F.A. Canli¹ and M. Pektas^2
1 Department of Biotechnology, Faculty of Agriculture, Suleyman Demirel University, Isparta, Turkey
² West Mediterranean Development Agency, Isparta, Turkey

SUMMARY This study was conducted to determine the effects of benzyladenine (BA) and BA plus gibberellin (GA) treatments on fruit size and quality of ‘Akca’ pear (Pyrus communis), a low yielding and a small fruited summer variety. Pear trees were sprayed to run off 14 d after full bloom with BA (50, 100 and 150 ppm) or BA+GA4+7 (concentrations of each chemical; 12.5, 25, and 50 ppm). Fruits were harvested and evaluated in terms of fruit size and quality parameters. Higher concentrations of BA+GA4+7 (25 and 50 ppm) and the medium concentration of BA (100 ppm) increased fruit weight, fruit diameter and fruit length. The highest fruit weights and the highest fruit lengths were obtained from 25 ppm BA+GA4+7 and 50 ppm BA+GA4+7 treatments. Compared to weight of control fruit (48.85 g), 25 ppm BA+GA4+7 applications resulted in a 20.2% increase in fruit weight (58.71 g). ‘Akca’ pear showed different responses to BA and BA + GA4+7 applications. In 25 and 50 ppm BA + GA4+7 treatments, the increases in fruit weight were accompanied by heavy reductions in yield (54.3% and 59.9%, respectively), while in 100 ppm BA application fruit size of ‘Akca’ pear was significantly improved (11.3%) with no influence on yield. Fruits treated with 25 ppm and 50 ppm BA+GA4+7 and 100 ppm BA had higher pedicel lengths than the control. Plant growth regulator (PGR) treated fruit had higher soluble solid content (SSC) than the untreated fruit. Treatments did not affect fruit pH. Higher rates of BA and BA+GA4+7 resulted in fruit that were darker, greener and less yellow. In conclusion, BA at 100 ppm can be a suitable tool for increasing fruit quality and size of low cropping and small fruited summer pears, with no negative influence on yield and fruit shape. Keywords BA, firmness, fruit color, fruit weight, GA4+7, Pyrus communis, SSC

Significance of this study What is already known on this subject? BA and BA+GA4+7 applications increase fruit size of some fruits. However there are a few studies on the effects of BA and GAs on fruit size of pear and these studies are limited to a few regions and varieties. There are no studies testing the effects of BA and BA+GA4+7 on fruit size of low yielding summer pears which do not require thinning. What are the new findings? BA at 100 ppm substantially improved fruit size of ‘Akca’ pear with no negative influence on yield and fruit shape. What is the expected impact on horticulture? This treatment can be potentially used to increase the fruit size and the quality of the low cropping and the small fruited summer pears.

