Timing of auxin treatment affects grape berry growth, ripening timing and the synchronicity of sugar accumulation

Abstract

Background and Aims: Climate change has resulted in earlier berry development and compressed harvests creating problems with harvesting and winery logistics and causing undesired modifications to grape and wine composition, such as elevated concentration of berry sugar and wine alcohol. Auxin treatment of grapevine bunches prior to veraison can counteract these adverse changes by delaying berry maturation. The most efficacious timing of 1-naphthaleneacetic acid (NAA) application along with the effects of application timing on berry growth, and berry and wine composition are yet to be identified. Methods and Results: Cabernet Sauvignon bunches were treated with 50 mg/L NAA at three different times prior to, and at, veraison. The nearer to veraison the NAA application the longer the delay in harvest. Compared with the Control the NAA treatment reduced berry shrivel and increased the synchronicity of berry populations in terms of the accumulation of TSS with only minor effects on berry composition and wine volatile compounds. Conclusions: Auxin treatment delayed ripening, reduced berry shrivel and increased ripening synchronicity with little effect on berry and wine composition. Significance of the Study: Auxin treatment of grape bunches could be used to manage problems caused by climate change, including, compressed harvests and ripening under hotter conditions, in a targeted manner in existing vineyards.

Integrated Analysis of Transcriptome and Metabolome to Unveil Impact on Enhancing Grape Aroma Quality with Synthetic Auxin: Spotlight the Mediation of ABA in Crosstalk with Auxin

“…The onset of grape ripening is triggered by the elevation of ABA and the decline of auxin . Previous studies have widely reported that prevéraison NAA application can delay the véraison and ripening of grapes. ,− ,, Our findings further demonstrated the inhibitory effect of NAA on grape ripening. Except for the delay in TSS accumulation, other parameters, such as pH value increase and TA decrease, were also observed to be delayed (as depicted in Figure ).…”

“…Davis et al observed that 16 days of preveŕaison NAA treatment (50 mg/L) resulted in the significantly higher concentration of β-damascenone in "Cabernet Sauvignon" wines than control wines. 18 He et al found that NAA (100 mg/L) application at 14 days preveŕaison increased the concentrations of most norisoprenoid compounds in the grapes E-L 38. 9 These results suggested that the synthetic auxin has a positive impact on the production of β-damascenone in harvested grapes.…”

“…The impact of NAA application concentration, timing of treatment, and grape varieties on aroma compounds varies, as previously noted in reports. [9][10][11][12]18,19 In our previous trials, we utilized an NAA concentration of 100 mg/L, which resulted in a 25 day postponement of the veŕaison. 9 Such prolonged delays could impede the commercial harvest matureness of grapes, specifically when temperatures plummet in October in northwestern China.…”

Effect of varying concentrations of melatonin on anthocyanin and sugar metabolism in grapes (Vitis labruscana L.)

“…It has been shown that IAA promotes plant growth at low concentrations, whereas conversely, high concentrations of IAA inhibit plant growth (Zafar et al, 2020). Furthermore, auxin application to grapevines prior to veraison delayed berry maturation, including sugar accumulation (Davies et al, 2022). Both melatonin and IAA are synthesized from tryptophan and have similar structures (Harderland, 2016;Zafar et al, 2020;Jahn et al, 2021).…”

“…ABA is primarily catabolized to 8′-hydroxy ABA by ABA 8′-hydroxylase, which is encoded by the CYP707A gene and then isomerized to phaseic acid (PA) (Saito et al, 2004). It has been shown that auxin treatments, such as 1-naphthaleneacetic acid (NAA) treatment, delays maturation in grapes; however, the effect depends on the timing of treatment (Davies et al, 2022).…”