Floral Induction of Mango Tommy Atkins at Submedio São Francisco Region, Brazil

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1 Floral Induction of Mango Tommy Atkins at Submedio São Francisco Region, Brazil G.J.N. Silva and E.M. Souza Universidade Estadual da Bahia Juazeiro - Bahia Brazil J.D. Rodrigues and E.O. Ono Universidade Estadual Paulista Botucatu - SP Brazil M.A.C. Mouco Embrapa Semi-Árido Petrolina - PE Brazil Keywords: plant growth retardants, soil applied, triazole Abstract Irregular production is a major problem in mango. In an attempt to overcome irregular bearing, effects of two antigibberellins on flowering were evaluated, uniconazole (0.25 g of active ingredient per meter of canopy tree diameter) and paclobutrazol (1.0 g of active ingredient per meter of canopy tree diameter). Treatments were applied as a soil drench using 2 L of solution per tree, in a commercial orchard of Tommy Atkins mango. Treatments were applied after the second vegetative flush commenced, subsequent to pruning. Branch growth was evaluated every 30 days after treatment application up to a maximum period of 90 days. The flowering percentage was recorded at 130 days. Ammonium nitrate (NH 4 NO 3 ) as a foliar spray (concentration of 0.75%) was applied five times at seven day intervals from 95 to 100 days after treatment application as a dormancy breaking treatment. It was found that both paclobutrazol (PBZ) and uniconazole (UCZ) significantly inhibited the development of vegetative growth compared to the control. Both treatments resulted in identical rates of flowering shoots, 87%; based on results, it can be concluded that the application of antigibberellins (PBZ and UCZ) inhibit vegetative development in mango Tommy Atkins, and promote high levels of flowering. Additional tests are being carried out in other farms to confirm these findings, for different cultivars and seasons. INTRODUCTION The production of mango can be developed in different climatic conditions, but it is commercially viable only within a well defined range of temperature, rainfall, altitude, insulation, relative humidity, and winds. The fruit is native to tropical climate, but it can be grown in sub-tropical regions of the planet. Mango is produced in all regions of Brazil, however, 94% of the national production occurs in the Southeast and the Northeast region (Agrianual, 2009). The production of mango in Brazil can be divided in two different phases: the first one was characterized by extensive cultivation of local varieties with little or no use of technology; the second one is characterized by a high level of technology, such as irrigation, floral induction and improved varieties (Silva and Correa, 2004). One of the main problems in mango cultivation, for almost all varieties, is irregular production. The use of plant growth regulators is reported to improve production uniformity which allows for improved phytosanitary and commercial outcomes. (Cunha et al., 1994). Flowering in mango is a process that may occur during an extensive period (up to several months) and can have its beginning altered, naturally or artificially, due to climatic conditions, yield of the former harvest, or use of specific crop management, including plant growth regulators (Davenport, 2007). Growth retardants inhibit the synthesis of GA and can be used to reduce the growth length of branches and hence vegetative growth management. Thus, three different types of plant growth retardants that interfere in the synthesis of gibberellin: Compounds of quaternary ammonium, for example the mepiquat chloride and chlormequat chloride, inhibit the conversion of geranil pyrophosphate to caurene. Cyclic Proc. IX th Intl. Mango Symposium Ed.: Ping Lu Acta Hort. 992, ISHS

