Apricot is a nutritious fruit being cultivated in temperate zones of the world (Bhat et al., 2013). Fruit quality and consumer acceptance of apricot is mostly defined by fruit firmness, size, flavor, and attractiveness. Fruit size and firmness are also the key factors affecting yield, marketability, and crop value for producers (Roussos et al., 2011). Fruit size is determined by genetic, cultural, and environmental factors (Badanes et al., 1998; Dirlewanger et al., 1999; Mratinic et al., 2011). It has long been established that fruit size can be increased by various cultural applications, such as external chemical treatments in the early phases of the fruit development (Canli and Orhan, 2009; Kappel and MacDonald, 2002).
Fruit size at harvest time is largely affected by cell division and cell enlargement at the initial periods of fruit development (Bohner and Bangerth, 1988; Zhang et al., 2005). Plant growth regulators [PGRs (auxins, gibberellins, and cytokinins)] are used in many fruit production systems to increase fruit size (Gillaspy et al., 1993; Jackson, 2003; Ozga and Reinecke, 2003).
Gibberellic acid (GA3) is used extensively in fruit species to increase fruit size including grape [Vitis vinifera (Zahedi et al., 2013; Zoffoli et al., 2009)] and sweet cherry [Prunus avium (Canli and Orhan, 2009; Choi et al., 2002; Clayton et al., 2006; Horvitz et al., 2003; Kappel and MacDonald, 2002; Kupferman, 1989; Lenahan et al., 2006; Sive and Resnizky, 1988; Usenik et al., 2005)]. The synthetic auxin 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) improved color and size of apricot when it was applied during the pit hardening phase (Bregoli et al., 2010). A preharvest spray of 25 mg·L−1 2,4-dichlorophenoxypropionic acid (2,4-DP) during pit hardening also improved fruit size and advanced fruit maturation in apricot (Agusti et al., 1994).
After harvest, softening of the apricot fruit adversely affects its marketability and value. GA3 treatments in sweet cherry delayed fruit ripening (Andrews and Shulin, 1995; Canli and Orhan, 2009; Choi et al., 2002; Demirsoy and Bilgener, 2000; Horvitz et al., 2003; Kappel and MacDonald, 2002; Usenik et al., 2005; Webster et al., 2006) and increased fruit firmness (Canli and Orhan, 2009; Choi et al., 2002; Einhorn et al., 2013; Kappel and MacDonald, 2002). Delayed fruit ripening enabled fruit to stay on trees longer resulting in increased fruit size and fruit firmness (Ju et al., 1999). Fruit firmness was increased by 100 ppm GA3 applied 21 d before harvest in ‘Patterson’ apricot (Southwick and Yeager, 1995).
Endogenous cytokinins stimulate cell division in young fruit (Stern et al., 2002). The effects of preharvest application of GA3, GA3 + 2,4-dichlorophenoxyacetic acid (2,4-D) + 1-napthaleneacetic acid (NAA), and GA4+7 + BA on fruit size of small-fruited summer pear (Pyrus communis) varieties were studied (Stern et al., 2007). While GA3 alone was not effective in increasing fruit sizes of pear, GA4+7 + BA application 14 d after full bloom increased fruit size. Similarly, BA was very effective in increasing fruit size of ‘Le Conte’ pear, but fruit size was not positively influenced by GA3 application (Yehia and Hassan, 2005). BA + GA4+7 applications also improved size of apple (Malus ×domestica) (Dennis, 2000).
Preharvest PGR applications that could improve fruit size, color, and precocity of apricot would enhance their marketability. While there are a few reports on the effects of BA and GA4+7 + BA on the fruit size and quality of pome fruit, there are no reports on the effects of these PGRs on the size and quality of apricots. Therefore, the aim of this study was to investigate the effects of BA and GA4+7 + BA on fruit quality of ‘Alyanak’ apricot.
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