Application of GA3 and girdling of branches on the production of extemporaneous fruits of 'Tahiti' acid lime

Aplicação de GA3 e anelamento de ramos na produção de frutos extemporâneos de limeiras ácidas 'Tahiti'

PLANT PRODUCTION PRODUÇÃO VEGETAL

Application of GA₃ and girdling of branches on the production of extemporaneous fruits of 'Tahiti' acid lime

Aplicação de GA₃ e anelamento de ramos na produção de frutos extemporâneos de limeiras ácidas 'Tahiti'

Cassiano Spaziani Pereira^I; Dalmo Lopes de Siqueira^II; Simone Valiati^III; Elisangela Ferrari^III

^IAgronomist, PhD. Instituto de Ciências Agrárias e Ambientais, Universidade Federal de Mato Grosso, Campus Sinop, Avenida Alexandre Ferronato, 1200, Reserva 35, Distrito Industrial, 78557-267, Sinop, Mato Grosso, Brazil. [e-mail] (corresponding author)

^IIAgronomist, PhD. Departamento de Fitotecnia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brazil. [e-mail]

^IIIAgronomy Undergraduate student. Instituto de Ciências Agrárias e Ambientais, Universidade Federal de Mato Grosso, Campus Sinop, Avenida Alexandre Ferronato, 1200, Reserva 35, Distrito Industrial, 78557-267, Sinop, Mato Grosso, Brazil. [e-mail]

RESUMO

The objective of this study was to evaluate the effect of girdling of branches and the application of GA₃, still in the main crop flowering on the formation of reproductive structures, the fruit set of the following extemporaneous flowering of 'Tahiti' acid lime. This work used a randomized block design with five replications in a 4x3 factorial design. The first factor was the foliar application of GA₃, 88 days before extemporaneous flowering at five concentrations (0, 7, 14 and 21 mg.L^-1). The second factor was the girdling times, 108 days before flowering onset (A108AF), 78 days before flowering (A78AF) plus no-girdling control (NG). In extemporaneous flowering, the proportion of buds, flowers and fruits that abscised was 38.75, 31.25 and 18.64% respectively and 11.34% of all reproductive structures formed were collected. GA₃ did not affect fruit set. Girdling increased fruit set by 229 and 256% at A108DAF and A78DAF respectively, in relation to NG plants. The GA₃ reduced the formation of floral structures, which resulted in a quadratic increase in field production by reducing the competition for photoassimilates among fruits. The concentration of 21 mg.L^-1 was the most productive, with 15.97 fruit.plant^-1.

Key words: flowering, gibberellin, phloem, reproductive structures.

ABSTRACT

Objetivou-se, neste trabalho, avaliar os efeitos do anelamento de ramos e da aplicação de GA₃, ainda na florada da safra principal, sobre a formação de estruturas reprodutivas, o pegamento e a produção de frutos da florada subsequente, extemporânea, de limeira ácida 'Tahiti'. Utilizou-se o delineamento experimental em blocos casualizados, com cinco repetições, em esquema fatorial 4 x 3. O primeiro fator foi a aplicação foliar de GA₃, 88 dias antes da florada extemporânea, nas concentrações (0, 7, 14 e 21 mg.L^-1). O segundo fator foram as épocas de anelamento, 108 dias antes do início do florescimento (A108AF), 78 dias antes do florescimento (A78AF), mais a testemunha, sem anelamento (SA). Na florada extemporânea, as proporções de botões florais, flores e frutos que sofreram abscisão foram de 38,75; 31,25 e 18,64%, respectivamente, e foram colhidas 11,34% de todas as estruturas reprodutivas formadas. O GA₃ não alterou o pegamento. O anelamento aumentou o pegamento dos frutos em 229 e 256%, aos A108DAF e A78DAF, respectivamente, em relação às plantas SA. O GA₃ reduziu a formação de estruturas florais, fato que propiciou aumento, de forma quadrática, da produção, por reduzir a concorrência por fotoassimilados entre os frutos, sendo a concentração de 21 mg.L^-1 a mais produtiva, com 15,97 frutos.planta^-1.