E-mail: fatihcanli@hotmail.com  

References

• Agusti, M., Juan, M., Almela, V., and Speroni, C. (1994). The effect of 2,4-DP on fruit development in apricots (Prunus armeniaca L.). Scientia Hort. 57, 51–57. https://doi.org/10.1016/0304-4238(94)90034-5.
• Antognozzi, E., Famiani, F., Proietti, P., Tombesi, A., Feranti, F., and Frenguelli, G. (1997). Effect of CPPU (cytokinin) treatments on fruit anatomical structure and quality in Actinidia deliciosa. Acta Hort. 444, 459–465. https://doi.org/10.17660/ActaHortic.1997.444.70.
• Basak, A., Rozpara, E., and Grzyb, Z. (1998). Use of bioregulators to reduce sweet cherry tree growth and to improve fruit quality. Acta Hort. 468, 719–723. https://doi.org/10.17660/ActaHortic.1998.468.91.
• Bohner, J., and Bangerth, F. (1988). Cell number, cell size and hormone level in semiisogenic mutants of Lycopersicon pimpinellifolium differing in fruit size. Physiol. Plant. 72, 316–320. https://doi.org/10.1111/j.1399-3054.1988.tb05839.x.
• Bregoli, A.M., Fabbroni, C., Raimondi, V., and Costa, G. (2010). Improving colour and size of apricot fruit by means of exogenous auxin application. Acta Hort. 862, 365–372. https://doi.org/10.17660/ActaHortic.2010.862.56.
• Canli, F.A., and Orhan, H. (2009). Effects of pre-harvest gibberellic acid applications on fruit quality of ‘0900 Ziraat’ sweet cherry. HortTechnology 19, 127–129.
• Canli, F.A., Pektas, M., and Kelen, M. (2009). Effects of pre-harvest plant growth regulator sprays on fruit quality of ‘Deveci’ pear (Pyrus communis L.). J. Appl. Biol. Sci. 3, 146–149.
• Choi, C., Wiersma, P.A., Toivonen, P., and Kappel, F. (2002). Fruit growth, firmness and cell wall hydrolytic enzyme activity during development of sweet cherry fruit treated with gibberellic acid (GA3). J. Hort. Sci. Biotechnol. 77, 615–621.
• Einhorn, T.C., Wang, Y., and Turner, J. (2013). Sweet cherry fruit firmness and post-harvest quality of late-maturing cultivars are improved with low-rate, single applications of gibberellic acid. HortScience 48, 1010–1017.
• Facteau, T.J., Rowe, K.E., and Chesnut, N.E. (1985). Response patterns of gibberellic acid-treated sweet cherry fruit at different soluble solids levels and leaf/fruit ratios. Scientia Hort. 27, 257–262. https://doi.org/10.1016/0304-4238(85)90030-5.
• Flaishman, A.F., Shargal, A., and Stern, R.A. (2001). The synthetic cytokinin CPPU increases fruit size and yield of ‘Spadona’ and ‘Costia’ pear (Pyrus communis L.). J. Hort. Sci. Biotechnol. 76, 145–149.
• Flaishman, A.F., Shargal, A., Shlizerman, L., Stern, A.R., Yadun, S.L., and Grafi, G. (2005). The synthetic Cytokinins CPPU and TDZ prolong the phase of cell division in developing Pear (Pyrus communis L.) fruit. Acta Hort. 671, 151–157. https://doi.org/10.17660/ActaHortic.2005.671.18.
• Horvitz, S., Godoy, C., López Camelo, A.F., Yommi, A., and Godoy, C. (2003). Application of gibberellic acid to 'Sweetheart' sweet cherries, Effects on fruit quality at harvest and during cold storage. ISHS Acta Hort. 628, 311–316. https://doi.org/10.17660/ActaHortic.2003.628.37.
• Itai, A. (2007). Pear. In Genome mapping and molecular breeding in plants. Fruit and nuts, C. Kole ed., (Berlin, Heidelberg, Germany: Springer-Verlag), pp. 137–156. https://doi.org/10.1007/978-3-540-34533-6_6.
• Kappel, F., and Macdonald, R.A. (2002). Gibberellic acid increases fruit firmness, fruit size, and delays maturity of ‘Sweetheart’ sweet cherry. J. Amer. Pomol. Soc. 56, 219–222.
• Lenahan, O.M., Whiting, M.D., and Elfving, D.C. (2006). Gibberellic acid inhibits floral bud development and improves ‘Bing’ sweet cherry fruit quality. HortScience 41, 654–659.
• Looney, N.E. (1993). Improving fruit size, appearance, and other aspects of fruit crop “quality” with plant bioregulating chemicals. Acta Hort. 329, 120–127. https://doi.org/10.17660/ActaHortic.1993.329.21.
• Ozga, J., and Reinecke, M.D. (2003). Hormonal interactions in fruit development. J. Plant Growth Regulat. 22, 73–81. https://doi.org/10.1007/s00344-003-0024-9.
• Southwick, S.M., and Yeager, J.T. (1995). Use of gibberellin formulations for improved fruit firmness and chemical thinning in ‘Patterson’ apricot. Acta Hort. 384, 425–430. https://doi.org/10.17660/ActaHortic.1995.384.67.
• Stern, A.R., Flaishman, M.A., and Shargal, A. (2002). Effect of the synthetic cytokinin CPPU on fruit size and yield of ‘Spodana’ pear. Acta Hort. 596, 797–801. https://doi.org/10.17660/ActaHortic.2002.596.138.
• Stern, A.R., and Flaishman, M.A. (2003). Benzyladenine effects on fruit size, fruit thinning and return yield of ‘Spodana’ and ‘Coscia’ pear. Scientia Hort. 98, 499–504. https://doi.org/10.1016/S0304-4238(03)00035-9.
• Stern, A.R., Doron, I., and Ben-Arie, R. (2007). Plant growth regulators increase the fruit size of ‘Spadona’ and ‘Coscia’ pears (Pyrus communis) in a warm climate. J. Hort. Sci. Biotechnol. 82, 3–7.
• Stylianidis, D.K., Sotiropoulos, T.E., Koukourikou, M.A., Voyiatzisa, D.G., and Therios, I.N. (2004). The effect of growth regulators on fruit shape and inorganic nutrient concentration in leaves and fruit of ‘Red Delicious’ apples. J. Biol. Res. 1, 75–80.
• Usenik, V., Kastelec, D., and Stampar, F. (2005). Physicochemical changes of sweet cherry fruits related to application of gibberellic acid. Food Chem. 90, 663–671. https://doi.org/10.1016/j.foodchem.2004.04.027.
• Wismer, P.T., Proctor, J.T.A., and Elfving, D.C. (1995). Benzyladenine affects cell division and cell size during apple fruit thinning. J. Amer. Soc. Hort. Sci. 120, 802–807.
• Yehia, A.T., and Hassan, H.S.A. (2005). Effect of some chemical treatments on fruiting of ‘Le Conte’ pears. J. Appl. Sci. Res. 1, 35–42.
• Yuan, R., and Greene, D.W. (2000). McIntosh apple fruit thinning by benzyladenine in relation to seed number and endogenous cytokinin level in fruit and leaves. Sci. Hort. 86, 127–134. https://doi.org/10.1016/S0304-4238(00)00142-4.
• Zahedi, M., Mortazavi, S., Moallemi, N., and Abdossi, V. (2013). Effect of pre-harvest application of gibberellic acid and ethephon on the quality of table grape. J. Ornamental Hort. Plants 3, 125–131.
• Zhang, C., Lee, U., and Tanabe, K. (2008). Hormonal regulation of fruit set, parthenogenesis induction and fruit expansion in Japanese pear. Plant Growth Regulat. 55, 231–240. https://doi.org/10.1007/s10725-008-9279-2.

Received: 6 August 2014 | Revised: 4 November 2014 | Accepted: 18 November 2014 | Published: 17 June 2015 | Available online: 17 June 2015