of sand and perlite as in the more expensive substrates.
3.3. Temperature effect (study 2) For this study, an interaction between clone and basal temperature was observed, and for this reason a separation analysis was performed (Table 4). For every clone, except 3.57.43, the substrate temperature did not significantly affect rooting percent in this study. However, for this clone which had the lowest overall rooting success, increasing the substrate temperature resulted in a 76% increase in rooting.
3.4. Substrate effect (study 2) In this study, significantly higher rooting occurred for cuttings in perlite:vermiculite (2:1) compared to perlite:vermiculite:peat (1:1:1) (Table 5), corroborating the results obtained in the first study.
3.5. Effect of clones, temperature and substrate (study 3) This third study was conducted to further corroborate the observations of the earlier studies. Table 3 Rooting percent of jojoba stem cuttings in five substrates; 14 April to 2 June 1994 Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1)
65.0a* 72.5ab 75.5ab 78.0b 80.5b
a
Ratios given are on a volume basis. * Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
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Table 4 Rooting percent of five jojoba clones at two basal temperatures; 14 April to 2 June 1994 Temperature (°C)
20–25 27–30
Clone (% rooting) 3.57.43
4.19.1
3.10.10
4.16.29
4.15.63
36.3a* 63.8b
71.2a 80.0a
77.5a 77.5a
82.5a 93.8a
87.5a 96.2a
* Different letters in the same column indicate significant differnces, 5% level, Duncan’s multiple range test.
Only two clones were included, those which had the highest and lowest rooting percentages in the earlier studies. An interaction between clones and basal temperature was present so that each clone was analyzed separately (Table 6). As in the earlier study, the clone that rooted the least (3.57.43) responded to increased substrate temperature, whereas the clone that rooted most did not. The effect of increased temperature on clone 3.57.43 was large, with a 100% increase in rooting. Rooting was less in this study than in the previous two studies, likely due to the fact that the minimum ambient air temperature during this study was lower. Again in this study, substrate composition did not significantly affect rooting (Table 7). The use of sand (100%), previously recommended by Maisari (1966), was not significantly different from other expensive substrates such as perlite:vermiculite. This suggests that sand could be safely used alone or in combination with other ingredients to reduce substrate cost. Exceptions to this would be if cuttings are being rooted in the containers and transported to the field or if the weight of the sand presents a problems. Table 5 Rooting percent of jojoba stem cuttings in two substrates; 14 April to 2 June 1994
4. Conclusions The selected Chilean clones differ significantly in percent rooting. Three of the five clones tested had higher than 80% rooting, which is commercially acceptable. Two of the five clones rooted at this level without the application of heat to the propagation pots, and exceeded 93% rooting with the application of heat. One of the five clones had less than 40% rooting without container heating, and 64% with heating. Substrate composition had little effect on rooting success; however, cuttings rooted well in sand (100%) or perlite:sand (2:1), two relatively lowcost substrates. Depending upon the season of propagation and the clone, it may not be necessary to use substrate heating. By properly managing a well-designed mist system and timing propagation to coincide with medium or high ambient temperatures, propagation cost can be significantly reduced. In Santiago, electricity can account for 17% of the total cost of producing rooted jojoba cuttings with heated propagation benches. The only clone that responded to increased substrate temperature was the one which rooted Table 6 Rooting percent of stem cuttings of two jojoba clones at two basal temperatures; 4 April to 28 June 1995 Temperature (°C)
Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite:vermiculite (2:1)
72.7a* 80.5b
10–12 20–25
Clone (% rooting) 3.57.43
4.15.63
18.5a* 37.0b
66.7a 67.5a
a
Ratios given are on a volume basis. * Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
* Different letters in the same column indicate significant differences, 5% level, Duncan’s multiple range test.
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L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
Table 7 Rooting percent of stem cuttings of two jojoba clones (3.57.43 and 4.15.63) in six different substrates; 4 April to 28 June 1995 Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1) Sand (100%)
38.1a* 40.9a 45.1a 36.8a 38.1a 31.2a
a
Ratios given are on a volume basis. * Same letters in the column indicate no significant differences; 5% level, Duncan’s multiple range test.
least, suggesting that difficult-to-root clones, which may have been discarded in the past, could be commercially useful with heat application during propagation.
