Ornamental Tomato Growth and Fruiting Response to Paclobutrazol

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1 Ornamental Tomato Growth and Fruiting Response to Paclobutrazol Paulo José de Moraes, José Antonio Saraiva Grossi *, Sabrina de Araújo Tinoco, Derly José Henriques da Silva, Paulo Roberto Cecon and José Geraldo Barbosa Plant Science Department, Federal University of Viçosa, Viçosa, MG, 7-, Brazil Computer Science Department, Federal University of Viçosa, Viçosa, MG, 7-, Brazil Keywords: Lycopersicon esculentum, plant growth retardant, ornamental, pot plant Abstract The effects of paclobutrazol on plant growth and fruiting characteristics in a new genetic access BGH tomato, from Germoplasm Bank of Federal University of Viçosa, were examined in two experiments. In one experiment, paclobutrazol was foliar sprayed times at concentrations of,,,, and 7 mg ai L -. In a second experiment, paclobutrazol drenches were applied once at,,,, and mg ai L -. Plant heigth was % shorter as paclobutrazol concentrations increased up to mg ai L - for foliar application. Similar effects were observed with the internode length. Stem diameter increased as paclobutrazol concentrations increased up to mg ai L - for drench application. The plants exhibited smaller leaf area and higher chlorophyll content as the paclobutrazol concentrations increased. Increasing paclobutrazol concentrations decreased fruit diameter but increased the number of red fruits. The number of cluster per plant and the number of cluster with fruits increased linearly by increasing drench paclobutrazol concentrations. Paclobutrazol was effective on controlling growth and fruit characteristics of a potential ornamental tomato BGH. INTRODUCTION Tomatoes have long been grown as vegetable crop in many parts of the world, while its presentation as a ornamental pot plant is more recent and follows the development of new cultivars. A new tomato BGH access, catalogued in Germoplasm Bank of Federal University of Viçosa, exhibits potential as ornamental pot plant if the growth can be controlled. Its main characteristics is the presence of small and cherry format fruits. However, the natural large size of this tomato access grown as potted plant has produced commercially unviable plants. The growth control by using chemical methods to improve aesthetical effects on potted ornamental plants has been studied for many years. Application of growth retardants is a common practice for commercial growers to achieve attractive compact potted grown plants. Researchers have reported that paclobutrazol ([RS,RS]--[- chlorophenyl]-,--dimethyl--[,,-triazol--yl]pentan--ol), a triazole plant growth regulator, has been observed to be effective in controlling vegetative growth and promoting compactness in the production of a number of ornamental plants including, Chrysanthemum morifolium (Barret, 9; Zalewska, 99), Lilium longiflorum (Jiao et al. 9), Euphorbia pulcherrima (Goulston and Shearing, 9), Tulips (McDaniel, 99) and vegetable species as Capsicum annuum (Starman, 99). Few reports on the effect of the triazoles on the production of tomatoes have been published. Souza-Machado et al. (999) reported that significant earliness in harvest maturity was recorded in paclobutrazol treated tomato plants but no significant total yield differences were recorded between the paclobutrazol and control plants. However, Giovinazzo et al. () found significant yield increases of % due to the paclobutrazol treatments together with earlier harvest maturity by %. Carr and Jaffe (99), studied tomato pith autolysis and reported that paclobutrazol decreased the internode length. Frost and Kretchman (97) reported that the growth of processed tomato plants and the fruit set percentage in terminal regions were reduced by the triazole coded RSW, but the number of flower clusters and flowers per cluster were not reduced. Proc. V th IS on New Flor. Crops Eds.: A.F.C. Tombolato and G.M. Dias-Tagliacozzo Acta Hort., ISHS 7

