Induction of unreduced megaspores in Eucommia ulmoides by high temperature treatment during megasporogenesis

Eucommia ulmoides Oliver is an important temperate species because it contains Eucommia rubber, iridoids, and other medicinal substances. Triploid breeding may be an effective way to improve the contents of gutta percha and other secondary metabolites in Eucommia leaves. To obtain triploid trees, 2n female gametes were induced by exposing female buds to high temperatures. The results showed that although the Eucommia female flower bud development is not synchronous, it still exhibits regularity. We estimated the period of megaspore mother cell meiosis based on the number of days since the adjacent male flower produced its pollen.Using female buds at 1-4 days after pollination, we obtained triploid seedlings after female buds were treated with different temperatures and durations to induce megaspore chromosome doubling. Among the offspring, 23 of Eucommia triploid seedlings were detected. Our findings indicate that the most suitable condition for inducing megaspore chromosome doubling occurred at 3 days after adjacent male tree produce pollen when the meiosis of the megasporocytes was between pachytene and diplotene. The best treatment of 45 A degrees C for 4 h gave triploid induction of 5.74 %.