Acknowledgements The authors thank Fondo de Fomento al Desarrollo Cientı´fico y Tecnolo´gico (FONDEF) for financial support, and Mr Miguel Madrid for his enthusiastic collaboration in this study.
References Abramovich, R., Tal, M., Forti, M., 1978. Vegetative propagation of Simmondsia chinensis (jojoba) by conventional methods: Hormone effects and seasonal variation. In: Guzma´n, W. (Ed.), La Jojoba. Proceedings of II International Conference on Jojoba and Its Uses, 10–12 February 1996, Ensenada, Baja California, Mexico, pp. 84–89. Botti, C., Doussoulin, E., Escobar, H., Zunino, C., 1990. Estudio de reproduccio´n vegetativa en jojoba (Simmondsia chinensis (Link) Schneider). In: Proc. of VIII International. Conf. on Jojoba and Its Uses, 17–21 June 1990, Asuncio´n,
.
Paraguay, pp. 194 – 210. Cardran, P., 1980. Clonal variations in rooting of Simmondsia chinensis (Link) Schneider. Unpublished M.S. Thesis, University of Arizona, Tucson, AZ, 98 pp. Dickson, W.J., Massey, F., 1957. Introduction to Statistical Analysis, McGraw Hill, New York, 474 pp. Feldman, W.R., Hogan, L., Palzkill, D.A., 1989. Factors affecting growth of jojoba cuttings in the liner stage. In: Puebla, M. (Ed.), Proc. of IV International Conf. on Jojoba, 5 – 8 November 1980, Hermosillo, Sonora, Me´xico, pp. 121 – 129. Hagen, R.H., 1990. Vegetative propagation of Cercidium, Parkinsonia and Prosopis species. Unpublished M.S. Thesis, University of Arizona, Tucson, AZ, 134 pp. Hartmann, H.T., Kester, D.E., Davies, F.T. Jr., 1990. Plant Propagation: Principles and Practices, 5th ed. Prentice Hall Career & Technology, Englewood Cliffs, New Jersey, 647 pp. Kelly, J.J., 1997. The effects of auxin levels, bottom heat and seasonal influences on the rooting of Leucophyllum candidum ‘Silver Cloud’. Unpublished M.S. Thesis, University of Arizona, Tucson, AZ. Lee, C.W., Palzkill, D.A., 1984. Propagation of jojoba by single node cuttings. HortScience 19, 841 – 842. Low, C.B., Hackett, W.P., 1981. Vegetative propagation of jojoba. Calif. Agric. 35, 12 – 13. Maisari, A., 1966. Factors affecting the rooting and transplanting of jojoba, Simmondsia chinensis (Link) Schneider. Unpublished M.S. Thesis, University of Arizona, Tucson, AZ, 33 pp. Palzkill, D.A., 1989. Propagation of jojoba by stem cuttings. In: Baldwin, A.R. (Ed.), Proc. Seventh International Conf. on Jojoba and Its Uses, 17 – 22 January 1988, Phoenix, Arizona. Am. Oil Chem. Soc., Champaign, IL, pp. 86 – 101. Palzkill, D.A., Feldman, W.R., 1993. Optimizing rooting of jojoba stem cuttings: Effects of basal wounding, rooting medium and depth of insertion in medium. J. Am. Oil Chem. Soc. 70, 1221 – 1224. Santiba´n˜ez, F., Etienne, M., Lailhacar, S., 1981. Delimitacio´n y caracterizacio´n de los ecosistemas de la I Regio´n de Chile. In: S. Lailhacar (Ed.), Sociedad Agrı´cola CORFOSACOR, 88 pp. Santiba´n˜ez, F., Luzio, W., Etienne, M., Lailhacar, S., 1982. Ana´lisis de los ecosistemas de la I Regio´n de Chile. In: S. Lailhacar (Ed.), Sociedad Agrı´cola CORFO-Univ. de Chile, 195 pp.
