SCTD
The experimental materials were planted at the Zhongjiang (Deyang, Sichuan province, China 3055'8.22" N, 10437'27.16'' E) experimental base of Sichuan Agricultural University in February 2020. SD and SC were obtained from the resource nursery. The experimental design used was complete randomized block with three replications, and it involved 40 plants per plot with spacing of 0.4 m between plants and 0.5 m between rows. At the start of the following June, anther samples from three developmental stages were isolated, immediately frozen in liquid nitrogen, and stored at -80C. The anther sizes of the three stages are 1.5-2.0, 3.0-3.5, and 4.5-5.0 mm, which were named as the tetrad (TD), young microspore (YM), and the mature pollen stage (MP), respectively.