High temperature treatment generates unreduced pollen in persimmon (Diospyros kaki Thunb.)

•The stages in meiotic were related to the phenotypic development of male flowers.•The presence of lagging chromosomes, triads and dyads was discovered during meiosis.•42 °C for 4 h produced the greatest amount of 2n pollen (up to 22.04%). Unreduced gametes (2n) are of significant value in plant polyploid breeding. Cross breeding using natural or artificially induced 2n pollen is one of the best procedures for generating persimmon nonaploids. Successful artificial induction of 2n pollen requires a comprehensive understanding of the microsporogenesis process and the timing of physicochemical treatment application. We observed the development of male flowers and the meiotic process in microspore mother cells of persimmon plants originating from the Hubei Mulan Grassland. Except for some abnormal phenomena, such as the lagging of chromosomes in metaphase I and the formation of triads and dyads, the meiotic process of microspore mother cells was normal. The stages in this process were related to the phenotypic development of male flowers, i.e., when the flower buds began to swell and the corolla and the calyx were flattened apically (April 8–12), the microspore mother cells began meiosis. This period was optimal for the physicochemical induction of 2n pollen. We also induced 2n pollen between zygotene and diplotene via high temperature exposure. The treatment combination of 42 °C for 4 h produced the greatest amount of diploid pollen (up to 22.04% of the total yield). Our results will enable progress in procedures that use naturally occurring or artificially induced 2n pollen for nonaploid breeding of persimmon.