.
Rooting of jojoba cuttings: the effect of clone, substrate composition and temperature Loreto Prat a, Claudia Botti a,*, David Palzkill b a
Facultad de Ciencias Agrarias y Forestales, Uni6ersidad de Chile, Santa Rosa 11315, P.O. Box 1004, Santiago, Chile b Drylands Institute, 2509 N. Campbell c 405, Tucson, AZ 85719, USA Received 10 December 1997; accepted 14 May 1998
Abstract Propagation of jojoba (Simmondsia chinensis (Link) Schneider) clones for commercial use is expensive. An investigation was conducted to improve the efficiency of this process. Rooting of semi-hardwood stem cuttings of jojoba was studied beginning on 14 April 1994 (mid-autumn). A factorial study using five clones and five substrates showed significant differences in rooting among clones, but no effect of substrate. When substrate temperature was varied, 20–25 and 27–30°C, an interaction was observed between clone and temperature. Only one of the five clones, the one with the lowest rooting percentage, rooted significantly better than the others at the higher temperature range. In another study using the two clones with the highest and lowest percent rooting in the first study, six substrates (the same five as in the first study plus a 100% sand substrate), and two substrate temperature ranges (10 – 12 and 20–25°C), significant differences in rooting between these two clones were again observed. Substrates had no significant effects on rooting. In this study, only the rooting of the lowest-rooting clone was increased by heating the substrate. In both studies with temperature differences, rooting of this clone was increased at the higher temperature. Rooting of the other clones, in both studies, was about the same at both substrate temperatures. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Vegetative propagation; Asexual propagation; Substrate Temperature
1. Introduction Jojoba (Simmondsia chinensis (Link) Schneider) is very heterogeneous and, due to its long life* Corresponding author. Tel.: + 56 2 6785768; fax: + 56 2 6785700; e-mail: [email protected]
cycle, development of true-breeding seed-propagated cultivars is unlikely in the foreseeable future. Because relatively large numbers of jojoba plants are planted per hectare, and nursery-produced plants are expensive, plant material costs are a significant part of the overall expense of establishing a commercial planting with high-
0926-6690/98/$ - see front matter © 1998 Elsevier Science B.V. All rights reserved. PII S0926-6690(98)00013-2
48
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
yielding clones. For profitable commercial production, an efficient vegetative propagation procedure is necessary. Several superior clones of jojoba that perform well in northern Chile have been identified; however, information on their rooting response is not available. For these, as well as for introduced clones, the need to optimize rooting of jojoba cuttings under Chilean conditions was recognized. Factors affecting the propagation of jojoba by stem cuttings have been reviewed (Palzkill, 1989). However, information is not available on the rooting response of the new Chilean clones, nor on responses to different propagation temperatures and to substrate materials commonly available. Several studies have found large differences in rooting between clones (Cardran, 1980; Low and Hackett, 1981; Lee and Palzkill, 1984) with some clones rooting so poorly as to be non-economical. In one study (Cardran, 1980), rooting response was observed to range from 0 to 96%. Substrates used successfully for jojoba propagation include: sand, vermiculite, perlite, sand and vermiculite (1:1), peat and polystyrene (1:1), perlite and vermiculite (1:1) and half-strength Hoagland’s solution (Maisari, 1966; Abramovich et al., 1978; Feldman et al., 1989; Low and Hackett, 1981; Lee and Palzkill, 1984; Palzkill and Feldman, 1993). Although various substrates have been used, comparative studies of the commonly used substrates have not been conducted, even though substrate cost can significantly affect production cost. For the commonly used substrate of perlite:vermiculite (1:1), the cost in Chile was estimated to be 15% of the total production cost. Peat, the other most commonly used ingredient in rooting substrates for jojoba, is equally, if not more, expensive on a volume basis. Currently, the costs ($US) of substrates in Chile per m3 are: peat= 107, perlite= 125, vermiculite = 108, sand = 17. In neighboring Argentina, where jojoba is also of interest, costs are even higher. In addition to being expensive, these materials can be difficult to obtain. Thus, identifying alternatives are desirable. Even though sand was reported to be satisfactory for jojoba propagation (Maisari, 1966), its use has been limited. Because sand is readily available and inexpensive (cost in
