Foliar applications of abscisic acid decrease the incidence of blossom-end rot in tomato fruit

• ABA foliar spray treatments decreased Ca in the leaf tissue.
• ABA foliar spray treatments increased Ca into the fruit tissue.
• ABA and Ca treatments decreased the incidence of BER.
• ABA foliar spray treatments decreased the incidence of BER under deficient Ca rates.

Various environmental stress factors, such as drought and high relative humidity, can cause calcium (Ca) deficiency and lead to physiological disorders such as blossom-end rot (BER) in tomato (Lycopersicon esculentum) fruit. Recent studies demonstrate that abscisic acid (ABA) triggers whole-plant and fruit-specific mechanisms to increase fruit Ca uptake and prevent BER development. The objective of this study was to examine the effects of foliar application of ABA and hydroponic Ca treatments in fertilizer solution on localized deficiency of Ca causing BER in tomato fruit. The application of 500 mg L−1 ABA foliar spray treatment significantly decreased Ca in the leaf tissue. Ca decreased by 10.7% in the leaf tissue when comparing the foliar application of ABA to the control. In addition, decreasing Ca treatments from the 180 mg L−1 to the Ca deficient treatment of 60 mg L−1 decreased Ca concentration in the leaf tissue by 39.5%. The interaction of ABA and Ca treatments had a significant effect on Ca concentration in the fruit tissue. Ca concentration increased 25.7% when comparing the 180 mg L−1 Ca and 0.0 mg L−1 ABA treatment to the combination treatment of 180 mg L−1 Ca and 500 mg L−1 ABA treatment. In addition, ABA treatments had statistically significant effect on Ca in tomato fruit proximal and distal tissue and increased the concentrations 14.7% and 34.6% in, respectively. The incidence of BER in tomato fruit tissue was lowest with ABA treatments and Ca treatment of 180 mg L−1. The incidence of BER decreased by 86.2% from the combination of 180 mg L−1 Ca and 0.0 mg L−1 ABA treatment to the combination treatment of 180 mg L−1 Ca and 500 mg L−1 ABA treatment. The results demonstrate that the application of ABA increased Ca in the fruit tissue as Ca treatments were decreased from the 180 mg L−1 Ca. Furthermore, our results demonstrate that, despite reducing total plant Ca uptake in the leaf tissue, the 500 mg L−1 ABA foliar spray treatments significantly reduced the incidence of BER development in tomato fruit. Thus, ABA could be an alternative treatment to increase Ca uptake into fruit and distribution into the distal tissue of the fruit relative to leaf uptake.