2 compounds containing one type of nitrogen, such as ancymidol, flurprimidol, paclobutrazol (PBZ) and uniconazole (UCZ), inhibit the conversion of ent-caureno to GAaldehyde, which is catalyzed by monoxigenases. The acylcyclohexanediones such as trinexapac-ethyl and prohexadione-ca, which block final reactions of the GA metabolism (conversion of GA 12 -aldehyde to different GAs), related to the action of dioxigenases (Rademacher, 1995). Nunez-Elisea et al. (1993) reported that the effects of the triazoles, paclobutrazol and uniconazole, on vegetative growth and flower induction in mango ( Tommy Atkins ) varied with temperature. High temperatures reduce the effects of these triazoles, favoring vegetative development. Among the cultivars grown in semi-arid conditions, Tommy Atkins occupies the largest area and many of its characteristics are very well accepted on the market. Other cultivars, such as Kent, Keitt and Palmer, have experienced an expansion in the region due to a growing consumer demand. MATERIAL AND METHODS The experiments were carried out in mango orchards of the cultivar Tommy Atkins, with micro and drip irrigation, located on the Andorinhas Empreendimentos Ltda farm ( N and E), within the Senador Nilo Coelho irrigated perimeter in Petrolina, Pernambuco State, as well as in other mango commercial orchards in the Middle Lower São Francisco River Basin in the cities of Casa Nova and Juazeiro, State of Bahia. In an attempt to overcome irregular bearing, effects of two anti gibberellins on flowering were evaluated, uniconazole at 0.25 g a.i. per linear meter of canopy diameter and paclobutrazol at 1.0 g a.i. per linear meter of canopy diameter. The treatments were applied in two liters of water per plant to the soil in circular furrows, 60 cm distant from the trunk at 10 cm of depth. Evaluations of branch growth were done 30 days after the products application, and the maximum base period was of 90 days and the percentage of flowering was measured at 130 days. The treatments were applied (October 15, 2007) on the second vegetative flush commenced after production pruning (August, 2007). The dormancy-breaking of the flower bud was done through five applications of Forth Nitron, liquid ammonium nitrate (NH 4 NO 3 ) via foliar spraying at a concentration of 0,75%, with intervals of seven days, starting after 95 days of the first spraying of the treatments. The experiment was designed as a randomized blocks: the two plant growth regulators (PBZ and UCZ) were tested and a control, resulted in three treatments and five replications. The data were statistically processed and the Tukey test at 5% probability used. The experimental plot consisted of 2 plants. For each plant, 10 branches were marked, and their lengths were evaluated at the second vegetative flush. As to the cultural practices, such as irrigation, fertilization, phytosanitary treatments and flowering management, all were used according to the Brazilian semi-arid conditions, as described by Albuquerque et al. (2002). RESULTS AND DISCUSSION As shown in Figure 1A, it was verified 90 days after single application of PBZ or UCZ via soil, inhibition of vegetative growth of mango Kent when compared to the control. PBZ and UCZ for 1.0 g a.i. and 0.25 g a.i. per linear meter of canopy diameter dosages reduced the length of the vegetative flush at 64.6% and 49.8%, respectively; PBZ and UCZ treatments differ statistically from the control. Research on PBZ intending to stop the vegetative growth of mango trees has already been confirmed by Nuñez-Elisea et al. (1996); Burondkar and Gunjate (1993); Kurian and Yer (1993); Nuñez-Elisea and Davenport (1995) and Ferrari and Sergent (1996). 150

3 The observation after one application of uniconazole showed an inhibition of development of the branches proportional to the single application of PBZ via soil, that is to say, lesser vegetative development with higher dosages. Basak and Niezborala (1989), using the product Sumi Seven (S-3307) based on UCZ as a foliar spray, verified an efficiency in inhibiting the vegetative development of apple trees, using dosages of 0.05% and 0.01%. These results were reported as well by Nuñez-Elisea et al. (1993), when testing uniconazole in the inhibition of vegetative development in mango Tommy Atkins. Vieira-Junior et al. (1999) tested the chlormequat chloride and uniconazole in dosages of 500; 1,000 and 1,500 mg L -1 and 400; 800 and 1,200 mg L -1, respectively, in the germination and growth of corn seedlings, and verified that chlormequat chloride proved to be efficient in inhibiting the germination and UCZ in inhibiting the growth. As to soy crop (Glycine max. L.), Rodrigues et al. (1998) studied the efficiency of UCZ (S-3307D) in its production with sprayings in the beginning of the flowering and concluded that the dosage of 10.0 g a.i. ha -1 was efficient in increasing the yield of the crop. Penter and Stassen (1999) tested chemical products to inhibit the vegetative development of avocado, and verified that Sunny, based on uniconazole, showed satisfactory results as a development inhibitor for this culture. Mango cultivars flower irregularly in tropical environments on low latitude, where there are periods with temperatures above 25 C and high air humidity and soil moisture occur. Under such conditions, the age of the buds at the time of initiation becomes the main fact to determine the bud outcome (Davenport, 2007). Work on PBZ to stop the vegetative development in mango have already been confirmed by Daziel and Lawrence (1987); Chen (1987); Tongumpai et al. (1989); Nuñez-Elisea et al. (1996); Burondkar and Gunjate (1993); Kurian and Yer (1993); Nuñez-Elisea and Davenport (1995) and Ferrari and Sergent (1996). The flowering of mango trees can occur during a long period, and its beginning can be naturally or artificially altered, due to climatic conditions, the yield of the previous harvest, or specific crop management, using plant growth regulators (Davenport and Nuñez-Elisea, 1997). Among the plant growth regulators used in fruit production, paclobutrazol has shown efficiency in mango flowering management (Mouco and Albuquerque, 2005) but it has the inconvenient that it must be applied to the soil and is more persistent in the plant and in the soil (Rademacher et al., 2006). For the flowering evaluation (Fig. 1B), identical flowering rates were observed both for PBZ and UCZ. When evaluating the flowering percentage after 130 days of the application of the treatments, it was verified that the treatment with PBZ and UCZ, at 1.0 g a.i. and 0.25 g a.i. per linear meter of canopy diameter dosages, respectively, showed the highest level of flowering. Thus, more tests are being done to confirm these results, involving other cultivars. CONCLUSION Based on the results of the test, it can be concluded that paclobutrazol, at a dosage of 1.0 g a.i. of active ingredient per meter of canopy tree diameter is as efficient as uniconazole at a dosage of 0.25 g a.i. per meter of canopy tree diameter in the inhibition of vegetative development and promotion of Tommy Atkins mango flowering. ACKNOWLEDGEMENTS We wish to thank the University of the State of Bahia UNEB, for their unrestricted support to the research; the Andorinhas Empreendimentos Ltda farm, for the partnership and for placing their area for our tests, and Nutriagro Agrícola, for providing the tested products. Literature Cited Agrianual São Paulo, FNP, p.370. Albuquerque, J.A.S. de, Medina, V.D. and Mouco, M.A. do C Indução floral. p In: P.J. de C. Genu and C.A. de Q. Pinto (eds.), A cultura da mangueira. Brasília, Embrapa Informação Tecnológica. 151

