Ethephon and Methyl Jasmonate Affect Fruit Detachment in Rabbiteye and Southern Highbush Blueberry

Abstract

<jats:p>Two abscission agents, ethephon and methyl jasmonate, were investigated in five studies to determine their potential for increasing fruit detachment during harvest in rabbiteye (<jats:italic>Vaccinium ashei</jats:italic> Reade) and southern highbush (hybrids based largely on <jats:italic>Vaccinium corymbosum</jats:italic> L. and <jats:italic>Vaccinium darrowi</jats:italic> Camp.) blueberry. In the first study with a rabbiteye blueberry genotype, T-451, ethephon applications up to 1000 mg·L<jats:sup>−1</jats:sup> did not affect fruit drop but reduced fruit detachment force (FDF) by up to 21%. In the second study with two southern highbush blueberry genotypes, ethephon (up to 1500 mg·L<jats:sup>−1</jats:sup>) and methyl jasmonate (MeJa; up to 10 m<jats:sc>m</jats:sc>) applications resulted in significant fruit drop in ‘Star’ but neither of the growth regulators affected the fruit detachment characteristics of ‘Farthing’. In a third study with rabbiteye blueberry genotypes, MeJa applications of 10, 20, and 30 m<jats:sc>m</jats:sc> displayed an increasing linear trend in fruit drop in ‘Climax’ and linear and quadratic trends in fruit drop in ‘Powderblue’. In a fourth study with ‘Powderblue’, MeJa (20 m<jats:sc>m</jats:sc>) and ethephon (1000 mg·L<jats:sup>−1</jats:sup>) applications resulted in rapid and significant fruit drop. The fruit drop induced by MeJa in this study was attenuated by the coapplication of aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor, suggesting that MeJa induced fruit detachment partly through its effects on ethylene biosynthesis. In another study with the southern highbush blueberry genotype, O’Neal, MeJa applications (20 m<jats:sc>m</jats:sc>) induced significant fruit drop but ethephon (1000 mg·L<jats:sup>−1</jats:sup>) applications did not affect fruit detachment. Overall, MeJa applications (20 m<jats:sc>m</jats:sc> or greater) generally induced rapid and extensive fruit abscission, often within 1 day after treatment. Applications of MeJa resulted in leaf yellowing and necrosis of leaf tips and margins, especially at high rates of application (20 m<jats:sc>m</jats:sc> or greater). Ethephon applications resulted in the abscission of mature and immature berries. Both ethephon and MeJa applications resulted in the detachment of the pedicel along with the fruit. Together, these data suggest that although ethephon and MeJa have the potential to be used as harvest aids in blueberry, the rates of application require further optimization to minimize potential phytotoxicity. Additionally, effective de-stemming of the berries may be essential if these compounds are to be used as harvest aids.</jats:p>

Fruit Detachment in Rabbiteye Blueberry: Abscission and Physical Separation

“…The difference in the extent of fruit detachment at the PPJ between MeJa and ethephon may be a reflection of the time taken for peak fruit loosening effects of these agents. The applications of MeJa generally resulted in high fruit detachment within 24 h, whereas fruit drop in response to ethephon applications was generally high at %48 h after treatment (Malladi et al, 2012). In earlier studies, preharvest treatment of ethephon followed by mechanical harvesting of highbush blueberry was reported to result in less than 5% ''stemmy fruit'' (Howell et al, 1976) in contrast to the observations described here and the study of Malladi et al (2012).…”

“…The applications of MeJa and ethephon resulted in 81% and 38% fruit detachment at the PPJ, respectively, in response to mechanical shaking. Similarly, Malladi et al (2012) reported that the majority of the fruit detachment in response to MeJa and ethephon treatments occurred at the PPJ in multiple rabbiteye blueberry genotypes as well as in southern highbush blueberry (hybrids largely derived from V. corymbosum and V. darrowi). Together, these data strongly indicate that fruit detachment in response to abscission agent applications was consistent across different cultivars and species of blueberry and occurred primarily at the PPJ.…”

“…The treatments were: 1) control; 2) MeJa (20 mM; Sigma-Aldrich, St. Louis, MO); and 3) ethephon (1000 mgÁL -1 ; Bayer CropScience, Kansas City, MO). These abscission agent treatments have been previously shown to induce rapid fruit detachment in multiple rabbiteye blueberry genotypes (Malladi et al, 2012). The treatments were performed when the majority (%75%) of the fruit on the plant was mature.…”

“…Hand harvesting and the majority of mechanical harvesting of blueberry cultivars typically result in fruit separation at the FPJ (Howell et al, 1976;Takeda et al, 2008). Recent studies indicate that fruit drop in response to the application of abscission agents such as ethephon (2-chloroethylphosphonic acid) and methyl jasmonate (MeJa) occurs primarily at the point of attachment of the pedicel to the peduncle in different types of blueberries (Malladi et al, 2012). This junction is referred to hereafter as the pedunclepedicel junction (PPJ).…”

On the use of Ethephon as abscising agent in cv. Crimson Seedless table grape production: Combination of Fruit Detachment Force, Fruit Drop and metabolomics

“…In fact, the application of abscission agents decreases the Fruit Detachment Force (FDF) required to separate berries from the stem thus facilitating mechanical harvesting of undamaged individual grape berries (Fidelibus, Cathline, & Burns, 2007). In particular, 2-chloroethylphosphonic acid (ETH), a commercial ethylenereleasing agent used as plant-growth regulator (Brown, 1997), has also been evaluated as a potential fruit loosening agent able to reduce the FDF in a wide range of fruit such as citrus (Citrus sinensis L.), grape (Vitis vinifera L.) (Uzquiza, González, González, Martín, & Uzquiza, 2013), olive (Olea europaea L.), and cherry (Prunus avium L.) (Malladi, Vashisth, & Johnson, 2012).…”