Palavras-chave: giberelina, floração, estruturas reprodutivas, floema.

INTRODUCTION

The flowering of Citrus reaches over 100,000 flowers per plant (Agusti et al., 1982), which becomes often excessive and damages the production, since less than 5% of this high production will be harvested (Pereira et al., 2011). The acid lime 'Tahiti', seedless variety, presents a more pronounced fruit abscission than cultivars with seeds. The fruit set in this variety is only 1.85% of September flowering and 0.46% of extemporaneous flowering (Spósito & Mourão Filho, 2003).

Despite being valued in the out of season fruit market, its production is almost impossible, mainly because of the large abscission of flowers in the extemporaneous flowering. The acid lime 'Tahiti' is a classic example. By presenting much crop seasonality and abscission of reproductive structures, any gain of fruit set and second flowering production, called extemporaneous, is of fundamental importance for farmers (Rufini et al., 2008).

One of the practices that can be used to increase production and fruit set is the girdling, whose function is to promote accumulation of carbohydrates in the aerial parts of plants (Rivas et al., 2006), by increasing the content of starch in the leaves (Pereira et al., 2011), which increases the activity of genes that will play roles in the synthesis of enzymes responsible for the availability of soluble sugars in leaves (Li et al., 2003).

The use of bio-regulators is another way of interfering in the production. One of the best known bio-regulator is gibberellic acid, which can be used as flowering inhibitor, in the most favorable time for the flowering, reducing the number of flowers.plant^-1, but increasing fruit set and fruit production by increasing the supply/ drain relationship aiming at higher extemporaneous fruit yield (Serciloto et al., 2003).

Exogenous application of GA₃ can reduce the excess of flower formation, generating better balance between the number of flowers and the carbohydrates in the plant, increasing the percentage of fruit set per plant, therefore the production of citrus in various flowerings (Maia et al., 2010).

Thus, the objective of this study was to evaluate the effects of girdling of branches and application of GA₃ at flowering of the main crop, on the fruit set and on production of fruits from the subsequent and extemporaneous flowering of 'Tahiti' acid lime.

MATERIAL AND METHODS

The experiment was carried out in the Fruit Division (Setor de Fruticultura) of the Federal University of Viçosa (UFV) - Viçosa, from the flowering onset in September 2007 to the end of the harvest in late June, 2008.

'Tahiti' lime trees [Citrus latifolia (Yu. Tanaka) Tanaka], grafted on Rangpur lime (C. limonia Osbeck) were used in the experiment. The trees were planted at a 5-m spacing between rows and 2.5 m between plants, not irrigated, at eight years old. In 2005, a drastic pruning was carried out so the trees presented canopy in growth stage.

A split fertilization was used, following recommendations of the Committee on Soil Fertility of Minas Gerais (1999).

The experimental design was a randomized block design with five replications in a 4 x 3 factorial. The first factor was the leaf application of GA₃, on September 13^th, 2007, 88 days before the extemporaneous flowering at four concentrations (0, 7, 14 and 21 mg L^-1). The second factor was the two girdling times. The first was carried out 108 days before flowering onset (A108AF), on August 21^st, 2007, and the second, 78 days before flowering (A78AF), on September 21^st, 2007, plus the control treatment with no girdling (NG).

Spray solution of GA₃ was prepared and applied on the same day (09/13/2007) and consisted of GA₃, water and a silicone glue spreader. The application of GA₃ was performed when about 80% of the normal blossom petals had suffered abscission, 88 days before extemporaneous blooming.

Girdlings were performed at 15 cm above the grafting point, breaking up the phloem at its entire circumference, removing portions of the peel with 5 mm of width.

Abscission of reproductive structures, the fruit set and fruit production were all evaluated.

To determine the abscission of reproductive structures, "Clarité" type nets were placed under the canopy of plants and, the reproductive structures were collected every 15 days, counted and classified into flower buds, flowers and fruits

Extemporaneous fruits were harvested weekly from late April to late June, when the fruits had light-green color and smooth peel, a characteristic of fruit with juice content higher than 40% (Gayet et al., 1995).

