Generation and identification of Brassica alboglabra-Brassica campestris monosomic alien addition lines.

Four monosomic alien addition lines (MAALs) for Brassica alboglabra-Brassica campestris were developed through digenomic triploid (ACC) backcrossing with the recurrent parent B. alboglabra (CC). The objectives of this study were to compare morphological traits, microsatellite markers (simple sequence repeats), chromosomal karyotypes, and meiotic behaviors. Based on the new chromosome nomenclature system established for Brassica, we preliminarily identified these MAALs as CC+A1, CC+A3, CC+A6, and CC+A7. Their alien chromosomes were transmittable through both female and male gametes at rates of 11.46%-26.53% and 4.88%-12.90%, respectively.

Determination of n+1 gamete transmission rate of trisomics and location of gene controlling 2n gamete formation in Chinese cabbage (Brassica rapa).

A set of trisomics of Chinese cabbage was used for determining the n+1 gamete transmission rate and locating the gene controlling 2n gamete formation on the corresponding chromosome. The results showed that the transmission rates of extra chromosomes in different trisomics varied from 0% to 15.38% by male gametes and from 0% to 17.39% by female gametes. Of the nine F(2) populations derived from the hybridizations between each trisomic and Bp058 (2n gamete material), only Tri-4xBp058 showed that the segregation ratio of plants without 2n gamete formation to plants with 2n gamete formation was 10.38:1, which fitted the expected segregation ratio of the trisomics (AAa) based on the 7.37% of n+1 gamete transmission through female and 5.88% through male. In other populations the segregation ratios varied from 2.48:1 to 3.72:1, which fitted the expected 3:1 segregation ratio of the bisomics (Aa). These results suggested that the gene controlling 2n gamete formation in Chinese cabbage Bp058 was located on chromosome 4. Further trisomic analysis based on the chromosome segregation and the incomplete stochastic chromatid segregation indicated that the gene locus was tightly linked to the centromere.