Fig. 1

Phenotypes of the gametes and seeds in yl. a Isolation of a yl mutant from BpCCR1 transgenic lines. WT, wild type birch. C11 and yl were the BpCCR1 overexpression lines. b Phenotypes of male inflorescence in WT, C11 and yl. c Fluorescein diacetate staining for pollen viability in WT, C11 and yl. Scale bars = 100 μm. d Phenotypes of infructescences and seeds in cross-combinations of WT × WT, C11 × WT and yl × WT. e 1000-seed weight of WT × WT, C11 × WT and yl × WT seeds. Scale bars = 1 cm (left) and 1 mm (right). f Germination rate of WT × WT, C11 × WT and yl × WT seeds. ** indicated P value < 0.01 (t test). Error bars represent the SD of three independent experiments