Gibberellin Inhibits Fruit Abscission Following Seed Abortion in Peach

Seed coats of developing fruit of peach [Prunus persica (L.) Batsch cvs . Redkist, Redskin, and Loring] were punctured at 31, 33, and 38 days after full bloom (DAFB), respectively. Injections of water, 390 mg GA 3 /liter, or 390 mg GA 4+7 /liter were made immediately following seed puncture. Seed puncture and water injection following puncture resulted in abscission of all fruit. Injection of GA 3 and GA 4+7 delayed abscission of `Redkist' and `Redskin' fruits of punctured seeds by 6 to 10 days. Both GA treatments resulted in normal growth into Stage II and increased fruit retention through Stage III in `Loring'. About 100 μl of 250, 500, or 1000 mg GA 3 /liter was injected into the locule of `Loring' fruits following seed puncture at 30, 40, or 50 DAFB. GA treatments at 30 DAFB resulted in≈ 75% fruit set in comparison to seeded control fruit, while fruit treated at 40 and 50 DAFB abscised by the end of Stage II. Increasing GA concentration from 250 to 1000 mg·liter -1 had no additional effect. Movement of the GA was examined by injecting 3 H-GA 1 into the locule following the puncture treatment. More than 97% remained in the fruit after 96 hours. The percentage of 3 H recovered in the seed cavity decreased over time, whereas recovered label increased in both endocarp and mesocarp. The results suggest a potential regulatory role for seed-produced gibberellins during early Stage I of development. We have identified an apparent change in tissue sensitivity to gibberellin induction of seedless fruit development between 30 and 40 DAFB in `Loring' peach.