Data were submitted to analysis of variance. For qualitative factors, the means were compared using the Turkey's test at 5% probability. As to the quantitative factor, models have been chosen based on the significance of the regression coefficients using the "t" test at 5% of probability of determination; in the value of r² (SQRegression/ SQtreatments) and at the model potential to explain the biological phenomenon.

RESULTS AND DISCUSSION

Plants in A78DAF treatment were the most productive, reaching 15.45 fruits per plant^-1, 35.27% more than the plants of the NG control, which produced 10.00 fruits per plant^-1. The A108DAF treatment plants have intermediate production, 11.05 fruits/plant, 9.5% more than NG and 28.48% less than A78 DAF plants.

The application of GA3 increased in a quadratic manner the production of 'Tahiti' acid lime plants. The highest number of harvested fruits occurred with the concentration of 21 mg.L^-1, with 15.97 fruits. Plant^-1, 62.3% more than the control, which produced 6.02 fruits per plant^-1 (Figure 1b).

The highest abscission of reproductive structures occurred at the stage of flower buds, representing 38.75% of all the structures formed. Flowers in anthesis corresponded to 31.25% and the fruits, to 18.64% of all abscission that occurred at extemporaneous flowering (Figure 2). Probably, this result is due to the lower connection between the structures and the plant at flowering onset. After all, it is known that the partition of nutrients and photoassimilates is made in the direction from the source to the drain and the drains regarded as the "strongest" or greater are those which display preferential flow in the plant. (Guedes et al., 2008).

Fruit set was not influenced by the application of GA₃. The A108DAF and A78DAF treatments increased fruit set by 229% and 256%, respectively, compared to NG, reaching values of 19.45% and 21.73% of fruit set, respectively, while NG plants had a fruit set of 8.48%. This result is due to the fact that, although the girdling had been performed still in the crop season, its effect lasted until the extemporaneous harvest, blocking the transport of photoassimilates through the phloem, from the aerial part to the roots, paralyzing the vegetative growth of plants (Pereira et al., 2010) and the reserves in the aerial part, as a consequence. Therefore, abscission of flower structures was reduced (Mehouachi et al., 2009; Pereira et al., 2011).

A reduction in fruit abscission was found with the application of GA₃ (Figure 3). At every 1 mg.L^-1 of bioregulator added to the spray volume, there was a reduction of 1.64 fruits per planta^-1 in abscission. This phenomenon occurred due to the effect that the GA₃ has on the flowering, which is in agreement with the results of Maia et al. (2010) in a study conducted with Ponkã tangerine trees (Citrus reticulata Blanco). The authors stated that the regulator reduces excessive flowering and may reduce the effect of production alternance, generating higher productivity, over the years of the tangerine trees.

The formation of 133.9 reproductive structures per plant was found in NG treatments, a value higher than those of A78DAF and A108DAF treatments, with means of 86.8 and 82.6, respectively (Figure 4a). However, this increased amount of reproductive structures did not mean greater fruit set or production and what occurred was just the opposite (Figures 1a and ⁵). This was due to the greater flower set of the regular crop flowering, which reduced the number of branches available for extemporaneous blossoms. Therefore, fewer flowers were formed in the subsequent flowering, the extemporaneous (Medina et al., 2005). Nevertheless, even with fewer flowers, girdling reduced the abscission even in that flowering (^{Figure 5}).

For the application of GA₃, the higher the concentration, the smaller the number of total reproductive structures formed (Figure 4b). The formation of 77 structures was found at a concentration of 21 mg.L^-1; 84.53 formed structures at 14 mg.L^-1; 113.87 at 7 mg.L^-1 and 129 reproductive structures at 0 mg.L^-1. Thus, this result is corroborating with earlier studies that indicated that the inhibitory effect of GA₃ on the flower differentiation, preventing, or decreasing the production of flowers (Maia et al., 2010). With the application of GA₃, the plant decreased the intake of assimilates involved in flowering (Serciloto et al., 2003), increasing the supply of carbohydrates to the fruits (Pereira et al., 2011).