Chile $US 17/m3), it was included in the comparison of the other more expensive materials. Specific studies on effect of substrate temperature have not been reported for jojoba propagation, although experience has suggested that best results are obtained with temperatures of 25– 30°C. Also, commonly used substrate temperatures for temperate and tropical species are 18–25 and 25–32°C, respectively (Hartmann et al., 1990). Because jojoba is considered to be more tropical than temperate, it is expected to root better at high temperatures. Also, recent studies on other Sonoran and Chihuahuan Desert species indicate that high temperatures can be beneficial for rooting stem cuttings of plants from hot deserts (Hagen, 1990; Kelly, 1997). Because energy for providing substrate heat is a major cost of the entire process (an estimated 17% in Chile), there is a need to quantify such a response. The objective of this investigation was to optimize a propagation system for the commercial production of five jojoba clones, which have gone through two cycles of selection in northern Chile. Studies of rooting of these clones in six different media, with or without substrate heating, were conducted.
2. Materials and methods Three studies were conducted, the first two from 14 April to 23 June 1994 and the third from 4 April to 28 June 1995. In the first study, the rooting of cuttings of five clones in five substrates was evaluated (Table 1). Substrates were comTable 1 Substrates and clones used in rooting study of jojoba, 14 April to 2 June 1994 Substratea
Cost ($US/m3)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1)
113 125 117 89 119
Clones studied: 3.57.43, 3.10.10, 4.15.63, 4.19.1, 4.16.29. a Ratios given are on a volume basis.
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
posed of ingredients that have been previously found to be satisfactory (Maisari, 1966; Abramovich et al., 1978; Feldman et al., 1989; Low and Hackett, 1981; Lee and Palzkill, 1984; Palzkill and Feldman, 1993). Cuttings were collected from plants maintained in fields in the extreme north of Chile (Region I) and were transported to Santiago in insulated boxes. Up to 5 days elapsed between the time cuttings were collected and placed on the propagation bench. Prior to planting them on the bench, they were re-cut below a node to approximately 20 cm length, and disinfected in a suspension of Captan (0.15%) and Benlate (0.04%). The basal ends of the cuttings were then submerged for 15 s in a solution of indole butyric acid (IBA, 2000 ppm) based on earlier studies (Botti et al., 1990). Cuttings were then inserted in containers (Pey-Pots, METSA Chile S.A., Santiago) with the appropriate substrate and placed on a propagation bed provided with electrical resistance heaters to control substrate temperature. During the course of the first study, the temperature of the substrate in the containers fluctuated between 27 and 30°C. Temperatures were monitored and recorded three times daily. Cuttings were misted 15 s every 30 min with a clock-controlled misting system. Relative humidity within the passively cooled, plasticcovered greenhouse fluctuated between 60 and 80%, and the ambient temperature ranged from 20 to 30°C. After 30 days on the propagation bench, fertilization was begun by drenching the rooting containers with a 100 ppm solution of nitrogen (urea) once every 15 days until the cuttings were removed from the propagation bench on day 75. A randomized complete block design was used with 25 treatments; five clones× five substrates. For each treatment, eight cuttings contained in an eight-celled Pey-Pot were used in each of five blocks positioned successively along the length of the propagation bench. For statistical analysis of data, the rooting percentage data were transformed using the Bliss method (Dickson and Massey, 1957). The second study was made to determine whether increasing basal temperature would improve rooting. This study was done in two propagation beds, the first with electrical resistance
49
cables set to maintain a substrate temperature of 27–30°C, and the second, without heating where substrate temperatures ranged from 20 to 25°C. A completely randomized design with 20 treatments was used. Treatments consisted of combinations of three factors: the two substrate temperatures, two substrates (peat:perlite:vermiculite, 1:1:1 and perlite:vermiculite, 2:1, by volume) and the same five clones used in the first study. Eight cuttings were used for each treatment in each of five blocks. Due to facility limitations, the temperature treatments in the different blocks were not randomized relative to each other, but were in adjacent benches at about the middle of the greenhouse. Ambient humidity and temperature were the same as the first study. The third study was used to corroborate the results obtained in the earlier studies, using only two clones (those of highest and lowest rooting in the first study), six substrates and two substrate temperatures (unheated (10–12°C) and heated (20–25°C)). Ambient temperature in the greenhouse in 1995 ranged from 6°C (minimum, night) to 28°C (maximum, day). A substrate consisting of 100% sand was included, along with the same five substrates used in the first study (Table 1). Clones used were 4.15.63 and 3.57.43. Cuttings were prepared using the same methods described for the first study. A completely randomized design with 24 treatments was used. For each treatment, a Pey-pot with six cuttings was used in each of three blocks.
