The Relationship of Apple Embryos and Their Cotyledons to Maturity, Dormancy, and the Potential to Form Shoots in Vitro

Abstract

Embryos extracted from developing apple fruit were cultured in vitro. Immature embryos (up to 4 weeks post anthesis), cultured without their testa and endosperm, produced only callus tissue. Six and a half-week-old embryos produced multiple shoots and the percentage of embryos producing shoots rather than callus tissue increased with time. Ten and a half-week-old embryos produced the highest number of shoots per embryo, after which a decrease in multiple shoot formation was observed with mature (14 weeks post anthesis) embryos producing 1 shoot and 1 root per embryo. Simultaneously, embryonic-axis free cotyledon cultures were established from embryos of various ages. Adventitious shoots developed from cotyledon explants, and the number of multiple shoots formed, increased with time (June-September). Cotyledons extracted periodically from mature fruit stored at 3°C continued to produce multiple shoots in culture, but this gradually decreased with time (15-120 days). After 6 months in cold storage, cotyledon explants failed to develop any shoots.