Synthetic apomixis transfers stably over multiple generations in hybrid rice

we reproduced the clonal plants of Fix (Fixation of rice heterozygosity) to T4 generation with 1.9~3.2% clonal seeds rate of Fix-T01th, T12th, T23th and T34th. The descendant clonal plants Fix-T0, T1, T2, T3 and T4 exhibited no discernible differences on plant morphology, clonal seeds rate (3.7~4.3%), genome, methylome and transcriptome. Unexpectedly, few aneuploids were identified in each generation. The visible morphology changes of aneuploids might be caused by chromosome segments elimination. Together, the synthetic apomixis was heritable through multiple generations and few aneuploids were induced when using the synthetic apomixis system. Overall design: Previously, the Fix-T0 plants were generated in the hybrid rice Chunyou84 (CY84) genetic background, an elite inter-subspecific hybrid rice from a cross between the maternal Chunjiang 16 A (16 A), a japonica male-sterile line, and the paternal C84, an indica-japonica intermediate-type line17. The Fix-T0 plants self-pollinated to T3 generation with screening diploids at each generation. The Fix-T0 and CY84 (corresponding control for Fix T0) plants were preserved to next generation via roots. The seeds from Fix offsprings (Fix T01th, T12th, T23th and T34th; Fix T0, T1, T2, T3 and T4), MiMe-T1 and Nipponbare variety (continuous self-pollinated four generations materials, coded as 1th, 2th, 3th and 4th) were soaked in deionized water at 37 °C in the dark for 2 d, and then transferred to a net floating on deionized water for further 5 d. The seedlings were cultured in a half-strength Kimura B nutrient solution (pH 5.4) for 21 d. Plant ploidy of the Fix offspring seedlings were identified using flow cytometry as described followings. All the confirmed seedlings were transferred to paddy field in Hangzhou. Plant growth in the field was managed according to local cultivation practices.