Chromosome segregation failure and cytokinesis defect producing unreduced pollen in the diploid rubber tree (Hevea brasiliensis (Willd. ex A. Juss.) Mull. Arg.)

The mechanism of unreduced gametogenesis is of great significance for understanding and utilising 2n gametes in the breeding of new varieties. In this study, a cultivated rubber tree clone that can produce triploid progeny and unreduced pollen was found. The triploid frequency of the progeny was determined by flow cytometry. The cytological mechanisms of unreduced pollen production were revealed by microsporogenesis and pollen development observation. Ploidy detection of offspring showed that the frequency of triploid progeny was different in different regions and years, ranging from 0% to 13.64%. Cytological studies showed that tripolar spindles and nuclei fusion in meiosis II and cytokinesis failure after meiosis are the mechanisms of unreduced pollen production. The fraction of 2n pollen and 4n pollen producing male flower was 36% and 14%, respectively. The occurrence of 2n pollen and 4n pollen in single male flowers was 0.19% and 0.10%, respectively. The average diameter of n, 2n, and 4n pollen grains were 39.38 mu m, 53.23 mu m, and 66.59 mu m, respectively. These results are the first to reveal the cytological mechanism of unreduced gametes production in Hevea brasiliensis and may have theoretical value for polyploidy breeding of rubber trees.

Automated summary

This study reveals the cytological mechanism of unreduced gamete production in Hevea brasiliensis, providing theoretical value for polyploidy breeding of rubber trees.