Influence of Aminoethoxyvinylglycine (AVG) on Yield and Quality of Nut Crops from a Commercial Pecan Orchard

Abstract

<jats:p>Excessive fruit drop (i.e., June drop) can limit orchard profitability of certain pecan [<jats:italic>Carya illinoinensis</jats:italic> (Wangenh.) K. Koch] cultivars. The present study examines efficacy of aminoethoxyvinylglycine (AVG; formulated as ReTain<jats:sup>®</jats:sup>; Valent BioSciences, Libertyville, IL), a natural ethylene inhibitor, for increasing nutmeat yield in a commercial ‘Desirable’ pecan orchard over a 2-year period. The 30-ha experiment consisted of two treatments (nontreated versus ReTain) in the first year, an “off” year in the orchard's alternate bearing cycle. The second year's study, an “on” year, consisted of four treatments (i.e., “08 nontreated + 09 nontreated,” “08ReTain + 09 nontreated,” “08 nontreated + 09 ReTain,” and “08ReTain + 09 ReTain”). AVG, as ReTain [132 mg·L<jats:sup>−1</jats:sup> a.i. (11.7 oz/acre)], was applied as two post-pollination canopy sprays (937 L·ha<jats:sup>−1</jats:sup>) 2 weeks apart in both years. During the “off” year, ReTain increased nut yield parameters with ReTain increasing kernel yield by 36% (704 kg·ha<jats:sup>−1</jats:sup> versus 516 kg·ha<jats:sup>−1</jats:sup>) over that of nontreated trees. In the subsequent “on” crop year, the trees exhibiting a ReTain-associated previous year yield increase of ≈36% exhibited a reduction in yield of ≈25%, thus largely negating the previous season's yield increase over a 2-year alternate bearing cycle. Additionally, ReTain-treated trees during the “on” year failed to exhibit an increase in yield parameters over that of the nontreated control. As a result of a lag effect on subsequent year yield parameters, ReTain offers potential as a crop-load management tool for ‘Desirable’ orchards in “off” years such as a year of relatively high nutmeat price followed by a year of relatively low price. There appears to be no positive effect on yield when used in a heavy crop-load “on” year of an alternate bearing cycle. Thus, ReTain might have benefit for stabilizing alternate bearing in ‘Desirable’ pecan orchards. Kernel quality (defined as percentage of nut weight as kernel) of individual nuts from “on” year trees was not as sensitive to units of yield increase as for individual nuts of “off” year trees, thus implying that the rate of assimilate partitioning to individual reproductive structures in “off”-year trees is not as great as that in “on”-year trees.</jats:p>

Investigating the role of potassium and urea to control fruit drop and to improve fruit quality of “Dhakki” date palm

“…It is also believed that fruit drop is caused due to an imbalance between auxin and ethylene level. Ethylene triggers the system for abscission layer formation, breaks down the cell walls leading to fruit drop ( Stover et al, 1998 , Wood, 2011 ). Hence, there is a need to adopt measures and approaches to reduce fruit drop, especially in date palm cultivars.…”

Differential Expression of Key Floral Initiation Genes in Response to Plant Growth Regulator Application and Alternate Bearing in Pecan

“…Exogenous treatment involving PGRs on pecan shoots has been shown to affect the return bloom of pistillate flowers in the subsequent season (Thompson et al, 2019;Wood, 2011aWood, , 2011bWood et al, 2009). The current study expanded this concept by identifying differences based on PGR treatment of the flowering homologs CpLFY and CpAP1.…”

“…Exogenous applications of PGRs can potentially be used as tools for modifying flowering behavior and mitigating AB in pecan, as well as in other species such as apple and citrus (Meland and Kaiser, 2011;Muñoz-Fambuena et al, 2012;Thompson et al, 2019;Wood, 2011aWood, , 2011bWood et al, 2009). For multiple fruit tree species, individual shoots have been shown to function independently with respect to AB, also known as branch autonomy (Chan and Cain, 1967;Monselise and Goldschmidt, 1982;Rascon, 2014;Rohla et al, 2007;Tombesi et al, 2011;Weinbaum et al, 2001;Wood, 1991Wood, , 2011b.…”

Exogenous Plant Growth Regulators Show Promise for Management of Alternate Bearing in Pecan

“…), wal-nut (Juglans spp. ), and pecan (Greene, 2000;Hagemann et al, 2015;Hassankhah et al, 2018;Muñoz-Fambuena et al, 2012;Wood, 2011aWood, , 2011bWood et al, 2009). Application of ethephon-suppressed endogenous gibberellin GA 3 (GA 3 ) production in apple when applied in early spring increased subsequent season flowering and fruit set (Ebert and Bangerth, 1981).…”

“…Exogenous application of ethephon to whole immature trees in Wood's (2011b) study increased both the subsequent season's percentage of new shoots with flowers and the number of nuts per cluster compared with the control group. The ethylene inhibitor AVG was proposed as a mitigation tool for AB because it increases fruit retention in off years and has a carryover effect in which subsequent season on-year production was reduced (Wood, 2011a(Wood, , 2011bWood et al, 2009).…”