Abstract:Two previously identified strong cold tolerant introgression lines of IL5243 and IL5335 from Dongxiang wild rice (Oryza rufipogon Griff.) were used to investigate the meiosis behavior,chromosome recombination and the molecular evidence of alien genes introgression.The results showed that the rate of pollen mother cells (PMC) with normal meiotic behavior in the IL5243 and IL5335 was to 89.93% and 90.22%,respectively.And they finally formed the normal mature pollen;The rates of pollen germination in vitro were (83.03±2.82)% and (81.96±1.73)%,respectively.There were no significant differences between the cold tolerant introgression lines and their parents.However,at meiosis I,the low frequency of abnormal chromosome behavior was observed in IL5243 and IL5335,such as univalent,8 shape bivalent,multivalent and some PMCs (3.95%~5.15%) exist lagging chromosomes at anaphase I and so on,which suggested that there were genetic exchange and recombination between cultivated rice and common wild rice.In addition,the high frequency of double nucleoli was observed at pachytene in the two cold tolerance introgression lines (IL5335 and IL5243 were 38.9% and 27.0%,respectively),while their parents only had one nucleolus.Through SSR markers and structure analysis,we further confirmed that introgression of some Dongxiang wild rice DNA fragments in the strong cold resistance introgression lines through chromosome exchange and recombination between the cultivated rice and the wild rice.These results laid a foundation for further excavating and using this rice cold tolerant gene in the future.