Fig. 1

Scanning electron microscopy images of 0 DPA and 1 DPA ovules illustrating fiber initiation on the ovule surface. This image shows four upland cotton lines, i.e., 69–6025-12 (a, e), Liao 1779 (b, f), 601 LSC (c, g) and J02–508 (d, f). Scale bars: 100 μm (a-h). i Statistical results of the initial fiber number per unit area at 0 DPA. j Statistical results of the initial fiber number per unit area at 1 DPA. The height of the column is the average of three counts, and the error bars indicate ± S.D. The columns in the graph are arranged from large to small. The letters above the columns indicate the significance level of the initial fiber numbers of the four cotton materials. The same letters indicate no significant difference, and different letters indicate the difference was significant