3. Results and discussion The overall rooting of the studies conducted in 1994 was unexpectedly high under the conditions imposed on the plants, where the stock plants in the saline soils received minimal maintenance, the cuttings were transported about 2000 km, and there was a delay of 5 days between collection and beginning of propagation. Average rooting in this year was 74.3% and compares favorably with other values reported in the literature (Low and Hackett, 1981; Botti et al., 1990). In 1995, rooting was much less than the previous year, averaging only 47.4%. An obvious difference in the condi-
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
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Table 2 Rooting percentage of stem cuttings of five jojoba clones; 14 April to 2 June 1994 Clone
Rooting (%)
3.57.43 4.19.1 3.10.10 4.16.29 4.15.63
43.5a* 72.5b 80.1b 81.5c 93.5c
* Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
tions between the two years was the much lower minimum air temperatures in the greenhouse in 1995, 6 vs. 10°C in 1994, and the associated lower substrate temperatures.
3.1. Clone effects (study 1) A significant clone effect on rooting was observed with clones 4.15.63 and 4.16.29 rooting significantly better than the others (Table 2). The range between lowest and highest rooting clones, 43.5 –93.5%, is large, but similar to the large clonal differences reported by others (Cardran, 1980; Low and Hackett, 1981; Lee and Palzkill, 1984). The cuttings were collected from mother plants located at two locations that are close to each other (Lluta, source of clones 3.57.43 and 3.10.10; Chaca, source of clones 4.19.1, 4.16.29 and 4.15.63) and where light, temperature and precipitation were similar (Santiba´n˜ez et al., 1981, 1982). This suggests that the large differences between clones were not due to the location of mother plants, but rather to genetic differences. The fact that the two highest rooting clones were not from the same location also supports this.
3.2. Substrate effect (study 1) Rooting substrate had little effect on rooting success (Table 3). Highest rooting percent occurred in perlite:vermiculite (2:1), but the results were not significantly better than in perlite:sand (2:1), perlite:vermiculite (1:1), or perlite (100%). Perlite:vermiculite:peat (1:1:1) resulted in the low-
est rooting percent, and the response was significantly less than in the two best substrates. It is likely that excessive water was retained by this medium causing damage to the base of the cuttings. Possibly by simply reducing the amount of water applied, rooting could be improved in this medium. It is important to note that rooting was as good in the substrate composed of sand and perlite as in the more expensive substrates.
3.3. Temperature effect (study 2) For this study, an interaction between clone and basal temperature was observed, and for this reason a separation analysis was performed (Table 4). For every clone, except 3.57.43, the substrate temperature did not significantly affect rooting percent in this study. However, for this clone which had the lowest overall rooting success, increasing the substrate temperature resulted in a 76% increase in rooting.
3.4. Substrate effect (study 2) In this study, significantly higher rooting occurred for cuttings in perlite:vermiculite (2:1) compared to perlite:vermiculite:peat (1:1:1) (Table 5), corroborating the results obtained in the first study.