4 Basak, A. and Niezborala, B The influence of Sumi 7 (S-3307D) on vegetative growth and bearing of apple trees. Acta Hort. 239: Burondkar, M.M. and Gunjate, R.T Control of vegetative growth and induction of regular and early cropping in Alphonso mango with paclobutrazol. Acta Hort. 341: Chen, W.S Endogenous growth substances in relation to shoot growth and flower bud development of mango. Journal of the American Society for Horticultural Science 112(2): Cunha, G.P., Sampaio, J.M.M., Nascimento, A.S., do Santos Filho, H.P. and Medina, V.M Manga para exportação: aspecto técnico da produção. Brasília, Embrapa-SPI, (Série publicações técnicas FRUPEX, 8). 35p. Davenport, T.L Reproductive physiology of mango. Brazilian Journal of Plant Physiology 19:14. Davenport, T.L Reproductive physiology. p In: R.E. Litz (ed.), The mango. CAB International, Wallingford. Daziel, J. and Lawrence, D.K Biochemical and biological effects of kaurene oxidase inhibitors, such as paclobutrazol. British Plant Growth Regulators Group Monograph 4:1-14. Ferrari, D.F. and Sergent, E.A Promoción de la floración y frutificación en mango (Mangifera indica L.) cv. Haden, com paclobutrazol. Revista de la Facultad de Agronomia, Maracay 22:9-17. Kurian, R.M. and Iyer, C.P Chemical regulation of tree size in mango (Mangifera indica L.) cv. Alphonse: II. Effects of growth retardants on flowering and fruit set. Journal of Horticultural Science 68(3): Mouco, M.A. do C. and Albuquerque, J.A.S. de Efeito do paclobutrazol em duas épocas de produção da mangueira. Bragantia, Campinas 64(2): Nunez-Elisea, R. and Davenport, T.L Effect of leaf age, duration of coal temperature treatment, and photoperiod on bud dormancy release and floral initiation in mango. Scientia Hort. 62(1-2): Nunez-Elisea, R., Davenport, T.L. and Caldeira M.L Bud initiation and morphogenesis in Tommy Atkins mango as affected by temperature and triazole growth retardants. Acta Hort. 341: Nunez-Elisea, R., Davenport, T.L. and Caldeira, M.L Control of bud morphogenesis in mango (Mangifera indica L.) by girdling defoliation and temperature modification. Journal of Horticultural Science 71(1): Penter, M.G. and Stassen, P.J.C Chemical manipulation as part of a management programme for improved fruit yield and quality in avocado orchards. South African Avocado Growers Association Yearbook 22: Rademacher, W Growth retardants: Biochemical features and applications in horticulture. Acta Hort. 394: Rademacher, W., Spinelli, F. and Costa, G Prohexadione-Ca: Modes of action of a multifunctional plant bioregulator for fruit trees. Acta Hort. 727: Silva, P.C.G. and Correia, R.C Sócioeconomia. Cultivo da Mangueira. Embrapa Semi-Árido, Petrolina, (Sistemas de Produção, 2). Available at: /socioeconomia.htm. Tongumpai, P., Hongsbhanich, N. and Voon, C.H Cultar for flowering regulation of mango in Thailand. Acta Hort. 239: Vieira-Junior, P.A., Smiderle, O., Castro, P.R.C., Marcos-Filho, J., Cícero, S.M., Scaranari, C. and Dias, C.T.S Efeitos dos reguladores de crescimento Chlormequat e Uniconazole na germinação das sementes e no crescimento de plântulas de milho. Revista Brasileira de Sementes 21(02):

5 Figurese A Fig. 1. Branch growth inhibition (A) and mango flowering rate (B) Tommy Atkins when submitted to the following treatments. Petrolina, PE, Brazil, B 153

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