ARS | Publication request: Interaction of BABA and ABA for drought resistance in apple

Submitted to: Plant Growth Regulator Society of America Meeting
Publication Type: Proceedings
Publication Acceptance Date: November 2, 2010
Publication Date: July 22, 2011
Citation: Tworkoski, T., Wisniewski, M.E., Artlip, T.S. 2011. Interaction of BABA and ABA for drought resistance in apple. Plant Growth Regulator Society of America Meeting. p. 142.

Technical Abstract: Insufficient water can kill or adversely affect the growth of newly planted apple (Malus ×domestica) trees. In modern intensive orchard systems with mature trees, water stress is often limiting to production. Trees can acquire drought resistance by sensing water stress and activating defense mechanisms, such as reduction of transpiration with stomata closure, and metabolic adjustments, such as accumulation of osmolytes. Drought resistance can also be induced indirectly by chemical or physical "priming", for example, by applications of abscisic acid (ABA). The non-protein compound DL-ß-aminobutyric acid (BABA) has been shown to confer plant protection against a wide range of biotic and abiotic stresses including ABA-dependant defense mechanisms. We hypothesized that ABA and BABA provided drought protection by related but different mechanisms that can improve survival of young apple seedlings exposed to water stress. Our objective was to determine the resistance to and recovery from the drought of apple seedlings treated with ABA and BABA. Three greenhouse experiments were conducted in which combinations of ABA and BABA were applied as a root drench at various concentrations and response to drought of one-year-old ‘Gala’ apple trees on their own root were evaluated. Changes in leaf water potential (WP), stomatal conductance (SC), transpiration (Ts), photosynthesis, and growth were measured during dehydration and rehydration. Pretreatment with BABA reduced predawn Ts, but BABA was not as effective as ABA in delaying drought-induced wilt of shoot tips. During the second week without water, both BABA- and ABA-treated trees had higher leaf WP than controls. In ABA-treated trees, higher leaf WP was associated with reduced SC and Ts. Combined applications of BABA and ABA provided the highest leaf WP, but significant synergy was not found. Compared with control trees, there was nearly 80% more shoot growth after one month following rewatering after drought in trees that received combined BABA & ABA (1.0 mM each). In these experiments dehydration protection was generally in the form of reduced stomatal conductance and transpiration that reduced water loss and maintained trees at a higher leaf water potential. Leaf senescence was more evident in ABA than BABA treated trees, and although growth resumed after drought, the amount of growth varied with the concentration of the priming treatments. Both compounds provided dehydration protection to young apple trees, but together, they were not statistically superior to either compound alone.