Abstract:

The microspore mother cell and correlation between meiosis process and flower bud external morphology of Ziziphus jujuba Mill.‘Wuhefeng’treated with colchicine were studied using squash preparation，and the ratio of 2n pollen was determined. The results showed that the first meiosis of microspore mother cell treated with colchicine was normal. Abnormal cytokinesis was observed at the prophaseⅡ；There were four types of spindle body at the metaphaseⅡ，i.e.，parallel type，vertical type， splay type，fusion type，accounting for 27.31%，19.35%，45.27% and 8.06%，respectively. Dyad，triad and tetrad were observed at tetrad stage，accounting for 6.00%，43.04% and 50.96%，respectively. Splay spindle body and fusion body（abnormal-position）were positively correlated with triad and dyad，respectively. The microspore mother cell analyses revealed that 2n pollen resulted from abnormal cytokinesis during prophaseⅡand spindles of abnormal-position during metaphaseⅡof microsporogenesis. And 96.97% of 2n pollen formation was controlled by abnormal-position spindle，which were genetically equivalent to first division restitution（FDR）type of gamete formation that can translate 80% heterozygosity. The other 2n pollens were genetically equivalent to second division restitution（SDR）type of gamete formation which can translate 40% heterozygosity. Thus 2n pollen produced from‘Wuhefeng’treated with colchicine can provide potential value for polyploidy breedingin Z. jujuba Mill. Microspore meiosis process had a corresponding relationship with flower bud external morphology. When the flower bud diameter reached 1.34 mm，microspore mother cells entered into meiosis. The pollen mother cells entered into tetrad period when the flower bud diameter reached 1.68 mm. When the flower bud diameter was more than 1.92 mm，the meiosis was finished and a large number of pollen grains formed. The optimal period of colchicine treatment for 2n pollen induction was at the end of leptotene，when flower bud diameter ranged from 1.34 mm to 1.42 mm. In this situation，the incidence rate of 2n pollen in‘Wuhefeng’jujube substantially increased up to 17.36% compared to the untreated natural one of only 0.

Key words: Ziziphus jujuba, colchicine treatment, meiosis, 2n pollen, pollen morphology