2 Triazoles are generally more effective in retarding growth when applied to the soil or directly to stems compared to foliar applications (Davis et al., 9). However, foliar and drench paclobutrazol applications have been studied on growth control of ornamental plant production (Anderson and Hartley, 99; Bañón et al., ). Despite the use of paclobutrazol in the industry on potted plants, no studies have been published concerning paclobutrazol efficacy for tomato as ornamental effects. Also, evaluation of the effect of paclobutrazol on growth and fruiting characteristics of a new tomato BGH has not been reported. The objective of this study was to investigate the effects of paclobutrazol on growth and fruiting characteristics of the BGH MATERIAL AND METHODS Plants of BGH Lycopersicon esculentum were propagated from seeds obtained at Germoplasm Bank of Federal University of Viçosa (BGH). Five weeks after sowing, each seedling of -cm height was transplanted on liter plastic round pot in soil based growing medium. Plants were grown in an unheated glasshouse under natural light in Viçosa, Minas Gerais State, southeast of Brazil ( o S, o W). Plants were fertilized with g of N-P O -K O per pot weeks after tranplanting, and g of N-P O -K O at fruit setting stage. Plants were irrigated every - days, also sprayed and drenched as needed for mite, insect and disease control. Ten different concentrations of paclobutrazol growth retardant were applied in two experiments, when plants have reached cm height. In experiment, paclobutrazol was foliar sprayed times at concentrations of,,,, and 7 mg ai L -, on the dates 9/7, /7 and //. At each application the plants were sprayed until run off, with ml of solution per plant. During each spray application the surface of the medium was covered with plastic material to keep the medium out of growth retardant contact. In experiment, paclobutrazol drenches were applied at ; ; ; ; and mg ai L -. Each plant was treated with ml of paclobutrazol solution. Control plants were sprayed or drenched with water only. Plant height was measured from the bottom of the pot to the top of the plant and the cm pot height was subtracted from the total measurement. Leaf chlorophyll content was measured using the Chlorophyll metter SPAD- (Spectrum Technologies Inc., Plainfield, IL). Plant height, internode length, stem diameter, fruit diameter and leaf chlorophyll content were recorded at 9 weeks after plant growth retardant application. Leaf area, number of red fruits, number of cluster per plant and number of cluster with fruit were recorded at the end of the experiments. Each experiment was laid out in a randomized complete block design with replications. Analysis of variance and polynomial regression were used in data analyses (SAEG, UFV, Viçosa, M.G.). The data were recorded and analysed separately for each experiment. RESULTS AND DISCUSSION The effective rate sprayed per plant, in experiment, were., 7.,.,. and. mg ai plant -, and the effective rate drenched per plant, in experiment, were,,, and mg ai pot -. All paclobutrazol treatments reduced plant height by at least % compared to the nontreated plants (Figs. and ). Plant heigth was % shorter as paclobutrazol concentration increased up to mg ai L - for foliar application (Fig. ) and the plant height was % shorter as the concentration increased up to mg ai L - for drench application (Fig. ). Additional increases in concentrations had little effect on plant height. In another experiment, ornamental pepper plants sprayed with only one application of paclobutrazol at concentrations of and 9 mg ai L - were % and % shorter than untreated plants, respectively. Also, ornamental pepper plants exhibited severe height retardation and phytotoxicity symptoms when paclobutrazol was drenched at concentration of mg ai L -. Similar effects were observed with the internode length. As the concentrations