CONCLUSIONS

The GA₃ increased production in a quadratic manner. The largest number of harvested fruits occurred with the concentration of 21 mg.L^-1.

The GA₃ reduces fruit abscission; however, it did not affect the fruit set.

Girdling increased extemporaneous fruit set. The plants girdled 78 days before flowering were the most productive.

Received: 18/07/2012; accepted: 28/08/2014.

• Agustí M, Garcia-Mari F & Guardiola JL (1982) The influence of flowering intensity on the shedding of reproductive structures in sweet orange. Scientia Horticulturae, 17:343-352.
• Comissão de Fertilidade do Solo do estado de Minas Gerais (1999) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5a aproximação. Viçosa, editora UFV. 359p.
• Gayet JP, Bleinroth EW, Matallo M, Garcia EEC, Garcia AE, Ardito EFG & Bordin MR (1995) Lima ácida 'Tahiti' para a exportação: procedimentos de colheita e pós-colheita. Brasília, EMBRAPA SPI. 36p.
• Guedes PA, Almeida OS, Lemos OL & Rebouças TNH (2008) Relação fonte-dreno na formação de frutos: uma revisão bibliográfica. Vitória da Conquista, Diálogos & Ciência. p.1-13.
• Li CY, Weiss D & Goldschimidt EE (2003) Girdling affects carbohydrates related gene expression in leaves bark and roots of alternate-bearing citrus trees. London, Annals of Botany. p.1-7.
• Maia E, Siqueira DM & Cecon PR (2010) Produção, florescimento e frutificação de tangerineira 'Poncã' submetida à aplicação de ácido giberélico. Ciência Rural, 40:507-512.
• Medina CL, Rena AB, Siqueira BR & Machado EC (2005) Fisiologia dos citros. In: Mattos Junior D, Negri JD, Pio RM & Pompeu Junior J (Eds.) Citros. Campinas, Instituto Agronômico e Fundag. p.147-195.
• Mehouachi J, Iglesias DJ, Agustí M & Talón M (2009) Delay of early fruitlet abscisión by Branco girdling in Citrus coincides with previous increases in carbohydrate and gibberelin concentra-tions. Dordrecht, Plant Growth Regulation, 58:15-23.
• Pereira CS, Siqueira DL, Salomão LCC, Cecon PR & Santos D (2010) Crescimento vegetativo e intensidade de cor verde das folhas de limeira ácida 'Tahiti' aneladas e tratadas com ácido giberélico. Ciência Rural, 40:1916-1921.
• Pereira CS, Siqueira DL, Salomão LCC, Cecon PR & Santos D (2011) Teores de carboidratos nas folhas e produção de limeiras ácida 'Tahiti' aneladas e tratadas com ácido giberélico. Revista Brasileira de Fruticultura, 33:706-712.
• Rivas F, Erner E, Alós E, Juan M, Almela V & Agustí M (2006) Girdling increases carbohydrate availability and fruit-set in citrus cultivars irrespective of parthenocarpic ability. Journal of Horticultural Science & Biotechnology, 81:89-295.
• Rufini JCM, Ramos JD, Mendonça V, Neto SEA, Pio LAS & Ferreira EA (2008) Prolongamento do período de colheita da tangerineira 'Ponkan' com aplicação de GA₃ e 2,4-D. Ciência Agrotecnologia, 32:834-839.
• Serciloto CM, Castro PRC, Ribeiro VR, Tavares S, Medina CL & Machado EC (2003) Biorreguladores na fixação dos frutos de lima ácida 'Tahiti'. Laranja, 24:383-395.
• Spósito MB & Mourão Filho FAA (2003) 'Ta-hiti' lime fruit set related to gibberellic acid applica-tion on out-of-season flowering and the accumulation of degree days. Fruits, 58:151-156.

Publication Dates

• Publication in this collection
  03 Feb 2015
• Date of issue
  Dec 2014

History

• Received
  18 July 2012
• Accepted
  28 Aug 2014