3.5. Effect of clones, temperature and substrate (study 3) This third study was conducted to further corroborate the observations of the earlier studies. Table 3 Rooting percent of jojoba stem cuttings in five substrates; 14 April to 2 June 1994 Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1)
65.0a* 72.5ab 75.5ab 78.0b 80.5b
a
Ratios given are on a volume basis. * Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
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Table 4 Rooting percent of five jojoba clones at two basal temperatures; 14 April to 2 June 1994 Temperature (°C)
20–25 27–30
Clone (% rooting) 3.57.43
4.19.1
3.10.10
4.16.29
4.15.63
36.3a* 63.8b
71.2a 80.0a
77.5a 77.5a
82.5a 93.8a
87.5a 96.2a
* Different letters in the same column indicate significant differnces, 5% level, Duncan’s multiple range test.
Only two clones were included, those which had the highest and lowest rooting percentages in the earlier studies. An interaction between clones and basal temperature was present so that each clone was analyzed separately (Table 6). As in the earlier study, the clone that rooted the least (3.57.43) responded to increased substrate temperature, whereas the clone that rooted most did not. The effect of increased temperature on clone 3.57.43 was large, with a 100% increase in rooting. Rooting was less in this study than in the previous two studies, likely due to the fact that the minimum ambient air temperature during this study was lower. Again in this study, substrate composition did not significantly affect rooting (Table 7). The use of sand (100%), previously recommended by Maisari (1966), was not significantly different from other expensive substrates such as perlite:vermiculite. This suggests that sand could be safely used alone or in combination with other ingredients to reduce substrate cost. Exceptions to this would be if cuttings are being rooted in the containers and transported to the field or if the weight of the sand presents a problems. Table 5 Rooting percent of jojoba stem cuttings in two substrates; 14 April to 2 June 1994
4. Conclusions The selected Chilean clones differ significantly in percent rooting. Three of the five clones tested had higher than 80% rooting, which is commercially acceptable. Two of the five clones rooted at this level without the application of heat to the propagation pots, and exceeded 93% rooting with the application of heat. One of the five clones had less than 40% rooting without container heating, and 64% with heating. Substrate composition had little effect on rooting success; however, cuttings rooted well in sand (100%) or perlite:sand (2:1), two relatively lowcost substrates. Depending upon the season of propagation and the clone, it may not be necessary to use substrate heating. By properly managing a well-designed mist system and timing propagation to coincide with medium or high ambient temperatures, propagation cost can be significantly reduced. In Santiago, electricity can account for 17% of the total cost of producing rooted jojoba cuttings with heated propagation benches. The only clone that responded to increased substrate temperature was the one which rooted Table 6 Rooting percent of stem cuttings of two jojoba clones at two basal temperatures; 4 April to 28 June 1995 Temperature (°C)
Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite:vermiculite (2:1)
72.7a* 80.5b
10–12 20–25
Clone (% rooting) 3.57.43
4.15.63
18.5a* 37.0b
66.7a 67.5a
a
Ratios given are on a volume basis. * Different letters indicate significant differences, 5% level, Duncan’s multiple range test.
* Different letters in the same column indicate significant differences, 5% level, Duncan’s multiple range test.
52
L. Prat et al. / Industrial Crops and Products 9 (1998) 47–52
Table 7 Rooting percent of stem cuttings of two jojoba clones (3.57.43 and 4.15.63) in six different substrates; 4 April to 28 June 1995 Substratea
Rooting (%)
Perlite:vermiculite:peat (1:1:1) Perlite (100%) Perlite:vermiculite (1:1) Perlite:sand (2:1) Perlite:vermiculite (2:1) Sand (100%)
38.1a* 40.9a 45.1a 36.8a 38.1a 31.2a
a
Ratios given are on a volume basis. * Same letters in the column indicate no significant differences; 5% level, Duncan’s multiple range test.
least, suggesting that difficult-to-root clones, which may have been discarded in the past, could be commercially useful with heat application during propagation.
Acknowledgements The authors thank Fondo de Fomento al Desarrollo Cientı´fico y Tecnolo´gico (FONDEF) for financial support, and Mr Miguel Madrid for his enthusiastic collaboration in this study.
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