3 increased the internode length decreased linearly (Fig. ). These results were similar with Carr and Jaffe (99). Stem diameter increased as paclobutrazol concentrations increased from to mg ai L - for drench application (Fig. ). As paclobutrazol sprayed concentration increased from to mg ai L - leaf area decreased linearly by cm, from to cm (Fig. ). All paclobutrazol treated plants exhibited greener leaves than untreated plants. Leaf chlorophyll content increased linearly with the paclobutrazol concentrations (Fig. ). Triazole-treated plants typically appear darker green, which has been correlated with increased chlorophyll content. However, it is not clear whether increased chlorophyll content is due to enhanced chlorophyll biosynthesis or is simply a concentrating effect due to reduced leaf expansion (Davis et al., 9). Increasing paclobutrazol concentrations decreased fruit diameter linearly (Fig. 7). Plants treated with the highest sprayed paclobutrazol concentration exhibited fruit diameter % smaller than untreated plants. The number of red fruits increased as the paclobutrazol drench concentrations increased (Fig. ). Earliness in harvest maturity in paclobutrazol treated tomato plants has been reported (Souza-Machado et al., 999; Giovinazzo et al., ). Also, Starman (99) reported that Holyday Cheer ornamental pepper linearly increased the red fruit percentage when uniconazole concentration was increased. The number of cluster per plant and the number of cluster with fruits increased linearly by increasing drench paclobutrazol concentrations (Figs. 9 and ). Giovinazzo et al. () found significant yield increases of % due to the paclobutrazol treatments. Frost and Kretchman (97) reported that the growth of processed tomato plants and the fruit set percentage in terminal regions were reduced by the triazole coded RSW, but the number of flower clusters and flowers per cluster were not reduced. CONCLUSIONS The paclobutrazol treated BGH tomato plants were greener, more compact, produced more red fruits with smaller fruit diameter. Paclobutrazol was effective on controlling growth and influenced fruit characteristics of a new tomato genetic material. Paclobutrazol can be effective to produce marketable size ornamental tomato plants. Literature Cited Anderson, R.G. and Hartley, G. 99. Use of growth retardants on santin flower, godetia, for pot plant production. Acta Hort. 7: -9. Bañón, S., González, A., Cano, E.A., Franco, J.A. and Fernández, J.A.. Growth, development and colour response of potted Dianthus caryophyllus cv. Mondriaan to paclobutrazol treatment. Scientia Horticulturae 9: Barret, J.E. 9. Chrysanthemum height control by ancymidol, PP and EL- dependent upon medium composition. HortScience 7:9-97. Carr, S.M. and Jaffe, M.J. 99. Pith autolysis in herbaceous, dicotyledonous plants: experimental manipulation of pith autolysis in several cultivated species. Annals of Botany 7:7-9. Davis, T.D., Steffens, G.L. and Sankhla, N. 9. Triazole plant growth regulators. Hort. Rev. :-. Frost, D.J. and Kretchman, D.W. 97. Use of growth retardants to improve ripening uniformity and yield of processing tomatoes. HortScience :-. Giovinazzo, R., Souza-Machado, V. and Hartz, T.K.. Paclobutrazol responses with processing tomato in France. Acta-Hort. :-. Goulston, G.H. and Shearing, S.J. 9. Review of the effects of paclobutrazol on ornamental pot plants. Acta Hort. 7:9-. Jiao, J., Tsujita, M.J. and Murr, D.P. 9. Effects of paclobutrazol and A-rest on growth, flowering, leaf carbohydrate and leaf senescence in Nellie White easter lily (Lilium longiflorum Thunb.). Scientia Hort. :-. McDaniel, G.L. 99. Postharvest height suppression of potted tulips with paclobutrazol. 9

4 HortScience ():-. Souza-Machado, V., Pitblado, R., Ali, A., May, P. and Bieche, B.J Paclobutrazol in tomato (Lycopersicon esculentum) for improved tolerance to early transplanting and earlier harvest maturity. Acta-Hort. 7:9-. Starman, T.W. 99. Ornamental pepper growth and fruiting response to uniconazole depends on application time. HortScience (9): Zalewska, M. 99. Growth regulators in pot culture of chrysanthemum cultivars Paloma, Poranek and Promyk. Acta Hort., -.

5 plant height (m) y =,97 -,7D +,9 D R =, 7 plant height (m) y = -.x +.9x -.x +.7 R =. Figure Effect of paclobutrazol foliar spray concentration (mg a.i. L-) on plant height (m) of BGH Figure Effect of paclobutrazol drench concentration (mg a.i. L - ) on plant height (m) of BGH internode length (cm) y = -,7x +,977 R =, 7 stem diameter (cm) y = -.x +.x +.77 R =.7 leaf area (cm ) fruit diameter (cm) number of clusters Figure Effect of paclobutrazol foliar spray concentration (mg a.i. L-) on internode length (cm) of BGH 7 y = -,9x +,7 R =,7 Figure Effect of paclobutrazol drench concentration (mg a.i. L - ) on leaf area (cm ) of BGH... Figure 7 y = -,9x +,.7 R =,. 9 7 Effect of paclobutrazol foliar spray concentration (mg a.i. L - ) on fruit diameter (cm) of BGH y =,9x +, R =, Figure 9 Effect of paclobutrazol drench concentration (mg a.i. L - ) on number of clusters of BGH chlorophyll content (spad) number of red fruits number of cluster with fruit Figure Figure 9 7 Effect of paclobutrazol drench concentration (mg a.i. L - ) on stem diameter (cm) of BGH Effect of paclobutrazol foliar spray concentration (mg a.i. L - ) on chlorophyll content (spad) of BGH Figure Effect of paclobutrazol drench concentration (mg a.i. L - ) on number of red fruits of BGH Figure y =,7x +,9 R =,9 7 y =.x -.x +.x +. R =.9 y =,x +, R =, Effect of paclobutrazol drench concentration (mg a.i. L - ) on number of cluster with fruit of BGH