The 2012 ASHS Annual Conference

Calcium (Ca) transport into leaves and fruit via xylem water movement is determined by transpiration rates and plant growth.  Phloem sap accounts for most of the water used for fruit expansion; however, Ca required for proper fruit development comes from xylem sap.  High leaf transpiration and vigorous vegetative growth is thought to restrict Ca movement into low-transpiring tomato fruit, a causal factor for the physiological disorder blossom end rot (BER).  ABA is known to regulate stomatal closure, leaf transpiration, and plant water potential.  Our objective was to analyze the effect of foliar ABA application on Ca partitioning, fruit quality, and incidences of BER in greenhouse-grown tomato (Lycopersicon esculentum var. Mountain Fresh Plus).  The experimental design was a randomized complete block in a split plot factorial arrangement consisting of main plots of Ca treatments at 60, 90 180 mg/L, and sub plots of ABA at 0 and 500 mg/L with 6 replications.  Calcium treatments were applied continuously through the irrigation system, while ABA treatments were applied foliarly once per week from anthesis to final harvest.  Marketable tomato fruit numbers were not influenced by Ca, ABA, or their treatment interactions.  Fruit size  significantly (P ≤ 0.05) increased with increasing Ca treatments.  Fruit size was also positively affected by ABA application (P ≤ 0.05).  There were significant (P ≤ 0.005) decreases in BER among Ca treatments, ranging from 1.58 fruit/cluster at 60 mg/L Ca treatment to 0.44 fruit/cluster at 180 mg/L Ca treatment.  ABA significantly (P ≤ 0.001) reduced BER from 1.63 to 0.48 fruit/cluster.  Fruit tissue Ca was positively influenced by Ca treatments (P ≤ 0.001), ABA application (P ≤ 0.001), and their interaction (P ≤ 0.05).  Fruit Ca concentration ranged from 26.62 to 63.67 µg/g dry weight (DW).  Tomato leaf Ca concentrations were significantly (P ≤ 0.001) different among Ca treatments and ranged from 2.1% to 4.1% DW and were positively correlated to Ca concentrations and consequently, incidence of BER in the fruit tissue.  Fructose and glucose increased significantly (P ≤ 0.05) with increasing Ca treatments ranging from 19.66 to 21.76 mg/g and 17.06 to 19.07 mg/g DW, respectively.  Fructose and glucose were also significantly (P ≤ 0.01) increased by ABA treated.  These data suggest that foliar application of the plant growth regulator ABA improved tomato fruit quality and increased Ca partitioning into tomato fruit tissue, thereby decreasing the incidence of BER.