Abscisic Acid and Soybean Oil Effects On Early Season Peach and Grape Phenology

Freezes during or following cold deacclimation of deciduous tree fruits often limit yields. Our research has shown  that soybean oil sprays before bud swell can delay peach bloom, reducing the potential of freeze damage. Research has shown that high levels of endogenous abscisic acid (ABA) are negatively associated with budbreak of several fruits. The objectives of this project were to determine if soybean oil and exogenous ABA sprays, separately or combined, delay grape bud and peach flower bud cold deacclimation and anthesis. ‘Niagara’ and ‘Golden Muscat’ grapes were sprayed with water (control), ABA 30025 (1000 mg/L), 3) ABA analog 30030 (50 mg/L), ABA 30025 (1000 mg/L) plus 2% TNsoy14 (96% soybean oil, a.i), or ABA 30030 (50 mg/L) plus 2% TNsoy14.  Sprays of the ABA 30030 analog delayed ‘Niagara’ bud development and reduced shoot growth until onset of flowering. The 30030 analog was more biologically active than 30025.  Both ABA formulations have potential to delay and/or reduce growth of grape vines. The 2% Tnsoy14 treatment did not affect ‘Niagara’ bud phenology or shoot growth but the addition of 2% TNsoy14 ABA tended to further reduce ‘Golden Muscat’ shoot growth. ‘Contender’ and ‘Nectar’ peach trees were sprayed on 22 February or 10 March with water, 8% TNsoy14, ABA 30025 (1000 mg/L), or 8% TNsoy14 plus ABA 30025 (1000 mg/L). The two peach cultivars differed in response to the treatments. The February sprays of 8% Tnsoy14 delayed ‘Nectar’ flower bud development and anthesis (by 3 days) compared to control trees but soy oil sprays in March tended to advance bloom of both cultivars. ‘Nectar’ trees sprayed with TNsoy14 tended to have slightly greater mortality of flower buds and less yields. However, soybean oil treated ‘Contender’ trees tended to have less bud mortality. The ABA treatments increased bud mortality on ‘Nectar’ trees (P=0.07) compared to control trees but reduced it on ‘Contender’ trees (P=0.02).