Karyotype analysis Chinese chive germplasms with different ploidy levels and their evolutionary relationships

Abstract Diploids, triploids and tetraploids were screened from the germplasm garden of Chinese chive in this study using flow cytometry and chromosome counting technologies. Their evolutionary status was analysed by karyotype comparison and microsporogenesis observation. Their relationships were determined and discussed. The karyotype formula of the diploids was 2n = 2x = 16 = 14m + 2sm (2SAT). The asymmetrical karyotype coefficient (As. K. C) was 57.02%, which indicates the 2A type. The karyotype formula of triploids was 2n = 3x= 24 = 18m + 6sm (2SAT), and the As. K. C was 57.49%, which indicates the 2A type. The karyotype formula of tetraploids was 2n = 4x = 32 = 26m + 4sm + 2st (2SAT), and the As. K. C was 57.80%, which indicates the 2A type. The karyotyping results suggested that the evolutionary status increased with increasing ploidy in Chinese chive. Abnormal chromosome synapsis and separation during microsporogenesis result in the formation of pollen of different sizes in triploids, suggesting that 2n gametes more easily form in triploids. Therefore, we speculate that tetraploids were formed by the combination of 2n gametes of a triploid and n gametes of a diploid. In this process, triploids are the most likely bridge for the formation of tetraploids in Chinese chive.